Jugular Foramen

CHAPTER 9

Jugular Foramen

Albert L. Rhoton, Jr., M.D.Department of Neurological Surgery, University of Florida, Gainesville, Florida

Key words: Cranial base, Cranial nerves, Jugular foramen, Microsurgical anatomy, Occipital bone, Skull base, Temporal bone, Venous sinuses

The jugular foramen is difficult to understand and toaccess surgically (3, 11, 15, 19, 24, 28). It is difficult toconceptualize because it varies in size and shape in

different crania, from side to side in the same cranium, andfrom its intracranial to extracranial end in the same foramen,and because of its complex irregular shape, its curved course,its formation by two bones, and the numerous nerves andvenous channels that pass through it (Fig. 9.1). The difficultiesin exposing this foramen are created by its deep location andthe surrounding structures, such as the carotid artery anteri-orly, the facial nerve laterally, the hypoglossal nerve medially,and the vertebral artery inferiorly, all of which block access tothe foramen and require careful management.

The jugular foramen is divided into three compartments:two venous and a neural or intrajugular compartment. Thevenous compartments consist of a larger posterolateral ve-nous channel, the sigmoid part, which receives the flow of thesigmoid sinus, and a smaller anteromedial venous channel,the petrosal part, which receives the drainage of the inferiorpetrosal sinus. The petrosal part forms a characteristic venousconfluens by also receiving tributaries from the hypoglossalcanal, petroclival fissure, and vertebral venous plexus. Thepetrosal part empties into the sigmoid part through an open-ing in the medial wall of the jugular bulb between the glos-sopharyngeal nerve anteriorly and the vagus and accessorynerves posteriorly. The intrajugular or neural part, throughwhich the glossopharyngeal, vagus, and accessory nervescourse, is located between the sigmoid and petrosal parts atthe site of the intrajugular processes of the temporal andoccipital bones, which are joined by a fibrous or osseousbridge. The glossopharyngeal, vagus, and accessory nervespenetrate the dura on the medial margin of the intrajugularprocess of the temporal bone to reach the medial wall of theinternal jugular vein. The operative approaches that accessvarious aspects of the foramen and adjacent areas are thepostauricular transtemporal, retrosigmoid, extreme lateraltranscondylar, and preauricular subtemporal-infratemporalapproaches.

OSSEOUS RELATIONSHIPS

The jugular foramen is located between the temporal boneand the occipital bone (Figs. 9.1 and 9.2). The right foramen is

usually larger than the left. In a previous study, we observedthat the right foramen was larger than the left in 68% of thecases, equal to the left in 12%, and smaller than the left in 20%(24). The foramen is configured around the sigmoid and in-ferior petrosal sinuses. It can be regarded as a hiatus betweenthe temporal and the occipital bones. The structures thattraverse the jugular foramen are the sigmoid sinus and jugu-lar bulb, the inferior petrosal sinus, meningeal branches of theascending pharyngeal and occipital arteries, the glossopharyn-geal, vagus, and accessory nerves with their ganglia, the tym-panic branch of the glossopharyngeal nerve (Jacobson’s nerve),the auricular branch of the vagus nerve (Arnold’s nerve), and thecochlear aqueduct.

The foramen is situated so that its long axis is directed fromposterolateral to anteromedial, giving it an anterolateral mar-gin formed by the temporal bone and a posteromedial marginformed by the occipital bone. From the intracranial end, it isdirected forward, medially, and downward. One cannot seethrough the foramen when viewing the skull from directlyabove or below because of its roof, formed by the lowersurface of the petrous part of the temporal bone. The foramen,when viewed from the intracranial side in a posterior toanterior direction, has a large oval lateral component, referredto as the sigmoid part, because it receives the drainage of thesigmoid sinus, and a small medial part, called the petrosalpart, because it receives the drainage of the inferior petro-sal sinus. The view through the foramen from directly belowreveals the part of the temporal bone forming the dome of thejugular bulb, rather than a clear opening.

The junction of the sigmoid and petrosal parts is the site ofbony prominences on the opposing surfaces of the temporaland occipital bones, called the intrajugular processes, whichare joined by a fibrous, or less commonly, and osseous bridge,the intrajugular septum, separating the sigmoid and petrosalpart of the foramen.

Although the margins of the jugular foramen are formed bythe petrosal part of the temporal bone and the condylar partof the occipital bone, the other parts of these bones also haveimportant relationships to the jugular foramen. The petro-clival fissure, the fissure between the lateral edge of the clivalpart of the occipital bone and the petrous part of the temporalbone, intersects the anteromedial edge of the foramen, and theoccipitomastoid suture, the suture between the mastoid por-

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tion of the temporal bone and the condylar part of the occip-ital bone, intersects its posterolateral edge.

The intrajugular processes of the temporal and occipitalbones divide the anterior and posterior edges of the foramen

between the sigmoid and petrosal parts. The intrajugularprocess of the temporal bone protrudes farther into the jugu-lar foramen than the opposite process from the occipital bone,and may infrequently reach the smaller intrajugular process

FIGURE 9.1. A–D. Osseous relationships. A, the jugular foramen is located between the temporal and occipital bones. One can-not see directly through the foramen from above, as shown, because it is directed forward under the temporal bone. The sigmoidgroove descends along the mastoid and crosses the occipitomastoid suture where it turns forward on the upper surface of the jugu-lar process of the occipital bone and enters the foramen by passing under the posterior part of the petrous temporal bone. B, theview directed from posterior and superior shows the shape of the foramen, which is not seen on the direct superior view. The fora-men has a larger lateral sigmoid part through which the sigmoid sinus empties and a smaller anteromedial petrosal part throughwhich the inferior petrosal sinus empties. The two parts are separated by the intrajugular processes of the occipital and temporalbones. The glossopharyngeal, vagus, and accessory nerves pass through the intrajugular portion of the foramen located betweenthe sigmoid and petrosal parts. The foramen is asymmetric from side to side with the right side often being larger as shown. Thecochlear aqueduct opens just above the anterior edge of the petrosal part. The vestibular aqueduct opens into the endolymphaticsac, which sits on the back of the temporal bone superolateral to the sigmoid part of the jugular foramen. C, jugular foramenviewed from directly below. One cannot see directly through the foramen from below because the foramen is covered above bythe part of the petrous temporal bone forming the jugular fossa, which houses the jugular bulb. The entrance into the carotid canalis located directly in front of the medial half of the jugular foramen. The stylomastoid foramen is located lateral and the anteriorhalf of the occipital condyle medial to the jugular foramen. The posterior condylar foramen is transversed by an emissary vein,which joins the sigmoid sinus. The hypoglossal canal passes above the middle third of the occipital condyle and opens laterally intothe interval between the jugular foramen and carotid canal. D, the view directed from anterior and backward reveals the shape ofthe jugular foramen. The roof over the foramen formed by the jugular fossa of the temporal bone is shaped to accommodate thejugular bulb. The posterior margin of the foramen is formed by the jugular process of the occipital bone, which connects the basal(clival) part of the occipital bone to the squamosal part. The petroclival fissure intersects the anteromedial margin of the petrosalpart of the foramen. Ac., acoustic; Car., carotid; Coch., cochlear; Cond., condyle; Fiss., fissure; For., foramen; Hypogl., hypoglossal;Int., internal; Intrajug., intrajugular; Jug., jugular; Mast., mastoid; Occip., occipital; Pet., petrous; Petrocliv., petroclival; Post., poste-rior; Proc., process; Sig., sigmoid; Squam., squamosal; Stylomast., stylomastoid; Temp., temporal; Vest., vestibular.

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of the occipital bone, dividing the jugular foramen into twobony foramina. A ridge, the intrajugular ridge, extends for-ward from the intrajugular process of the temporal bonealong the medial edge of the jugular bulb (Fig. 9.1). Theglossopharyngeal nerve courses along its medial edge. Occa-sionally, the edge of this ridge extends medially toward theadjacent part of the temporal bone to create a deep groove inwhich the nerve courses or it may reach the temporal bone to

form a canal, which surrounds the glossopharyngeal nerve asit passes through the jugular foramen.

