Computed tomography in leptomeningeal spread of tumor.

Computed tomography proved insensitive to leptomeningeal spread of hematologic malignancies including leukemia, lymphoma, and malignant histiocytosis. In only 3% of patients did it directly demonstrate leptomeningeal tumor. In comparison, the detection rate of leptomeningeal tumor secondary to carcinoma was 44% and for melanoma, 100%. Intracranial subarachnoid seeding from primary brain gliomas was detected in each instance. The simultaneous presence of parenchymal metastases with leptomeningeal carcinomatosis occurred in 18% of patients with nonhematologic malignancies. Computed tomography evidence of communicating hydrocephalus, previously thought to be a major factor in clinical symptomatology, occurred in only 11% of patients.