Rare case of diffuse spinal arachnoiditis following a complicated vertebral artery dissection.

Spinal arachnoiditis (SA) is an extremely rare and delayed complication of subarachnoid hemorrhage (SAH). Little is known about its underlying pathogenesis and subsequent clinical course. A middle-aged patient presented with the worst headache of her life and a grade 3 SAH of the basal-cisterns and posterior fossa was identified on Computed Tomography scans (CT). Angiography revealed a ruptured dissecting aneurysm of the left vertebral artery (VA-V4), as well as an unruptured left Anterior Cerebral Artery (ACA-A1) aneurysm. The VA aneurysm was treated with flow diversion. The patient re-ruptured the stented aneurysm, another telescoping pipeline was placed. The patient developed polymicrobial ventriculitis, and returned several months later complaining of paraparesis and left sided weakness. Magnetic Resonance Imaging (MRI) revealed diffuse thecal dural thickening from the cervicomedullary junction to the sacrum. Loculations, diffuse edema and cord compression were noticed along the inferior surface of the cerebellum, and the cervico-thoracic spine with a T4-T6 syrinx. The patient underwent a posterior (T4-T8) spinal fusion and (T5-T7) decompression with arachnoid-cyst fenestration and placement of a subarachnoid-pleural shunt. On latest follow-up, the patient is weaning off the thoraco-lumbosacral orthosis and ambulating with a cane. SA is often a complicated two-staged disease in which a "free interval phase" separates the initial inflammatory reaction (IIR) from the late adhesive phase. Posterior fossa bleeding, warranting prolonged surveillance, additional bleeding and ventriculitis might augment the risk and the severity of arachnoiditis.