Dichotic-listening performance and intracarotid injections of amobarbital in children and adolescents. Preoperative and postoperative comparisons
K. Hugdahl, G. Carlsson, P. Uvebrant and A. J. Lundervold
Department of Biological and Medical Psychology, University of Bergen, Norway. hugdahl@psych.uib.no
BACKGROUND: Dichotic listening (DL) to consonant-vowel syllables is
frequently used in clinical and experimental studies of brain laterality.
However, the paradigm of consonant-vowel syllables has not been thoroughly
validated through a comparison with injections of amobarbital sodium
(Amytal). OBJECTIVE: To validate the DL test for hemisphere dominance
preoperatively vs postoperatively with the results from intracarotid
injections of amobarbital (i.e., the Wada test) in epileptic children and
adolescents. DESIGN AND MAIN OUTCOME MEASURES: Patients were tested with DL
preoperatively and at 6-month follow-up. Correct reports in the DL tests
were entered in a stepwise discriminant analysis for calculation of correct
classification of hemisphere dominance with the results from the injections
of amobarbital as the grouping variable. Correct reports from the right and
left ears on the consonant-vowel DL test were compared preoperatively and
postoperatively, separated for the subjects with regard to language
dominance in the left and right hemispheres. SETTING: The Department of
Pediatrics, Ostra Hospital, University of Goteborg, Goteborg, Sweden.
PATIENTS: Thirteen children and adolescents between the ages of 10 and 19
years, who were surgically treated for resistant epilepsy, were included in
the study. The operated area corresponded with morphological changes and
functional dysfunctions according to findings from computed tomography,
magnetic resonance imaging, single photon emission computed tomography, and
electroencephalography. RESULTS: The results of the Wada tests revealed
that 10 subjects had left hemisphere language dominance, with 3 subjects
having right hemisphere language dominance. All 3 subjects with right
hemisphere language dominance showed a left ear advantage on the DL test
preoperatively and postoperatively, with 8 and 7 of the 10 subjects with
left hemisphere dominance showing a right ear advantage, preoperatively and
postoperatively, respectively. However, according to discriminant analysis,
knowledge of the DL performance led to a correct classification according
to the Wada test results in 12 (92%) of the 13 subjects. CONCLUSIONS: A
quantitative classification procedure like discriminant analysis may be
more sensitive when predicting hemisphere speech dominance from DL data
than a qualitative procedure based on the ear advantage dichotomy. The ear
advantage dichotomy may actually introduce arbitrary left-right categories
that do not correspond to the actual clustering of the data.
