“Benign paroxysmal positional vertigo (BPPV) is the most common vertiginous disorder in the community. The cardinal symptom is sudden vertigo induced by a change in head position: turning over in bed, lying down in bed (or at the dentist or hairdresser), looking up, stooping, or any sudden change in head position. There is a wide spectrum of severity. Mild symptoms are inconsistent positional vertigo. Moderate symptoms are frequent positional attacks with disequilibrium between. When severe, vertigo is provoked by most head movements, giving an impression of continuous vertigo. The symptoms can last for days, weeks, months, or years, or be recurrent over many years.”

National Library of Medicine (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3144715/)