The central nervous system in childhood leukemia: I. The arachnoid

Abstract

A histopathologic study was performed to evaluate the distribution and extension of intracranial leukemic infiltrates and their relationship to other morphological disturbances of the central nervous system (CNS) in childhood acute lymphocytic leukemia. Of 126 brains examined, 70 had arachnoid leukemia at the time of autopsy. The earliest evidence of leukemia was seen in the walls of superficial arachnoid veins. With more advanced arachnoid leukemia, the disease was seen to extend into the deep arachnoid surrounding blood vessels as they course through the brain. The arachnoid leukemia followed a predictable expanding pattern to eventual invasion of brain parenchyma with destruction of the pia-glial membrane. Leukemic infiltrate at the capillary-neural tissue interface was present only following destruction of pia-glial membrane secondary to deep arachnoid leukemia. Arachnoid fibrosis and certain brain parenchymatous lesions were found in association with arachnoid leukemia. The brain lesions included gliosis, necrosis, cerebral hemorrhage, and nonhemorrhagic degenerative encephalopathy. This study demonstrates that CNS leukemia is primarily an arachnoid disease. Disturbances of brain parenchyma apparently result from leukemic extension through pia-glial membrane or interference with local perfusion due to constriction of blood vessels by perivascular arachnoid leukemia.