Anatomy of the lesser occipital nerve in relation to cervicogenic headache

A novel 3D anatomical visualization system to avoid injuries of nerves in retrosigmoid approach

The retro-sigmoid approach (RA), widely used during different neurosurgical procedures, is burdened by the risk of injuries of the nerves that cross that region contributing to possible postoperative complications. By using, anatomage table (AT), a novel 3D anatomical visualization system, we described the nerves passing through the retromastoid area including the great occipital nerve (GON), the lesser occipital nerve (LON) and the great auricular nerve (GAN), and their courses from the origins, till terminal branches. Moreover, using dedicated software, we measured distances between the nerves and well-recognizable bony landmarks. After identifying the nerves and their distances from bony landmarks, we observed that the safest and risk-free skin incision should be made in an area delimited, superiorly from the superior nuchal line (or slightly higher), and inferiorly from a plane passing at 1-1.5 cm above the mastoid tip. The lateral aspect of such an area should not exceed 9.5-10 cm from the inion, while the medial one should be more than 7 cm far from the inion. This anatomical information has been useful in defining anatomical landmarks and reducing the risk of complications, mainly related to nerve injury, in RA. In-depth neuroanatomic knowledge of the cutaneous nerves of the retromastoid area is essential to minimize the complications related to their injury during different neurosurgical approaches. Our findings suggest that the AT is a reliable tool to enhance understanding of the anatomy, and thus contributing to the refinement of surgical techniques.

Morphological and morphometric anatomy of the lesser occipital nerve and its possible clinical relevance

The lesser occipital nerve (LON) has one of the most variations among occipital nerves. We aimed to investigate morphological and morphometric features of LON. A total of 24 cadavers, 14 males (58%) and 10 females (42%), were dissected bilaterally. LON was classified into 3 types. The number of branches and the perpendicular distances of the point where LON emerged from the posterior border of sternocleidomastoid muscle to vertical and transverse lines passing through external occipital protuberance were determined. The shortest distance between LON and great auricular nerve (GAN), and linear distance of LON to its branching point were measured. The most common variant was Type 1 (30 sides, 62.5%), followed by Type 2 (12 sides, 25%) and Type 3 (6 sides, 12.5%), respectively. In males, Type 1 (22 sides, 78.6%) was the most common, while Type 1 (8 sides, 40%) and Type 2 (8 sides, 40%) were equally common and the most common in females. On 48 sides, 2-9 branches of LON were observed. The perpendicular distance of said point to vertical and transverse lines was meanly 63.69 ± 11.28 mm and 78.83 ± 17.21 mm, respectively. The shortest distance between LON and GAN was meanly 16.62 ± 10.59 mm. The linear distance of LON to its branching point was meanly 31.24 ± 15.95 mm. The findings reported in this paper may help clinicians in estimating the location of the nerve and/or its branches for block or decompression surgery as well as preservation of LON during related procedures.

Migraine Surgery and Determination of Success over Time by Trigger Site: A Systematic Review of the Literature

BACKGROUND

Migraine headache is a debilitating disorder that produces high costs and compromises patient quality of life. This study aimed to evaluate surgery success and the longevity of the surgical benefit by trigger site.

METHODS

A systematic literature review was performed by querying the PubMed, Embase, Scopus, and Web of Science databases. The keywords "surgery," "migraine," "outcomes," "headache index," and synonyms in titles and abstracts were used to perform the search.

RESULTS

A total of 17 articles published between 2009 and 2019 met the inclusion criteria. Six studies were prospective and 11 were retrospective. Most of the studies (77.8%, 77.8%, and 80%, respectively) reported success of migraine surgery at 12-month follow-up for trigger sites I, II, and III, respectively. For trigger site IV, the greatest Migraine Headache Index reduction (93.4%) was observed at 12-month follow-up, and the earliest Migraine Headache Index reductions (80.3% and 74.6%) were observed at 6-month follow-up. All studies that evaluated trigger sites V and VI identified surgery success at 12-month follow-up. Migraine surgery was found to remain beneficial at 22 months for trigger sites I, II, III, and IV.

CONCLUSIONS

The symptomatic improvement may initially be evident at 6 months for trigger site IV and at 12 months for trigger sites I, II, III, V, and VI. Surgical benefit in trigger sites I, II, III, and IV can persist after 22 months. Further studies are required to evaluate results at longer follow-up.

