Abstracts

Intracarotid amobarbital (IA) is widely used in determination of language and memory lateralization prior to epilepsy surgery. We have observed on a few occasions that the EEG during IA showed a rhythmic ictal-like pattern ususally with no associated clinical manifestations. The objectives of this study was to analyze the clinical characteristics of patients who developed this phenomenon.
Between 1999 and 2002, 26 patients underwent IA. Prior to the IA procedure all patients underwent a comprehensive presurgical evaluation including video-EEG monitoring and Neuropsychological testing. The dose of amobarbital varied between 75 to 125 mg, based on weight. During all IA injections EEG and video recording were performed. A retrospective chart and IA EEG review was performed. We searched for patients who developed a rhythmic ictal-like EEG pattern during the IA. Their clinical characteristics were compared to patients without this EEG pattern that served as a control group.
7 patients had an ictal-like evolving rhythmic sharp wave activity of 3-5 HZ throughout the injected hemisphere (5 ipsilateral to the side of injection with both left and right injection; 1 with injection of the side contralateral to seizure focus;1 with bilateral ictal EEG changes with injection of either side). Clinical signs were noted in one patient. These patients were younger (18 vs 36 p[lt] 0.001) and had shorter duration of epilepsy (6 vs 19, p[lt]0.01) compared to the control group.
In addition 7 patients had behavioral changes (5 agitation/combativeness, 2 confusion/obtundation) with injection of the side contralateral to the seizure focus. Six of these patients had no ictal like pattern on EEG. These patients were younger (25 vs. 36 years, p[lt]0.05), had shorter duration of epilepsy (8 vs. 19 years, p[lt]0.01) and had significantly lower IQ (68.57 vs. 83.93, p[lt]0.01), verbal IQ ( 68.00 vs. 85.86, p[lt]0.01) and working memory index (72.29 and 84.21, p[lt]0.01).
Using video-EEG monitoring during IA injetions, we observed rhythmic ictal-like EEG patterns ipsilateral to the IA injections in 27% of our patients with no relation to the side of the seizure focus. Whether these changes represent actual seizure activity remain uncertain. Younger age, shorter duration of epilepsy were predisposing factors.
Behavioral changes such as agitation and lethargy noted during IA were usually unrelated to the ictal-like EEG patterns but were seen also in the younger patients with lower IQ and developental delay.
We believe that video-EEG evaluation can add valuable information to the interpreation of the IA assesment, particularly in younger patients with impaired cognition, predisposed to behavioral changes during IA injection.