The EEG in Cerebral Edema

Summary

The freezing lesion used to induce cerebral edema leads to epileptic changes in the EEG probably unrelated to cerebral edema. This makes the freezing lesion inappropriate in studies to evaluate the EEG effects of cerebral edema.

Local cortical coagulation lesions produced cerebral edema without clinical or electrographic evidence of epilepsy.

Moderate amounts of cerebral edema of vasogenic variety do not produce delta activity in the EEG. With massive amounts of edema, delta activity was present, but was seen only in animals without a wide craniectomy. It was probably secondary to midbrain and diencephalic disturbances resulting from increased volume of the brain rigidly contained within the cranial cavity.

Cerebral edema has both clinical and electroencephalographic effects and monitoring these effects in experimental studies is feasible, although techniques of inducing very large amounts of edema without decompression of the brain would be necessary to consistently produce EEG and clinical changes.