Wada memory asymmetry scores and postoperative memory outcome in left temporal epilepsy

BACKGROUND Memory asymmetry scores are used in intracarotid amobarbital procedure (IAP) to predict memory outcome after anterior temporal lobectomy (ATL) in patients with temporal lobe epilepsy (TLE). Reversed asymmetry (RA) of memory scores occurs in a minority of patients, with better memory performance observed following contralateral injection. Left ATL patients with RA are reported to have poorer postoperative verbal memory outcome. Studies also suggest that dysphasia during language dominant left hemisphere injection may contribute to lower right-sided memory scores seen in RA. PURPOSE To examine the role of dysphasia in RA and investigate the relationship between RA scores and memory outcome after ATL. METHOD IAP asymmetry scores and duration of speech arrest following bilateral IAP injection were examined in 50 patients with unilateral left TLE. Postoperative memory outcome was examined in a subset of patients (n=31). RESULTS Thirty-nine percent of patients had RA on IAP. The duration of speech arrest after left injection was significantly longer in the RA group compared to the expected asymmetry (EA) group. RA was not associated with negative postoperative memory outcome. CONCLUSIONS In left TLE patients, RA of IAP memory scores does not preclude good postoperative memory outcome. Prolonged speech arrest after left injection may lower right side memory scores contributing to misleading RA. Memory asymmetry patterns are sensitive to IAP protocol effects; therefore, RA may not be a robust predictor of memory outcome following left ATL.