Curr Pain Headache Rep (2014) 18:411 DOI 10.1007/s11916-014-0411-x
UNCOMMON HEADACHE SYNDROMES (J AILANI, SECTION EDITOR)
Occipital Neuralgia Carrie Dougherty
Published online: 16 April 2014 # Springer Science+Business Media New York 2014
Abstract Occipital pain is a common complaint amongst patients with headache, and the differential can include many primary headache disorders such as cervicogenic headache or migraine. Occipital neuralgia is an uncommon cause of occipital pain characterized by paroxysmal lancinating pain in the distribution of the greater, lesser or third occipital nerves. Greater occipital nerve blockade with anesthetics and/or corticosteroids can aid in confirming the diagnosis and providing pain relief. However, nerve blocks are also effective in migraine headache and misdiagnosis can result in a false positive. Physical therapy and preventive medication with antiepileptics and tricyclic antidepressants are often effective treatments for occipital neuralgia. Refractory cases may require intervention with pulsed radiofrequency or occipital nerve stimulation. Keywords Greater occipital nerve . Occipital neuralgia . Occipital nerve block . Occipital nerve stimulation . Pulsed radiofrequency
Introduction Occipital neuralgia (ON) as primary headache disorder is a challenging diagnosis. The International Headache Society diagnostic criteria for ON are listed in Table 1 [1••]. The overlap between ON and migraine is evident. Pain in migraine headache is by definition severe, and episodes of stabbing pain can accompany the typical throbbing or pulsating quality
[2]. Allodynia and occipital tenderness are also common in migraine, and the response of migraine to occipital nerve blocks is well described [3–6]. Thus, the most important section of the diagnostic criteria may be to ensure that the symptoms described by the patient are not better accounted by an alternate diagnosis. A careful history and physical exam are critical components to accurately identifying ON and distinguishing it from other headache disorders with similar presentations.
Anatomy ON can involve the greater occipital, lesser occipital or third occipital nerves. The greater occipital nerve (GON) originates from the medial branch of the dorsal ramus of C2. The GON ascends between the inferior oblique capitis muscle and semispinalis capitis and pierces the semispinalis. It then runs rostrolateral deep to the trapezius muscle and pierces the aponeurosis of the trapezius slightly inferior to the superior nuchal ridge, where it becomes subcutaneous and lies medial to the occipital artery [7]. The GON provides cutaneous sensory innervation to the posterior scalp from the external occipital protuberance to the vertex. The lesser occipital nerve (LON) originates from branches of C2 and C3 in the cervical plexus. It travels along the posterior border of the sternocleidomastoid muscle and innervates the lateral scalp superior and posterior to the auricle [8]. The third occipital nerve branches from C3 and innervates the upper neck and lower occipital scalp [8].
This article is part of the Topical Collection on Uncommon Headache Syndromes C. Dougherty (*) Department of Neurology, Medstar Georgetown University Hospital, 3800 Reservoir Road NW, 7 PHC, Washington, DC 20007, USA e-mail: [email protected]
Pathophysiology The etiology of occipital neuralgia is unknown and most presentations are considered idiopathic. Posterior head trauma
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Table 1 The International Headache Society diagnostic criteria for occipital neuralgia
Clinical Presentation
A. Unilateral or bilateral pain fulfilling criteria B–E B. Pain is located in the distribution of the greater, lesser and/or third occipital nerves C. Pain has two of the following three characteristics: 1. recurring in paroxysmal attacks lasting from a few seconds to minutes 2. severe intensity 3. shooting, stabbing or sharp in quality D. Pain is associated with both of the following: 1. dysesthesia and/or allodynia apparent during innocuous stimulation of the scalp and/or hair
There are no epidemiological studies that document the incidence or prevalence of ON. Hammond and Danta characterized 23 cases of ON and found that it is more commonly unilateral (85 %). Distribution of pain and paresthesia were consistent with GON involvement in 90 %, LON in 10 % and both nerves in 9 % of the cases [19]. The hallmark of ON is paroxysmal lancinating pain that patients often describe as stabbing, shooting, electric or “shock-like.” The pain typically originates in the occiput and radiates toward the vertex. A dull aching pain may persist between paroxysms, but this characteristic was eliminated from the diagnostic criteria in the most recent International Classification of Headache Disorders (ICHD) update [1••]. Dull occipital ache as a primary complaint should prompt evaluation for causes of referred occipital pain. Patients may describe allodynia or dysesthesia of the scalp in the distribution of the nerve, with sensitivity to touch or pressure on the scalp. Patients may avoid activities such as brushing their hair, wearing a hat or lying on a pillow. Tenderness to palpation along the course of the nerve is common. Various authors suggest that a positive Tinel’s sign, where numbness or tingling is elicited with percussion over the occipital condyle, is more specific for ON than tenderness or the patient’s description of pain; however, this has not been clinically investigated [20, 21]. Kuhn et al. published a prospective case series of 12 patients presenting to the emergency room with symptoms of occipital neuralgia and reported that frequently associated symptoms included tinnitus, scalp paresthesia, nausea, dizziness, and visual disturbances [22]. Symptoms originating from structures beyond the distribution of the GON are thought to be due to interactions between nociceptive afferents from the cervical roots and trigeminal nerve that converge in the spinal cord [23]. Temporary improvement of these symptoms after treatment with anesthetic blockade of the GON is diagnostic [1••]. However, migraine and cluster headache also respond to GON block, resulting in a false positive [24].
