It's a sudden peripheral vestibular disorder, best known as vestibular neuropathy or neuritis, which is characterized by a very abrupt onset of rotational vertigo with nausea and vomiting, an instability when walking, even sometimes a complete ataxia. Moving the head aggravates symptoms.
The first symptoms often occur a few days or weeks after a common viral infection of upper aerodigestive tracts.
Neither auditory nor neurological signs are associated with the clinical picture.
After a few days or weeks, the symptoms gradually diminish and finally disappear completely.
The clinical examination and the videonystagmography (VNG) both highlight a spontaneous nystagmus, vigorous and beating away from the diseased labyrinth. In the initial deficit phase, the spontaneous nystagmus is classified as the third degree in Alexander's classification.
It gradually decreases in intensity to finally disappear after a few days or a few weeks.
Caloric testing shows a hyporeflexia or vestibular loss on the side of the infected ear.
An evaluation of the otolithic function can be performed by measuring the vertical subjective and the sacculo-collic reflex.
It seems to correspond to an inflammatory disease of the vestibular nerve.
According to Schuknecht and Kitamura's histopathological work, there is a total or subtotal degeneration of the vestibular nerve while the ductal structures and utricular inner ear remain healthy.
The virus (neurotropic virus of the herpes family) is favored, firstly because of the epidemic and often recurrent symptomatology.
Bilateral peripheral vestibular deficits, with normal hearing, can occur immediately on both sides or sequentially.
In this case, the deficit reaches each ear separately one after the other, in a time which can vary from several months to several years
In approximately 50% of the cases, the etiology remains unknown.
Several etiological factors such as neurotoxic exposure, immune deficiency diseases, systemic diseases (such as blood pressure, diabetes, hypothyroidism) could play a part in a bilateral vestibulopathy occurrence.