Bilateral Ethmoido-frontal Mucoceles Presenting as Isolated Left Superior Oblique Muscle Palsy: A Case Report

Abstract

Aims: To report an uncommon presentation of isolated left superior oblique muscle palsy associated with bilateral ethmoido-frontal mucoceles, and to emphasise the role of detailed neuroimaging interpretation in multidisciplinary management. Presentation of Case: A 59-year-old man presented with a 2-month history of progressive vertical binocular diplopia. Routine ophthalmic examination was normal, with preserved visual acuity, normal pupillary responses and intraocular pressure, and no clinically detectable proptosis, ptosis, periorbital inflammation or fundus abnormality. Ocular motility assessment and a Lancaster red-green screen test documented isolated left superior oblique muscle palsy. Orbito-cerebral magnetic resonance imaging revealed bilateral ethmoido-frontal mucoceles. Specialist radiological review showed that the left-sided lesion measured 13 × 20 mm in the axial plane and 19 mm in height, with localised intraorbital extension and direct contact with the left superior oblique muscle. The right-sided lesion measured 15 × 25 mm in the axial plane and 30 mm in height, with discrete extension into the adjacent subcutaneous soft tissues. No intracranial extension was detected. The patient was referred for endoscopic sinus marsupialisation and drainage. Discussion: Fronto-ethmoidal mucoceles usually present with orbital signs such as proptosis, globe displacement or broader motility disturbance. In this case, focal mechanical contact with the superior oblique muscle produced an isolated motility pattern clinically resembling trochlear nerve palsy. Conclusion: Acquired extraocular muscle palsy warrants neuro-orbital imaging, even when routine ophthalmic findings are reassuring. Careful radiological interpretation is important for defining anatomical involvement and guiding endoscopic management.