2. either or both of the following: a. tenderness over the affected nerve branches b. trigger points at the emergence of the greater occipital nerve or in the area of distribution of C2 E. Pain is eased temporarily by local anesthetic block of the affected nerve F. Not better accounted for by another ICHD-3 diagnosis. The pain of occipital neuralgia may reach the fronto-orbital area through trigeminocervical inter-neuronal connections in the trigeminal spinal nuclei. Occipital neuralgia must be distinguished from occipital referral of pain arising from the atlantoaxial or upper zygapophyseal joints, or from tender trigger points in neck muscles or their insertions Modified from the Headache Classification Committee of the International Headache Society [1••]
and whiplash injuries resulting in nerve injury have been proposed [9]. Anatomical entrapment and irritation due to myofascial spasm has been suggested at various locations along the nerve’s path, including where the GON branches from C2 between the axis and atlas, between the inferior oblique and semispinalis, as it pierces the belly of the semispinalis, and as it pierces the aponeurosis of the trapezius [10]. Sonography of the GON as it runs between the inferior oblique capitis and semispinalis capitis suggested greater cross sectional area on the symptomatic as compared to asymptomatic side in individuals with unilateral ON, as is seen in medial nerve entrapment [11•]. However, the study was limited by small sample size and has not been repeated. A variety of case reports have identified potential structural lesions that presented as ON. White et al. described a posterior inferior cerebellar artery impinging the dorsal upper cervical roots that presented as refractory ON. However, symptom resolution included sectioning of the C2 dorsal roots, making it difficult to determine if the presentation was due to C2 neuralgia or ON [12]. Dural arteriovenous fistulas, cervical cord cavernous angiomas, neurosyphillis, multiple sclerosis and myelitis have all been identified as secondary causes of ON [12–18]. Neuroimaging, including magnetic resonance imaging (MRI) of the brain and cervical spine to evaluate for structural or infiltrative lesions, is prudent.
Differential Diagnosis Given the overlap in presentation between ON and other primary headache disorders, it is important to consider migraine, cluster headache, hemicrania continua and tension type headache. Temporal arteritis involving the occipital artery can present with occipital headache and scalp tenderness [25, 26]. C2 neuralgia also presents with lancinating occipital pain and can result from compressive and inflammatory lesions of the C2 nerve root. C2 neuralgia is more likely to involve ipsilateral lacrimation and ciliary injection than ON [27].
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Postherpetic neuralgia involving the C2 nerve root or GON should be evaluated with careful inspection of the scalp. Dull, aching occipital head and neck pain is likely cervicogenic headache, and results from referred pain from structures innervated by the first three upper cervical spinal nerves such as the atlantoaxial joints, C2-3 intervertebral disc and zygopophyseal joint, the posterior fossa and various upper posterior neck muscles [27]. Cervical medial branch blocks can help distinguish if neck pain originates in the upper zygopophyseal joints.
Treatment Initial conservative treatment includes rest, periodic warm or cold compress, massage and physical therapy, directed at alleviating secondary muscle tension and improving posture [28]. Anti-inflammatory medications and muscle relaxants may reduce acute pain. Antiepileptic drugs (AEDs) such as carbamazepine, gabapentin, pregabalin, baclofen, and tricyclic antidepressants (TCAs) have reported efficacy in reducing the frequency and severity of attacks, but have not been systematically evaluated in the treatment of ON [25, 28]. In our experience, Gabapentin 300–600 mg qhs or Nortriptyline 30–50 mg qhs are each effective.