The drainage of the sigmoid sinus is directed forward into thesigmoid portion of the foramen, where a high domed recess,the jugular fossa, forms a roof over the top of the jugular bulb(Figs. 9.1 and 9.3). This recess, which has its summit slightlylateral to the entrance of the sigmoid sinus, is usually larger onthe right side of the skull, reflecting the larger sigmoid sinus on

FIGURE 9.1. E–H. E and F, another jugular foramen. Left side: E, the sutures have been forced open to show the relationshipof the foramen to the petroclival and occipitomastoid sutures. The jugular foramen has a larger lateral part, the sigmoid part,which receives the drainage of the sigmoid sinus, and a smaller medial part, the petrosal part, which receives the drainage ofthe inferior petrosal sinus. The intrajugular process of the occipital bone is somewhat more prominent than shown in C andprojects forward toward the intrajugular process of the temporal bone. The hamate process normally extends along themedial edge of the petrosal part of the foramen to the adjacent part of the temporal bone, but in this case the sutures wereforced open, leaving an interval between the hamate process and the temporal bone. F, enlarged view. G and H, another jug-ular foramen. G, the intrajugular process of the temporal bone projects into the interval between the sigmoid and petrosalparts of the foramen. A ridge, the intrajugular ridge, extends forward from the intrajugular process along the medial side ofthe jugular bulb. The glossopharyngeal nerve passes forward along the medial side of the intrajugular process and ridge. Thevagus and accessory nerves enter the dura on the medial side of the process, but quickly descend and do not pass forwardalong the medial edge of the ridge as does the glossopharyngeal nerve. The jugular process of the occipital bone often has asmall prominence on its surface that projects toward the intrajugular process of the temporal bone, and in some foramina,the intrajugular processes of the two bones are joined by an osseous bridge that converts the foramen into two osseousforamina. In this case, the intrajugular process of the occipital bone is absent. H, enlarged view. The cochlear aqueductopens above the petrosal part of the foramen and the site where the glossopharyngeal nerve enters the intrajugular part ofthe foramen on the medial side of the intrajugular process. The vestibular aqueduct opens onto the posterior surface of thetemporal bone superolateral to the jugular foramen.

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that side. The dome of the recess is usually smooth as it conformsto the jugular bulb, but the summit may also be ridged andirregular. A small triangular recess, the pyramidal fossa, extendsforward on the medial side of the intrajugular process of thetemporal bone along the anterior wall of the petrosal part of the

foramen. The external aperture of the cochlear canaliculus,which houses the perilymphatic duct and a tubular prolongationof the dura mater, opens into the anterior apex of the pyramidalfossa. The glossopharyngeal nerve enters this fossa below thepoint at which the cochlear aqueduct joins its apex.

FIGURE 9.2. Osseous relationships. A, lateral view.The styloid process projects downward and the facialnerve exits the stylomastoid foramen on the lateralside, and both block lateral access to the jugularforamen. The mandibular condyle blocks access tothe foramen from anteriorly and the vertebral arteryascending through the C1 transverse process limitsaccess from behind. The transverse process of C1 sitsbehind and often indents the posterior wall of theinternal jugular vein. B, inferior view of the jugularforamen. The jugular foramen is located lateral to theanterior half of the occipital condyle. The temporalbone forms the dome over the jugular bulb. Thejugular process of the occipital bone forms theposterior margin of the jugular foramen. The jugular

foramen and carotid canal are separated by a narrow bony ridge, which is penetrated medially by the tympaniccanaliculus through which passes the tympanic branch of the glossopharyngeal nerve (Jacobson’s nerve). This branchof the nerve passes forward across the promontory in the medial part of the tympanic cavity, then crosses the floor ofthe middle fossa as the lesser petrosal nerve, and eventually reaches the otic ganglion, providing parasympatheticinnervation to the parotid gland. The anterior wall of the sigmoid part of the foramen is the site of a shallow groove acrosswhich the auricular branch of the vagus nerve (Arnold’s nerve) passes to enter the mastoid canaliculus. It exits the mastoidthrough the tympanomastoid suture. C, lateral view of the left temporal bone. A small fiber (arrow) placed in the tympaniccanaliculus, shown in B, exits the canaliculus in the middle ear where the fibers of the tympanic branch of the glossopharyngealnerve cross the promontory, and then regroup to cross the floor of the middle fossa as the lesser petrosal nerve. The styloidprocess projects downward lateral to the jugular foramen. Aur., auricular; Br., branch; Canalic., canaliculus; Car., carotid; CN,cranial nerve; Cond., condyle; Ext., external; Fiss., fissure; For., foramen; Jug., jugular; Mandib., mandibular; Occip., occipital;Petrotymp., petrotympanic; Proc., process; Trans., transverse; Tymp., tympanic.

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The jugular process of the condylar portion of the occipitalbone, which extends behind the jugular foramen and connectsthe clival and squamosal parts of the occipital bone, forms theposteromedial wall of the foramen. This process extends lat-erally from the area above the posterior half of the occipitalcondyle and is penetrated by the hypoglossal canal. The uppersurface of the jugular process of the occipital bone in the areasuperomedial to the foramen presents an oval prominence, thejugular tubercle, which is located above the hypoglossal canal.The jugular tubercle often has a shallow furrow marking the siteof passage of the glossopharyngeal, vagus, and accessory nervesacross its surface. The terminal end of the sigmoid sinus coursesforward on the superior surface of the jugular process in a deephook-like groove, the sigmoid sulcus, which is directed mediallyinto the sigmoid portion of the jugular foramen.

On the lateral wall of the jugular foramen, a few millimetersinside the external edge, just behind the point at which theoccipitomastoid suture crosses the lateral edge of the foramen,is a small foramen, the mastoid canaliculus, and a shallowgroove leading from medial to lateral across the anterior wall ofthe sigmoid part to the mastoid canaliculus (Figs. 9.2 and 9.3).The auricular branch of the vagus nerve (Arnold’s nerve)courses along the groove and enters the canaliculus. The nervepasses through the mastoid and exits the bone in the inferolateralpart of the tympanomastoid suture. At the site where the intra-jugular ridge of the temporal bone meets the carotid ridge, asmall canal, the tympanic canaliculus, is directed upward, lead-ing the tympanic branch arising from the inferior glossopharyn-geal ganglion (Jacobson’s nerve) to the tympanic cavity (Figs.9.2). Looking from below at the extracranial orifice of the jugularforamen, it can be recognized that the glossopharyngeal nervecourses along the medial side of the intrajugular process andridge to reach the area below the tympanic canaliculus.

ADJACENT BONY STRUCTURES

On the intracranial side, the petrosal part of the foramen islocated approximately 5 mm below the porus of the internalcanal and 5 mm above the intracranial orifice of the hypoglos-sal canal (Figs. 9.2 and 9.4). The lateral edge of the foramen islocated below and in approximately the sagittal planethrough the lateral end of the internal acoustic meatus. Thejugular tubercle, a rounded prominence located at the junctionof the basal and condylar parts of the occipital bone, is situatedapproximately 8 mm medial to the medial edge of the jugularforamen. The otic capsule, which is situated in the petrous partof the temporal bone and which contains the semicircular canalsand cochlea, is located superior to the dome of the jugular bulb.

The occipital condyle is located along the lateral margin ofthe anterior half of the foramen magnum in the area belowand medial to the jugular foramen.

The hypoglossal canals, which pass through the condylarpart of the occipital bone in the area above the occipitalcondyles, are located medial to the jugular foramina (Figs. 9.1and 9.3). The intracranial end of the hypoglossal canal issituated below the jugular tubercle approximately 5 mm in-feromedial to the petrosal part of the jugular foramen andseveral millimeters below the lower part of the petroclival

fissure. A more detailed review is included in the chapter onthe far-lateral approach.

