Postarachnoiditis Anterior Spinal Arachnoid Cyst Formation with Compressive Myelopathy: Report of 2 Cases.

Background: Spinal cystic arachnoiditis is a rare complication of a subarachnoid haemorrhage or infectious meningitis. The inflammatory process leads to fibrosis, adhesions, and in severe cases cyst formation. Large arachnoid cysts are an uncommon cause of compressive myelopathy. The majority are located posterior of the spinal cord at the thoracic level. Anterior cyst formation is exceptional, especially at the cervical region.

Case Description: We present 2 cases of progressive myelopathy secondary to anterior arachnoid cyst formation. In a 54-year-old female a large anterior symptomatic thoracic cyst arose 4 years after rupture of a posterior inferior cerebellar artery aneurysm. The other 59-year-old-patient, however, developed an anterior cervical cyst only weeks after a varicella meningoencephalitis. Both female patients were treated with a decompressive laminectomy and wide fenestration of the cysts. Partial recovery was obtained in 1 patient, but there was no improvement in the other case.

Conclusions: Spinal cystic arachnoiditis with anterior cyst formation is an extremely rare complication of subarachnoid haemorrhage and infectious meningitis but can cause severe neurologic deficits. Clinicians should be aware of this rare complication. Due to the risk of irreversible spinal cord injury, rapid surgical intervention is recommended in most cases.