A 68-year-old woman arrives at the emergency room with rapid onset double vision that began shortly after she awoke. When she looks to the right, the patient's vision deteriorates. She does not have a headache, weakness, or numbness. The patient has a lengthy history of high blood pressure, hyperlipidemia, and type 2 diabetes. The blood pressure is 160/90 mm Hg, and the pulse rate is 86 beats per minute. Except for the ocular abnormalities depicted in the figure below, the neurologic evaluation, including visual acuity, is normal. A lesion involving which of the following structures is most likely causing the observed ocular findings in this patient?

Question

A 68-year-old woman arrives at the emergency room with rapid onset double vision that began shortly after she awoke. When she looks to the right, the patient's vision deteriorates. She does not have a headache, weakness, or numbness. The patient has a lengthy history of high blood pressure, hyperlipidemia, and type 2 diabetes. The blood pressure is 160/90 mm Hg, and the pulse rate is 86 beats per minute. Except for the ocular abnormalities depicted in the figure below, the neurologic evaluation, including visual acuity, is normal.  A lesion involving which of the following structures is most likely causing the observed ocular findings in this patient?

Quizplus · Accepted Answer

Eductional Objective: Internuclear ophthalmoplegia is a disorder of impaired horizontal gaze caused by a lesion in the medial longitudinal fasciculus (MLF).  The affected eye (ipsilateral to the lesion) is unable to adduct while the contralateral eye is able to abduct (often with associated nystagmus).  Convergence and the pupillary light reflex are preserved because these pathways bypass the MLF.

A 68-Year-Old Woman Arrives at the Emergency Room with Rapid