There are several categories of neurologic disease, the temporal profile of which mimic the cerebrovascular disorders. Migraine may do so, but the history usually provides the diagnosis. A seizure may be followed by a prolonged focal deficit (Todd paralysis) but is rarely the initial event in a stroke; the setting in which these symptoms occur and their subsequent course clarify the clinical situation. Tumor, infection, inflammation, degeneration, and nutritional deficiency are unlikely to manifest themselves precipitously, although rarely a primary or metastatic brain tumor produces a focal deficit of abrupt onset (see later). Trauma, of course, occurs abruptly but usually offers no problem in diagnosis. In multiple sclerosis and other demyelinative diseases, there may be an abrupt onset or exacerbation of symptoms, but for the most part they occur in a different age group and clinical setting. Conversely, a stroke-like onset of cerebral symptoms in a young adult should always raise a suspicion of demyelinative disease. A stroke developing over a period of several days usually progresses in a stepwise fashion, increments of deficit being added abruptly from time to time. A slow, gradual, downhill course over a period of 2 weeks or more indicates that the lesion is probably not vascular but rather neoplastic, demyelinative, infectious (abscess) or granulomatous, or a subdural hematoma.
In regard to the focal neurologic deficits of cerebrovascular disease, many of the nonvascular diseases may produce symptoms that are much the same, and the diagnosis cannot rest solely on this aspect of the clinical picture. Nonetheless, specific patterns of neurologic signs are so highly characteristic of vascular occlusion—for example, the lateral medullary syndrome—that they mark the disease as a stroke. Conversely, certain disturbances are hardly ever attributable to ischemic stroke—for example, diabetes insipidus, fever, bitemporal hemianopia, parkinsonism, generalized myoclonus, repeated falls, and isolated cranial-nerve palsies—and their presence may be of help in excluding vascular disease. Finally, the diagnosis of cerebrovascular disease should always be made on positive data, not by exclusion.
A few conditions are so often confused with cerebrovascular diseases that they merit further comment. Miscellaneous conditions occasionally taken to be a stroke are migraine; Bell palsy; Stokes-Adams syncopal attacks; a severe attack of labyrinthine vertigo; diabetic ophthalmoplegia; acute ulnar, radial, or peroneal palsy; embolism to a limb; and temporal arteritis associated with blindness all of which are discussed in later parts of this chapter.
A brain tumor, especially a rapidly growing glioblastoma or lymphoma, may produce a severe hemiplegia rapidly. Also, the neurologic deficit caused by cancer metastatic to the cerebrum may evolve rapidly, almost at a stroke-like pace. Moreover, in rare cases of brain tumor, a hemiplegia may be preceded by transitory episodes of neurologic deficit, indistinguishable from TIAs. The presence of the tumor and its effects on the cerebrum may make it difficult for the patient to articulate a clear history. A lack of detailed history may also be responsible for the opposite diagnostic error, that is, mistaking a relatively slowly evolving stroke (usually caused by internal carotid artery or basilar occlusion) for a tumor. CT and MRI usually settle the problem. A brain abscess or inflammatory necrotic lesion—for example, herpes encephalitis or toxoplasmosis—may also develop rapidly.