The anterior margin of the jugular foramen, when viewedextracranially, is formed by the narrow ridge of temporalbone, the carotid ridge, which separates the foramen and thecarotid canal (Figs. 9.1 and 9.2). The tympanic canaliculus openson or near the medial part of the carotid ridge. The styloidprocess and the stylomastoid foramen are located lateral to theouter orifice of the jugular foramen, with the styloid processbeing located slightly anteromedial to the stylomastoid foramen.The facial nerve exits the stylomastoid foramen approximately 5mm lateral to the lateral edge of the jugular foramen. The ante-rior margin of the jugular foramen is located just behind the partof the tympanic bone that forms the posterior wall of the tem-poromandibular joint and the anterior and inferior wall of theexternal auditory canal. The vaginal process of the tympanicbone, which separates both the carotid canal and sigmoid part ofthe foramen from the glenoid fossa, is the site of attachmentof the styloid process to the skull base. The styloid processprojects downward from the vaginal process of the tympanicbone, lateral to the foramen. The digastric groove is directedposteriorly from the styloid process along the medial margin ofthe mastoid process. Access to the jugular foramen is blockedlaterally by mastoid and styloid processes, the transverse processof the atlas, and the mandibular ramus (Figs. 9.3 and 9.4).

The tympanic cavity, which is located medial to the tym-panic membrane, is situated above and lateral to the jugularbulb and the sharp right-angled curve, called the lateral bend, atthe junction of the vertical and horizontal segments of the pe-trous carotid artery (Fig. 9.4). Several structures that may beexposed during surgery for lesions in the jugular foramen arethe vertical and horizontal segments of the petrous portion of theinternal carotid artery, the eustachian tube, and the tensor tym-pani muscle. Both the cochlea and semicircular canals are locatedin the petrous part of the temporal bone above the dome of thejugular bulb (Fig. 9.4). The facial nerve in the temporal bone,which often blocks access to lesions in the jugular foramen,descends through the mastoid lateral to the jugular bulb. Theendolymphatic sac is situated on the posterior surface of the pe-trous bone between the two layers of the dura in the corner atwhich the sigmoid sinus changes its course from a verticaldirection to a horizontal one (Figs. 9.3 and 9.5).

Dural architecture

At the intracranial orifice, the jugular foramen is dividedinto three compartments by the dura mater: the petrosal com-partment situated anteromedially, the sigmoid compartmentsituated posterolaterally, and the intrajugular or neural com-partment situated between the petrosal and sigmoid parts atthe site of the intrajugular processes of the temporal andoccipital bones, the intrajugular septum, and the glossopha-ryngeal, vagus, and accessory nerves (Figs. 9.3 and 9.5). Thedura over the intrajugular part of the foramen, which islocated anteromedial to the sigmoid part, has two character-istic perforations, a glossopharyngeal meatus, through whichthe glossopharyngeal nerve passes, and a vagal meatus,through which the vagus and accessory nerves pass (Figs. 9.5



FIGURE 9.3. A, posterior superior view of the jugular foramen. The sigmoid sulcus makes a sharp turn just before emptyinginto the sigmoid portion of the jugular foramen. The inferior petrosal sinus extends along the petroclival fissure and entersthe petrosal part of the foramen. The nerves enter the intrajugular part of the foramen located between the sigmoid andpetrosal parts. The outlined area shows the approximate site from which B to F were taken. B, the sigmoid sinus descends inthe sigmoid sulcus and makes a sharp anterior turn to enter the jugular foramen. The jugular bulb extends upward under thepetrous temporal bone toward the internal acoustic meatus. The endolymphatic sac is located above the lower portion of thesigmoid sinus on the back of the temporal bone and opens above through the vestibular aqueduct into the vestibule. Theglossopharyngeal, vagus and accessory nerves penetrate the dura on the medial side of the intrajugular process. C, the duracovering the jugular foramen and the jugular bulb have been removed. The nerves penetrate the dura on the medial side ofthe intrajugular process of the temporal bone. The intrajugular ridge extends forward along the medial side of the jugularbulb. D, enlarged view. The glossopharyngeal nerve passes forward along the medial side of the intrajugular ridge, but thevagus and accessory nerves, although entering the dura on the medial side of the intrajugular process, almost immediatelyturn downward and do not course along the medial edge of the intrajugular ridge in the medial wall of the jugular bulb, as

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and 9.6) (24). Both meatus are located on the medial side of theintrajugular processes and septum. The glossopharyngeal andvagal meatus are consistently separated by a dural septumranging in width from 0.5 to 4.9 mm (13). The only intraduralsite at which the glossopharyngeal nerve is consistently dis-tinguishable from the vagus nerve is just proximal to thisdural septum. The close origins of the glossopharyngeal andvagus nerves at the brainstem, and the arachnoidal adhesionsbetween the two in their course through the subarachnoidspace may make separation difficult except in the area justproximal to the dural septum. The superior glossopharyngealganglion is easily visible intracranially in about one-third ofnerves. The superior ganglion of the vagus can be seen in-tracranially in only one-sixth of nerves. Although the cranialand spinal portions of the accessory nerve most frequentlyenter the vagal meatus together, a dural septum may separatethem.

The upper and lateral margins of the intrajugular part of theforamen are the site of a characteristic thick dural fold thatforms a roof or lip that projects inferiorly and medially topartially cover the glossopharyngeal and vagal meatus (Figs.9.5 and 9.6). This structure, called the jugular dural fold, wasossified on both sides in one specimen (13, 16, 17, 24, 31). Thelip projects most prominently over the glossopharyngeal me-atus and is comparable to, but smaller than, the posterior lipof the internal acoustic meatus. It is either predominantlybony or fibrous and may project a maximum of 2.5 mm overthe margin of the glossopharyngeal meatus. The vagal lip isless prominent, projecting a maximum of 1 mm over thelateral margin of the vagal meatus.

Neural relationships

The glossopharyngeal, vagus, and accessory nerves arisefrom the medulla as a line of rootlets situated along theposterior edge of the inferior olive in the postolivary sulcus(Figs. 9.3 and 9.5). The hypoglossal nerve arises as a line ofrootlets that exit the brainstem along the anterior margin ofthe lower two-thirds of the olive in the preolivary sulcus, agroove between the olive and medullary pyramid.

The glossopharyngeal nerve, at the point at which it pene-trates the dural glossopharyngeal meatus, turns abruptly for-ward and then downward and courses through the jugularforamen in the groove leading from the pyramidal fossa be-low the opening of the cochlear aqueduct and along the

medial side of the intrajugular ridge. After the nerve exits thejugular foramen, it turns forward, crossing the lateral surfaceof the internal carotid artery deep to the styloid process. As thenerve transverses the jugular foramen, it expands at the site of itssuperior and inferior ganglia (Fig. 9.5). At the external orificeof the jugular foramen, it gives rise to the tympanic branch(Jacobson’s nerve), which traverses the tympanic canaliculus toenter the tympanic cavity where it gives rise to the tympanicplexus, the fibers of which course in shallow grooves on thepromontory and regroup to form the lesser petrosal nerve, pro-viding parasympathetic innervation by way of the otic ganglionto the parotid gland.

The vagal rootlets enter the dural subcompartment, calledthe vagal meatus, inferior to the glossopharyngeal meatusfrom which it is separated by a dural septum (Figs. 9.5 and9.6). It is joined by the accessory nerve as it enters the dura.After its rootlets gather in the intracranial orifice of the fora-men, the vagus nerve expands at the superior ganglion, whichis about 2.5 mm in length, and ends below the extracranialorifice of the foramen. It sits on the dura, covering the jugularforamen, and there, along the medial side of the intrajugu-lar process of the temporal bone, it turns downward. At thesuperior ganglion, the vagus nerve communicates with the ac-cessory nerve, a portion of which blends into the ganglion.The auricular branch (Arnold’s nerve) arises at the level of thesuperior vagal ganglion and is joined by a branch from the in-ferior glossopharyngeal ganglion (Fig. 9.3). The auricularbranch passes laterally in a shallow groove on the anteriorwall of the jugular bulb to reach the lateral wall of the jugularfossa, where it enters the mastoid canaliculus and ascendstoward the vertical (mastoid) segment of the facial canal,giving off an ascending branch to the facial nerve as it crosseslateral to it before turning downward to exit the temporalbone through the tympanomastoid fissure.

