Clinical Anatomy 20:235–238 (2007)

ORIGINAL COMMUNICATION

Landmarks for the Identification of the Cutaneous of the Occiput and Nuchal Regions

R. SHANE TUBBS,* E. GEORGE SALTER, JOHN C. WELLONS III, JEFFREY P. BLOUNT, AND W. JERRY OAKES Pediatric Neurosurgery, Children’s Hospital, Birmingham, Alabama

Although surgical procedures are often performed over the posterior head and , surgical landmarks for avoiding the cutaneous nerves in this region are surprisingly lacking in the literature. Twelve adult cadaveric specimens under- went dissection of the cutaneous nerves overlying the posterior head and neck, and mensuration was made between these structures and easily identifi- able surrounding bony landmarks. All specimens were found to have a third occipital (TON), (LON), and (GON), and we found that the TON was, on average, 3 mm lateral to the external occipital protuberance (EOP). Small branches were found to cross the midline and communicate with the contralateral TON inferior to the EOP in the majority of sides. The mean diameter of the main TON trunk was 1.3 mm. This trunk became subcutaneous at a mean of 6 cm inferior to the EOP. The GON was found to lie at a mean distance of 4 cm lateral to the EOP. On all but three sides, a small medial branch was found that ran medially from the GON to the TON *1 cm superior to a horizontal line drawn through the EOP. The GON was found to pierce the semispinalis capitis muscle on average 2 cm superior to the intermastoid line. The mean diameter of the GON was 3.5 mm. The GON was found to branch into medial and lateral branches on average 0.5 cm superior to the EOP. The LON was found to branch into a medial and lateral component at approximately the midpoint between a horizontal line drawn through the EOP and the intermastoid line. The main LON trunk was found on average 7 cm lateral to the EOP. In specimens with a mastoid branch of the great auricular nerve (GAN), this branch was found at a mean of 9 cm lateral to the EOP. The main trunk of this branch of the GAN was found to lie on average 1 cm superior to the mastoid tip. Easily identifiable bony land- marks for identification of the cutaneous nerves over the posterior head and neck can aid the surgeon in more precisely identifying these structures and avoiding complications. Although the occipital nerves were found to freely com- municate with one another, avoiding the main nerve trunks could lessen post- operative or postprocedural morbidity. Moreover, clinicians who need to localize the occipital nerves for the treatment of occipital neuralgia could do so more reliably with better external landmarks. Clin. Anat. 20:235–238, 2007. VC 2006 Wiley-Liss, Inc.

Key words: neck; head; skin; iatrogenic; injury; anatomy

*Correspondence to: R. Shane Tubbs; Pediatric Neurosurgery, Children’s Hospital, 1600 7th Avenue South ACC 400, Birming- INTRODUCTION ham, AL 35233, USA. E-mail: [email protected] The posterior head and neck is an area where neurosur- Received 26 July 2005; Revised 22 November 2005; Accepted gical intervention often occurs (e.g., approaches to the fora- 29 November 2005 men magnum, cerebellopontine angle, and upper cervical Published online 30 August 2006 in Wiley InterScience (www. spine). In addition to these surgical approaches, procedures interscience.wiley.com). DOI 10.1002/ca.20297