An Update on the Diagnosis, Treatment, and Management of Occipital Neuralgia

ABSTRACT

This report intends to summarize the underlying pathophysiology, relevant symptoms, appropriate diagnostic workup, necessary imaging, and medical and surgical treatments of occipital neuralgia (ON). This was done through a comprehensive literature review of peer-reviewed literature throughout the most relevant databases. The current understanding of ON is that it causes neuropathic pain in the distribution of the greater occipital nerve, the lesser occipital nerve, the third occipital nerve or a combination of the 3. It is currently a subset of headaches although there is some debate if ON should be its own condition. Occipital neuralgia causes chronic, sharp, stabbing pain in the upper neck, back of the head, and behind the ears that can radiate to the front of the head. Diagnosis is typically clinical and patients present with intermittent, painful episodes associated with the occipital region and the nerves described above. Most cases are unilateral pain, however bilateral pain can be present and the pain can radiate to the frontal region and face. Physical examination is the first step in management of this disease and patients may demonstrate tenderness over the greater occipital and lesser occipital nerves. Anesthetics like 1% to 2% lidocaine or 0.25% to 0.5% bupivacaine can be used to block these nerves and anti-inflammatory drugs like corticosteroids can be used in combination to prevent compressive symptoms. Other treatments like botulinum toxin and radiofrequency ablation have shown promise and require more research. Surgical decompression through resection of the obliquus capitis inferior is the definitive treatment however there are significant risks associated with this procedure.

A Rare Anatomical Variation of the Lesser Occipital Nerve

The lesser occipital nerve (LON) is a cutaneous branch of the cervical plexus that arises from the second and sometimes the third spinal nerve and innervates the scalp. During routine dissection of the neck, the LON was observed to arise directly from the spinal accessory nerve. The aberrant nerve measured 1.9 mm in diameter and 10.2 cm in length. Although anatomical variations of the LON such as duplication and triplication have been observed, we believe the origination of this nerve directly and exclusively from the spinal accessory nerve is exceedingly rare. The current case adds to the sparse literature on the variations of the LON and might be of interest to clinicians treating neurological conditions or surgeons operating in the area.

Occipital neuralgia: anatomic considerations

Occipital neuralgia is a debilitating disorder first described in 1821 as recurrent headaches localized in the occipital region. Other symptoms that have been associated with this condition include paroxysmal burning and aching pain in the distribution of the greater, lesser, or third occipital nerves. Several etiologies have been identified in the cause of occipital neuralgia and include, but are not limited to, trauma, fibrositis, myositis, fracture of the atlas, and compression of the C-2 nerve root, C1-2 arthrosis syndrome, atlantoaxial lateral mass osteoarthritis, hypertrophic cervical pachymeningitis, cervical cord tumor, Chiari malformation, and neurosyphilis. The management of occipital neuralgia can include conservative approaches and/or surgical interventions. Occipital neuralgia is a multifactorial problem where multiple anatomic areas/structures may be involved with this pathology. A review of these etiologies may provide guidance in better understanding occipital neuralgia.

The effect of radiofrequency neurotomy of lower cervical medial branches on cervicogenic headache

OBJECTIVE

Cervicogenic headache (CGH) is known to be mainly related with upper cervical problems. In this study, the effect of radiofrequency neurotomy (RFN) for lower cervical (C4-7) medial branches on CGH was evaluated.

METHODS

Eleven patients with neck pain and headache, who were treated with lower cervical RFN due to supposed lower cervical zygapophysial joint pain without symptomatic intervertebral disc problem or stenosis, were enrolled in this study. CGH was diagnosed according to the diagnostic criteria of the cervicogenic headache international study group. Visual analogue scale (VAS) score and degree of VAS improvement (VASi) (%) were checked for evaluation of the effect of lower cervical RFN on CGH.

RESULTS

The VAS score at 6 months after RFN was 2.7±1.3, which were significantly decreased comparing to the VAS score before RFN, 8.1±1.1 (p<0.001). The VASi at 6 months after RFN was 63.8±17.1%. There was no serious complication.

CONCLUSION

Our data suggest that lower cervical disorders can play a role in the genesis of headache in addition to the upper cervical disorders or independently.

Landmarks for the identification of the cutaneous nerves of the occiput and nuchal regions

Although surgical procedures are often performed over the posterior head and neck, surgical landmarks for avoiding the cutaneous nerves in this region are surprisingly lacking in the literature. Twelve adult cadaveric specimens underwent dissection of the cutaneous nerves overlying the posterior head and neck, and mensuration was made between these structures and easily identifiable surrounding bony landmarks. All specimens were found to have a third occipital nerve (TON), lesser occipital nerve (LON), and greater occipital nerve (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 approximately 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 landmarks 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 communicate with one another, avoiding the main nerve trunks could lessen postoperative 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.

