Cosmetic

The Anatomy of the Greater Occipital Nerve:Implications for the Etiology of MigraineHeadachesScott W. Mosser, M.D., Bahman Guyuron, M.D., Jeffrey E. Janis, M.D., and Rod J. Rohrich, M.D.Cleveland, Ohio; and Dallas, Texas

An interest in pursuing new theories of the underlyingetiology of migraine headaches has been sparked by pre-viously published reports of an association between ame-lioration of migraine headache symptoms and corrugatorresection during endoscopic brow lift. This theory hasfurther been reinforced by recent publications document-ing improvement in migraine headaches following injec-tion of botulinum A toxin. There are thought to be fourmajor “trigger points” along the course of several periph-eral nerves that may cause migraine headaches. Amongthese peripheral nerves is the greater occipital nerve. Forthis reason, the authors have undertaken an anatomicstudy of this nerve to determine its usual course, potentialanatomic variations, and possible points of potential en-trapment or compression. The results of this anatomicstudy have enhanced further development of techniquesdesigned to address these points of entrapment/compres-sion and potentially lead to relief of migraine headachescaused by this mechanism. Twenty cadaver heads frompatients with an unknown history of migraine headacheswere dissected to trace the normal course of the greateroccipital nerve from the semispinalis muscle penetrationto the superior nuchal line. Standardized measurementswere performed on 14 specimens to determine the loca-tion of the emergence of the nerve using the midline andoccipital protuberance as landmarks. On the basis of thisinformation, the location of emergence was determinedto be at a point centered approximately 3 cm below theoccipital protuberance and 1.5 cm lateral to the midline.This location can, in turn, be used to guide the practi-tioner performing chemodenervation of the semispinaliscapitis muscle in an attempt to provide migraine symptomrelief. (Plast. Reconstr. Surg. 113: 693, 2004.)

Traditionally, migraine headaches arethought to be related to an underlying cen-trally based neurovascular phenomenon. How-ever, recent evidence suggests that a more pe-

ripheral mechanism may play a significant role.Four peripheral areas have been identified astrigger points for migraine headaches. Threeare in the frontal, temporal, and occipital re-gions (relating to the supraorbital, zygomatico-temporal, and greater occipital sensory nerveregions, respectively), while the fourth is re-lated to turbinate and septal pathology.

One of the senior authors (B.G.) recentlydescribed the unexpected amelioration or res-olution of migraine headaches after endo-scopic brow lift with corrugator supercilii re-section.1 In that retrospective study,approximately 39 percent of patients with ahistory of migraines reported complete resolu-tion of their symptoms, while 41 percent ob-served significant improvement. A follow-upprospective study by the same author foundthat 55 percent of patients treated with botuli-num toxin A (to their corrugators) demon-strated complete elimination of their headachesymptoms, while almost 28 percent experi-enced significant improvement. Furthermore,in those patients who responded favorably tobotulinum toxin injection, subsequent surgicalresection of corrugator supercilii muscle (withor without release of the zygomaticotemporalbranch of the trigeminal nerve) resulted inelimination or significant improvement inheadaches in 96 percent of patients.2

These promising results have begged thequestion of whether this technique can be ap-plied to other trigger points with the same

From Case Western Reserve University and the Division of Plastic Surgery, University of Texas Southwestern Medical Center. Received forpublication August 13, 2002; revised July 8, 2003.

Presented at the Annual Scientific Meeting of the Texas Society of Plastic Surgeons, September of 2002, and at the 42nd Annual Plastic SurgerySenior Residents Conference in Los Angeles, California, March of 2003. Awarded the Plastic Surgery Educational Foundation Best Research PaperAward, March of 2003.

DOI: 10.1097/01.PRS.0000101502.22727.5D

693

outcome. The focus of this study was to identifythe site of muscular investment of the greateroccipital nerve and to determine external land-marks to aid in precise injection of botulinumtoxin A and operative location of this region.

