Leptomeningeal dissemination of primary central nervous system tumors of childhood.

Presymptomatic craniospinal radiation therapy improves the rate of survival for children with brain tumors, which frequently metastasize to the leptomeninges. Radiotherapy may cause neurological damage and should be used only in patients considered to be at highest risk for leptomeningeal dissemination (LMS) at either the time of initial diagnosis or onset of disease relapse. We reviewed 314 consecutive patients with brain tumors to determine the incidence, timing, and importance of LMS. LMS occurred in 60 (19%) children. LMS occurred before diagnosis in 30 patients, as the only site of relapse or simultaneously with local first disease recurrence in 17 patients, and after local disease recurrence in 13 patients. Children with primitive neuroectodermal tumors, anaplastic gliomas, and ependymomas most frequently had LMS. Patients with primitive neuroectodermal tumors and posterior fossa anaplastic gliomas frequently had LMS before diagnosis or at the onset of relapse, whereas patients with ependymomas had LMS after local disease relapse. Both myelography and cerebrospinal fluid cytological examination are required to diagnose LMS.