The main trunk of the vagus nerve (or, more accurately, thesuperior ganglion) courses anterior and inferior as it crossesbelow the midportion of the intrajugular process of the tem-poral bone (Figs. 9.3 and 9.5). At the intracranial orifice of theforamen, the intrajugular process of the temporal bone sepa-rates the ganglion from the sigmoid sinus. In most cases, inthe area immediately below the dura at the level of the intra-jugular processes, there are no fibrous bands between theglossopharyngeal nerve and the vagal ganglion.

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does the glossopharyngeal nerve. The auricular branch of the vagus nerve (Arnold’s Nerve) arises from the vagus nerve,passes along the groove in the anterior wall of the jugular fossa, and penetrates the mastoid canaliculus in the lateral wall ofthe fossa. E, the nerves entering the jugular foramen have been displaced downward. The intrajugular process of the temporalbone projects backward to join the intrajugular process of the occipital bone, thus forming an osseous bridge that divides theforamen into two parts. The vagus and accessory nerves pass lateral to the osseous bridge and the inferior petrosal sinusdescends below the bridge to open into the internal jugular vein. F, the hypoglossal nerve has been exposed on the lateralside of the occipital condyle. It exits the hypoglossal canal and joins the glossopharyngeal, vagus, and accessory nerves belowthe jugular foramen in the interval between the internal carotid artery and internal jugular vein. A., artery; Ac., acoustic;Aur., auricular; Br., branch; Car., carotid; CN, cranial nerve; Cond., condyle; Endolymph., endolymphatic; Gang., ganglion;Inf., inferior; Intrajug., intrajugular; Jug., jugular; Occip., occipital; Pet., petrosal, petrous; Petrocliv., petroclival; Proc., pro-cess; Sig., sigmoid; Sup., superior; Temp., temporal; Vert., vertebral; Vestib., vestibular.



FIGURE 9.4. A–D. Stepwise dissectionof the structures superficial to andsurrounding the jugular foramen. A,the skin and scalp around the ear havebeen reflected to expose the arealateral to the jugular foramen. Thesternocleidomastoid is exposed behindand the parotid gland in front of theear. The greater occipital nerve andoccipital artery reach the subcutaneoustissues by passing between theattachment of the trapezius andsternocleidomastoid muscles to thesuperior nuchal line. The externalacoustic meatus is located a littleforward of the deep site of the jugularbulb. B, removal of the superficialmuscles and parotid gland exposes thefacial nerve, temporalis and massetermuscles, posterior belly of thedigastric, and the internal jugular vein.The sternocleidomastoid muscle hasbeen reflected backward to expose theaccessory nerve entering its deepsurface. C, the mandibular ramus andcondyle, medial and lateral pterygoidmuscles, and posterior belly of thedigastric have been removed to exposethe styloid process, which is locatedlateral to the jugular foramen. Theinternal carotid artery ascends to enterthe carotid canal in front of the jugularforamen. Both the jugular foramen andcarotid canal are situated behind thetympanic part of the temporal bone,which forms the posterior wall of thecondylar fossa. The tensor and levatorvela palatini muscles are attached tothe eustachian tube in the area belowthe horizontal segment of the petrouscarotid. The infratemporal fossa islocated below the greater wing of thesphenoid. The mandibular nerve passes through the foramen ovale to enter the upper part of the infratemporal fossa. Branches of theascending pharyngeal artery pass through the jugular foramen to supply the surrounding dura. The hypoglossal nerve passes forwardacross the external and internal carotid artery. D, the styloid process has been removed to expose the glossopharyngeal, vagus, accessory,and hypoglossal nerves descending between the internal carotid artery and the internal jugular vein in the area immediately below thejugular foramen. The glossopharyngeal nerve descends along the lateral side of the internal carotid artery. The accessory nerve passesbackward across the lateral surface of the internal jugular vein. The hypoglossal nerve passes through the hypoglossal canal, which islocated below and medial to the jugular foramen, and descends with the nerves exiting the jugular foramen. The occipital artery givesrise to a meningeal branch, which passes through the jugular foramen to supply the surrounding dura, and to the stylomastoid artery,which passes through the stylomastoid foramen with the facial nerve. A., artery; Asc., ascending; Aur., auricular; Br., branch; Cap.,capitis; Car., carotid; Chor. Tymp., chorda tympani; CN, cranial nerve; Cond., condylar; Dors., dorsal; Eust., eustachian; Ext., external;Fiss., fissure; Gl., gland; Gr., greater; Inf., inferior; Int., internal; Jug., jugular; Laryn., laryngeal; Lat., lateral, lateralis; Lev., levator; Long.,longus; M., muscle; Mast., mastoid; Men., meningeal; N., nerve; Obl., oblique; Occip., occipital; Pal., palatini; Pet., petrosal, petrous;Pharyn., pharyngeal; Post., posterior; Proc., process; Pteryg., pterygoid; Rec., rectus; Retromandib., retromandibular; Scap., scapulae; Seg.,segment; Semicirc., semicircular; Sig., sigmoid; Squamotymp., squamotympanic; Sternocleidomast., sternocleidomastoid; Stylogloss.,styloglossus; Stylomast., stylomastoid; Stylophar., stylopharyngeus; Submandib., submandibular; Sup., superior; Temp., temporal; Tens.,tensor; TM., temporomandibular; Trans., transverse; Tymp., tympanic, tympany; V., vein; Vel., veli; Vent., ventral; Vert., vertebral.

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The vagus nerve exits the jugular foramen vertically, retain-ing an intimate relationship to the accessory nerve (Figs. 9.3–9.5). At the level the two nerves exit the jugular foramen, theyare located behind the glossopharyngeal nerve on the pos-

teromedial wall of the internal jugular vein. As the vagusnerve passes lateral to the outer orifice of the hypoglossalcanal, it is joined by the hypoglossal nerve medially. Thevagus nerve begins to expand at the site of the inferior vagal

FIGURE 9.4. E–H. E, the superiorand inferior oblique have beenexposed by reflecting the moresuperficial muscles. The C1transverse process and rectuscapitis lateralis rest against theposterior surface of the internaljugular vein. The rectus capitislateralis attaches to the jugularprocess of the occipital bone at theposterior margin of the jugularforamen. Retracting the levatorscapulae exposes the segment ofthe vertebral artery ascendingthrough the C2 transverse foramenin front of the ventral ramus of theC2 nerve root. The vertebral artery,as it passes medially along theupper surface of the posterior archof the atlas, is situated in the floorof the suboccipital triangle locatedbetween the superior and inferioroblique and rectus capitis posteriormajor. F, the internal carotid arteryhas been displaced posteriorly toexpose the branches of theascending pharyngeal, which passthrough the foramen lacerum,jugular foramen, and hypoglossalcanal to supply the surroundingdura. The chorda tympani exits theskull in the medial part of thecondylar fossa by first passingthrough the petrotympanic andthen along the squamotympanicsutures. G, the tympanic boneforming the lower and anteriormargin of the external meatus hasbeen removed, but the tympanicsulcus to which the tympanic mem-brane attaches has been preserved.

The surface of the temporal and occipital bones surrounding the jugular foramen and carotid canal have an irregular surface thatserves as the attachment of the upper end of the carotid sheath. The mastoid segment of the facial nerve and the stylomastoid fora-men are situated lateral to the jugular bulb. The chorda tympani arises from the mastoid segment of the facial nerve and coursesalong the deep side of the tympanic membrane crossing the neck of the malleus. It exits the skull by passing through the petrotym-panic and squamotympanic sutures and joins the lingual branch of the mandibular nerve distally. The carotid ridge separates thecarotid canal and jugular foramen. Meningeal branches of the ascending pharyngeal and occipital arteries enter the jugular fora-men. The glossopharyngeal, vagus, and accessory nerves pass through the jugular foramen on the medial side of the jugular bulb.H, the tympanic ring and bone lateral to the tympanic cavity have been removed. The internal carotid artery has been displacedforward out of the carotid canal to expose the carotid sympathetic nerves that ascend with the artery. The glossopharyngeal, vagus,accessory, and hypoglossal nerves exit the skull on the medial side of the internal carotid artery and jugular vein. The glossopha-ryngeal and hypoglossal nerves pass forward along the lateral surface of the internal carotid artery, and the accessory nerve de-scends posteriorly across the lateral surface of the internal jugular vein. The vagus nerve descends in the carotid sheath.



