A 26-year-old man presented with a 3 week history of progressive limb weakness and parasthesia following symptoms suggestive of a viral illness. He also developed diplopia, dysarthria and dysphagia. He was known to have glioblastoma multiforme (GBM) and had undergone debulking surgery, radiotherapy and two cycles of adjuvant chemotherapy with temozolamide. His intracranial disease was well controlled on MRI follow up. Examination demonstrated nuchal rigidity and a flaccid asymmetrical quadriplegia with absent reflexes. Gullian Barre syndrome was thought likely. MRI brain and spine with contrast showed no new changes. Nerve conduction studies showed minor F wave abnormalities. Lumbar puncture showed CSF opening pressure of 40 cm, CSF protein of 0.49 g/l and glucose of 1.4 mmol/l (plasma glucose of 7 mmol/l). Cytological analysis revealed plump abnormal cells with mitotic figures confirming the diagnosis of leptomeningeal metastasis from GBM. The patient deteriorated rapidly and died. Leptomeningeal disease occurs infrequently in GBM, but spinal leptomeningeal disease mimicking GBS is extremely rare late event. Contrast MRI does not always show leptomeningeal disease.