Abstracts

Rationale: Patients with medical intractable epilepsy undergo WADA test for evaluation of memory reserve of the contralateral temporal lobe. Transient shivering during the WADA procedure is thought to be related to perfusion of the anterior circulation, transiently removing the tonic inhibition of the anterior thermoregulatory center due to drug effect. It is also believed that hippocampus is perfused primarily by the posterior circulation and effects just on the anterior circulation of the sodium amytal may be inadequate to properly test hippocampal memory function. We hypothesize that if the shivering occurs during WADA test, it suggest only effect on the anterior circulation, and the memory score will be higher. In case the effect is on anterior and posterior circulation, then the memory score will be affected. Methods: A retrospective chart review of the information on patients undergoing WADA test for pre surgical evaluation for epilepsy surgery was performed. Presence of shivering and memory score on each injection was recorded. Statistical analysis was done to determine the factors that influence the memory score, including dominance of the hemisphere and side of seizure onset. Results: A total of 208 consecutive injections in 104 patients were included in our study. We created two groups: shivering and non-shivering. Shivering was noted after 62 injections. A difference between memory score in shivering group was significantly higher (p=0.02) compared to the non-shivering group. When we divided patients into concordant side of seizure onset (unilateral only) and shivering versus discordant side of onset and shivering, we found no effect on memory performance (F(1,68)=0.04, p=0.84, n.s.). Conclusions: Patients with shivering during the WADA suggest that posterior circulation was not affected with effects from sodium amytal and the effect on memory will be limited, memory score will be higher. Thus, shivering can be used as a surrogate for inadequate effect on the hippocampus and raises the concerns about reliability of the WADA memory score.