Chiari-like malformation in Cavalier King Charles Spaniels impacts brainstem auditory-evoked response latency results.

Abstract

To evaluate hearing loss in Cavalier King Charles Spaniels (CKCS), breed-specific brainstem auditory-evoked response (BAER) testing parameters are needed to help assess the Chiari-like malformation (CM) grade. The purpose of this study was to establish breed-specific BAER data and to determine if BAER indexes differed based on the CM grade. We hypothesized that there would be latency differences based on the CM grade. 20 CKCS without apparent hearing abnormalities as assessed by the owners. Under general anesthesia, CKCS underwent a CT scan (to assess the middle ear), BAER testing, and MRI (to assess the grade of CM). No CKCS had CM0. Nine (45%) CKCS had CM1; 11 (55%) had CM2. All had at least 1 morphologic abnormality in waveforms. Absolute and interpeak latencies were reported for all CKCS and compared between CM grades. The median threshold for CKCS with CM1 was 39 and for CM2 was 46. Absolute latencies for CKCS with CM2 were consistently longer than those for CKCS with CM1 with the exception of waves II and V at 33 dB. Significant differences were found for wave V at 102 dB ( P = .04) and wave II at 74 dB (P = .008). Interpeak latency comparisons were inconsistent between CM1 and CM2. Breed-specific BAER data for CKCS with CM1 and CM2 were established. The results suggest that CM impacts BAER latency results, but the influence of the malformation is not always statistically significant or predictable.