A 35 year-old right-handed white male was admitted to the hospital after a convulsion following changes in his antiepileptic drug regimen. He developed normally until 11 years of age when he experienced his first "grand mal" seizure. A brain MRI was normal and an EEG demonstrated "right temporal sharps". Partial epilepsy was diagnosed and treated with CBZ. Infrequent seizures with impaired consciousness occurred only "if he forgot to take his medication". Due to migraine headaches he was begun on VPA. 5 days later he had a breakthrough seizures prompting ED visitation. A CT was normal and a CBZ level was 3 ug/dl. He was given additional CBZ and VPA was discontinued. He quickly stabilized and returned to normal. An EEG next morning prior to discharge was performed with "ongoing seizure activity".
Figure: Scalp EEG demonstrating frequent left mid-termporal spike-and-wave discharges maximal at T3 with a broad regional temporal field. Recording parameters included an A-P longitudinal bipolar montage with central linked chain, sensitivity of 7 uV, display speed of 30 mm/sec and filters of 1-70 Hz.
The EEG supports the clinical diagnosis of epilepsy when interictal epileptiform discharges (IEDs) are present. Use of the term "seizures activity" does not represent ictal activity but as in our case interictal discharges. The distribution of IEDs helps to classify the epileptogenic zone. Discharges localized to the anterior and mid-temporal electrode derivations (as above) suggest one of the temporal lobe epilepsies. The intra-discharge frequency of generalized spike-and-slow waves (GSW) carries clinical ramifications with < 3 Hz a surrogate for encephalopathy and those > 3 Hz of presumed genetic origin. Epilepsy syndromes may be suggested by "faster" (> 3 Hz) frequencies as in JME where frequencies of up to 5 Hz are seen. High clinical seizure frequencies have previously been associated with a greater likelihood of detecting IEDs. However the relationship between IED frequency and clinical epilepsy severity is incongruent (1). Our patient had no impairment despite the high frequency of the IEDs and probably demonstrated the greater number of IEDs on EEG due to the recent seizure which has been found to have a higher incidence when EEG is obtained in the immediate post-ictal time period (2).
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