Progressive hemiparesis due to spino-laminar anomaly of the axis—a case report and literature review

INTRODUCTION: Some of the most common developmental malformations of the axis include anomalies of the odontoid, for example, hypoplasia or aplasia. Isolated anomalies of the posterior arch of the axis rarely occur. This study reports a unique case of congenital anomaly of the neural arch of the axis vertebra, which manifested clinically as progressive hemiparesis. CASE PRESENTATION: A 33-year-old man presented with progressive weakness of the right upper and lower limbs that had lasted 18 months. The patient reported loss of right-hand dexterity in the 6 months period before he consulted us. Plain radiographs, computed tomography (CT), and magnetic resonance imaging (MRI) revealed C5–C6 block vertebra, primary canal stenosis and spino-laminar anomaly of the axis, along with invagination of the lamina into the canal causing severe cord compression. DISCUSSION: The anomalous posterior element of the axis was excised, and the cord was decompressed. The presence of congenital stenosis and block vertebrae at the C5–C6 level necessitated decompression and instrumentation between C2–C6. Simultaneous occurrence of a posterior arch anomaly, primary canal stenosis, and block vertebra has not been previously described. A cervical spine anomaly presenting as hemiparesis is uncommon in clinical practice. Information enabling clinicians to identify causative anomaly and determine the appropriate surgical intervention is useful, and can facilitate a good clinical outcome.