EEG in brain abscess: its value in localization compared to other diagnostic tests.

The EEG records of 13 cases of brain abscess were reviewed for their value in localization. Of the 11 cases of supratentorial abscesses localization was achieved in 10, and correct lateralization in the remaining 1 case. Two other cases were cerebellar abscesses; 1 of them showed a false cerebral localization; the other showed no focal abnormalities. The most consistent EEG localizing sign was focal arrhythmic delta waves. These were as slow as 0.5 c/sec in 6 of the 13 cases. Epileptiform discharges in the pre-operative EEG were seen in 4 of the 13 cases. Asymmetry of beta activity correctly lateralized the abscess in 7 of the 11 supratentorial abscesses. Generalized abnormalities when present correlated with depression of consciousness rather than with the duration of illness or the presence of raised intracranial pressure. Indium brain scans were done in 6 supratentorial abscesses and provided correct or approximate localization in 5. Carotid angiograms were also done in 7 cases and localized the abscess in 6. Our findings show that the EEG is comparable to brain scans and contrast radiological studies in localizing supratentorial abscesses. We feel that the combination of EEGs and brain scanslization in suspected brain abscess.