Neurosurg Focus / Volume 33 / August 2012

Neurosurg Focus 33 (2):E7, 2012

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The posterior petrosal approach has met with con-siderable success in the management of complex neoplastic and cerebrovascular lesions.1–3,9,13,27,28,30,

31,33,34,36 At the mere expense of meticulous bone work to preserve the labyrinth and skeletonize the sigmoid sinus, this approach affords a wide exposure, minimizing opera-tive distance and brain retraction, and affording multiple working angles to the neurosurgical target and adjacent vascular anatomy.1–3,9,13 These advantages are only fully realized by the division of the tentorium and superior pe-trosal sinus and mobilization of a completely skeleton-ized sigmoid sinus. This contrasts with early work in the otolaryngology literature in which the exposure was lim-ited superiorly by the tentorium and posteriorly by the sigmoid sinus.12,18,19 To add exposure, some have divided the sigmoid sinus;8,11,17,19,32 however, with meticulous skeletonization and mobilization of the sinus as in the petrosal approach, this potentially dangerous maneuver can be avoided.3,28 In addition, retraction of the dural ve-nous sinuses and temporal lobe is performed in one unit, in contrast to nonpetrosal approaches (such as the com-bined retrosigmoid-subtemporal approach) that place added traction on the vein of Labbé with retraction.3,28 In this article, we review the history of the posterior petrosal approach, from its predecessors in the early otolaryngol-ogy literature through its evolution as a combined supra-

and infratentorial exposure with modern extensions and modifications.

Early WorkEarly petrous bone work dates back to 1904, when a

translabyrinthine approach in combination with a suboc-cipital craniectomy was performed to expose an acoustic nerve neoplasm.10 Unfortunately, due to excessive blood loss and infection risks this approach was largely aban-doned over the ensuing decades, until it was revived in the otolaryngology literature in the 1960s.12,19 Over the ensuing 2 decades, the literature clearly recognized 3 variants of the petrosectomy—a lateral petrosectomy that spared the labyrinth entirely (retrolabyrinthine),12,18 a translabyrinthine approach,12,19 and a complete petrosec-tomy or transcochlear approach.21 The latter, described by House and Hitselberger in 1976, entailed transposition of the facial nerve with the petrosectomy. This was soon modified by Jenkins and Fisch22 in 1980, who kept the nerve skeletonized in its bony canal without transposi-tion to potentially mitigate the risk of postoperative facial nerve palsy (transotic approach). These approaches are summarized in Table 1.

Early additions to the standard translabyrinthine ap-

Evolution of the posterior petrosal approach

Bradley a. Gross, M.d., daryoush Tavanaiepour, M.d., rose du, M.d., ph.d., ossaMa al-MefTy, M.d., and ian f. dunn, M.d.Department of Neurological Surgery, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts

In this article, the authors review the history of the posterior petrosal approach. The early foundation of the ret-rolabyrinthine lateral petrosectomy has its roots in the otolaryngology literature. These early approaches were limited in exposure by the tentorium superiorly and the sigmoid sinus posteriorly. Although the concept of a transtentorial approach was originally combined with a complete labyrinthectomy, Hakuba and colleagues described the expansive exposure afforded by sectioning the tentorium and superior petrosal sinus and mobilizing a skeletonized sigmoid sinus. This maneuver serves as the key step in allowing for the full, combined supra- and infratentorial exposure that the posterior petrosal approach provides. In contrast to Hakuba et al.’s approach, which used a partial labyrinthec-tomy, modern approaches often preserve the entire labyrinth (retrolabyrinthine approach). For added exposure, the latter can be combined with the anterior petrosal approach, allowing for the preservation of hearing and an enhanced view of the surgical target. The authors review the evolution of the petrosal approach and highlight its applicability.(http://thejns.org/doi/abs/10.3171/2012.6.FOCUS12133)

Key Words      •      transpetrosal approach      •      retrolabyrinthine approach      •      presigmoid approach      •      petrosal approach      •      combined approach      •      skull base

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B. A. Gross et al.

