Abstracts

Dichotic listening tests are a valuable tool as an initial gauge of cerebral dominance for language in the presurgical evaluation of patients with epilepsy. The Wexler-Halwes Dichotic Fused Words test (FW) is believed to provide a sensitive estimate of speech dominance, but it has been difficult to translate (as a rhymed fused words test) into other languages. Thus it is necessary to administer it in English to all patients, and its validity in non-anglophone populations is unknown., We compared FW scores for 100 anglophone and 100 francophone right-handed patients who had been considered so likely to have typical, left-hemisphere speech representation that an intracarotid amobarbital procedure (IAP) was not necessary. Subsequently, we examined a series of 60 patients in whom speech dominance was documented by IAP, and compared their FW scores as a function of language (English or French) and speech lateralization (left, N=20 in each language group, vs. right, N=10 in each language group)., On verbal dichotic listening tests, individuals with left-hemisphere speech dominance are expected to hear more items correctly with the right ear. On the Wexler-Halwes FW test, 85% of healthy volunteers show this right-ear advantage¹. In our large right-handed sample, 89% of anglophones and 83% of francophones showed a right-ear advantage, with no difference according to language group. However, the percentage of those with a clinically meaningful difference (arbitrarily defined as right ear minus left ear score of 10 or more) was higher in anglophones (68%) than in francophones (52%), p=0.02. In the sample of patients with confirmed speech lateralization, distribution of the FW scores did not differ between the two language groups. Sixty-five percent of patients in both language groups with documented left-hemisphere speech showed a meaningful right-ear advantage, and most patients with right-hemisphere speech displayed the expected left-ear advantage (100% of francophones and 90% of anglophones)., Results obtained with the Wexler-Halwes Fused Words test are very stable, as we found the same percentage of right-ear advantage in our right-handed patients as reported for healthy volunteers in the original paper¹. Although it is a good screening test for atypical cerebral dominance, it does yield some false positive results (failure to show a clinically meaningful right-ear advantage), more frequently for francophones than anglophones. However, most right-hemisphere speech cases were detected with the test, yielding a very low false negative rate in either language. Our results suggest that the FW test can be used with non-anglophone populations.
^1. WEXLER, B.E. and HALWES, T. Neuropsychologia 21, 59-66, 1983., (Supported by Canadian Institutes of Health Research.)