Review Question - QID 214695

A 63-year-old woman presents to the emergency department with complaints of vertigo. The patient reports a history of vertigo that usually resolves with her prescribed meclizine. Her present episode began about 2 hours ago and is associated with nausea, emesis, and a 6/10 headache in the occipital region. She took her usual dose of meclizine, but vertigo remains persistent. Any movement exacerbates her vertigo. She denies any vision changes, chest pain, shortness of breath, weight changes, or fever but reports “a bout of cold” 2 weeks ago. Her past medical history includes hypertension, hyperlipidemia, and hypothyroidism. A physical examination demonstrates rotary nystagmus, decreased finger-to-nose and heel-to-shin on the left side, and a left-leaning gait. Cranial nerves II-XII are intact; strength and sensation are intact and symmetrical. What is the most likely explanation for this patient’s symptoms?