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proach included its combination with a suboccipital cra-niectomy10,17 and, importantly, opening of the tentorium, as described by King26 in 1970. The latter was a key step in the evolution of the modern petrosal approach, provid-ing an expanded, combined supra- and infratentorial ex-posure.

Evolution to the Modern Posterior  Petrosal Approach

In 1977, Hakuba et al.16 expanded on the concept of a combined supra- and infratentorial exposure, describ-ing 1 case in a patient with a clival meningioma that was approached via a combined supra- and infratentorial pe-trosal approach with partial labyrinthectomy. The patient these authors described did well postoperatively without hearing loss. Crucial maneuvers in the description includ-ed the meticulous complete skeletonization and mobiliza-tion of the sigmoid sinus after division of the tentorium and superior petrosal sinus; these steps serve as the key foundation of the modern posterior petrosal approach. Hakuba’s description essentially served as a predecessor to the modern transcrusal (partial labyrinthectomy) ap-proach;6,20,35 although hearing is not obligately sacrificed as in the complete labyrinthectomy, hearing loss is seen in up to 42% of cases.6 In contrast, Al-Mefty et al.’s1 poste-rior petrosal approach entails skeletonization of the semi-circular canals without sacrifice of the labyrinth. This presigmoid, retrolabyrinthine approach has served as the backbone in the approach to innumerable neoplastic and vascular lesions over the past 3 decades.1–3,9,27,28,30,31,33,34,36

The Posterior Petrosal ApproachThe posterior petrosal approach is performed with

the patient positioned supine, with the head turned 40°–60° after placing a roll under the ipsilateral shoulder. The head is extended to ensure that the petrous bone is the highest point in the field. After fixation in a Mayfield head holder, monitoring leads are placed for somatosen-sory evoked potentials, brainstem auditory evoked poten-tials, and select cranial nerves.

An incision is fashioned from the zygoma just ante-

rior to the ear, extending 2 fingerbreadths above the pin-na and descending posterior and inferior to the mastoid process. The skin flap is rotated anteriorly and inferiorly, after which the temporalis muscle fascia is reflected infe-riorly in continuity with the sternocleidomastoid muscle and fascia. The temporalis muscle is released superiorly and reflected inferiorly. Four bur holes are then placed—2 in the posterior fossa and 2 supratentorially, spanning the transverse sinus, after which a combined posterior fossa and middle fossa craniotomy flap is raised. The mastoid cortex is then removed as a single piece and a mastoidec-tomy is performed to skeletonize the sigmoid sinus down to the jugular bulb (Figs. 1 and 2). The latter maneuver is crucial in allowing for maximal mobilization of the sinus after opening the tentorium. The presigmoid dura mater is then exposed by completing a standard retrolabyrin-thine petrosectomy, and then it is opened from the level of the jugular bulb and extended superiorly toward the su-perior petrosal sinus. An incision is also made in the tem-poral lobe dura, taking great care to preserve the vein of Labbé. The superior petrosal sinus is then coagulated and cut, and the temporal and presigmoid durotomies are con-nected. The tentorium is cut parallel to the petrous ridge behind the tentorial entry of the fourth cranial nerve. The

TABLE 1: Petrosectomy variants*

Variant Description Risk Profile Selected Studies

retrolabyrinthine skeletonization of the semicircular canals lowest risk of CN VII & VIII palsy & CSF leak Graham, 1975; Hitselberger & Pulec, 1972partial labyrin- thectomy†

posterior & superior semicircular canals are opened

18–42% risk of hearing loss‡ Hakuba et al., 1977

translabyrinthine labyrinthectomy hearing loss Fraenkel et al., 1904; Graham, 1975; Hitsel- berger & Raney, 1964

transotic complete petrosectomy, except facial nerve skeletonized in its bony canal

hearing loss Jenkins & Fisch, 1980

transcochlear complete petrosectomy w/ transposition of facial nerve

hearing loss, greatest risk of CN VII palsy & CSF leak

House & Hitselberger, 1976

* CN = cranial nerve.† Some have referred to this as the transcrusal approach (see Brandt et al. and Horgan et al.). ‡ See Brandt et al. and Sekhar et al.

