Anatomy clinical correlates Quiz: Ace Your Exams

A 25-year-old woman comes to the office to evaluate intermittent painful double vision for three days. Her symptoms occur only when looking laterally. The patient has myopia and has been wearing corrective lenses for ten years. Ten days ago, the patient fell off her bike and was seen in the emergency department. During that visit, a head CT scan was performed and was unremarkable. Current medications include oral contraceptive pills. Vitals are within normal limits. On examination, the pupils are equal and reactive to light. Corrected visual acuity is 20/40 in each eye. The left eye abducts with attempted left gaze, but the right eye remains stationary. The right eye abducts and exhibits horizontal nystagmus with a rightward gaze, but the left eye remains stationary. The patient can converge both eyes without associated nystagmus. Fundoscopy reveals bilateral disc hyperemia. Injury to which of the following structures is the most likely etiology of this patient's ocular symptoms?