Congenital Unilateral Atlanto-Occipital Rotatory Subluxation: Rare Cause of C1 Neuralgia

Case report.

We report a rare case of congenital unilateral rotatory atlanto-occipital subluxation that presented with left C1 neuralgia.

Secondary occipital neuralgia is commonly attributed to pathologies of the atlanto-axial joint and C2/C3 nerve involvement. Our case depicts a model of slow creeping atlanto-occipital subluxation due to a rare left C1 superior articular facet dysplasia with C1 foraminal stenosis presenting as C1 neuralgia. We discuss the eitology and patho-anatomy of this rare undescribed presentation.

A 42-year-old gentleman presented with deteriorating and intractable left occipital headache of 6 months duration. The neck disability index (NDI) was 64%. Cervical MR/computed tomography scan showed a unilateral C1 facet dysmorphism with a left sided C1 foramen bony compression. There was no central canal stenosis.

Posterior left C1 arch excision and decompression of C1 foramina with occipital-cervical fusion relieved C1 neuralgia.

Our case depicts a model of slow creeping deformation due to left C1 superior articular facet dysplasia. An abnormal facet slope allowed the occipital condyle to migrate posteriorly and medially leading to crowding of the left C1 foramen. Although the etiology was congenital, the neck spasm was delayed till fourth decade. A secondary C1 foramen stenosis led to C1 occipital neuralgia that presented as an intractable headache.

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