Express: Chronic Trismus in a Cat With an Extra-Axial Mass Causing Compression of the Pons.

A 15-year-old, female, neutered, domestic short hair (DSH) cat presented with a 5-month history of dysphagia which progressed to an inability to open the mouth, resulting in poor prehension of food and subsequent weight loss. Neurological examination revealed an ambulatory vestibular ataxia with reduced postural reactions in all four limbs. There was a head tilt to the right and a positional rotatory nystagmus. The mandibular range of motion was greatly reduced at 20mm compared to a normal cat (62 ± 8 mm (median 63, range 41–84)). Magnetic resonance (MR) imaging of the brain revealed a solitary, large, extra-axial mass at the level of the pons, extending from the level of the caudal colliculi to the level of the cerebellar nuclei. The cat was subsequently euthanised and post-mortem histopathology was declined. To our knowledge, this is the first case report of a pontine lesion causing trismus in a cat and although rare should be considered as a differential for trismus in the feline population.