Abstracts

RATIONALE: Patients undergoing the Intracarotid Amobarbital Procedure (IAP) are often amnestic for the display of memory items and fail to recall any of the displayed items spontaneously. The purpose of this study was to determine if the occurrence of this phenomena provides any information additional to that provided by recognition memory scores themselves, especially in instances where the subsequent memory scores for both hemisphere are good.
METHODS: A retrospective review of 156 of the most recent IAPs performed at our center identified 28 patients who experienced amnesia for the display of stimuli and complete failure of spontaneous recall on one or both injections, with subsequent memory scores in both hemispheres greater than or equal to 8/12. All of these patients had a diagnosis of medically refractory partial epilepsy and underwent the IAP as part of a comprehensive presurgical work-up. During the IAP, memory for 8 objects and 4 line-drawings was evaluated through an initial evaluation of the patients memory for the display of items and spontaneous recall of the displayed items, followed by yes/no recognition testing. Variables examined for predictive value included gender, education, handedness, location of the seizure focus, age of onset, contralateral recognition memory scores, and language dominance.
RESULTS: 24 (85.7 %) of the 28 patients identified displayed amnesia for stimulus display and complete failure of spontaneous recall after injection of one hemisphere only. Of these, 23 (95.8%) instances occurred on injections contralateral to the patients seizure focus (12 with left and 11 with right hemispheric foci). The one exception was a patient with non-lateralizing presurgical data, awaiting an intracranial bilateral strip study. None of the other demographic or IAP variables examined, including contralateral hemispheric memory score were statistically significant predictors of failure of spontaneous recall in this group of patients. Of the 4 patients who displayed the phenomenon on injections of both hemispheres, 3 had Video-EEG and imaging data that did not clearly lateralize the seizure focus, and one patient had clear evidence of left mesial temporal sclerosis but failed surgical resection of the focus (Engel[scquote]s Class II outcome).
CONCLUSIONS: Amnesia for the display of memory items with complete failure of spontaneous recall is indicative of a significant dysfunction in the contralateral hemisphere, even when the recognition memory scores do not suggest this. Instances where this occurs bilaterally should alert the clinicians to the possibility of bilateral independent seizure foci.