Leptomeningeal dissemination of malignant gliomas. Incidence, diagnosis and outcome.

To understand the clinicopathology features of leptomeningeal dissemination of malignant gliomas, a total of 157 consecutive patients treated between 1978 and 1989 were analysed. Twenty-two patients (14%) were judged to have dissemination. In 20 patients, the dissemination was diagnosed antemortem. Eleven patients had neurological deficits due to dissemination, whereas the other 9 without these had CT or myelographic evidence of dissemination. The peak incidence of dissemination was seen in the first and second decades of life. The mean age of 22 patients with dissemination was 31 years, significantly lower than that (44.5 years) of patients without dissemination. Fifteen patients developed dissemination within one year after diagnosis (early dissemination), 60% of them were less than 30 years of age. All patients with late dissemination (more than one year after diagnosis) underwent a second craniotomy for tumour removal before dissemination, while none of the 15 patients with early dissemination did. Survival after diagnosis in patients with dissemination was shorter, although statistically not significant, than that of patients without dissemination. Survival after dissemination was limited in all patients (mean 19 weeks, range 2-39 weeks). Immunohistochemical study revealed that the disseminated tumour expressed less glial fibrillary acidic protein than the primary tumour. Our results suggest that dissemination does not seem to result from extended survival of the patients, but may occur at any time in malignant gliomas. Some malignant gliomas, especially in younger patients, have a capability to acquire biological characteristics suitable for dissemination in the earlier stage of the disease.