Background and objective: The intracarotid amobarbital procedure, or
Wada test, is the method of choice to determine hemispheric
representation of language, and is routinely used in the presurgical
evaluation for intractable epilepsy. Some investigators perform
comprehensive language assessments, but others base language
lateralization solely on speech arrest. This study sought to determine
whether speech arrest alone during Wada testing provides valid data
regarding language lateralization. Methods: The subjects (previously
reported) were 21 patients evaluated for intractable epilepsy, who
underwent language lateralization by Wada testing and functional MRI
(FMRI). For each patient, language representation was determined by
calculating: (1) a Wada laterality index based exclusively on speech
arrest; (2) a Wada laterality index based on comprehensive language
assessment; and (3) an FMRI laterality quotient. Correlation
coefficients and categorical classifications were analyzed. Results:
There was no significant correlation between the Wada laterality
quotient derived from duration of speech arrest and either the
comprehensive Wada language laterality score (r= .35, p= .12) or FMRI
language laterality score (r= .32, p= .16). Categorical classification
as left, right or bilateral language also showed marked discordance
between speech arrest and the other two methods. Conclusion: Duration
of speech arrest during Wada testing is not a valid measure of
language dominance.