Abstracts

RATIONALE: To determine the relationship between MRI hippocampal volumetric and T2 relaxometry data, and Wada test performances in temporal lobectomy candidates. OBJECTIVE: At the end of this presentation participants should be able to discuss relationships between hippocampal MRI data and Wada memory testing.
METHODS: Left hemisphere language dominant temporal lobectomy candidates underwent Wada testing and MRI examinations including volumetric and quantitative T2 pulse sequences. Patients underwent a comprehensive presurgical evaluation including neurologic and neuropsychological examinations, and prolonged EEG/Video monitoring. Follow-up neuropsychological testing was completed approximately 4 months after surgery.
Wada testing utilized 100 mg. of amobarbital diluted in 10 cc. of sterile water introduced into the internal carotid artery via transcutaneous femoral catheterization. Eight objects were presented after confirmation of hemiparesis, and a recognition trial with 16 foils was conducted 10 minutes after the last object presentation. Incorrect recognitions were multiplied by .5 and subtracted from correct Wada recognitions. The side ipsilateral to the ictal focus was usually injected first followed by the contralateral injection at least 25 minutes later.
RESULTS: In Right TLE patients the right hippocampal body (r = .43, n = 26) and tail (r = .41, n = 26) segments were correlated with the left injection memory. Correlations with hippocampal T2 values and the difference between hippocampal volumes were not significant. In Left TLE patients the right injection memory was correlated with the left hippocampal body T2 signal (r = -.36, n = 39) and difference between hippocampal volumes (r = -.34, n = 39).
Backward stepping muliple regression analyses identified preoperative AVLT delayed memory (partial r = .36) and right Wada memory (partial r = .54) as the two predictors of postoperative AVLT delayed verbal recall in Left TLE patients. In Right TLE patients preoperative delayed verbal memory from WMS-R Logical Memory (r = .67) and the right injection Wada memory (r = .46) were the best predictors for postoperative Logical Memory delayed recall.
CONCLUSIONS: Wada memory testing including left and right internal carotid amobarbital injections accomplished on the same day is significantly associated with quantitative MRI hippocampal volume and T2 measurements. Individual, i.e. left or right, internal carotid amobarbital injections for Wada memory testing are correlated with verbal memory outcomes in both right and left temporal lobectomy patients. In Left TLE patients, these results suggest that injection of amobarbital into the right internal carotid artery to measure functional adequacy of structures ipsilateral to ictal onset predicts verbal memory outcome. The data do not support right hippocampal functional reserve as a direct predictor of postoperative verbal memory change. Wada testing provides information concerning risk for verbal memory decline after temporal lobectomy in addition to information that is provided by MRI data.
[Supported by: R55 NS28374 from the National Institutes of Health Awarded to C.R. Jack, Jr., M.D.]