Occurs due to increased endolymph within the cochlea and labyrinth (endolymphatic hydrops)
First attack usually occurs in patients >65yrs
Usually is unilateral but may become bilateral with time
Ménière's disease
Vestibular/otologic
Wellens' syndrome
Benign paroxysmal positional vertigo 
Benign paroxysmal positional vertigo
Traumatic 
Sheehan's syndrome
Infection