Abstract
BACKGROUND: Orbital myositis is an idiopathic, inflammatory, non-infectious condition, typically confined to more than one extraocular muscle and usually targeting young females in their third decade. CASE REPORT: We describe a case of orbital myositis uncommonly afflicting an adult male. He initially presented with a sensation of dizziness when turning his head and mobilising, together with right-sided orbital pain that failed to respond to the vestibular sedative cinnarizine. Failure to resolve and development of diplopia initially prompted a working diagnosis of ocular myasthenia gravis. On further investigation using HESS charting, paresis in the inferior and medial rectus and superior oblique ocular muscles of the right eye were elicited correlating with clinical examination. However, the lack of response to low dose steroids and acetylcholinesterase inhibitors, together with a negative screen for myasthenia antibodies, precluded a diagnosis of ocular myaesthenia gravis from being made. Other investigations included a high creatinine kinase and lactate dehydrogenase which indicated pathology in the extraocular muscles themselves. An MRI scan showed normal extraocular muscle thickness while excluding other orbital pathology. Exclusion of a variety of other conditions subsequently led to a diagnosis of orbital myositis. CONCLUSION: Response to high dose steroids consolidated this diagnosis with a rapid response ascertained clinically by resolution of pseudo-vertigo and pain, as well as the ophthalmoplegia with follow-up on HESS charting. We aim to raise awareness of this rare condition that carries a good response to steroids.