Chronic oculomotor nerve palsy secondary to a sphenoid–cavernous sinus lesion in an adolescent: a case report and literature review

Oculomotor nerve (cranial nerve III) palsy in children and adolescents is uncommon and typically suggests an underlying structural lesion rather than microvascular ischemia. Sphenoid sinus disease represents a rare cause of ocular cranial neuropathies and most frequently affects the abducens nerve. Consequently, isolated chronic oculomotor nerve palsy secondary to sphenoid sinus pathology is an unusual clinical presentation. We report a 16-year-old male who presented with long-standing right ocular deviation and progressive limitation of eye movements beginning in early childhood. Neuro-ophthalmic examination demonstrated severe limitation of adduction, elevation, and depression of the right eye associated with a large-angle exotropia and a fixed dilated pupil, consistent with chronic oculomotor nerve palsy. Notably, no ptosis of the right upper eyelid was observed despite the severity of the motor deficit, a finding that is discussed in the context of divisional and fascicular nerve involvement. The patient had a prior history of a sphenoid sinus lesion treated with functional endoscopic sinus surgery and partial resection. Histopathological examination revealed a histiocyte-rich lesion with surrounding fibrosis. Magnetic resonance imaging obtained during the current evaluation demonstrated postoperative changes with arrested pneumatization of the right sphenoid sinus, with no evidence of residual or recurrent mass lesion, and diffuse fatty atrophy of the right medial and inferior rectus muscles consistent with long-standing denervation. This case highlights a rare presentation of chronic isolated oculomotor nerve palsy associated with sphenoid–cavernous sinus pathology in an adolescent. The close anatomical relationship between the sphenoid sinus and the cavernous sinus provides a plausible mechanism for selective involvement of the oculomotor nerve. Early recognition of sphenoid sinus lesions in pediatric patients presenting with unexplained strabismus or cranial nerve deficits is essential to prevent irreversible neuro-ophthalmic sequelae.