Abstracts

The evaluation of patients with intractable epilepsy for surgery includes video-monitoring, MRI brain, NP evaluation and the Wada test for evaluation of language and memory function. A cerebral angiogram is done prior to Wada test to assess the hemispheric blood flow. Paresis of the contralateral arm indicates an adequate injection and interruption of language will indicate language dominance. Memory items are presented during this phase. Memory for information presented during this phase is assessed after return to the baseline, which usually occurs after 5-10 minutes with Amobarbital. The second hemisphere is then studied similarly after app. 30 minutes. Use of Amobarbital for this procedure is well established. Due to the shortage in supply of Amobarbital at the Cleveland Clinic, Methohexital, a very short acting barbiturate has been in use since March of 2001. Since then, app. hundred patients have received this medication for Wada test.
The purpose of this study is to investigate the effectiveness of Methohexital as an anesthetic agent for memory and language testing and to correlate this with MRI findings and the side of epilepsy. Its short life enables it to be used as a sedative agent for minor procedures in children, but there are only two studies in the literature regarding its effectiveness as an agent for the Wada test.
We selected 20 consecutive patients with definite evidence of unilateral mesial temporal sclerosis (MTS) on MRI and both interictal and ictal findings localized to the same temporal lobe as the MTS on MRI. We excluded patients with extra temporal epilepsy, tumors, AVM, and bilateral hippocampal atrophy among 107 consecutive patients who underwent Wada testing at the Cleveland Clinic between March of 2001 to March of 2002. We studied the correlation of their memory scores with the side of MTS on MRI and epilepsy. In addition 17/20 patients had neuropsychological testing and the results were compared with the findings on the Wada test .
The mean age of the 20 patients was 35+/- SD 12 yrs. Seventeen patients were right handed, one patient was left handed and two patients were ambidextrous. Language was localized on the left side in 15 of 17 right handed patients, both ambidextrous patients and one left handed patient. Language was bilateral in two right handed patients. 12/20 patients had epileptic foci based on interictal and ictal EEG findings in the right temporal lobe and 8/20 patients in the left temporal lobe.
12/20 patients had poor memory scores on the side of their MTS and epileptic foci (concordant). In 3 patients the poor memory scores were discordant with the side of MTS and epilepsy and in 4/20 patients memory was intact bilaterally. One patient had poor interpretation of the test because of prolonged aphasia.
Wada test using Methohexital is a good predictor of memory function and can be used as a substitute for Amobarbital in combination with the neuropsychological testing.