BACKGROUND

Anatomy texts describe the course of thegreater occipital nerve as curving mediallyaround the semispinalis muscle and only pierc-ing a fascial plane in the region of the superiornuchal line.3,4 Other anatomy texts and furtherstudies have shown, however, that in the vastmajority of cases, the greater occipital nerveactually pierces the semispinalis muscle on itsway to the subcutaneous layer.5–8 This muscu-lar investment of the greater occipital nervemay be a source of compression, entrapment,or irritation. Several elegant anatomic studiesexist that describe the course of the nerve, yetthe clinician cannot readily find the greateroccipital nerve course through the semispinalismuscle on the basis of useful external land-marks. This study was designed to review theanatomy, corroborate the previous findings,and identify topographic landmarks for accu-rate injection of botulinum A toxin.

MATERIALS AND METHODS

Twenty fresh human cadaver heads were ob-tained and shaved (40 greater occipital nervestotal). The first six cadavers were used to studythe course of the greater occipital nerve and itsrelationship to the semispinalis capitis only. Inthe remaining 14 specimens (28 greater occip-ital nerve specimens), a marking and measure-ment protocol was used. The skin was markedvertically in the midline using the spinous pro-cesses and the external occipital protuberance.A horizontal line was drawn extending betweenthe external auditory canals and through theoccipital protuberance (Fig. 1).

A 19-gauge needle was dipped in methyleneblue and passed perpendicularly through theskin to mark the subcutaneous tissue alongthese lines and at the occipital protuberance.This allowed measurements in the deeper lay-ers of dissection to accurately correlate withthese external landmarks. Flaps of skin andsubcutaneous tissue were elevated to exposethe galea, superior nuchal line, and trapeziusmuscle bilaterally (Fig. 2, above, left).

The trapezius muscle with oblique fibers waselevated to reveal the splenius and semispinalismuscle layer, and the greater occipital nerve

was found to be piercing the semispinalis mus-cle in this region (Fig. 2, above, center).

Using a 25-gauge needle, the nerve wasmarked with methylene blue at the site of itsexit through the muscle, and this point wasmeasured laterally from the midline and infe-riorly from the occipital protuberance. Next,the semispinalis muscle with vertical fibers waselevated along its medial border and the deeppenetration of the nerve was noted, which wasalso marked (Fig. 2, above, right and below, left).

After muscle division, the distance betweenthe two markings on the nerve was measured,representing the intramuscular course (Fig. 2,below, right).

It was noted that in all specimens this repre-sented the approximate thickness of the mus-cle, because the nerve did not run significantlycranially or caudally within the muscle; instead,it essentially pierced the structure, running di-rectly from deep to superficial. The nervewidth was also measured 5 mm proximal to thesite of muscle penetration (point A), at the siteof emergence (point B), and 5 mm distal to thesite of emergence (point C).

RESULTS

On both sides of all 20 cadavers (40 sites),the greater occipital nerve was found to piercethe semispinalis capitis. For the 14 heads inwhich measurements were taken, the mean dis-

FIG. 1. Marking of cadaver head. Auditory canals and oc-cipital protuberance were marked externally and then trans-cutaneously with methylene blue.

694 PLASTIC AND RECONSTRUCTIVE SURGERY, February 2004

tance of emergence of the greater occipitalnerve from the midline was 14.1 mm on theright and 13.8 mm on the left (SD, 4.4 mm and4.3 mm, respectively). The mean point ofemergence inferior to the occipital protuber-ance was 29.1 mm on the right and 28.7 mm onthe left (SD, 7.8 mm on the right and 6.6 mmon the left). The mean distance of intramuscu-lar investment was 7.6 mm on the right and 8.9mm on the left (SD, 2.9 mm and 3.2 mm,respectively) (Table I).

