Anaplastic oligodendroglioma, WHO grade III, status post treatment. There are postoperative findings related to left craniotomy with a resection cavity in the left frontal and temporal lobes and a persistent overlying extra-axial fluid collection. There is intrinsic T1 hyperintensity and susceptibility effect along the posterior margins of the surgical cavity, with development of superimposed patchy enhancement superficially along the posteromedial margin of the resection cavity. There also appears to be slightly increased confluent T2 hyperintensity in the surrounding brain parenchyma. There is also interval development of high T2 signal and enhancement in the anterior cingulate region and along the straight gyri with adjacent gyriform mildly restricted diffusion and T2 hyperintensity. There is also diffuse enhancement along the surfaces of multiple cranial nerves and brainstem, cerebellum, including along the surfaces of the fourth ventricle. There is an unchanged subcentimeter area of T2 hyperintensity superficially along the lateral aspect of the right occipital lobe. The ventricular system and a subcentimeter arachnoid cyst in the right posterior cingulate region appear unchanged. There is no midline shift or herniation. The major cerebral flow voids are intact. The orbits are grossly unremarkable.
Post-treatment findings in the left the left frontal and temporal lobes without what may represent incipient local tumor progression and apparent cerebrospinal fluid dissemination to the anterior frontal lobe regions bilaterally, as well within the posterior fossa and along multiple cranial nerves. The leptomeningeal disease in the frontal regions may be associated with a vasculitic ischemic effect.