In one series of fatal cerebral thrombosis, 90% had clear CSF and most of the remaining 10% had xanthochromia. WBC counts were usually normal; about 15% had a small increase in cell count (usually < 50/mm3). CSF protein level was normal in 50% of cases and usually less than 100 mg/ 100 ml in the remainder. CT or MRI is the best method of demonstrating the lesion. CT is better in the first week.