This uncommon neuralgia has various etiologies, primarily categorized as neurogenic, vascular, muscular, or osteogenic. Parenthetically, it is important to note that the C1 root, suboccipital nerve, is entirely motor in function, having no sensory component in contrast to all other nerve roots. Trauma to the C2 root due to traction injury or secondary to the arthritic changes at the atlantoaxial joint are the primary causes of occipital neuralgia. Another postulated but unproven mechanical cause includes nerve entrapment with sustained contraction or spasm of the posterior neck muscles. Osteogenic origins include osteoarthritis and arthritic degeneration of the spine leading to nerve entrapment by hypertrophied atlantoaxial ligaments. Instances of vascular etiology include irritation of C1/C2 nerve roots by diverging branches of the posterior inferior cerebellar artery and extremely rare dural arteriovenous fistulas in the cervical regions. Tumors of the second and third cervical dorsal roots and multiple sclerosis account for more uncommon, neurogenic causes. Most often, however, the inciting factor is not identified with clinical evaluation, and the neuropathic changes in greater or lesser occipital nerve are considered idiopathic. Perhaps these pathophysiologic mechanisms will be more easily identified with the increased availability of 3-tesla magnetic resonance imaging (MRI), providing more accurate detail.
Occipital neuralgia is typically described as stabbing pain with periods of aching pain between the paroxysmal episodes. Retro-orbital pain may be explained by the convergence of nociceptive pathways in the dorsal root of C2 and the pars caudalis division of the spinal trigeminal nucleus. In addition, visual deficits, ringing in the ears, dizziness, and nasal congestion may accompany painful periods due to the involvement of cranial nerves (CNs) VIII, IX, and X and the cervical sympathetic trunk. Stress-induced muscle tension headaches may also occur. On physical examination, dysesthesia is elicited along the greater and lesser occipital nerve, as well as tenderness to palpation. Diagnosis is confirmed via diagnostic nerve block of the occipital nerve, along with imaging scans to identify any suspected lesions.
Effective management depends on whether an identifiable entrapment mechanism is identified. If so, surgical intervention or decompression is a viable option. Occipital nerve blocks are often effective at attenuating pain intensity in this region. Most treatments, however, are aimed at symptom reduction and relief of any accompanying muscle tension. Empiric use of drugs based on efficacy data from other neuropathic syndromes is common. These agents include adjuvants, such as tricyclic antidepressants, and anticonvulsants, such as carbamazepine or gabapentin. Botulinum toxin type A injections are also used. Local anesthetic and corticosteroid injections to the greater occipital nerve are variably effective. Pulsed radio frequency of the C2 or C3 dorsal root ganglion is currently being evaluated in small preliminary studies. There is an emerging body of evidence to support the use of subcutaneous peripheral nerve stimulation in intractable, severe cases of occipital neuralgia.