Extraocular muscle involvement in a dog with focal myasthenia gravis

Abstract

An 8‐year‐old, female, entire toy poodle presented with external ophthalmoplegia, facial and laryngeal paralysis and megaoesophagus. Neostigmine methylsulfate administration yielded a positive response, and acetylcholine receptor autoantibody titres confirmed a diagnosis of myasthenia gravis. No cranial mediastinal mass was identified on thoracic radiographs. The patient initially demonstrated a favourable response to treatment with an acetylcholinesterase inhibitor, but was ultimately euthanased due to ongoing regurgitation resulting in severe aspiration pneumonia. No appendicular muscle weakness was noted at any point, including up to the time of euthanasia approximately 4 weeks after the initial onset of clinical signs. This is the first report of external ophthalmoplegia in a dog with focal myasthenia gravis.