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

•Spinal arachnoiditis is an extremely rare and delayed complication of subarachnoid hemorrhage.•Spinal arachnoiditis is often a complicated two-staged disease.•Spinal cord compression and syrinx might manifest from spinal arachnoiditis.•Posterior fossa bleeding, warrants prolonged surveillance.•Re-bleeding and ventriculitis might augment the risk and the severity of arachnoiditis.