A 56 years old woman presents with a 3-week history of imbalance, right-sided hearing loss, and tinnitus. She reports having an upper respiratory infection 1 week before the onset of her symptoms. Her symptoms began with a severe episode of room-spinning vertigo with associated nausea and vomiting that lasted all day. The next day she noticed right-sided, high pitched tinnitus and was unable to use the telephone in her right ear. She now reports constant imbalance and slight vertigo with quick head turns to the right. What is the most likely diagnosis?