Normative Brainstem Auditory Evoked Responses in Cavalier King Charles Spaniels with Chiari-like Malformation

Abstract: Background-Hearing in dogs can be evaluated using brainstem auditory evoked response (BAER) testing. Cavalier King Charles spaniels (CKCS) are prone to Chiari-like malformation (CM).

Hypothesis/Objectives-To evaluate hearing loss in CKCS, BAER parameters are needed in reference to presence or absence of CM. The purpose was to establish normative BAER data. The specific aim was to determine if BAER indices differed based on CM grade. We hypothesized that CM would result in latency differences in CKCS with CM grade 2 (CM2) compared to those with CM0 and CM1.

Animals-Twenty CKCS without apparent hearing abnormalities assessed by owner.

Methods-Prospective case series. Under general anesthesia, CKCS underwent CT scan (assess middle ear), BAER testing, MRI (assess presence/grade of CM).

Results-Nine (45%) CKCS had CM1; 11 (55%) had CM2. All had at least one morphologic abnormality in waveforms. Absolute and interpeak latencies were reported for all CKCS and compared between CM grades. Median threshold for CKCS with CM1 was 39 and CM2 was 46. Absolute latencies for CKCS with CM2 were consistently longer than those for CKCS with CM1 with exception of Wave II, V at 33 dB. Significant differences were found for wave V at 102 dB (p = 0.04), wave II at 74 dB (p = 0.008). Interpeak latency comparisons were inconsistent between CM1 and CM2.

Conclusions and clinical importance-Normative BAER data for CKCS with CM1 and CM2 were established. Results suggest CM impacts BAER latency results, but influence is not always statistically significant or predictable.