VC 2006 Wiley-Liss, Inc. 236 Tubbs et al. such as halo pin and Mayfield pin placement and nerve blocks for occipital neuralgia necessitate a good working knowledge of the cutaneous nerves in this region so as to minimize complications such as severe dysesthesias follow- ing their injury (Sindou and Mertens, 1994). Bogduk (1982) has pointed out the risk of inducing anesthesia dolorosa by cutting these nerves with incisions over the posterior head and neck. Likewise, Ebraheim et al. (1996) have stressed complications of halo pin placement, such as traumatic neu- roma formation. Additionally, locating the nerves over the posterior head and neck for the surgical treatment of occipi- tal neuralgia requires a thorough knowledge of their anat- omy, which is not adequately addressed in standard ana- tomical textbooks. The nerves of this area from lateral to medial are the lesser occipital nerve (LON), the greater occi- pital nerve (GON) (Arnold’s nerve), and the (TON) (least occipital nerve) (Barna and Hashmi, 2004). Most lateral, the great auricular nerve (GAN) may have a mastoid branch (McKinney and Gottlieb, 1985). Rarely, the (dorsal ramus of C1) which normally innervates primarily the muscles of the sends a small cutaneous filament to the occiput (Bogduk, 1982). At a submuscular level, the suboccipital nerve and branches of the second and third dorsal rami intercommunicate to form the posterior of Cruveilhier (Pick and Howden, 1974) (Fig. 1). The LON is derived from the second and third cervical ventral rami and ascends toward the occiput by running parallel to the posterior border of the sternocleidomastoid muscle. Near the cranium it perforates the deep fascia, and is continued superiorly over the occiput where it supplies the integument and communicates with the GON medially Fig. 1. Schematic drawing of the posterior view of (Lucas et al., 1994) (Fig. 1). the head and neck. Horizontal lines are drawn through The medial branch of the dorsal ramus of the second the inion (superior line) and left (not seen) and right cervical nerve is referred to as the GON. Gawel and Roth- mastoid tips (inferior line). The TON is shown at (a), the bart (1992) have suggested that this nerve may also have left GON is shown at (b), the left LON is just inferior to fibers derived from the dorsal ramus of C3. This nerve (c), and the mastoid branch of the GAN is seen just passes between the inferior capitis oblique and semispinalis superior to (d). Note the posterior arch of the (e) capitis muscles and ascends to pierce this latter muscle and with the suboccipital nerve and superior the . At this point, it travels with the occipital to this bony structure within the suboccipital triangle artery to supply the integument of the scalp as far anterior (composed of the rectus capitis posterior major, superior as the vertex of the . Medially and over the occiput, capitis oblique, and inferior capitis oblique). In addition, this nerve communicates with the TON and laterally with observe the deep intercommunication between the TON, the LON (Fig. 1). suboccipital nerve, and GON. The TON arises deep to the trapezius from the medial branch of the dorsal ramus of the third cervical nerve. This of the cutaneous nerves (great auricular, lesser occipital, nerve ascends medial to the GON and is connected to it both greater occipital, and third occipital) of the posterior head over the occiput and as the GON rounds the inferior edge of and neck, and measurements were made between these the inferior capitis oblique (Bogduk, 1982). The medial ter- nerves and surrounding superficial bony landmarks. Five minal branch of the TON supplies the skin over the rostral males and seven females were used in this study. All mea- end of the neck and the occiput near the external occipital surements were made with calipers. Measurements protuberance (EOP). More lateral branches of this nerve are included the diameters of the LON, GON, and TON as they directed toward the mastoid process. were found over the occiput and adjacent cranium. Meas- The GAN arises from the ventral rami of cervical nerves ured distances were made from superior to the intermastoid two and three, and ascends toward the posterior cranium line (a line connecting the inferior tips of the mastoid proc- by curving from around the posterior border of the sterno- esses) (Fig. 1) and distances superior to a horizontal line cleidomastoid. This nerve is mainly distributed to the auricle drawn through the EOP and lateral to this bony landmark. and parotid regions but may have a mastoid branch that Statistical analysis was made between left and right sides communicates with the LON posteriorly (Fig. 1). and genders using Student’s t-tests.