FIGURE 9.4. I–N. I, lateral view of mastoid and tympanic cavity before removing the tympanic ring. The tympanic segment of the facialnerve passes below the lateral semicircular canal and turns downward as the mastoid segment to exit the stylomastoid foramen. Thestylomastoid foramen and the mastoid segment are located lateral to the jugular bulb. The semicircular canals are located above the jugu-lar bulb. J, a probe has been placed in the eustachian tube, which passes downward, forward, and medially from the tympanic cavity andacross the front of the petrous carotid. The third trigeminal division passes through the foramen ovale on the lateral side of the eustachiantube. K, enlarged view of the tympanic ring with the tympanic membrane removed. The tensor tympany muscle passes backward abovethe eustachian tube and gives rise to a tendon that turns sharply lateral around the trochleiform process to attach to the malleus. Thechorda tympani crosses the inner surface of the tympanic membrane and neck of the malleus. The round window opens into the vesti-bule. The stapes sit in the oval window. The promontory is located lateral to the basal turn of the cochlea. L, the floor of the middle fossaand the tympanic sulcus have been removed to expose the jugular bulb and petrous carotid. The greater petrosal nerve courses along thefloor of the middle fossa on the upper surface of the petrous carotid. The deep petrosal nerve arises from the sympathetic bundles on theinternal carotid artery. The deep and greater petrosal nerves join to form the vidian nerve, which passes forward through the vidian canalto join the maxillary nerve and pterygopalatine ganglion in the pterygopalatine fossa. The pharyngobasilar fascia and upper part of the

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ganglion just below the foramen and is approximately 2.5 cmin length.

Accessory nerveAlthough the cranial and spinal portions of the accessory

nerve most frequently enter the vagal meatus together, theymay infrequently be separated by a dural septum. The spinalportion ascends toward the foramen magnum by crawlingalong the surface of the dura and may even be buried in thedura below the foramen magnum (Figs. 9.3, 9.5, and 9.6). Atthe dural orifice of the jugular foramen, the nerve is oftenindistinguishable from the vagus nerve. The accessory nerveusually enters the same dural subcompartment as the vagusnerve and often adheres and blends into the vagus nerve atthe level of the superior vagal ganglion. The accessory nervedeparts the vagal ganglion after it exits the jugular foramenand descends obliquely laterally between the internal carotidartery and internal jugular vein and then backward across thelateral surface of the vein to reach its muscles. Approximately30% of nerves descend along the medial, rather than thelateral, surface of the internal jugular vein (8).

Hypoglossal nerveThe hypoglossal nerve does not traverse the jugular fora-

men (Figs. 9.3–9.5). However, it joins the nerves exiting thejugular foramen just below the skull and runs with them inthe carotid sheath. The nerve exits the inferolateral part of thehypoglossal canal and passes adjacent to the vagus nerve,descends between the internal carotid artery and the internaljugular vein to the level of the transverse process of the atlas,where it turns abruptly forward along the lateral surface ofthe internal carotid artery toward the tongue, leaving only theansa cervicalis to descend with the major vessels.

ARTERIAL RELATIONSHIPS

The arteries that may be involved in pathological abnor-malities at the jugular foramen include the upper cervical andpetrous portions of the internal carotid artery, the posteriorlydirected branches of the external carotid artery, and the upperportion of the vertebral artery (Fig. 9.4).

Internal carotid artery

The internal carotid artery passes, almost straightly up-ward, posterior to the external carotid artery and anterome-dial to the internal jugular vein, to reach the carotid canal (Fig.9.4). At the level of the skull base, the internal jugular veincourses just posterior to the internal carotid artery, beingseparated from it by the carotid ridge. Between them, the

glossopharyngeal nerve is located laterally and the vagus,accessory, and hypoglossal nerves medially.

After the internal carotid artery enters the carotid canalwith the carotid sympathetic nerves and surrounding venousplexus, it ascends a short distance (the vertical segment),reaching the area below and slightly behind the cochlea,where it turns anteromedially at a right angle (the site of thelateral bend) and courses horizontally (the horizontal seg-ment) toward the petrous apex (Fig. 9.4). At the medial edgeof the foramen lacerum, it turns sharply upward at the site ofthe medial bend to enter the posterior part of the cavernoussinus.

External carotid artery

The external carotid artery ascends anterior to the internalcarotid artery. Proximal to its terminal bifurcation into themaxillary and the superficial temporal arteries, it gives rise tosix branches, which can be divided into anterior and posteriorgroups according to their directions. The latter group is re-lated to the jugular foramen.

The ascending pharyngeal artery, the first branch of theposterior group, often provides the most prominent supply tothe meninges around the jugular foramen (Fig. 9.4) (18). Itarises either at the bifurcation or from the lowest part of theexternal or internal carotid arteries. Rarely it arises from theorigin of the occipital artery. It courses upward between theinternal and the external carotid arteries, giving rise to nu-merous branches to neighboring muscles, nerves, and lymphnodes. Its meningeal branches pass through the foramenlacerum to be distributed to the dura lining the middle fossaand through the jugular foramen or the hypoglossal canal tosupply the surrounding dura of the posterior cranial fossa.The ascending pharyngeal artery also gives rise to the inferiortympanic artery, which reaches the tympanic cavity by way ofthe tympanic canaliculus along with the tympanic branch ofthe glossopharyngeal nerve.

The occipital artery, the second and largest branch of theposterior group, arises from the posterior surface of the ex-ternal carotid artery and courses obliquely upward betweenthe posterior belly of the digastric muscle and the internaljugular vein (Fig. 9.4). Its meningeal branches, which enter theposterior fossa through the jugular foramen or the condylarcanal, may make a significant contribution to tumors of thejugular foramen.

The posterior auricular artery, the last branch in the poste-rior group, arises above the posterior belly of the digastricmuscle and travels between the parotid gland and the styloidprocess. At the anterior margin of the mastoid process, itdivides into auricular and occipital branches, which are dis-

Š

longus capitis have been reflected downward to expose the lower margin of the clivus. M, the jugular bulb has been removed from thejugular fossa located below the vestibule and semicircular canals. The vertical segment of the petrous carotid has been removed. Thecochlea, which has been opened, is located above the lateral genu of the petrous carotid. The tympanic segment of the facial nervepasses posteriorly below the lateral semicircular canal. N, the retrosigmoid and presigmoid dura have been opened. The lateral wall ofthe vestibule and cochlea have been removed. The vestibule, semicircular canals, and cochlea are exposed above the jugular bulb andlateral genu of the petrous carotid.



tributed to the postauricular and the occipital regions respec-tively. The stylomastoid branch, which arises below the stylo-mastoid foramen, enters the stylomastoid foramen to supplythe facial nerve. Its loss can lead to a facial palsy even though

it anastomoses with the petrosal branch of the middle men-ingeal artery. The posterior auricular branch may share acommon trunk with the occipital artery, or sometimes it isabsent, in which case, the occipital artery gives rise to the

