AUTONOMOUS VERSUS DEPENDENT - A CLASSIFICATION OF BILATERAL LANGUAGE REPRESENTATION BY INTRACAROTID AMOBARBITAL PROCEDURE

Many studies have reported and analyzed the results of the intracarotid amobarbital procedure (IAP). Our study objective was to investigate bihemispheric language representation. We retrospectively reviewed the results of 165 IAPs performed in the evaluation of candidates for epilepsy surgery. Language function was assessed primarily by the duration of speech arrest. Three different sets of criteria were used: absolute duration, side-to-side difference, and laterality index. Only subjects whose dominance for language was classified as bilateral by two of the three methods were considered bilateral. There were 126 (76%) patients with language representation only in the left hemisphere, and 20 (12%) had language representation only in the right. Nineteen patients (12%) had evidence of speech in both hemispheres. Of these 19, 10 demonstrated return of speech soon after each injection; the remaining 9 patients demonstrated prolonged speech arrest after both injections. We conclude that two distinct patterns of bilateral language representation may exist: one in which each hemisphere is dependent on the other (''bilateral dependent'') and one in which each hemisphere can support language independently (''bilateral autonomous'').