Abstracts

Rationale: The relevance of IAP has been a topic of debate over the years and the use of this procedure has significantly decreased, mainly because it poses risk factors and concerns with reliability and validity. Another controversy has been the anatomical cerebrovascular variability among patients putting in question the intracranial brain structures affected during IAP since the internal carotid artery only supplies the anterior hippocampus via the anterior choroidal artery. The hippocampus is mainly irrigated by the vertebrobasilar system supplied by the posterior cerebral artery. Thus the hippocampus may potentially be unaffected by an ICA injection. Memory impairment is hypothesized to be due to lateral cortical inactivation only. We demonstrate in two patients that sodium amytal injection does inactivate hippocampal structures as injection occurred with intracranial EEG monitoring. Methods: Two medically refractory patients with focal seizure and secondary generalization had IAP with intracranial electrodes implanted along the axis of the hippocampus, as well as over the lateral temporal cortex. One patient had left and the other right-sided mesial temporal sclerosis as well as hippocampus atrophy. Both patients had bilateral hippocampal and temporal lateral electrodes implanted. IAP was performed on both sides in patient one, and only on the left side in patient two according to clinical requirements. Results: In both patients there was clear suppression patterns in the hippocampal structures, that also involved the anterior portion of the hippocampus. Slow wave activity was increased. Slowing and burst suppression also occurred over the lateral temporal structures, implicating that both medial and lateral temporal structures are involved during IAP. This indicates that large memory networks are inactivated during the test and that IAP testing is valid for hippocampal function. Conclusions: IAP definitely inactivates the hippocampal structures, however inactivation is widespread and also involves large areas of the cortex. Our case series shows that IAP is valid for memory testing.