STIMULUS TIMING EFFECTS ON WADA MEMORY TESTING

Objective: To determine the effects of presenting Wada memory stimuli at different times after intracarotid amobarbital injection on Wada me mory asymmetries. Design: Wada memory asymmetries from three timing se ries were related to the laterality of eventual temporal lobectomy. Se tting: Academic institution epilepsy surgery program. Patients: Forty- three patients with complex partial seizures who later underwent anter ior temporal lobectomy (left temporal lobectomy, 24 patients; right te mporal lobectomy, 19 patients). No patient included had abnormalities on magnetic resonance imaging scans to suggest a lesion other than gli osis. Results: Memory performance for objects whose presentation began approximately 45 seconds after amobarbital administration differentia ted laterality of seizure onset. Memory for items presented later and after partial return of language (on average 3 minutes 40 seconds post injection) also differed as a function of ipsilateral vs contralateral injection, but at a lower level of statistical significance. Memory f or items presented last during the procedure (on average 6 minutes pos tinjection) discriminated seizure groups at a still lower level of sta tistical significance. When used to predict lateralized temporal lobe impairment in individual patients, early object memory performance was significantly better than memory performance employing either middle (56%) or late (43%) stimulus presentation timings. Conclusion: The res ults of early object memory testing are superior to those obtained fro m stimulus presentation later in the procedure in documenting temporal lobe dysfunction associated with a lateralized seizure onset.