Grossly, the brain is atrophic, chiefly the frontal lobes. The leptomeninges are thickened and adherent to the cortical surface. The ventricles are dilated. Histologically, the leptomeninges are infiltrated with lymphocytes and plasma cells. Perivascular infiltrations are found in the cerebral cortex and subcortical gray structures.
Most mycotic infections are opportunistic.
They develop in patients who receive long-term antibiotics, cytotoxic drugs, or immunosuppressive drugs, in organ transplant recipients, AIDS patients, and IV substance abusers. The primary infection is usually in the lungs and dissemination is hematogenous. The fungus produces a subacute or chronic meningitis. From the subarachnoid space, the yeasts may extend into the brain parenchyma along the perivascular space. Here they expand and create a soap-bubble appearance.