First case of presumed trigemino-oculomotor synkinesis in a dog

An 11-year old, intact male Border Collie was referred with a history of subacute and progressive left eye exophthalmos and mydriasis associated with reduced pupillary light reflex, ventrolateral strabismus, and absence of physiologic nystagmus in the left eye. Neuroanatomical localization was consistent with a left oculomotor neuropathy, involving the general somatic and visceral parasympathetic efferent components. Computed tomography and magnetic resonance imaging of the head were performed. Imaging findings were consistent with an infectious-inflammatory process involving the left retrobulbar space and regional muscles, extending intracranially through the left orbital fissure. Cerebrospinal fluid (CSF) was collected from the cerebellomedullary cistern, and the analysis revealed albuminocytologic dissociation. The dog was treated with amoxicillin and clavulanic acid and prednisolone at anti-inflammatory dose; a significant improvement of neurologic status was observed afterward. However, 4 weeks after the initial presentation, the dog showed an abnormal, bilateral adduction of both eyes and third eyelid protrusion of the left eye while chewing the leash; the dog's mental status was normal, and the patient did not appear to be in discomfort during these episodes. A presumptive diagnosis of acquired trigemino-oculomotor synkinesis, induced by the intracranial inflammation was made. To the authors' best knowledge, this is the first case of presumed trigemino-oculomotor synkinesis reported in veterinary medicine.