Vestibular neuronitis is a form of peripheral vestibular disorder.
It causes a sudden onset single attack of vertigo, often associated with a viral illness such as influenza. It is a common cause for severe vertigo, often accompanied by nausea/vomiting, and spectacular nystagmus (most medical students' first introduction to nystagmus) and which can last for a few days at worst, with a gradual apparent recovery.
The original article which coined the term vestibular neuronitis described probably what is now called epidemic labyrinthitis. This is not usually associated with any hearing loss/cochlear symptoms which is the reason for the original term vestibular neuronitis suggesting that just the vestibular and not the cochlear nerve was "inflamed" hence the "-itis". The term is a useful descriptive term for peripheral vestibular symptoms with no cochlear signs, but no longer has any agreed diagnostic meaning.
Epidemic labyrinthitis (also probably inaccurate, but universally accepted to describe this possibly most common disease causing vertigo) is most often self-limiting, and accompanied by total recovery of the vertigo.
Interestingly some audio-vestibular centres suggest that recovery is actually due to central compensation for the damage to the vestibular system and that sensitive tests of vestibular function will show the damage is still present although symptomless. "Epidemic labyrinthitis" will respond very well to vestibular sedatives in the acute phase, and does not need any other treatment. Obviously if this very typical pattern is not met, then the differential diagnosis of vertigo must be embarked upon.