An informed differential diagnosis requires analyzing the imaging features in the context of the clinical presentation of the patient. A wedge-shaped cortical lesion, involving both gray and white-matter, presenting with an acute neurologic deficit is probably an ischemic infarction. Multiple cortical/subcortical round nodular enhancing lesions are likely metastatic. Large deep white-matter masses suggest a diffuse glioma: with heterogenous enhancement likely glioblastoma, while similar lesions without enhancement may be a lower-grade (WHO2,3) astrocytoma. Oligodendroglioma looks similar, but adds conglomerate calcifications. In contrast, largely fluid lesions with enhancement limited to a mural nodule are usually circumscribed gliomas—amenable to surgical extirpation. The most common extraaxial masses are meningioma and vestibular schwannoma. Schwannomas characteristically arise within the internal auditory canal, then spread into the cerebello-pontine angle cistern of the posterior fossa. Most meningiomas are supratentorial, around the cerebral hemisphere convexity.
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