Giant Somatosensory Evoked Potentials Coincident With Epileptiform Discharges in Acutely Comatose Patients.
BACKGROUND
The amplitude of the cortically generated somatosensory evoked potential (SSEP) is used to predict outcome in comatose patients. The relationship between epileptiform discharges and SSEP amplitude has not been elucidated in those patients.


METHODS
Bilateral median nerve SSEP and electroencephalograph (EEG) studies were performed in a comatose patient (patient 1) 1 day after cardiac surgery and repeated 4 days later. He had tranexamic acid administered before and during surgery. Another comatose patient (patient 2) had the same studies performed 1 day after sustaining 10 minutes of pulseless electrical cardiac activity.


RESULTS
Both comatose patients had epileptiform discharges (on EEG) that were coincident with giant cortically generated SSEPs. In patient 1, the EEG and SSEP studies repeated 5 days postoperatively showed no epileptiform discharges, and the cortically generated SSEP amplitude was decreased (normalized) compared with that obtained one day postoperatively. He emerged from coma and had a good recovery. Patient 2 died shortly after EEG and SSEP testing.


CONCLUSIONS
Epileptiform discharges were associated with giant cortically generated median nerve SSEP amplitude (tranexamic acid was implicated in patient 1 and anoxic brain injury in patient 2). Accordingly, those who use the amplitude of cortically generated SSEPs for predicting outcome in comatose patients should consider the presence of epileptiform discharges (detected by EEG) as a potential confounding factor.
1Department of Medical Imaging,The Ottawa Hospital,Ottawa,Ontario,Canada.
David A
DA
Houlden
2Department of Medicine,Neurology,Sunnybrook Health Science Centre,Toronto,Ontario,Canada.
Mark I
MI
Boulos
2Department of Medicine,Neurology,Sunnybrook Health Science Centre,Toronto,Ontario,Canada.
Brian J
BJ
Murray
3Clinical Neurological Sciences,University of Western Ontario,London,Ontario,Canada.
Loretta
L
Norton
3Clinical Neurological Sciences,University of Western Ontario,London,Ontario,Canada.
G Bryan
GB
Young
D000208:Acute Disease; D000369:Aged, 80 and over; D003128:Coma / Q000150:complications*; D004569:Electroencephalography; D004827:Epilepsy / Q000209:etiology*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006323:Heart Arrest / Q000150:complications; D006801:Humans; D008297:Male; D014057:Tomography, X-Ray Computed
Brain hypoxia; electroencephalography; neurophysiology; seizures; somatosensor; somatosensory evoked potentials