MATERIALS AND METHODS RESULTS

In the prone position, 12 adult formalin-fixed cadavers All specimens were found to have a LON, GON, and TON. (aged 50–89 years, mean 75 years) underwent dissection We were unable to locate a mastoid branch of the GAN on Nerves of Occiput and Nuchal Regions 237 eight sides. A cutaneous branch of the suboccipital nerve neurectomy, decompression of the C2 dorsal root ganglion, was not found in any specimen. No surgical scars were ganglionectomy, occipital nerve stimulator placement, and found over the posterior head and neck in any specimen. radiofrequency lesions of the C2 dorsal root (Stechison and We found that the TON was 0–4 mm (mean 3 mm) lateral Mullin, 1994; Barna and Hashmi, 2004). to the EOP and that in all but two sides (one left and one The GON was found to lie at a mean distance of 4 cm lat- right in separate specimens) that this nerve had a lateral eral to the EOP and this nerve was found to pierce the small communicating branch to the GON that branched just semispinalis capitis muscle on average 2 cm superior to the inferior to the EOP. Additionally, very small branches were intermastoid line (Fig. 1). Stechison and Mullin (1994) have found to cross the midline and communicate with the con- found that the dorsal root ganglion of C2 is located approxi- tralateral TON inferior to the EOP in the majority of sides (n mately 2 mm from the inferior aspect of the posterior arch = 7). These branches were always less than 0.5 mm in di- of C1 and that this ganglion was 15 mm from the midline. ameter. The mean diameter of the main TON trunk was 1.3 Mosser et al. (2004) have found that the GON emerges mm (range 0.5–2 mm). This trunk became subcutaneous from the semispinalis capitis muscle *14 mm from the mid- at a mean of 6 cm inferior to the plane of the EOP (range line and that this site was roughly 30 mm inferior to the 4–7.5 cm) (mean of 3 cm inferior to the intermastoid line) EOP. However, Bovim et al. (1991) have written that in rou- and this most often occurred in the lateral aspect of the tine clinical work, they have had success in blocking this nuchal ligament. The GON was found to lie at a mean dis- nerve 2 cm inferior to the EOP and 2 cm lateral to the midline. tance of 4 cm lateral to the EOP (range 3.5–6.5 cm). On all Vital et al. (1989) have cited measured distances of this nerve but three sides, a small medial branch was found that ran as dichotomous as 3 cm lateral to and superior to the EOP to medially from the GON to the TON *1 cm superior to a hor- 6 cm lateral to and 3 cm superior to this bony landmark. The izontal line drawn through the EOP (Fig. 1). These medial mean diameter of the GON at this point was 3.5 mm. branches when present coursed at approximately 308 to- The GON was found to branch into medial and lateral ward the midline. The GON was found to pierce the semispi- branches on average 0.5 cm superior to the EOP. Bogduk nalis capitis muscle on average 2 cm (range 1.5–3.3 cm) (1982) has stated that the GON divides into its terminal superior to the intermastoid line (Fig. 1). One right side branches just inferior to the superior nuchal line. In con- demonstrated two branches of the GON as it pierced the trast, Ebraheim et al. (1996) have described this nerve as semispinalis capitis muscle that reunited into a single trunk dividing into medial, middle, and lateral branches 1 cm infe- 2 cm inferior to the EOP. The mean diameter of the GON rior to the EOP with the lateral branch ascending at a mean was 3.5 mm (range 2.8–4.1 mm). The GON was found to angle of 388. These authors also found that the lateral branch into medial and lateral branches on average 0.5 cm branch is most often found *5 cm lateral to the