Isolated abducens nerve palsy following upper respiratory infection in a patient with ipsilateral chronic sphenoid sinusitis

The abducens nerve, which is vulnerable because of its complex anatomy at the skull base, is seldom affected by acute or severe sphenoid sinusitis. Notably, abducens nerve palsy following asymptomatic chronic rhinosinusitis (CRS) in a healthy young individual after a mild upper respiratory infection (URI) remains undocumented in the literature. Herein, we report a case of acute unilateral abducens neuropathy in a healthy 35-year-old woman with CRS in the ipsilateral sphenoid sinus, following a mild URI 2 weeks earlier. She presented with sudden-onset diplopia, was afebrile, and had normal serum inflammatory biomarkers. Comprehensive ophthalmological and neurological exams revealed no abnormalities except limited lateral gaze in the left eye. Imaging revealed mucosal swelling on the hyperpneumatized left sphenoid sinus, which thinned the clivus and positioned the inflamed mucosa close to the Dorello's canal, likely facilitating the spread of inflammation to the ipsilateral abducens nerve. Urgent endoscopic sinus surgery combined with systemic corticosteroids and antibiotics led to complete resolution by postoperative day 10. The present case demonstrates acute abducens nerve neuropathy from URI-induced exacerbation of sphenoid sinus CRS with specific anatomical predispositions.