Unilateral external and internal ophthalmoplegia caused by intracranial meningioma in a dog

Abstract

Unilateral internal and external ophthalmoplegia caused by an intracranial meningioma occurred in a 15‐year‐old Belgian Sheepdog. The dog initially presented with ventro‐lateral strabismus of the left eye, and ptosis of the left upper eyelid. Anisocoria was present with the left pupil fixed and dilated. Both eyes were visual. Neuro‐ophthalmic evaluation revealed a lesion located in the left oculomotor nerve. Pharmacological testing with dilute pilocarpine (0.1% in artificial tears) revealed evidence of parasympathetic denervation of the left eye. Further evaluation via magnetic resonance imaging (MRI) revealed a well‐defined mass to the left of midline and lateral to the sella turcica. An attempt was made to excise/debulk the mass due to worsening conditions and the dog died the following day. Necropsy revealed a mass of randomly arranged bundles and streams of spindle cells. Immunohistochemistry demonstrated a strong avidity for vimentin and a negative response for S‐100 protein. These findings suggest a diagnosis of meningioma.