Occipital neuralgia: a symptomatic case caused by an abnormal left vertebral artery

Abstract

Occipital neuralgia is a condition defined by the International Headache Society [1] as a paroxysmal jabbing pain in the distribution of the greater or lesser occipital nerves or of the third occipital nerve; it is sometimes accompanied by diminished sensation or dysaesthesia in the affected area and it is commonly associated with tenderness over the nerve concerned. Diagnostic criteria include the following: paroxysmal stabbing pain, with or without persistent aching between paroxysms, in the distribution of the greater, lesser and/or third occipital nerves, tenderness over the affected nerve and pain temporarily eased by local anesthetic block of the nerve [1]. The greater occipital nerve is more frequently involved (90%) as compared to the nervus occipitalis minor (10%); in 8.7% both occipital nerves are responsible for the neuralgia [2]. Occipital neuralgia is typically referred as an idiopathic condition, although secondary etiologies must be ruled out; occipital nerves can be irritated by different conditions, in particular vascular, neurogenic, muscolar-tendinous, osteogenic and tumoral etiologies must be ruled out [3]. As far as vascular etiology concerns, fenestrated arteria vertebralis pressing on C1-C2 nerve roots and aberrant course of the vertebral artery have been reported as rare causes of occipital neuralgia [4, 5]. We report a symptomatic case of occipital neuralgia, caused by a left vertebral artery, appearing hypertrophic and shifted back at the level of the first and second cervical vertebrae. A 78-year-old woman presented with episodes of stabbing paroxysmal headache in the left occipital region, over the previous 4 months; pain was intermittent and sharp, described as jabbing, starting in the left suboccipital region at the base of the skull near the midline, involving the entire posterior and lateral scalp and occasionally radiating toward the vertex. Episodes progressively increased in frequency, reaching multiple attacks per day, so she referred to the Headache Centre of the Institute of Neurology, at Pisa University. Neurological examination was normal, no hypo or dysesthesia in the area of the greater or lesser occipital nerves was reported; pressure over the course of the greater occipital nerve evoked tenderness. Suspecting an occipital neuralgia, a non-enhanced brain MRI with particular attention to the craniocervical junction was performed. MRI examination showed a hypertrophic aspect of the left vertebral artery, that appeared shifted back at the level of the first and second cervical vertebrae (Fig. 1a, b). In the meanwhile a pharmacological treatment was started, in particular, because of the age and general conditions of the patient, before administering carbamazepine or oxcarbazepine, i.e. the first-line drugs for cranial neuralgias [6], the more tolerable pregabalin was tried. Pregabalin was tapered to a dose of 300 mg/daily, with consistent improvement in pain control, in particular attacks progressively decreased in frequency and pain remission was achieved after 1 month of treatment; the follow-up is still at 8 months and the patient is in treatment with pregabalin at the maintenance dose of 150 mg/daily, with good efficay and tollerability. A neurosurgical evaluation was performed and the hypertrophic and shifted back aspect of the left vertebral artery was considered as an anatomic variant, without pathological significance and, mainly the age of the patient and the good response to pregabalin, discouraged a surgical approach. C. Lucchesi (&) S. Gori Department of Neurosciences, Institute of Neurology, University of Pisa, Via Roma, 67, 56126 Pisa, Italy e-mail: cinzia.lucchesi@gmail.com