FIGURE 9.5. A, posterior view of the intracranial aspect of the left jugular foramen. The glossopharyngeal, vagus, and accessory nervespierce the dural roof of the jugular foramen. The glossopharyngeal nerve is separated from the vagus nerve by a narrow dural septum.The jugular dural fold projects downward and medially from the lateral and upper margin of the jugular foramen over the site at whichthe nerves enter the dura roof of the foramen. The facial and vestibulocochlear nerves and labyrinthine artery enter the internal acousticmeatus. The subarcuate branch of the anteroinferior cerebellar artery enters the subarcuate fossa. The endolymphatic sac is locatedbetween the dural layers lateral to the jugular foramen. A bridging vein from the medulla joins the inferior petrosal sinus on the medialside of the jugular bulb. B, the dura has been removed from the posterior surface of the temporal bone. The intrajugular processes of thetemporal and occipital bones, which are connected by a fibrous bridge, the intrajugular septum, separates the sigmoid and petrosal partsof the foramen. The glossopharyngeal, vagus, and accessory nerves enter the intrajugular part of the foramen by penetrating the dura onthe medial side of the intrajugular process of the temporal bone. C, the glossopharyngeal nerve enters the jugular foramen below thecochlear aqueduct. The vagus nerve enters the jugular foramen behind the glossopharyngeal nerve. The auricular branch of the vagusnerve (Arnold’s nerve) arises at the level of the superior ganglion and passes around the anterior wall of the jugular bulb. The acces-sory nerve is formed by multiple rootlets, which arise from the medulla and spinal cord. The accessory rootlets collect together to form abundle that blends into the lower margin of the vagus nerve at the level of the jugular foramen. The lower vagal and accessory roots passacross the surface of the jugular tubercle. D, enlarged view. The glossopharyngeal nerve expands at the site of the superior and inferiorganglia. The superior ganglion of the vagus nerve is located at the level of or just below the dural roof of the foramen, and the infe-rior ganglion is located below the foramen at the level of the atlanto-occipital joint. A., artery; Atl., atlanto-; Aur., auricular; Br., branch;Bridg., bridging; Car., carotid; CN, cranial nerve; Coch., cochlear; Cond., condyle; Endolymph., endolymphatic; Gang., ganglion; Glosso-phar., glossopharyngeal; Hypogl., hypoglossal; Inf., inferior; Int., internal; Intrajug., intrajugular; Jug., jugular; Labyr., labyrinthine; Lat.,lateral; Occip., occipital; Pet., petrosal; Proc., process; Sig., sigmoid; Subarc., subarcuate; Sup., superior; Temp., temporal; Vert., vertebral.

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stylomastoid artery. Members of the anterior group, whoseorigins may be visualized in exposing lesions of the jugularforamen, include the superior thyroid, lingual, and facialarteries.

Vertebral artery

The vertebral artery, as it ascends to reach and passthrough the transverse foramen of the atlas, is located belowand behind the jugular foramen (Fig. 9.4). Branches encoun-tered in approaches to lesions of the jugular foramen include

the meningeal, posterior spinal, and posteroinferior cerebellarartery.

VENOUS RELATIONSHIPS

The jugular bulb and adjacent part of the internal jugularvein receives drainage from both intracranial and extracranialsources, which include the sigmoid and inferior petrosal si-nuses, the vertebral venous plexus, the venous plexus of thehypoglossal canal, the posterior condylar emissary vein, and

FIGURE 9.6. Retrosigmoid approach to jugular foramen. A, the detail shows the site of the vertical scalp incision and rightretrosigmoid craniotomy. The cerebellum has been elevated to expose the nerves in the right cerebellopontine angle. Theglossopharyngeal and vagal nerves are separated by the dural septum at the level of the dural roof of the jugular foramen.The glossopharyngeal nerve enters the glossopharyngeal meatus and the vagus nerve enters the vagal meatus with thebranches of the accessory nerve. Both meatus are very shallow compared with the internal acoustic meatus. The superior andlateral margins of both meatus project downward and medially over the nerves entering the meatus. The vertebral artery dis-places the hypoglossal rootlets of Cranial Nerve XII posteriorly so that they intermingle with the rootlets of the accessorynerve. B, another specimen showing the relationship of the rhomboid lip and choroid plexus protruding from the foramen ofLuschka to the glossopharyngeal and vagus nerves. The choroid plexus protrudes laterally behind the glossopharyngeal nerves.The rhomboid lip is a thin layer of neural tissue that forms the ventral margin of the foramen of Luschka at the outer end ofthe lateral recess. C and D, enlarged view of two jugular foramina. The glossopharyngeal and vagus nerves are consistentlyseparated by a dural septum at the level of the roof over the jugular foramen. The jugular dural fold projects downward andmedially over the lateral edge of the glossopharyngeal and vagal meatus and over the site at which the nerves penetrate thedura. A., artery; A.I.C.A., anteroinferior cerebellar artery; Chor., choroid; CN, cranial nerve; Glossophar., glossopharyngeal;Jug., jugular; Plex., plexus; Vert., vertebral.



the vein coursing along the inferior aspect of the petroclivalfissure (Figs. 9.4 and 9.5).

Sigmoid sinus and jugular bulb

The sigmoid sinus is the largest channel emptying into thejugular foramen (Figs. 9.1 and 9.3–9.5). After coursing downthe sigmoid sulcus, the sinus turns anteriorly toward thejugular foramen, crossing the occipitomastoid suture imme-diately proximal to the foramen. From there, the sinus isdirected forward below the petrous temporal bone at the siteof the jugular bulb. The upward bulging of the superiormargin of the jugular bulb creates a rounded fossa in thelower surface of the temporal bone below the internal audi-tory canal. The dome of the jugular bulb may extend upwardin the posterior wall of the internal auditory canal to the levelof the upper margin of the canal. The bulb is usually larger onthe right side, reflecting the larger diameter of the sigmoidsinus on that side. From the level of the jugular bulb, flow isdirected downward behind the tympanic bone and the carotidcanal into the internal jugular vein.

Inferior petrosal sinus and venous confluens

The foramen also receives the inflow from the inferiorpetrosal sinus and the venous confluens in the petrosal part ofthe foramen. The inferior petrosal sinus, which courses on theintracranial surface of the petroclival fissure, communicatesthe cavernous sinus and basilar venous plexus at its upperend and with the jugular bulb at its lower end (Figs. 9.3 and9.5). The inferior petrosal sinus, as it enters the petrosal part ofthe jugular foramen, forms a plexiform confluens with thevenous plexus of the hypoglossal canal, the inferior petro-clival vein, and tributaries from the vertebral venous plexusand posterior condylar emissary vein. This confluens, whichfills the petrosal part of the foramen, usually consists of amain channel, 2 to 3 mm in diameter, and several smallerchannels, less than 1 mm in diameter. It empties into themedial aspect of the jugular bulb through one or two open-ings in the venous walls between the glossopharyngeal andvagus nerves or into the internal jugular vein below theextracranial orifice.

The inferior petroclival vein courses along the extracranialsurface of the petroclival fissure and is a mirror image of theinferior petrosal sinus, which courses along the intracranialsurface of the fissure (Fig. 9.5). It empties into the venousconfluens at the lower end of the inferior petrosal sinus at orjust below the extracranial orifice of the jugular foramen oreven above it, through bony clefts between the temporal andoccipital bones.

Bridging veins

A bridging vein, which courses posterior to the glossopha-ryngeal, vagus, and accessory nerves from the dorsolateralmedulla to the lower end of the sigmoid sinus, is present inabout one-third of cerebellopontine angles (Fig. 9.5, also seeFig. 3.12). Infrequently, a bridging vein extends from theventral medulla to the lower margin of the inferior petrosalsinus in front of the nerves.

MUSCULAR RELATIONSHIPS

Several muscles that are encountered in the surgical ap-proaches to the jugular foramen and that provide importantlandmarks in the approach are reviewed in detail in thechapters on the foramen magnum and temporal bone (Fig.9.4). These include the sternocleidomastoid, situated superfi-cially in the lateral neck, and the splenius capitis, longissimuscapitis, levator scapulae, and scalenus medius muscles in adeeper muscular layer.

More anteriorly is the posterior belly of the digastric mus-cle, which arises in the digastric groove located medial to themastoid process and the longissimus capitis. The styloid pro-cess and its attached muscles appear in the triangular zonebounded by the posterior belly of the digastric, the externalauditory canal, and the mandibular ramus. Reflecting thedigastric muscle exposes the transverse process of the atlas,which is covered by the attachments of numerous muscles,including the superior and inferior obliques, which form theupper and lower margin of the suboccipital triangle. Therectus capitis lateralis muscle is the muscle most intimatelyrelated to the jugular foramen. It extends vertically behind theinternal jugular vein from the transverse process of the atlasto the jugular process of the occipital bone.