midline. superior to the EOP (range 0–2.5 cm). The LON was found We did not appreciate three such distinct branches but to branch into a medial and lateral component at approxi- rather a medial and lateral branch with the medial branch mately the midpoint between a horizontal line drawn often providing a sizable lateral branch. Sindou and Mertens through the EOP and the intermastoid line. (1994) have found the portion of the GON adjacent to the The main LON trunk was found on average 7 cm lateral EOP between the medial and middle one thirds of a line to the EOP (range 6–9 cm) and this nerve was found to lie connecting this bony process to the mastoid tip. Inciden- at a mean of 3 cm medial to the tip of the mastoid process. tally, the is normally found just lateral to In specimens with a mastoid branch of the GAN, this branch the GON in the proximity of the EOP. Schmidt and Adel- was found at a mean of 9 cm lateral to the EOP (range 8– mann (2001) have noted that the occipital artery travels at 11 cm). The main trunk of this branch of the GAN was a mean distance of 3.92 cm on the right side and 4.4 cm on found on average to lie 1 cm superior to the mastoid tip. the left side from the midline. Overall, we found that the areas of the posterior head Pain in the region of the LON is a frequent component of and neck that were less concentrated with these nerve cervicogenic headache often brought about by physical trunks were the midline and a midpoint between a line exertion (Okuda et al., 2001). Raffaelli et al. (1987) have drawn between the EOP and mastoid tip. No significant dif- stated that injection of the LON can be performed inferior ferences were found between left or right sides or genders to the medial groove of the mastoid tip and 1 cm superior (Student’s t-test; P > 0.05). to its tip. Becser et al. (1998) reported that this nerve most frequently first branched inferior to the superior nuchal line in their specimens. However, this line is often difficult to DISCUSSION palpate and thus is not as useful a landmark as the EOP or mastoid process. Barna and Hashmi (2004) have stated Greater occipital neuralgia (Arnold’s neuralgia) is charac- that the LON is about 2.5 cm lateral to the occipital artery terized by a lancinating pain extending from the suboccipi- over the occiput. We found that the LON branched into a tal region up to the cranial vertex. This pathology may be medial and lateral component at approximately the mid- idiopathic or may appear following a history of cervical point between a horizontal line drawn through the EOP and trauma (e.g., whiplash injury) (Stechison and Mullin, the intermastoid line. The main LON trunk was found on av- 1994), osteophyte formation on the C2 vertebrae (Clavel erage 7 cm lateral to the EOP, and this nerve was found to lie and Clavel, 1996), arthritis of the C2 vertebrae (Ward, at a mean of 3 cm medial to the tip of the mastoid process. 2003), cervical cord tumors (Clavel and Clavel, 1996), Lord et al. (1994) have reported a 27% (95% confidence Chiari I malformation (cerebellar tonsillar ectopia inferior to interval) incidence of TON headache in post whiplash the ) (Gille et al., 2004), or muscle patients. Third occipital neurotomy has been performed for entrapment (Magnusson et al., 1996; Mosser et al., 2004) patients with this neuralgia (Govind et al., 2003). Lang (e.g., inferior capitis oblique, semispinalis capitis, or trape- (1993) has reported that this nerve becomes subcutaneous zius muscles). Invasive treatments for this disorder include *5 cm inferior to the EOP and *7 mm lateral to the mid- nerve blocks, neurolytic injections, C2 dorsal rhizotomy, line. We found the TON was 0–4 mm lateral to the EOP. 238 Tubbs et al.

