a 61-year-old woman presents with intermittent episodes of feeling like she was spinning for 1 week. she states the episodes are brief; however, they occur 2 - 3 times per day. it is worse when she turns to her right side while lying in bed. even when she is not dizzy, she feels off balance. she denies tinnitus, decreased hearing, fever, syncope, nausea, vomiting, diplopia, or any other related symptoms. during the dix-hallpike maneuver, the patient exhibits nystagmus, with her eyes beating upward and torsionally when the right ear is turned downward. the nystagmus diminished with each time the maneuver was performed. question: based on the above description, what is the most likely diagnosis?