On the posterior neck are the trapezius muscle, spleniuscapitis, and semispinalis capitis. Beneath the semispinalis ca-pitis muscle, three muscles arise between the inferior nuchalline and the margin of the foramen magnum: the rectus capitisposterior major and minor and the superior oblique muscle.The suboccipital triangle, an area defined by the opposingmargins of the rectus capitis posterior major and the superiorand inferior oblique muscles, is the site at which the vertebralartery courses along the upper posterior surface of the atlas.

SURGICAL APPROACHES

Postauricular transtemporal approach

The postauricular transtemporal approach accesses the re-gion from laterally, through the mastoid, and from below,through the neck (Fig. 9.7) (2, 4, 5). A C-shaped postauricularskin incision provides the exposure for a mastoidectomy andthe neck dissection. The external auditory canal is either pre-served or transected, depending on the anterior extent of thepathological abnormality. The neck dissection is completedinitially to gain control of the major vessels and the branchessupplying the tumor. The internal carotid artery, branches ofthe external carotid artery, internal jugular vein, and lowercranial nerves are exposed in the carotid sheath. A mastoid-ectomy with extensive drilling of the infralabyrinthine regionaccesses the jugular bulb. A limited mastoidectomy confinedto the area behind the stylomastoid foramen and mastoidsegment of the facial nerve, combined with removal of theadjacent part of the jugular process of the temporal bone, willprovide access to the posterior and posterolateral aspect of thejugular foramen. Three obstacles to exposure of the full lateralhalf of the jugular foramen, the facial nerve, styloid process,and rectus capitis lateralis muscle are dealt with by transpos-ing the facial nerve, removing the styloid process, and divid-

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ing the rectus capitis lateralis muscle. Anterior extensions ofthe pathological abnormality are reached by sacrificing theexternal and the middle ear structures. Sensorineural hearingcan be preserved by maintaining the foot plate of the stapes inthe oval window to avoid opening the labyrinth. Intracranialextensions of the lesion are reached by the retrosigmoid orpresigmoid approaches after adding a suboccipital craniec-tomy. The lesion can be removed by a transtemporal infral-abyrinthine approach directed through the temporal bonebelow the labyrinth without the neck dissection, if the ex-tracranial extension of the lesion is not prominent. The expo-

sure can be extended by opening the otic capsule (translaby-rinthine approach).

Retrosigmoid approach

A pathological abnormality located predominantly intra-durally can be resected by the retrosigmoid approach (Fig.9.6). A lateral suboccipital craniectomy exposes the dura be-hind the sigmoid sinus. The dura is opened, and the cerebel-lum is gently elevated away from the posterior surface of thetemporal bone to expose the cisterns in the cerebellopontine

FIGURE 9.7. A–D. Postauricular exposure of the jugular foramen. A, the detail shows the site of the scalp incision. TheC-shaped retroauricular incision provides access for the mastoidectomy, neck dissection, and parotid gland displacement. Thescalp flap has been reflected forward to expose the sternocleidomastoid and the posterior part of the parotid gland. B, themore superficial muscles and the posterior belly of the digastric have been reflected to expose the internal jugular vein andthe attachment of the superior and inferior oblique to the transverse process of C1. A mastoidectomy has been completed toexpose the facial nerve, sigmoid sinus, and capsule of the semicircular canals. C, enlarged view of the mastoidectomy. Thejugular bulb is exposed below the semicircular canals. The chorda tympani arises from the mastoid segment of the facialnerve and passes upward and forward. The tympanic segment of the facial nerve courses below the lateral canal. D, enlargedview of the caudal part of the exposure shown in C. The facial nerve and styloid process cover the extracranial orifice of thejugular foramen. The facial nerve crosses the lateral surface of the styloid process. The stylomastoid artery arises from thepostauricular artery. The rectus capitis lateralis attaches to the jugular process of the occipital bone behind the jugular fora-men. A., artery; Aur., auricular; Cap., capitis; Car., carotid; Chor. Tymp., chorda tympani; CN, cranial nerve; Coch., cochlear;Gl., gland; Gr., greater; Inf., inferior; Int., internal; Intrajug., intrajugular; Jug., jugular; Laryn., laryngeal; Lat., lateral, latera-lis; M., muscle; Med., medial; Mid., middle; N., nerve; Obl., oblique; Occip., occipital; Pet., petrosal, petrous; Post., posterior;Proc., process; Rec., rectus; Semicirc., semicircular; Sig., sigmoid; Sternocleidomast., sternocleidomastoid; Stylomast., stylo-mastoid; Sup., superior; Symp., sympathetic; Tr., trunk; Trans., transverse; V., vein.



angle and the intracranial aspect of the cranial nerves enteringthe jugular foramen, hypoglossal canal, and internal acousticmeatus.

Far-lateral approach

An extended modification of the retrosigmoid approach, thefar-lateral approach, the subject of another chapter in this issue,may be selected if the tumor extends down to the foramen

magnum in front of or lateral to the lower brainstem (10, 30, 32,33). In this approach, the jugular foramen is opened from be-hind. The dura is opened and the cerebellum elevated to exposethe intracranial extension of the pathological abnormality at thelower clivus and at the foramen magnum. Several variations,depending on the location and extent of the pathological abnor-mality, include drilling the jugular tubercle extradurally andremoving bone above without disturbing the condyle (21, 33).The extradural reduction of the jugular tubercle aids in minimiz-

FIGURE 9.7. E–H. E, the external auditory canal has been transected and the middle ear structures have been removed,except the stapes, which has been left in the oval window. The lateral edge of the jugular foramen has been exposed by com-pleting the mastoidectomy, transposing the facial nerve anteriorly, and fracturing the styloid process across its base andreflecting it caudally. The rectus capitis lateralis has been detached from the jugular process of the occipital bone. Thepetrous carotid is surrounded in the carotid canal by a venous plexus. F, a segment of the sigmoid sinus, jugular bulb, andinternal jugular vein have been removed. The lateral wall of the jugular bulb has been removed while preserving the medialwall and exposing the opening of the inferior petrosal sinus into the jugular bulb. Removing the venous wall exposes the glos-sopharyngeal, vagus, accessory, and hypoglossal nerves, which are hidden deep to the vein. The main inflow from the petro-sal confluens is directed between the glossopharyngeal and vagus nerves. G, the medial venous wall of the jugular bulb hasbeen removed. The intrajugular ridge extends forward from the intrajugular process, which divides the jugular foramenbetween the sigmoid and petrosal parts. The glossopharyngeal, vagus, and accessory nerves enter the dura on the medial sideof the intrajugular process, but only the glossopharyngeal nerve courses through the foramen entirely on the medial side of theintrajugular ridge. The vagus nerve also enters the dura on the medial side of the intrajugular process, but does not course alongthe medial side of the intrajugular ridge. H, the intrajugular process and ridge have been removed to expose the passage of theglossopharyngeal, vagus, and accessory nerves through the jugular foramen. The tip of a right-angle probe identifies the junction ofthe cochlear aqueduct with the pyramidal fossa, just above where the glossopharyngeal nerve penetrates the dura.

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ing the retraction of the brainstem needed to reach the areaanterior to the medulla and pontomedullary junction.

Preauricular subtemporal-infratemporal approach

The preauricular subtemporal-infratemporal approach, re-viewed in detail in the chapter on the temporal bone (see Figs.8.10 and 8.18), exposes the jugular foramen anteriorly. It maybe selected for tumors that extend along the petrous portion ofthe internal carotid artery, through the eustachian tube, orthrough the cancellous portion of the petrous apex (29). Apreauricular hemicoronal scalp incision is extended down toat least the level of the tragus and possibly into the cervicalregion, depending on the extent of the pathological findingand whether a neck dissection is needed. The zygomatic archis removed or reflected downward with the temporalis mus-cle, taking care to preserve the frontal branch of the facialnerve. A frontotemporal bone flap, which may include thesuperior or lateral orbital rim, is elevated, and the glenoidfossa and the mandibular condyle with the joint capsule areeither dislocated inferiorly or removed. The dura is elevated,and the bone of the middle fossa medial to the glenoid fossais removed until the carotid canal is opened. The eustachiantube and the tensor tympani muscle, which course anterior tothe carotid canal, are sacrificed during this procedure, takingcare to protect the lower cranial nerves as they exit the jugularforamen. The styloid process is divided at its base, and theinternal carotid artery is reflected anteriorly to gain access tothe clivus and anterior aspect of the jugular foramen. Drillingcan be extended to the posterior fossa through Kawase’striangle or through the clivus to the contralateral internalcarotid artery (14).

