Hearing assessment in Pomeranian dogs with and without Chiari-like malformation based on brainstem auditory evoked...

Chiari-like malformation (CM) has been associated with hearing abnormalities in humans and Cavalier King Charles Spaniels, but hearing function has not previously been assessed in Pomeranians with CM. This pilot study evaluated whether Pomeranians with predominantly mild CM exhibit abnormalities in brainstem auditory evoked responses (BAER).

Forty-two Pomeranian dogs underwent MRI and BAER testing. Dogs were classified according to CM severity based on MRI findings. Thirty-two dogs were classified as CM affected (31 CM1, 1 CM2), and 10 dogs served as CM0 controls. Suprathreshold BAER recordings were obtained under general anaesthesia at intensities from 20 to 90 decibels normalised hearing level (dBnHL). Absolute latencies of waves I, III and V, and interpeak intervals I-III, III-V and I-V were measured for both ears. Reference ranges were established from control dogs, and a linear mixed-effects model was used to assess the effects of group and ear side on latency values.

No significant differences were identified between CM and control dogs for any BAER wave latency or interpeak interval. There was substantial overlap between groups across all stimulus intensities. However, a significant ear effect was observed, with the right ear showing slightly longer latencies than the left ear (estimate = 0.047, t = 3.67, p < 0.001).

These findings suggest that mild CM in Pomeranians does not result in measurable abnormalities in BAER. Further studies, including a larger number of dogs with moderate or severe CM, particularly CM2, and incorporating morphometric analyses and BAER amplitude measurements, are warranted.