Occipital Nerve Block The utility of anesthetic block of the GON and LON to both confirm the diagnosis and provide temporary pain relief make it a high-yield intervention. Several studies have demonstrated the efficacy of occipital nerve block in alleviating ON. Kuhn et al. retrospectively evaluated ten subjects who responded to initial infiltration of the GON with 0.5 % bupivacaine followed by corticosteroid [25]. All patients acutely reported a minimum of 80 % pain relief. At follow-up, the duration of benefit lasted 1 week in three patients, 2 weeks in three patients, 1 month in one patient, and completely aborted the headache in two patients who were followed for 2.5 and 4 months, respectively [23]. Anthony retrospectively evaluated 184 ON patients treated with corticosteroid injection and found a mean duration of 31 days of pain relief [29].
Technique Anatomical landmarks are used to guide anesthetic blockade of the GON. Loukas et al. performed anatomical dissection of the GON on 100 adult cadavers and determined that ideal injection site is 2 cm lateral and 2 cm inferior to the external occipital protruberance [10]. The occipital artery runs laterally to the nerve and palpating for pulsation can help confirm the
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correct location. Pressure or palpation in this area may also elicit pain and paresthesia. The LON is lateral to the GON along the superior nuchal ridge, approximately one-third of the distance between the mastoid and the external occipital protruberance [30]. Anesthetic blockade typically contains 2 to 3 mL of lidocaine or bupivacaine, often combined in a 1:1 ratio. Corticosteroids can be added to the anesthetics, typically methylprednisolone or triamcinolone [31]. There are no studies that confirm that the addition of steroids increase the efficacy or duration of response in occipital neuralgia. A randomized trial of ONB for migraine determined that the addition of triamcinolone did not improve outcomes [32]. Corticosteroids do increase the risk of adverse reactions, including alopecia, cutaneous atrophy and, with repeated injections, Cushing’s syndrome due to systemic absorption [32, 33]. For these reasons, our practice does not routinely use corticosteroids in ONBs for the treatment of ON. Injections should not be performed on patients with a known cranial defect or history of craniotomy in the area of the injection, as inadvertent subarachnoid injection has been reported [34]. Aspiration prior to injection is important to avoid intravascular injection, given the close proximity of the occipital artery to the GON. Other, more common, side effects include dizziness, lightheadedness, injection site soreness, and rarely, vasovagal syncope. In addition to the local effects of anesthesia on the peripheral nerve, it has been proposed that the efficacy of ONB in ON is due to central modulation via interactions between afferent input into the cervical dorsal horn and trigeminal nucleus caudalis [35, 36].
Pulsed Radiofrequency For patients with ON refractory to pharmacologic treatment and ONB, neuromodulation with pulsed radiofrequency (PRF) and subcutaneous nerve stimulation offer promising treatment options. PRF exposes the nerve to a train of shortduration, high-voltage radiofrequency pulses. PRF was developed as an alternative to continuous radiofrequency lesioning, which has been used in various neuralgias but can be complicated by post-procedure deafferentation pain [37]. PRF theoretically decreases pain by inducing a low-intensity electrical field around sensory nerves that inhibits long-term potentiation in nociceptive afferents [38]. Vanelderen et al. conducted a prospective analysis of 19 patients with ON treated with PRF, and reported significant decrease of the mean visual analog scale (VAS) and a significant decrease in medication use as measured by a Medication Quantification Scale. Slightly more than half the patients reported that pain improved substantially, as measured by a Likert scale, at 6-month follow-up [39]. Huang et al. retrospectively evaluated 102
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patients treated with PRF for ON and found that 51 % reported ≥50 % pain relief at 3-month follow-up. Investigators also identified predictors of treatment response including traumatic etiology, lower diagnostic nerve block volumes, and multiple rounds of PRF treatment [40].
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may also respond to occipital nerve block, and thus must be carefully considered in the differential. Conservative treatment with physical therapy and low dose AEDs or TCAs is often effective. However, refractory cases may respond to pulse radiofrequency or occipital nerve stimulation. Compliance with Ethics Guidelines
Occipital Nerve Stimulation Weiner and Reed demonstrated that implanted occipital nerve stimulator with percutaneous leads was effective for medically refractory ON in 1999. Of the 13 implanted patients, over 80 % demonstrated good to excellent pain relief at a minimum of 1.5 years of follow-up [41]. Slavin et al. conducted a retrospective analysis of 14 patients with medically refractory ON who underwent 5–7 day trial insertion. Ten patients who demonstrated a>50 % pain reduction during the trial period received a permanent subcutaneous stimulator. At a minimum follow-up of 5 months and a mean of 22 months, seven patients continued to demonstrate adequate pain relief and decrease in oral pain medication intake [42]. Several subsequent studies have shown similar results [43–46]. Potential complications of occipital nerve stimulator include lead migration, infection, electrode fractures, and hardware erosion [42].
