A 38-year -old man was hospitalized seven weeks prior to the present admission with generalized weakness and pain. He was treated with plasmapheresis and immunoglobulin for a presumptive diagnosis of Guillain-Barre. His condition worsened with CNS failures, respiratory insufficiency, anisocoria and shoulder myoclonus. CT scan revealed a right-sided parietal mass which was poorly vascularized on angiography. Stereotactic biopsy revealed an anaplastic (high grade, 3) astrocytoma.