Factors Affecting Impaired Reaction in Wada Test

Seo, Dae Won; Na, Duk L

Abstract

BACKGROUND: The Wada test is an essential part of the preoperative evaluations in candidates for epilepsy surgery. Impaired reactions (IR) to intracarotid sodium amytal infusions include: confusion, disorientation, and decreased respon-siveness, thereby confounding test results. We retrospectively analyzed the factors affecting the impaired reactions (IR) regarding both individual and methodologic factors.
METHODS
Subjects included 202 patients (age;28.5+/-9.48, range:8 to 64 years, M:F=113:89) with intractable epilepsy. Patients with IR (IR group) and those without IR (Non-IR group) were compared with respect to individual factors such as: age, sex, epilepsy syndromes, injected hemispheres, dominan-cy as well as methodologic factors including amobarbital doses. With regards to the dose of amobarbital, the total accu-mulated dose as well as the initial injected dose, were used.
RESULTS
IR was observed in 50 patients (24.7%). Compared to the non-IR group, the IR group had more prolonged, contralateral weakness and total test times, but the same duration of EEG changes. IR occurred more frequently with injections into the left hemisphere (p<0.001), the dominant hemi-sphere (p<0.0001), and contralateral hemisphere of epileptic focus (p<0.07). The IR group received significantly higher amounts of amobarbital than the non-IR group (p<0.05). Considering the oversedation as well as the undersedation of amobarbital together, 100mg of amobarbital was the most appropriate dose in the Wada test.
CONCLUSIONS
These results suggest that dominant hemisphere injections and usage of higher doses of amobarbital can frequently produce IR in the Wada test. The ideal dose of amobarbital in the Wada test for Korean patients should be 100mg.