An 18-year-old man with a known glioblastoma multiforme, previously treated with de-bulking, chemotherapy, radiation and steroids, underwent a repeat craniotomy after presenting with several days of intractable vomiting and headache. Postoperatively, he developed progressive delirium, bilateral sixth and seventh nerve palsies, dysphagia and ascending weakness of the upper and lower limbs. Within five postoperative days, he was quadraparetic, areflexic and had marked extraocular muscle and facial weakness, dysphagia, dysphonia and respiratory muscle weakness. The patient was started empirically on intravenous immunoglobulin for suspected Guillain-Barré syndrome (GBS). The following day, lumbar puncture demonstrated elevated protein (1.96g/l; normal <0.45), and a reduced glucose (0.5 mmol/l) and elevated red (4125x106 per litre) and white cell (214x106 per litre) counts in the cerebrospinal fluid (the red cells were felt to be related to surgery). The cell differential included 69% neutrophils, 3% lymphocytes, 15% monocytes and 13% blast-like cells. Gram stains and cultures of the cerebrospinal fluid were negative.