28th May 2025

A 75-year-old man with a history of hypertension presents with a sudden onset dysarthria and severe confusion.

A 75-year-old man with a history of hypertension presents with a sudden onset dysarthria and severe confusion. He has been noted to have a long non-compliance with his antihypertensive medication, as his wife explains. On examination, he is unable to comply with a full neurological exam, but on close observation you noted that his left eye is fixed horizontally and that when attempting to follow prompts, his right eye is capable only of limited adduction as per the below picture, developing a horizontal jerk nystagmus in the right eye when he attempts to follow your prompts. You also note weakness of his right upper limb.

Given his presentation, where is his lesion likely to be present?

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