DISCUSSION

Pathologies

Tumors are the most common lesions to affect the jugularforamen; the majority are chemodectomas (glomus jugularetumor), neurinomas, and meningiomas, with a small percent-age of other tumors, such as chondrosarcomas and chordo-mas (12, 25). The glomus jugulare tumor arises either in theadventitia of the jugular dome or from the intumescencesalong the tympanic branch of the glossopharyngeal nerve orthe auricular branch of the vagus nerve in the jugular foramen(9). Tumors of the same nature that arise in the tympaniccavity or in the mastoid on branches of these nerves arereferred to as glomus tympanicum tumors. Small glomusjugulare tumors remain confined within the jugular foramen.However, the tumor can extend as follows: 1) along the eu-stachian tube into the nasopharynx and through the foraminaat the base of the skull, 2) along the carotid artery to themiddle fossa, 3) through the intracranial orifice of the jugularforamen or along the hypoglossal canal to the posterior fossa,4) through the tegmen tympani to the floor of the middlefossa, 5) through the round window and the internal acousticmeatus to the cerebellopontine angle, and 6) through theextracranial orifice of the jugular foramen to the upper cervi-cal region.

Neuromas arise either from the glossopharyngeal, vagus, orthe accessory nerves, and meningiomas from arachnoid gran-ulations in the jugular bulb or venous sinuses. Although eachtumor has characteristic patterns of invasion and destruction,the basic anatomic environment is similar to that of the glo-mus jugulare tumor.

Selection of surgical approach

The approaches to the jugular foramen can be categorizedinto three groups: 1) a lateral group directed through themastoid bone, 2) a posterior group directed through the pos-terior cranial fossa, and 3) an anterior group directed throughthe tympanic bone. This categorization is based on the ana-tomic fact that the block of the temporal bone, excluding thesquamous part, is regarded as an irregular pyramid, havingits base on the mastoid surface. In addition, the middle fossaapproaches could be categorized as in the “superior group”and the neck dissection upward to the jugular foramen as inthe “inferior group.” However, the latter approaches are usu-ally not suitable when used alone for pathological abnormal-ities of the jugular foramen.

Lateral approachThe lateral approach directed through a mastoidectomy,

used alone or in combination with other approaches, is theroute most commonly selected for lesions extending throughthe jugular foramen (7, 12, 22). Because the jugular foramen issituated under the otic capsule, the approach basic to thisgroup is called the infralabyrinthine approach. The facialnerve is frequently transposed anteriorly to drill the boneinferior to the labyrinth. Avoiding injury to the facial nerve isone of the key points in the lateral approaches (1). Even withspecial care, some degree of transient facial palsy is common,possibly because of disturbance to the nerve’s vasculature.The surgical field can be widened anteriorly by sacrificing theexternal auditory canal and middle ear structures or mediallyby drilling away the otic capsule (translabyrinthine approach)or cochlea (transcochlear approach).

The postauricular transtemporal approach, when combinedwith a neck dissection, provides satisfactory exposure of thejugular foramen, mastoid air cells, tympanic cavity, and theextracranial structures in and around the carotid sheath. Re-moval of the styloid process along with transposition of thefacial nerve facilitates wide opening of the extracranial orificeof the jugular foramen and provides access to the lower partof the petrous portion of the internal carotid artery. A widerexposure for the extracranial tumor can be obtained by re-moving the transverse process of the atlas or dislocating orresecting the mandibular condyle. The intracranial extensionof the tumor is approached either retrosigmoidally or presig-moidally after adding a lateral suboccipital craniectomy orcraniotomy (4, 6, 10, 26, 27).

Posterior approachThis group includes the retrosigmoid approach and its

more extensive far-lateral and transcondylar variants. Theseapproaches are suited to the intracranial portion of the tu-



mors. The conventional retrosigmoid approach provides accessto the cerebellopontine angle and the intracranial orifice of thejugular foramen. However, extensions of the tumor throughthe foramen magnum or medially into the clivus are beyond thereach of this approach. The far-lateral and transcondylar modi-fications access these areas, providing an upward view frombelow by opening the posterolateral quarter of the foramenmagnum and removing the posterior part of the occipital con-dyle. The posterior and posterolateral margin of the jugularforamen can be accessed by removing the part of the jugu-lar process of the occipital bone located behind the jugularforamen and the portion of the mastoid located behind themastoid segment of the facial nerve and stylomastoid fora-men. A flatter view toward the midline clivus is obtained byadditional extradural drilling of the jugular tubercle, althoughdrilling in front of these nerves risks damaging the nerves asthey cross the jugular tubercle (21, 23).

Anterior approachThe preauricular subtemporal-infratemporal approach is a

major variant of this group of approaches. It uses the pathwayanterior to the external auditory canal and through the tym-panic bone, which are exposed by removal or displacement ofthe glenoid fossa and the temporomandibular joint. The ap-proach alone can access the anterior part of the jugular fora-men after reflecting the petrous portion of the internal carotidartery anteriorly. Further extensive drilling will expose themiddle to upper clivus anteriorly. However, this approach ismost often combined with a lateral approach to access ananterior extension of the pathology (22). Fisch et al. call thiscombined approach the infratemporal fossa approach, Type Bor C according to the anterior extension of the exposure (4).

The selection of the optimal approach requires an under-standing of the nature and the extension of the lesion. Thecombination of two or three approaches may be needed eitherin stages or in combination in one operative procedure (4, 25).Preoperative embolization will often reduce the blood losswith a vascular tumor. Intraoperative electrophysiologicalmonitoring is of great help in avoiding nerve injury, in locat-ing the neural trajectory in and around the tumor, or inpredicting postoperative neural function (3, 20). Carefullyplanned reconstruction is required to reduce postoperativecomplications, especially leakage of cerebrospinal fluid, andto achieve a satisfactory cosmetic result.

Reprint requests: Albert L. Rhoton, Jr., M.D., Department of Neuro-logical Surgery, University of Florida Brain Institute, P.O. Box 100265,100 S. Newell Drive, Building 59, L2–100, Gainesville, FL 32610-0265.

REFERENCES

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21. Matsushima, T, Ikezaki K, Nagata S, Inoue T, Natori Y, Fukui M,Rhoton AL Jr: Microsurgical anatomy for lateral approaches to theforamen magnum: With special reference to the far-lateral ap-proach and the transcondylar approach, in Nakagawa H (ed):Surgical Anatomy for Microneurosurgery VII. Tokyo, SciMed Publi-cations, 1995, pp 81–89.

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27. Samii M, Babu RP, Tatagiba M, Sepehrnia A: Surgical treatment ofjugular foramen schwannomas. J Neurosurg 82:924–932, 1995.

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31. Silverstein H, Willcox TO, Rosenberg SI, Seidman MD: The jug-ular dural fold: A helpful base landmark to the cranial nerves.Skull Base Surg 5:57–61, 1995.

32. Spetzler RF, Grahm TW: The far-lateral approach to the inferiorclivus and the upper cervical region: Technical note. BarrowNeurol Inst Q 6:35–38, 1990.

33. Wen HT, Rhoton AL Jr, Katsuta T, de Oliveira E: Microsurgicalanatomy of the transcondylar, supracondylar, and paracondylarextensions of the far-lateral approach. J Neurosurg 87:555–585,1997.

Cranial cavity with posterior fossa structures, including cerebellum and cranial nerves, from, Andreas Vesalius, DeHumani Corporis Fabrica. Basel, Ex officina Ioannis Oporini, 1543. Courtesy, Rare Book Room, Norris Medical Library,

Keck School of Medicine, Los Angeles, California. (Also see pages S27, S68, and S209.)



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Jugular Foramen