Acute encephalopathy after initiation of cranial irradiation for meningeal leukaemia.

Five patients experienced severe encephalopathy within hours of receiving their initial dose of cranial irradiation for the treatment of central-nervous-system leukaemia. Neurological findings included cranial-nerve palsies, seizures, ataxia, depressed consciousness, increased intracranial pressure, and signs of herniation. Symptoms developed within 3-30 hours of the first radiation treatment of 50-200 rad. Each patient had also received one or more injections of intrathecal chemotherapy before encephalopathy developed. The aetiology of this syndrome is uncertain but may involve transient cerebral oedema and/or an altered blood-brain barrier produced by the combination of intrathecal chemotherapy and cranial irradiation.