ABSTRACT
Three main non-neoplastic lesions should be considered in the differential diagnosis. The first is ischemic infarction. Older patients with intracranial tumors often present with transient symptoms presumably due to seizures. Unlike the short-lived focal seizures occurring with other epileptogenic lesions, these episodes may last many minutes to hours, are often associated with abnormalities of cognition and behavior, and typically cause ‘negative’ signs, e.g. hemiparesis, but not typical tonic-clonic seizure activity. Because of their length, they may be confused with transient ischemic attacks or even small resolving cerebral infarcts. A CT scan without contrast may show an area of hypodensity that is interpreted as cerebral infarction. However, CT hypodensity associated with intrinsic brain tumors is usually restricted to white matter and does not involve cortex. On the contrary, cerebral infarction is generally triangular-shaped with the base at the cortical surface. A contrast-enhanced MR scan often, but not always, establishes the diagnosis. Hyperintensity on a diffusion-weighted MRI is characteristic of acute ischemia, but we
have often encountered a similar finding in brain tumors. Subacute infarcts that prominently enhance can also be difficult to differentiate from a tumor. Often, the clinical history, pattern of enhancement (i.e. ribbonlike following cortical gyri) and surrounding edema (little in subacute infarct, much in brain tumor) help clarify the diagnosis.