Botulinum Toxin Type A There are two published studies to date evaluating botulinum toxin type A as a treatment for ON. A retrospective case series of six patients by Kapural et al. demonstrated a reduction of pain on the VAS from 8±1.8 to 2±2.7 for a mean duration of 16.3±3.2 weeks [47]. Subsequently, Taylor et al. published a prospective pilot study of six patients with ON treated with botulinum toxin type A with 12-week follow-up. There was improvement in sharp, shooting pain and quality of life measures, but no significant improvement on dull, aching pain or pins, needles type pain, and no reduction in pain medication usage [48]. Due to the modest results and small sample size from which they are derived, we do not routinely treat refractory ON with botulinum toxin A in our practice.
Conclusion Occipital neuralgia is an uncommon primary headache disorder characterized by intermittent, sharp stabbing occipital pain. Diagnosis is made by history, clinical examination and positive response to anesthetic block of the greater occipital nerve. Cervicogenic headache and migraine can manifest with similar symptoms including occipital pain and allodynia, and
Conflict of Interest Dr. Carrie Dougherty declares no potential conflicts of interest relevant to this article. Human and Animal Rights and Informed Consent This article does not contain any studies with human or animal subjects performed by any of the authors.
References Papers of particular interest, published recently, have been highlighted as: • Of importance •• Of major importance 1.•• Headache Classification Committee of the International Headache Society: International Classification of Headache Disorders, 3rd edition (beta version). Cephalalgia 2013, 33:629–808. This recently published update of the ICHD includes more specific diagnostic criteria for occipital neuralgia. The previous ICHD-2 only included tenderness over the affected area, whereas current criteria also require the presence of dysesthesia or allodynia. The update also removed mention of persistent aching between paroxysms. 2. Kelman L. Pain characteristics of the acute migraine attack. Headache. 2006;46:942–53. 3. Afridi SK, Shields KG, Bhola R, Goadsby PJ. Greater occipital nerve injection in primary headache syndromes: prolonged effects from a single injection. Pain. 2006;122:126–9. 4. Ashkenazi A, Young WB. The effects of greater occipital nerve block and trigger point injection on brush allodynia and pain in migraine. Headache. 2005;45:350–4. 5. Caputi CA, Firetto V. Therapeutic blockade of greater occipital and supraorbital nerves in migraine patients. Headache. 1997;37:174–9. 6. Gale GD, Caputi CA, Firetto V. Therapeutic blockade of the greater occipital and supraorbital nerves in migraine patients. Headache. 1998;38:57. 7. Guvencer M, Akyer P, Sayhan S, Tetik S. The importance of the greater occipital nerve in the occipital and suboccipital region for nerve blockade and surgical approaches- an anatomical study on cadavers. Clin Neurol Neurosurg. 2011;113:289–94. 8. Lang J. Musculature. In: Clinical anatomy of the cervical spine. New York: Thieme Medical Publishers; 1993, p. 127. 9. Magnusson T, Ragnarsson T, Bjornsson A: Occipital nerve release in patients with whiplash trauma and occipital neuralgia. Headache 1996, 36:32–6. 10. Loukas M, El-Sedfy A, Tubbs RS, et al. Identification of greater occipital nerve landmarks for the treatment of occipital neuralgia. Folia Morphol (Warsz). 2006;65:337–42. 11.• Cho JC, Haun DW, Kettner NW. Sonographic evaluation of the greater occipital nerve in unilateral occipital neuralgia. J Ultrasound Med. 2012;31:37–42. This study utilizes ultrasound to evaluate changes in the cross sectional area and circumference of symptomatic occipital nerves in patients with unilateral occipital neuralgia.
