A 45-year-old woman presents with a six-week history of brief episodes where she feels like the room is spinning around her. These episodes are most severe when she lies on her right side with her ear down and are accompanied by nausea. She reports no issues with hearing or tinnitus. On examination, she exhibits rotatory nystagmus that begins several seconds after assuming the right lateral decubitus position and resolves after a minute. Repeated positioning in the same position results in the attenuation of the nystagmus. Audiometry testing shows normal hearing. What is the likely diagnosis for this patient?