A review of electroencephalograms done at the Kenyatta National Hospital, Nairobi.

Background: Electroencephalogram based studies done elsewhere suggest that epileptiform activity originates predominantly from the left cortical hemisphere. There is evidence that partial epilepsies (focal spike and wave epileptiform discharges on tracings) connotes focal; secondary structural cortical dysfunction. Studies seeking similar findings have not been done locally.

Objective: To review electroencephalograms (EEGs) done at Kenyatta National Hospital (KNH); looking for various types of epileptiform discharges and their cerebral cortex of origin.

Design: Retrospective observational study.

Setting: Kenyatta National Hospital, Nairobi, Kenya--from January 1986 to June 2004.

Results: A total 10431 EEG records were reviewed. Ninety Eight percent of referrals for EEG evaluation was for clinical differential diagnosis of epilepsy. Abnormal EEGs comprised 32.2% of the study population. Epileptiform abnormalities (i.e. focal spike and wave, generalized spike and wave and 3Hz spike and wave) discharges accounted for 75.2% of all abnormal EEG waveform discharges. Of the epileptiform abnormalities, focal spike and wave discharges comprised 71%. Focal spike and wave discharge implies a possible secondary aetiology of epilepsy. The left cerebral hemisphere was the origin of 49.8% of focal spike and wave epileptiform EEG discharges. Multifocal loci in cerebral cortices (i.e. frontal, temporal and parietal) were the foci of origin of abnormal EEG waveforms in 69.9% of recordings.

Conclusion: Focal spike and wave epileptiform discharges, with attendant likely secondary aetiology of epilepsy is predominantly evident in this study. It contrasts findings from western literature. The left cerebral hemisphere is more epileptogenic as is noted in other studies.