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Ashkenazi A, Matro R, Shaw JW, et al. Greater occipital nerve block using local anaesthetics alone or with triamcinolone for transformed migraine: a randomized comparative study. J Neurol Neurosurg Psychiatry. 2008;79:415–7. 33. Shields KG, Levy MJ, Goadsby PJ. Alopecia and cutaneous atrophy after greater occipital nerve infiltration with corticosteroid. Neurology. 2004;63:2193–4. 34. Okuda Y, Matsumoto T, Shinohara M, et al. Sudden unconsciousness during a lesser occipital nerve block in a patient with the occipital bone defect. Eur J Anaesthesiol. 2001;18:829–32. 35. Goadsby PJ, Zagami AS. Stimulation of the superior sagittal sinus increases metabolic activity and blood flow in certain regions of the brainstem and upper cervical spinal cord of the cat. Brain. 1991;114:1001–11. 36. Goadsby PJ, Hoskin KL, Knight YE. Stimulation of the greater occipital nerve increases metabolic activity in the trigeminal nucleus caudalis and cervical dorsal horn of the cat. Pain. 1997;73:23–8. 37. Navani A, Mahajan G, Kreis P, et al. A case of pulsed radiofrequency lesioning for occipital neuralgia. Pain Med. 2006;7:453–6. 38. Chua NH, Vissers KC, Sluijter ME. Pulsed radiofrequency treatment in interventional pain management: mechanisms and potential indications- a review. Acta Neurochir (Wien). 2011;153:763–71. 39. Vanelderen P, Rouwette T, De Vooght P, et al. Pulsed radiofrequency for the treatment of occipital neuralgia: a prospective study with six months of follow-up. Reg Anesth Pain Med. 2010;35:148–51. 40. Huang JHY, Galvagno SM, Hameed M, et al. Occipital nerve pulsed radiofrequency treatment: a multi-center study evaluating predictors of outcome. Pain Med. 2012;13:489–97. 41. Weiner RL, Reed KL. Peripheral neurostimulation for control of intractable occipital neuralgia. Neuromodulation. 1999;2:217–21. 42. Slavin KV, Nersesyan H, Wess C. Peripheral neurostimulation for treatment of intractable occipital neuralgia. Neurosurgery. 2006;58: 112–8. 43. Johnston CS, Sundaraj R. Occipital nerve stimulation for the treatment of occipital neuralgia-eight case studies. Neuromodulation. 2006;9:41–7. 44. Melvin EA, Jordan ER, Weiner RL, Primm D. Using peripheral nerve stimulation to reduce the pain of c2-mediated headaches: a preliminary report. Pain Phys. 2007;10:453–60. 45. Shaladi A, Crestani F, Saltari R, Piva B. Percutaneous electrical nerve stimulation of peripheral nerve for the intractable occipital neuralgia. Recenti Prog Med. 2008;99:295–301. 46. Magown P, Garcia R, Beauprie I, Mendez IM. Occipital nerve stimulation for intractable occipital neuralgia: an open surgical technique. Clin Neurosurg. 2009;56:119–24. 47. Kapural L, Stillman M, Kapural M, et al. Botulinum toxin occipital nerve block for the treatment of sever occipital neuralgia: a case series. Pain Pract. 2007;7:337–40. 48. Taylor M, Silva S, Cottrell C. Botulinum toxin type-a (botox) in the treatment of occipital neuralgia: a pilot study. Headache. 2008;48: 1476–81.
UNCOMMON HEADACHE SYNDROMES (J AILANI, SECTION EDITOR)
Occipital Neuralgia Carrie Dougherty
Published online: 16 April 2014 # Springer Science+Business Media New York 2014
Abstract Occipital pain is a common complaint amongst patients with headache, and the differential can include many primary headache disorders such as cervicogenic headache or migraine. Occipital neuralgia is an uncommon cause of occipital pain characterized by paroxysmal lancinating pain in the distribution of the greater, lesser or third occipital nerves. Greater occipital nerve blockade with anesthetics and/or corticosteroids can aid in confirming the diagnosis and providing pain relief. However, nerve blocks are also effective in migraine headache and misdiagnosis can result in a false positive. Physical therapy and preventive medication with antiepileptics and tricyclic antidepressants are often effective treatments for occipital neuralgia. Refractory cases may require intervention with pulsed radiofrequency or occipital nerve stimulation. Keywords Greater occipital nerve . Occipital neuralgia . Occipital nerve block . Occipital nerve stimulation . Pulsed radiofrequency
Introduction Occipital neuralgia (ON) as primary headache disorder is a challenging diagnosis. The International Headache Society diagnostic criteria for ON are listed in Table 1 [1••]. The overlap between ON and migraine is evident. Pain in migraine headache is by definition severe, and episodes of stabbing pain can accompany the typical throbbing or pulsating quality
[2]. Allodynia and occipital tenderness are also common in migraine, and the response of migraine to occipital nerve blocks is well described [3–6]. Thus, the most important section of the diagnostic criteria may be to ensure that the symptoms described by the patient are not better accounted by an alternate diagnosis. A careful history and physical exam are critical components to accurately identifying ON and distinguishing it from other headache disorders with similar presentations.