Triplication of the lesser occipital nerve

Triplication of the lesser occipital nerve (LON) was observed bilaterally in an adult male cadaver during routine prosection of the posterior triangle. The three LONs were studied to determine the clinical importance of this variation. The origin of one LON was from a nerve to the trapezius that had a common origin with the trunk of the supraclavicular nerve (C3,4) from the cervical plexus. Such a common origin of a LON may explain the pain referred to the shoulder and arm that is experienced by some patients with cervicogenic headache. Another LON ran across the roof of the posterior triangle, passed through the trapezius and was closely related to the point of exit of the greater occipital nerve (GON) from the trapezius. This LON supplied the nape of the neck, back of the scalp and the auricle. The anomalous course taken by this LON through the trapezius may be an explanation for cervicogenic headache precipitated by neck movement. The close relationship of this variant LON to the exit of the GON from the trapezius seems to be relevant to the management of cervicogenic headache. The authors suggest that the reason for the complete pain relief experienced by some patients with cervicogenic headache by anesthetic blockade of the GON may be because both the GON and LON are blocked simultaneously due to their proximity in these patients.

Medial portion of M. Temporalis and its potential involvement in facial pain

We describe the morphology, functional capabilities, and clinical anatomical implications of the medial portion of the temporalis muscle. Although recognized in Brazilian, German, French, and Hispanic American textbooks of anatomy, this portion of the temporalis has been unappreciated in those published in England and the United States. Given its morphology, and functional anatomy as revealed in this paper, we conclude that the medial portion of the temporalis could entrap the maxillary nerve and its zygomatic branches inside the pterygopalatine fossa. On these bases we identify this portion of the temporalis as a possible factor in the etiology of some forms of tic douloureux.

Extracranial nerves in the posterior part of the head. Anatomic variations and their possible clinical significance

STUDY DESIGN

An anatomic study of the peripheral nerves innervating the occipital region.

OBJECTIVES

To study the topography of the extracranial occipital nerves, to define optimal locations for anesthetic nerve blockades, to provide guidelines to use with the suboccipital surgical approach, and to search for structures with putative pathogenetic implications in cases of unilateral headache.

SUMMARY OF BACKGROUND DATA

There is little consensus in the literature concerning the sensory innervation of the scalp. Previous clinical and morphologic studies have not proven the existence of an entrapment mechanism in cases of unilateral head pain. Specific sites for anesthetic blockades have been defined only partly with reference to topographic landmarks.

METHODS

The topography of the greater occipital (n = 20), the minor occipital (n = 19), and the greater auricular nerves (n = 17) was studied by dissection of 10 embalmed cadavers. Measurements of internerve distances and distances to defined landmarks were supplemented by drawings and photographs.

RESULTS

A great variability in nerve topography was seen interindividually and intraindividually. The greater occipital nerve ascended between 5 mm and 28 mm from the midline along the intermastoid line. The minor occipital nerve was found between 32 mm and 90 mm from the midline along the same landmark. In most cases, both the greater occipital nerve and the minor occipital nerve pierced the aponeurosis after branching. Thirteen greater occipital nerves and eight minor occipital nerves also were embedded in this tissue. Twelve of the 20 greater occipital nerves formed a rich network around the occipital artery. However, anatomic structures with an imminent risk of causing entrapment were not observed.

CONCLUSION

The results of this study suggest that optimal locations for blockade techniques should be reconsidered. The acquired knowledge concerning greater auricular and minor occipital nerves behind the sternocleidomastoid muscle may aid in preventing intraoperative injuries.

Cervicogenic headache: a personal view

Cervicogenic headache describes pain referred along the upper three cervical roots and is a common source of headache in the over fifties. A review of clinical features, anatomy, and investigations using neural blockade shows several clinical pictures. Diseases of the cranio-vertebral junction, e.g. syringomyelia, and tonsilar descent, can produce mechanical or hydrodynamic head and neck pain. Pre-existent migraine and tension headache may be precipitated or aggravated by cervical spondylosis, but the anatomical mechanism is unclear. Headaches which arise from and are primarily caused by disorders in the cervical spine are exemplified by spondylosis and acute whiplash injury, but are usually transient. Evidence for a cervicogenic mechanism of chronic whiplash headache is, however, lacking.