Auditory brainstem responses in autism: brainstem dysfunction or peripheral hearing loss?

Iwata (1993) looked at every ABR paper on kids with autism. The goal was to see if slow brainstem timing is a core trait of autism.

The review pulled together studies that used clicks or tones to measure hearing nerve and brainstem speed.

Latencies were all over the map. Some labs found delays, others found normal speed, so no clear pattern emerged.

A bigger issue showed up: many kids with autism also had middle-ear or cochlear hearing loss. This could fake a brainstem delay.

Barthelemy et al. (1989) tested the same population two years earlier and found normal ABRs. Their clean null result now makes sense; hearing loss in other samples likely created the mixed picture Iwata (1993) reports.

Tanguay et al. (1982) first floated the idea that brainstem damage triggers autism. Iwata (1993) walks that claim back, showing the evidence is too shaky to treat brainstem timing as a biomarker.

Later work moved upstream. Hogg et al. (1995) and Touchette et al. (1985) recorded cortical ERPs and found real auditory processing problems, but these happen in the cortex, not the brainstem.

Bhaumik et al. (2009) folded the ABR literature into a wider ERP review and reached the same verdict: brainstem measures are not reliable autism markers.

Before you label a child as non-responsive, run a quick hearing screening. Middle-ear fluid or undetected loss can masquerade as brainstem involvement and waste therapy time. If hearing is clear and language delays persist, shift your assessment to cortical ERP or behavioral listening tasks; the action is farther up the auditory pathway.