Anatomy ON can involve the greater occipital, lesser occipital or third occipital nerves. The greater occipital nerve (GON) originates from the medial branch of the dorsal ramus of C2. The GON ascends between the inferior oblique capitis muscle and semispinalis capitis and pierces the semispinalis. It then runs rostrolateral deep to the trapezius muscle and pierces the aponeurosis of the trapezius slightly inferior to the superior nuchal ridge, where it becomes subcutaneous and lies medial to the occipital artery [7]. The GON provides cutaneous sensory innervation to the posterior scalp from the external occipital protuberance to the vertex. The lesser occipital nerve (LON) originates from branches of C2 and C3 in the cervical plexus. It travels along the posterior border of the sternocleidomastoid muscle and innervates the lateral scalp superior and posterior to the auricle [8]. The third occipital nerve branches from C3 and innervates the upper neck and lower occipital scalp [8].
This article is part of the Topical Collection on Uncommon Headache Syndromes C. Dougherty (*) Department of Neurology, Medstar Georgetown University Hospital, 3800 Reservoir Road NW, 7 PHC, Washington, DC 20007, USA e-mail: [email protected]
Pathophysiology The etiology of occipital neuralgia is unknown and most presentations are considered idiopathic. Posterior head trauma
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Table 1 The International Headache Society diagnostic criteria for occipital neuralgia
Clinical Presentation
A. Unilateral or bilateral pain fulfilling criteria B–E B. Pain is located in the distribution of the greater, lesser and/or third occipital nerves C. Pain has two of the following three characteristics: 1. recurring in paroxysmal attacks lasting from a few seconds to minutes 2. severe intensity 3. shooting, stabbing or sharp in quality D. Pain is associated with both of the following: 1. dysesthesia and/or allodynia apparent during innocuous stimulation of the scalp and/or hair
There are no epidemiological studies that document the incidence or prevalence of ON. Hammond and Danta characterized 23 cases of ON and found that it is more commonly unilateral (85 %). Distribution of pain and paresthesia were consistent with GON involvement in 90 %, LON in 10 % and both nerves in 9 % of the cases [19]. The hallmark of ON is paroxysmal lancinating pain that patients often describe as stabbing, shooting, electric or “shock-like.” The pain typically originates in the occiput and radiates toward the vertex. A dull aching pain may persist between paroxysms, but this characteristic was eliminated from the diagnostic criteria in the most recent International Classification of Headache Disorders (ICHD) update [1••]. Dull occipital ache as a primary complaint should prompt evaluation for causes of referred occipital pain. Patients may describe allodynia or dysesthesia of the scalp in the distribution of the nerve, with sensitivity to touch or pressure on the scalp. Patients may avoid activities such as brushing their hair, wearing a hat or lying on a pillow. Tenderness to palpation along the course of the nerve is common. Various authors suggest that a positive Tinel’s sign, where numbness or tingling is elicited with percussion over the occipital condyle, is more specific for ON than tenderness or the patient’s description of pain; however, this has not been clinically investigated [20, 21]. Kuhn et al. published a prospective case series of 12 patients presenting to the emergency room with symptoms of occipital neuralgia and reported that frequently associated symptoms included tinnitus, scalp paresthesia, nausea, dizziness, and visual disturbances [22]. Symptoms originating from structures beyond the distribution of the GON are thought to be due to interactions between nociceptive afferents from the cervical roots and trigeminal nerve that converge in the spinal cord [23]. Temporary improvement of these symptoms after treatment with anesthetic blockade of the GON is diagnostic [1••]. However, migraine and cluster headache also respond to GON block, resulting in a false positive [24].