The mean diameter of the main TON trunk was 1.3 mm. Gille O, Lavignolle B, Vital JM. 2004. Surgical treatment of greater This trunk became subcutaneous at a mean of 6 cm inferior occipital neuralgia by neurolysis of the greater occipital nerve to the EOP and a mean of 3 cm inferior to the intermastoid and sectioning of the inferior oblique muscle. Spine 29:828–832. line and this most often occurred in the lateral aspect of the Govind J, King W, Bailey B, Bogduk N. 2003. Radiofrequency neurotomy for the treatment of third occipital headache. J nuchal ligament. Neurol Neurosurg Psychiatry 74:88–93. Although we were unable to find reports of injury to the Lang J. 1993. Clinical Anatomy of the Cervical Spine. New York: mastoid branch of the GAN it is possible that this nerve Thieme. injury occurs especially with procedures such as retromas- Lord SM, Barnsley L, Wallis BJ, Bogduk N. 1994. Third occipital toid approaches to the posterior cranial fossa. This nerve nerve headache: A prevalence study. J Neurol Neurosurg Psychi- may be duplicated (Pantaloni and Sullivan, 2000). Although atry 57:1187–1190. of an unclear etiology, some have found that the GAN may Lucas GDA, Laudanna A, Chopard RP, Raffaelli E Jr. 1994. Anatomy be involved in some cases of tic douloureux (Wyburn- of the lesser occipital nerve in relation to cervicogenic headache. Mason, 1953; Pantaloni and Sullivan, 2000). This branch Clin Anat 7:90–96. Magnu´sson T, Ragnarsson T, Bjo¨rnsson A. 1996. Occipital nerve was not found in the majority of our specimens. release in patients with whiplash trauma and occipital neuralgia. Headache 36:32–36. McKinney P, Gottlieb J. 1985. The relationship of the great auricular CONCLUSIONS nerve to the superficial musculoaponeurotic system. Ann Plast Surg 14:310–314. Our study has documented potentially useful superficial Mosser SW, Guyuron B, Janis JE, Rohrich RJ. 2004. The anatomy of bony landmarks for the identification of the cutaneous the greater occipital nerve: Implications for the etiology of mi- graine headaches. Plast Reconstr Surg 113:693–697. nerves of the posterior head and neck. We found that the Okuda Y, Matsumoto T, Shinohara M, Kitajima T, Kim P. 2001. Sudden areas of the posterior head and neck that were less concen- unconsciousness during a lesser occipital nerve block in a patient trated with these nerve trunks were the midline and a mid- with the defect. Eur J Anaesthesiol 18:829–832. point between a line drawn between the EOP and mastoid Pantaloni M, Sullivan P. 2000. Relevance of the lesser occipital nerve tip. It is our hope that these data will aid the surgeon and in facial rejuvenation surgery. Plast Reconstr Surg 105:2594– clinician in avoiding complications in this region. 2599. Pick TP, Howden R. 1974. Gray’s Anatomy Descriptive and Surgical. Philadelphia: Running Press. Raffaelli E Jr., Martins OJ, dos Santos A, Filho PD. 1987. Minor occi- REFERENCES pital neuralgia. Cephalalgia 7:173–174. Schmidt D, Adelmann G. 2001. The course of the occipital artery— Barna S, Hashmi M. 2004. Occipital neuralgia. Pain Manage Rounds An anatomical investigation for biopsy in suspected vasculitis. 1:1–4. Eur J Med Res 6:235–241. Becser N, Bovim G, Sjaastad O. 1998. Extracranial nerves in the Sindou M, Mertens P. 1994. Posterior fossa approaches with preser- posterior part of the head. Anatomic variations and their possi- vation of the sensory occipital nerves: Microsurgical anatomy ble clinical significance. Spine 23:1435–1441. and surgical implications. In: Samii M, editor. Skull Base Sur- Bogduk N. 1982. The clinical anatomy of the cervical dorsal rami. gery. Basel: Karger. p 719–722. Spine 7:319–330. Stechison MT, Mullin BB. 1994. Surgical treatment of greater occipital Bovim G, Bonamico L, Fredriksen TA, Lindboe CF, Stolt-Nielsen A, neuralgia: An appraisal of strategies. Acta Neurochir 131:236– Sjaastad O. 1991. Topographic variations in the peripheral 240. course of the greater occipital nerve: Autopsy study with clinical Vital JM, Grenier F, Dautheribes M, Baspeyre H, Lavignolle B, Se´ne´gas correlations. Spine 16:475–478. J. 1989. An anatomic and dynamic study of the greater occipital Clavel M, Clavel P. 1996. Occipital neuralgia secondary to exuberant nerve (n. of Arnold). Applications to the treatment of Arnold’s neu- callus formation: Case report. J Neurosurg 85:1170–1171. ralgia. Surg Radiol Anat 11:205–210. Ebraheim NA, Lu J, Biyani A, Brown JA. 1996. Anatomic considera- Ward JB. 2003. Greater occipital nerve block. Semin Neurol 23:59–62. tions of halo pin placement. Am J Orthop 25:754–756. Wyburn-Mason R. 1953. The nature of tic douloureux: Treatment by Gawel MJ, Rothbart PJ. 1992. Occipital nerve block in the manage- alcohol block or section of the great auricular nerve. Brit Med J ment of headache and cervical pain. Cephalalgia 12:9–13. 2:119–122.