Incidence, cause, outcome and possible risk factors associated with facial nerve paralysis in dogs in a Sydney population (2001-2016): a retrospective study

Objective This study aims to assess the incidence and causes of facial nerve paralysis (FNP) in dogs in the Sydney region. Its outcome and possible risk factors are investigated to prognosticate and aid design of diagnostic and treatment plans. Design Retrospective case study. Methods Client-owned dogs presented to the University Veterinary Teaching Hospital, Sydney (UVTHS), between 2001 and 2016 with FNP were included (n = 122). The incidence of each cause of FNP was investigated. A reference population of noncases seen at the UVTHS during the same time period was used to study the association between idiopathic facial nerve paralysis (IFNP) and gender, age and breed. Results IFNP (29.5%) was the most common diagnosis. Male dogs (odds ratio [OR], 2.3) had increased odds of IFNP compared with female dogs. Age was a significant risk factor for both the occurrence of FNP and IFNP. There was higher occurrence of IFNP among middle-aged dogs (5-13 years) and reduced risk in juvenile dogs (less than 2 years). Cavalier King Charles Spaniels were over-represented for FNP (OR, 6.9) and IFNP (OR, 17.5). For IFNP, 6 of 16 dogs with known follow-up showed definitive resolution within 3 years of diagnosis. Concurrent vestibular signs were common in dogs with middle/inner ear abnormality and intracranial disease; and were also seen in 50% of dogs with IFNP. Conclusion The results of this study demonstrate statistical predilections in age, gender and breed for IFNP. Guarded prognosis for recovery should be given to dogs diagnosed with IFNP and supportive management instigated.