TABLE IResults from Measurements of Site of Greater Occipital

Nerve Emergence from Semispinalis

Right (mm) Left (mm)

Point of emergence from midline,mean � SD 14.1 � 4.4 13.8 � 4.3

Point of emergence inferior tooccipital protuberance, mean �SD 29.1 � 7.8 28.7 � 6.6

Intramuscular investment, mean� SD 7.6 � 2.9 8.9 � 3.2

FIG. 2. (Above, left) Elevated scalp and subcutaneous tissue. The trapezius has been elevated on the specimen’s right sideto reveal the semispinalis and splenius muscles. (Above, center) Greater occipital nerve seen running through the semispinalismuscle. (Above, right) Superficial marking of the greater occipital nerve. (Below, left) Deep marking of the greater occipitalnerve. Dashed line marks the midline. (Below, right) Division of overlying muscle to measure intramuscular distance. GON,greater occipital nerve.

Vol. 113, No. 2 / GREATER OCCIPITAL NERVE 695

On the basis of our measurements and meandistribution of the emergence of 28 greateroccipital nerves, we have concluded that thereis a region 1.5 cm in diameter that is centeredapproximately 3 cm below and 1.5 cm lateral tothe occipital protuberance where the muscularinvestment of the greater occipital nerve canbe reliably interrupted, either pharmacologi-cally or surgically (Fig. 3).

Nerve width changed on average from 2.7mm to 2.4 mm on the right and 3.0 mm to 2.9mm on the left as it came through the muscle(Table II). Though the overall trend in nervewidth was to become slightly smaller as itemerged through the semispinalis, paired t testanalysis of nerve width did not demonstratestatistical significance with respect to a changein nerve diameter around the site of emer-gence in this study (Table III).

DISCUSSION

In 1982, Bogduk8 traced the routes of thesensory nerves from the cervical rami. The

greater occipital nerve, which is the continua-tion of the medial branch of the C2 dorsalroot, was traced from the dorsal root to itsultimate arborization in the subcutaneous tis-sue above the superior nuchal line. An impor-tant finding of this elegant study was that thesemispinalis muscle was the only site of consis-tent muscular investment of the greater occip-ital nerve.

In 1991, Bovim et al.7 revisited the anatomiccourse of the greater occipital nerve and, con-trary to Bogduk’s earlier work, found threepotential sources of muscular investment. Intheir study, 40 greater occipital nerve speci-mens were dissected in 20 fresh cadaver heads.Their results demonstrated that the greateroccipital nerve pierced the semispinalis mostoften (36 of 40, or 90 percent of the time),followed by the trapezius (18 of 40; 45 percentof the time), and only rarely did it pierce theinferior oblique (three of 40; 7.5 percent of thetime). Though the authors described a dis-tance from the occipital protuberance to thesemispinalis penetration, which on average waslocated 1.6 cm laterally and 3.7 cm inferiorly,they did not report a standard deviation.Therefore, the distribution of their measure-ments around the mean is unknown, whichdetracts from the clinical applicability of theirresults.

Although previous authors have developedelaborate means of standardizing head posi-tion and internal reference lines for locatingthe greater occipital nerve, we were able toachieve a high degree of consistency in locat-ing the emergence of the greater occipitalnerve using external landmarks. As mentionedabove, the greater occipital nerve has beendescribed as piercing several muscles along itslength, specifically the inferior oblique, thetrapezius, and the semispinalis. Theoretically,any one (or combination) of these muscularinvestments could serve as a source of compres-sion or irritation of the nerve. In contrast toothers,9 we have found in our study that thereis little or no muscular investment of thegreater occipital nerve through the trapeziusand therefore it is not likely to be a probablesite of compression. We did find, however, thatthe only consistent transmuscular course was inthe region of the semispinalis, which is themost likely point of compression or irritation.

Based on early evidence suggesting a moreperipheral mechanism for migraine head-aches,2 this study attempted to further eluci-

FIG. 3. Marking of area of nerve localization bilaterally.Black dot is the occipital protuberance and the green ovals markthe site of greater occipital nerve emergence bilaterally to 1SD.

696 PLASTIC AND RECONSTRUCTIVE SURGERY, February 2004

date the anatomic course of one particularnerve, the greater occipital nerve, and detectpossible points of muscle or fascial entrap-ment, which may lead to compression or irri-tation. The clinical sequelae of muscular paral-ysis and surgical release of the greater occipitalnerve using this data are now being studied. Ifoutcomes correlate with results from our priorexperience in the corrugator region, the casefor a peripheral mechanism as the etiology ofmigraine headaches (and the existence of trig-ger points) is strengthened. To our knowledge,there has been no attempt to utilize botulinumtoxin in the suboccipital region specifically toaddress migraine headaches. We are currentlyusing this information to begin injections andhave started performing surgical release of thisnerve with institutional review board approvalfrom two different centers.

