In their study, Maziade et al1 presented
challenging data concerning a possible early brainstem auditory evoked potential
response marker for an autistic phenotype. The authors demonstrated that the
I-III interpeak latency (IPL) of brainstem auditory-evoked potentials (BAEP)
was prolonged not only in persons with autism, but also in their unaffected
first-degree relatives compared with age-matched controls. By providing a
neurophysiological marker of the autistic phenotype, this finding could be
very important to our understanding of autism. However, the authors reported
that in 52% of families, neither the proband nor the relatives showed an abnormally
prolonged IPL. This finding suggests that BAEP-impaired and -nonimpaired subjects
might represent subgroups, and that they should be separated for analysis.
If prolonged ILP is not a continuous but a dichotomous variable, and thus
indicates subgroups rather than a continuous spectrum, then neither a correlation
with autistic symptoms for the whole sample nor the average IPL is likely
to be informative in revealing the exact nature of this phenomenon.