Spinal arachnoiditis and cyst formation with subarachnoid haemorrhage.

We present the case of a 58-year-old lady with p-ANCA vasculitis who suffered a WFNS grade 1 subarachnoid haemorrhage (Fisher grade 1) secondary to a ruptured left posterior inferior cerebellar artery aneurysm and then developed a rare complication of radiologically progressive spinal arachnoiditis despite maintained clinical response to definitive treatment measures.