Myoclonus in geriatric dogs and its association with canine cognitive dysfunction: an online survey

An increasing number of dogs are presented with suspected canine cognitive dysfunction (CCD), and a subset also exhibits myoclonus.

Because CCD shares multiple pathological and pathophysiological features with Alzheimer's disease in humans, and myoclonus has been linked to neurodegenerative disorders in people, the aim of the study was to describe myoclonus in dogs with clinical signs of CCD.

An anonymous online survey for owners of geriatric dogs (over 7 years of age), consisting of 46 questions, was conducted. The survey included items on signalment, the Canine Dementia Scale (CADES), and myoclonus. CCD was defined based on a CADES score of >8. It was available online in both German and English from April to June 2024.

Of the 401 participants, 148 dogs were excluded due their young age, under 7 years and incomplete CADES-Score. Among the remaining respondents, 89% of owners reported that their dog showed signs of CCD. Overall, 146/164 (89.0%) dogs exhibited both CADES-defined CCD and myoclonus. However, no statistical significance was found between the co-occurrence of CCD screen status and the presence of myoclonus (p = 0.45). Predominantly, myoclonus occurred spontaneously (72.6%, n = 119), stress-induced (15.2%, n = 25), and light-induced (11.6%, n = 19). Noise-induced and feeding-induced myoclonus were the least common trigger (3.0%, n = 5 each), as well as no answer given (0.6%, n = 1). Ten dogs had multiple trigger causes.

Myoclonus was commonly co-reported alongside CADES-defined CCD by respondents. Although no statistically significant association between CCD and myoclonus was detected, CCD should be considered among the differential diagnosis in geriatric dogs presenting with myoclonus, particularly in the context of concurrent cognitive decline.