What is indicated by focal or unilateral suppression and slowing on an EEG?

Focal or unilateral suppression and slowing on an EEG is primarily indicative of localized brain dysfunction, which can occur in various conditions. One significant condition associated with these EEG findings is a subdural hematoma. A subdural hematoma occurs when there is bleeding between the outer protective covering of the brain and the surface of the brain itself, often due to trauma. This bleeding can create pressure on specific areas of the brain, leading to reduced electrical activity (suppression) and slower brain waves in the affected hemisphere, which is reflected in the EEG.

In contrast, generalized seizure disorders typically present with widespread abnormal electrical activity, affecting both hemispheres rather than causing localized suppression and slowing. Drowsiness in an elderly patient might show generalized slowing but wouldn’t typically demonstrate focal suppression. Renal failure can lead to generalized changes in an EEG due to metabolic disturbances but does not usually cause focal or unilateral findings. Therefore, the presence of focal or unilateral suppression and slowing clearly aligns with the pathophysiological effects of a subdural hematoma.