Abstracts

Rationale: Burst-suppression (BS) consists of periodic bursts of high-voltage slow waves and sharp waves in the electroencephalogram (EEG), alternating with attenuation of the background activity. Typical bihemispheric BS, whether pharmacologically-induced or secondary to encephalopathy, is often viewed as a non-epileptic phenomenon. On the other hand, unihemispheric BS is rare and its clinical significance is poorly understood. Methods: Two patients whose initial EEG tracings showed unihemispheric BS underwent continuous EEG monitoring in the intensive care unit. Patient-1 is a 56-year-old woman with a left temporoparietal tumor who presented in convulsive status epilepticus. Her EEG showed left hemispheric BS after clinical seizure termination with lorazepam and propofol. Patient-2 is a 39-year-old woman with multiple medical problems and a vague history of seizure disorder. After undergoing abdominal surgery, she experienced a convulsive seizure prompting treatment with propofol. Her EEG showed left hemispheric BS. Results: In both cases, titration of propofol resulted in disappearance of unihemispheric BS. The brain MRI of Patient-1 showed a mass lesion in the left anterior parietal area predominantly involving the white matter and the deep diencephalic structures with mass effect. The brain CT of Patient-2 showed left hemispheric encephalomalacia predominantly involving the left posterior parietal lobe. Both patients improved and were discharged from the hospital. Conclusions: The prevailing view that typical bihemispheric BS is a non-epileptic phenomenon should not be automatically extrapolated to unihemispheric BS. In the two cases presented, clinical seizures occurred and unihemispheric BS resolved easily with propofol, suggesting that an epileptic mechanism may be responsible for unihemispheric BS.