2. either or both of the following: a. tenderness over the affected nerve branches b. trigger points at the emergence of the greater occipital nerve or in the area of distribution of C2 E. Pain is eased temporarily by local anesthetic block of the affected nerve F. Not better accounted for by another ICHD-3 diagnosis. The pain of occipital neuralgia may reach the fronto-orbital area through trigeminocervical inter-neuronal connections in the trigeminal spinal nuclei. Occipital neuralgia must be distinguished from occipital referral of pain arising from the atlantoaxial or upper zygapophyseal joints, or from tender trigger points in neck muscles or their insertions Modified from the Headache Classification Committee of the International Headache Society [1••]
and whiplash injuries resulting in nerve injury have been proposed [9]. Anatomical entrapment and irritation due to myofascial spasm has been suggested at various locations along the nerve’s path, including where the GON branches from C2 between the axis and atlas, between the inferior oblique and semispinalis, as it pierces the belly of the semispinalis, and as it pierces the aponeurosis of the trapezius [10]. Sonography of the GON as it runs between the inferior oblique capitis and semispinalis capitis suggested greater cross sectional area on the symptomatic as compared to asymptomatic side in individuals with unilateral ON, as is seen in medial nerve entrapment [11•]. However, the study was limited by small sample size and has not been repeated. A variety of case reports have identified potential structural lesions that presented as ON. White et al. described a posterior inferior cerebellar artery impinging the dorsal upper cervical roots that presented as refractory ON. However, symptom resolution included sectioning of the C2 dorsal roots, making it difficult to determine if the presentation was due to C2 neuralgia or ON [12]. Dural arteriovenous fistulas, cervical cord cavernous angiomas, neurosyphillis, multiple sclerosis and myelitis have all been identified as secondary causes of ON [12–18]. Neuroimaging, including magnetic resonance imaging (MRI) of the brain and cervical spine to evaluate for structural or infiltrative lesions, is prudent.
Differential Diagnosis Given the overlap in presentation between ON and other primary headache disorders, it is important to consider migraine, cluster headache, hemicrania continua and tension type headache. Temporal arteritis involving the occipital artery can present with occipital headache and scalp tenderness [25, 26]. C2 neuralgia also presents with lancinating occipital pain and can result from compressive and inflammatory lesions of the C2 nerve root. C2 neuralgia is more likely to involve ipsilateral lacrimation and ciliary injection than ON [27].
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Postherpetic neuralgia involving the C2 nerve root or GON should be evaluated with careful inspection of the scalp. Dull, aching occipital head and neck pain is likely cervicogenic headache, and results from referred pain from structures innervated by the first three upper cervical spinal nerves such as the atlantoaxial joints, C2-3 intervertebral disc and zygopophyseal joint, the posterior fossa and various upper posterior neck muscles [27]. Cervical medial branch blocks can help distinguish if neck pain originates in the upper zygopophyseal joints.
Treatment Initial conservative treatment includes rest, periodic warm or cold compress, massage and physical therapy, directed at alleviating secondary muscle tension and improving posture [28]. Anti-inflammatory medications and muscle relaxants may reduce acute pain. Antiepileptic drugs (AEDs) such as carbamazepine, gabapentin, pregabalin, baclofen, and tricyclic antidepressants (TCAs) have reported efficacy in reducing the frequency and severity of attacks, but have not been systematically evaluated in the treatment of ON [25, 28]. In our experience, Gabapentin 300–600 mg qhs or Nortriptyline 30–50 mg qhs are each effective.
Occipital Nerve Block The utility of anesthetic block of the GON and LON to both confirm the diagnosis and provide temporary pain relief make it a high-yield intervention. Several studies have demonstrated the efficacy of occipital nerve block in alleviating ON. Kuhn et al. retrospectively evaluated ten subjects who responded to initial infiltration of the GON with 0.5 % bupivacaine followed by corticosteroid [25]. All patients acutely reported a minimum of 80 % pain relief. At follow-up, the duration of benefit lasted 1 week in three patients, 2 weeks in three patients, 1 month in one patient, and completely aborted the headache in two patients who were followed for 2.5 and 4 months, respectively [23]. Anthony retrospectively evaluated 184 ON patients treated with corticosteroid injection and found a mean duration of 31 days of pain relief [29].
