Otopathy secondary to trigeminal schwannoma in a Quarter Horse

Abstract

SummaryOtitis media secondary to trigeminal nerve (CN‐V) paralysis is described in dogs and humans but not in horses. An 18‐month‐old Quarter Horse colt was presented with history of mastication difficulties and a nonhealing corneal ulcer. Clinical findings were consistent with paralysis of the right CN‐V. Computed tomography imaging showed otopathy media and a mass at the root of the CN‐V. The colt was euthanised due to poor prognosis. Post‐mortem magnetic resonance imaging showed enlargement of the right CN‐V which was slightly hyperintense on T2W. Histopathology of the mass revealed fusiform tumoural cells, positive on vimentin‐ and S100 immunohistochemistry, consistent with a schwannoma. Otitis media was presumed secondary to CN‐V paralysis and denervation of the right tensor veli palatini muscle involved in opening of the Eustachian tube. This is the first case of trigeminal schwannoma and secondary otopathy media described in a horse, which highlights the importance of imaging in investigating trigeminal nerve paralysis.