International Headache Society defines Occipital neuralgia (ON ) as “Unilateral or bilateral paroxysmal, shooting or stabbing pain in the posterior part of the scalp, in the distribution(s) of greater, lesser and /or third occipital nerves, sometimes accompanied by diminished sensations or dysesthesia in the associated area and commonly associated with tenderness over the involved nerve(s)”.
Occipital neuralgia is a highly underdiagnosed cause of headache.
Symptoms:
ON is a painful condition of posterior head in the distribution of Greater occipital, Lesser occipital nerves and/or Third occipital nerve (TON ).
Patients presenting with headache originating at the skull base should be evaluated for ON.
ON presents as a paroxysmal, lancinating or stabbing pain lasting for few minutes and therefore, a continuous aching pain indicates different diagnosis.
ICHD-3 criteria require that patient also has tenderness, allodynia, and/or dysesthesia over the affected area. Pain usually begins unilaterally, but may extend into bilateral distribution over time. In one-third of patients bilateral symptoms are present.
Anatomy of Occipital nerves and pathophysiology:
The Greater occipital nerve (GON ) arises from dorsal ramus of C2 spinal nerve, and curves around inferior border of the inferior oblique muscle to ascend on its superficial surface. Then it penetrates semispinalis capitis and splenius muscles to end subcutaneously near the nuchal line by penetrating the trapezius muscle or the fascia.
Lesser occipital nerve (LON ) arise from C2 ventral ramus, loops inferior to spinal accessory nerve, ascends along the posterior border of the sternocleidomastoid muscle, pierces deep cervical fascia and runs across the posterior edge of the sternocleidomastoid insertion and into the superficial fascia of the scalp. It splits into 3 branches: auricular, mastoid and occipital.
Third occipital nerve( TON ) arises from the dorsal ramus of C3. It divides into lateral and medial branches. Medial branch divides into superficial and deep branches, the superficial branch being the TON. It then curves around the dorsolateral surface of C2-C3 and travels along the semispinalis capitis muscle. It turns dorsally at the C2 spinous process, piercing semispinalis capitis, splenius capitis and trapezius muscles and innervates small cutaneous area below the superior nuchal line. The TON sends many branches to GON and LON potentially making it difficult to separate symptoms due to the TON alone.
The GON can be entrapped anywhere from its origin, to cause neuralgia. These sites include the C2 nerve root, inferior oblique muscle, semispinalis capitis muscle, and where the penetrates trapezius muscle, and instances where occipital artery and GON intersect. The occipital nerve is quite large, 2.5 to 3.5 mm in diameter, which may predispose it to compressive pathology. Muscle hypertrophy, tensing or spasm of musculature in the area has been postulated to contribute to compression, and surgical sectioning of muscles in close approximation with the GON has led to pain relief. In certain cases, trauma and the formation of fibrocartilage calluses or other structural changes to the bony anatomy of the skull or spine can lead to ON. Arnold-chiari malformation or Arteriovenous malformations may cause compression.
Other causes of ON include
- Osteoarthritis of upper cervical facet joints
- Trauma to the occipital nerves
- Cervical disc disease
- Tumors
- Gout
- Diabetes
- Infection
- Autoimmune conditions.
Diagnosis:
A thorough history and physical examination followed by a diagnostic local anesthesia injection under ultrasound guidance is required to diagnose ON. The patient should have pain relief with the nerve block for at least the duration of action of the local anesthetic.
Treatment:
- Conservative management with antidepressants, SNRIs, or Gabapentinoids gives relief for many patients.
- Following diagnostic blocks, therapeutic block with local anesthesia and steroid may be given to alleviate symptoms.
- Botulinum toxin A injection has lower side effect profile, with many trials demonstrating 50% or more improvement.