Fig. 1. Photograph showing a left-sided craniotomy flap (diamond denotes the anterior/middle fossa component for orientation). The ar-row points to the 1-piece mastoidectomy.

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Posterior petrosal approach

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sigmoid sinus is then reflected posteriorly and the tempo-ral lobe gently retracted with the tentorium.3,9,28

The senior author has used the standard posterior pe-trosal approach in more than 160 cases spanning a period of 3 decades. Although most often used for meningiomas, this approach has been applied to numerous schwanno-mas, epidermoid lesions, chordomas, craniopharyngio-mas, paragangliomas, aneurysms, and brainstem cavern-ous malformations. Crucial technological elements of this technique include the adjunctive use of neuromoni-toring, neuronavigation, and the application of advances in neuroanesthesia.

Although this approach provides an expansive com-bined supra- and infratentorial exposure, it may be limit-ed in cases in which the lesion crosses the midline, enters the anterior cavernous sinus, or extends below the jugular tubercle. In addition, a high jugular bulb or a prominent sigmoid sinus may significantly restrict the presigmoid corridor. The inability to divide the superior petrosal si-nus due to the patient’s venous drainage may also restrict the approach (Fig. 3). To address these limitations, several modifications to the approach, as delineated below, have been cultivated.

ModificationsExtended Posterior Petrosal Approaches

Additional petrous bone resection via either a partial or complete labyrinthectomy or a complete petrosectomy has been described in combination with the posterior pe-trosal approach.6,13,16,35,36 Indeed, Hakuba et al.’s16 original approach was essentially a posterior petrosal approach with partial labyrinthectomy, a predecessor to the trans-crusal approach in the modern literature.6,20 However, this approach does not preserve hearing at comparable rates to the standard retrolabyrinthine posterior petrosal ap-proach.2,3,6,34

In patients without serviceable hearing requiring additional exposure, one may enhance the exposure by performing a complete labyrinthectomy or petrosectomy, if needed.13 We call the former the petrosal translabyrin-

thine approach to distinguish it from the traditional in-fratentorial translabyrinthine approach without mobiliza-tion of the sinus. These 2 approaches differ significantly in the degree of exposure afforded to the neurosurgeon, and should remain as 2 distinguished entities in neuro-surgical parlance. When performing a complete petrosec-tomy, we advocate skeletonization of the facial nerve in its bony canal rather than complete exposure and trans-position (petrosal transotic).13 We often consider these ap-proaches for more expansive lesions with ample medial extent, or in cases with unfavorable venous anatomy such as a high jugular bulb or prominent sigmoid sinus.

Combined ApproachesIf additional exposure is desired and hearing is not

compromised preoperatively, we use the combined petro-sal approach. Although the posterior petrosal approach itself has been called the “combined approach” in ear-ly literature due to its combined supra- and infratento-rial exposure,8,36 modern “combined approaches” have instead combined it with the anterior petrosal (petrous apicectomy) approach in an effort to provide greater ex-posure without sacrificing the labyrinth (Fig. 4).7,9 The anterior petrosal approach was originally described by Bochenek and Kukwa5 in 1975. Popularized by Kawase et al.,25 it is sometimes referred to as the Kawase approach. This approach affords posterior fossa access from the middle fossa and permits access to a variety of lesions, including neoplasms, aneurysms, and vascular malforma-tions.4,23–25,29

The concept of combining an anterior and a posterior petrosal approach was originally described by Hakuba et al.15 in 1988. In this original account, these authors com-bined their posterior petrosal partial labyrinthectomy ap-proach with a petrous apicectomy in the management of 8 clival meningiomas, although hearing was only preserved in 1 of 3 cases with serviceable hearing preoperatively. In an effort to fully preserve hearing, we use a combina-tion of the anterior petrosal approach and the standard

Fig. 2. Photograph showing a right-sided exposure of the middle fossa and posterior fossa after the combined posterior and middle fossa craniotomy and mastoidectomy (diamond denotes the anterior/middle fossa component for orientation). Fig. 3. This preoperative 3-dynamic CT angiography/CT venography

study demonstrates drainage of the vein of Labbé into the right superior petrosal sinus, contraindicating its division.

