# Children with autism spectrum disorder and attention deficit hyperactivity disorder have evidence of sensory nerve degeneration

## TL;DR

This study found signs of sensory nerve degeneration in children with autism and ADHD using a non-invasive eye imaging technique.

## Contribution

The study is the first to use corneal confocal microscopy to detect sensory nerve changes in children with ASD and ADHD.

## Key findings

- Children with ASD+ADHD and ASD had significantly lower corneal nerve branch density compared to healthy controls.
- Corneal nerve fiber length was reduced in children with ASD but not in those with ASD+ADHD.
- No correlation was found between corneal nerve parameters and ASD severity.

## Abstract

An increasing body of evidence supports the role of altered sensory processing in autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). This exploratory study undertook corneal confocal microscopy (CCM) to assess for differences in corneal nerve fiber density (CNFD), branch density (CNBD) and fiber length (CNFL) in relation to ASD severity in children with ASD+ADHD (n = 21), ASD (n = 6) and healthy controls (HC) (n = 15). CNBD was significantly lower in children with ASD+ADHD (P = 0.002) and ASD (P < 0.001) and CNFL was significantly lower in children with ASD (P = 0.02) compared to HC. However, CNFD (mean difference = 2.28, 95% CI [−5.84, 10.40], P > 0.99) CNBD (mean difference = 14.1, 95% CI [−8.22, 36.4], p = 0.37) and CNFL (mean difference = 2.46, 95% CI [−2.28, 7.20], p = 0.61) did not differ between ASD+ADHD and ASD. CNFD (P = 0.876), CNBD (P = 0.405) and CNFL (P = 0.606) did not correlate with the severity of ASD. Corneal confocal microscopy reveals sensory nerve degeneration in children with ASD+ADHD and ASD alone compared to controls. Larger studies integrating CCM with sensory and cognitive assessment are required to determine the utility of CCM as a clinical screening strategy for neurodegneration in ASD, ADHD and ASD-ADHD combined.