Technique Anatomical landmarks are used to guide anesthetic blockade of the GON. Loukas et al. performed anatomical dissection of the GON on 100 adult cadavers and determined that ideal injection site is 2 cm lateral and 2 cm inferior to the external occipital protruberance [10]. The occipital artery runs laterally to the nerve and palpating for pulsation can help confirm the
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correct location. Pressure or palpation in this area may also elicit pain and paresthesia. The LON is lateral to the GON along the superior nuchal ridge, approximately one-third of the distance between the mastoid and the external occipital protruberance [30]. Anesthetic blockade typically contains 2 to 3 mL of lidocaine or bupivacaine, often combined in a 1:1 ratio. Corticosteroids can be added to the anesthetics, typically methylprednisolone or triamcinolone [31]. There are no studies that confirm that the addition of steroids increase the efficacy or duration of response in occipital neuralgia. A randomized trial of ONB for migraine determined that the addition of triamcinolone did not improve outcomes [32]. Corticosteroids do increase the risk of adverse reactions, including alopecia, cutaneous atrophy and, with repeated injections, Cushing’s syndrome due to systemic absorption [32, 33]. For these reasons, our practice does not routinely use corticosteroids in ONBs for the treatment of ON. Injections should not be performed on patients with a known cranial defect or history of craniotomy in the area of the injection, as inadvertent subarachnoid injection has been reported [34]. Aspiration prior to injection is important to avoid intravascular injection, given the close proximity of the occipital artery to the GON. Other, more common, side effects include dizziness, lightheadedness, injection site soreness, and rarely, vasovagal syncope. In addition to the local effects of anesthesia on the peripheral nerve, it has been proposed that the efficacy of ONB in ON is due to central modulation via interactions between afferent input into the cervical dorsal horn and trigeminal nucleus caudalis [35, 36].
Pulsed Radiofrequency For patients with ON refractory to pharmacologic treatment and ONB, neuromodulation with pulsed radiofrequency (PRF) and subcutaneous nerve stimulation offer promising treatment options. PRF exposes the nerve to a train of shortduration, high-voltage radiofrequency pulses. PRF was developed as an alternative to continuous radiofrequency lesioning, which has been used in various neuralgias but can be complicated by post-procedure deafferentation pain [37]. PRF theoretically decreases pain by inducing a low-intensity electrical field around sensory nerves that inhibits long-term potentiation in nociceptive afferents [38]. Vanelderen et al. conducted a prospective analysis of 19 patients with ON treated with PRF, and reported significant decrease of the mean visual analog scale (VAS) and a significant decrease in medication use as measured by a Medication Quantification Scale. Slightly more than half the patients reported that pain improved substantially, as measured by a Likert scale, at 6-month follow-up [39]. Huang et al. retrospectively evaluated 102
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patients treated with PRF for ON and found that 51 % reported ≥50 % pain relief at 3-month follow-up. Investigators also identified predictors of treatment response including traumatic etiology, lower diagnostic nerve block volumes, and multiple rounds of PRF treatment [40].
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may also respond to occipital nerve block, and thus must be carefully considered in the differential. Conservative treatment with physical therapy and low dose AEDs or TCAs is often effective. However, refractory cases may respond to pulse radiofrequency or occipital nerve stimulation. Compliance with Ethics Guidelines
Occipital Nerve Stimulation Weiner and Reed demonstrated that implanted occipital nerve stimulator with percutaneous leads was effective for medically refractory ON in 1999. Of the 13 implanted patients, over 80 % demonstrated good to excellent pain relief at a minimum of 1.5 years of follow-up [41]. Slavin et al. conducted a retrospective analysis of 14 patients with medically refractory ON who underwent 5–7 day trial insertion. Ten patients who demonstrated a>50 % pain reduction during the trial period received a permanent subcutaneous stimulator. At a minimum follow-up of 5 months and a mean of 22 months, seven patients continued to demonstrate adequate pain relief and decrease in oral pain medication intake [42]. Several subsequent studies have shown similar results [43–46]. Potential complications of occipital nerve stimulator include lead migration, infection, electrode fractures, and hardware erosion [42].
Botulinum Toxin Type A There are two published studies to date evaluating botulinum toxin type A as a treatment for ON. A retrospective case series of six patients by Kapural et al. demonstrated a reduction of pain on the VAS from 8±1.8 to 2±2.7 for a mean duration of 16.3±3.2 weeks [47]. Subsequently, Taylor et al. published a prospective pilot study of six patients with ON treated with botulinum toxin type A with 12-week follow-up. There was improvement in sharp, shooting pain and quality of life measures, but no significant improvement on dull, aching pain or pins, needles type pain, and no reduction in pain medication usage [48]. Due to the modest results and small sample size from which they are derived, we do not routinely treat refractory ON with botulinum toxin A in our practice.
Conclusion Occipital neuralgia is an uncommon primary headache disorder characterized by intermittent, sharp stabbing occipital pain. Diagnosis is made by history, clinical examination and positive response to anesthetic block of the greater occipital nerve. Cervicogenic headache and migraine can manifest with similar symptoms including occipital pain and allodynia, and
Conflict of Interest Dr. Carrie Dougherty declares no potential conflicts of interest relevant to this article. Human and Animal Rights and Informed Consent This article does not contain any studies with human or animal subjects performed by any of the authors.
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