Mixed speech dominance in the Intracarotid Sodium Amytal Procedure: validity and criteria issues.

An international survey was conducted of 55 epilepsy surgery programs (from 10 countries) that conduct the Intracarotid Sodium Amytal Procedure (IAP). Respondents reported large differences in the prevalence of mixed speech dominance (MSD) in their patient populations. These differences are shown to be due in part to disagreement about the criteria for the demonstration of speech production from the non-speech-dominant hemisphere. The disagreement may be related to differences in the administration and interpretation of the IAP as well as the validity of the construct of MSD. The prevalence of MSD in various patient populations cannot be determined until standard procedures for the administration of the IAP are adopted and until the validity of criteria for MSD is demonstrated. Clinical implications of these results are discussed.