Serial Electroencephalography in Vascular Lesions of the Brain

Abstract

The initial changes after a vascular insult to the brain depend upon the localization of the lesion and upon associated phenomena such as vasospasm and edema. With a superficial lesion, delta activity is prominent, but minimal or absent in deep subcortical lesions. Rapid resolution (2-5 days) is seen in cerebral vasospasm. In cerebral edema secondary to a thrombotic lesion, there may be increasing delta activity which usually begins to resolve within 10-14 days. Resolution of delta activity in a regressive lesion such as thrombosis or embolus is usually complete by the 3d mo. but varies with the size and severity of the lesion. Serial changes in amplitude asymmetry occur but are usually stable by the 6th mo. In the 1st week, with or without a delta focus, there is almost universal voltage reduction ipsilateral to the lesion. This may be replaced by 1 or more phases of increased amplitude each usually lasting 7 to 14 or more days. Increased voltage usually does not appear until after resolution of slow activity. Permanent ipsilateral voltage reduction is usally present by the 6th mo. In a regressive lesion, the presence of delta activity indicates that further organic improvement is possible, hence a guarded prognosis. Absence of delta activity in the presence of neurologic defect indicates either a deep lesion (such as brain stem or internal capsule) or that max. recovery has occurred, hence indicating poor prognosis for further functional recovery.