CONCLUSIONS

There is evidence to suggest that the under-lying etiology of migraine symptomatology maybe peripherally rather than centrally mediated.Trigger points along peripheral nerves havebeen identified, and preliminary evidence sug-gests that interruption of these trigger pointsleads to improvement of the patient’s symp-toms. This study was designed to specificallyaddress one trigger point, the greater occipitalnerve, and to define its anatomic location sothat points of chemodenervation using exter-

nal landmarks can be used to relieve migrainesymptoms. Our study has resulted in the iden-tification of an area approximately 1.5 cm indiameter, 3 cm inferior to the occipital protu-berance and 1.5 cm lateral to the midline, thatcorresponds to the location of the greater oc-cipital nerve as it emerges from the underlyingsemispinalis. The utility of this information willbe determined in further studies.

Bahman Guyuron, M.D.Zeeba Ambulatory Surgery Center29017 Cedar RoadCleveland, Ohio 44124

ACKNOWLEDGMENTS

The authors gratefully acknowledge the invaluable assis-tance from Spencer Brown, Ph.D., and Debbie Noble in thepreparation of the manuscript.

REFERENCES

1. Guyuron, B., Varghai, A., Michelow, B. J., Thomas, T.,and Davis, J. Corrugator supercilii muscle resectionand migraine headaches. Plast. Reconstr. Surg. 106: 429,2000.

2. Guyuron, B., Tucker, T., and Davis, J. Surgical treat-ment of migraine headaches. Plast. Reconstr. Surg. 109:2183, 2002.

3. Netter, F. H. Atlas of Human Anatomy. Summit, N.J.:Ciba-Geigy Corporation, 1989.

4. Moore, K. L. Clinically Oriented Anatomy, 3rd Ed. Balti-more: Williams & Wilkins, 1992.

5. Grant, J. C. B. (Ed.). An Atlas of Anatomy, 6th Ed. Bal-timore: Williams & Wilkins, 1972. Pp. 24, 472, 490–494.

6. Becser, N., Bovim, G., and Sjaastad, O. Extracranialnerves in the posterior part of the head: Anatomicvariations and their possible clinical significance. Spine23: 1435, 1998.

7. Bovim, G., Bonamico, L., Fredriksen, T. A., Lindboe,C. F., Stolt-Nielsen, A., and Sjaastad, O. Topographicvariations in the peripheral course of the greater oc-cipital nerve: Autopsy study with clinical correlations.Spine 16: 475, 1991.

8. Bogduk, N. The clinical anatomy of the cervical dorsalrami. Spine 7: 319, 1982.

9. Bovim, G., Fredriksen, T. A., Stolt-Nielsen, A., and Sjaas-tad, O. Neurolysis of the greater occipital nerve incervicogenic headache: A follow up study. Headache32: 175, 1992.

TABLE IIWidth of Nerve around the Site of Emergence

Average Width5-mm Proximal

Average Width atEmergence

Average Width5-mm Distal Regression p

Right 2.7 mm 2.6 mm 2.4 mm 0.233Left 3.0 mm 2.8 mm 2.9 mm 0.822

TABLE IIIResults of Comparison of Nerve Widths at Various Points*

Comparison of Nerve WidthMeasurement Groups Paired t test p

Group A—group B 0.84Group A—group C 0.77Group B—group C 0.65

* Group A represents nerve widths at a point 5 mm proximal to superficialnerve emergence from the semispinalis muscle. Group B represents nervewidths at the location of superficial emergence. Group C represents nervewidths at a 5 mm distal to the point of superficial emergence. There was nostatistically significant change in nerve width across these points.

Vol. 113, No. 2 / GREATER OCCIPITAL NERVE 697