B. A. Gross et al.

4 Neurosurg Focus / Volume 33 / August 2012

retrolabyrinthine posterior petrosal approach.7,9 This ap-proach has led to rewarding results in the management of a variety of neoplastic lesions.7 It minimizes the risk of postoperative facial nerve palsy and hearing loss, in com-parison with approaches sacrificing the labyrinth, while providing improved exposure of the petroclival junction, middle clivus, Meckel cave, and posterior cavernous si-nus. It also provides several additional axes of exposure with an added anterior subtemporal corridor.

Preservation of the Superior Petrosal SinusA meticulous evaluation of the patient’s cerebrovascu-

lar anatomy is a crucial component of preoperative plan-ning prior to the performance of the petrosal approach. Knowledge of arterial feeding vessels to a vascular neo-plasm should dictate the early avenue of approach to al-low for devascularization of the lesion. On the other hand, evaluation of the patient’s venous anatomy is also crucial in any case in which ligation of the superior petrosal sinus is considered. In cases in which the vein of Labbé, im-portant bridging veins, or the sphenoparietal sinus drain into the superior petrosal sinus, it should not be sacrificed (Fig. 3). For such cases, a modification of the traditional approach may be considered.14 After performing the stan-dard temporooccipital craniotomy and retrolabyrinthine lateral petrosectomy, the superior petrosal sinus is freed from its groove in the petrous ridge and skeletonized by drilling the petrous ridge. The presigmoid dura is then opened and the incision is extended under the superior petrosal sinus to the Meckel cave. The tentorium under the superior petrosal sinus is separated from the Meckel cave and lifted upward, effectively connecting the middle and posterior fossa under the tentorium.14 This affords an exposure almost comparable to that of the standard pos-terior petrosal approach while limiting undesirable post-operative venous complications.

ConclusionsThe posterior petrosal approach is derived from the

retrolabyrinthine exposure described in the early otolar-yngology literature in combination with the combined supra- and infratentorial exposure described in Hakuba et al.’s early report. The key feature of this approach is the liberal skeletonization of the sigmoid sinus and sub-

sequent mobilization after division of the tentorium and superior petrosal sinus. A modified posterior petrosal ap-proach can be performed in cases in which the superior petrosal sinus cannot be sacrificed; the sinus is skeleton-ized and freed, and the dural opening is extended from the presigmoid region under the superior petrosal sinus to the Meckel cave. In lieu of performing a partial or complete labyrinthectomy to sacrifice hearing, one may combine the posterior petrosal approach with an anterior petrosal approach when additional exposure is needed.

Disclosure

The authors report no conflict of interest concerning the mate-rials or methods used in this study or the findings specified in this paper.

Author contributions to the study and manuscript prepara-tion include the following. Conception and design: Dunn, Gross, Al-Mefty. Acquisition of data: Dunn, Gross, Al-Mefty. Analysis and interpretation of data: all authors. Drafting the article: all authors. Critically revising the article: all authors. Reviewed submitted ver-sion of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Dunn. Study supervision: Dunn, Du, Al-Mefty.

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Fig. 4. Postoperative axial CT scans demonstrating the standard ret-rolabyrinthine lateral petrosectomy (arrowhead, left) and the combined petrosal approach (right; arrowhead denotes retrolabyrinthine lateral petrosectomy, and arrow denotes petrous apicectomy).

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Manuscript submitted April 15, 2012.Accepted June 27, 2012.Please include this information when citing this paper: DOI:

10.3171/2012.6.FOCUS12133.Address correspondence to: Ian F. Dunn, M.D., Department of

Neurological Surgery, Brigham and Women’s Hospital and Harvard Medical School, 75 Francis Street, Boston, Massachusetts 02115. email: idunn@partners.org.