In 1861, Prosper Ménière first describes the unknown pathogenic pressure syndrome that is dealt with in this section.

Hydrops is a swelling of the membranous labyrinth due to an imbalance between the secretion system and the excretion of endolymph.
During crises, which appear at random in patients with Ménière-like syndromes, there is a disruption at some point of this membranous labyrinth. The pressure, which up to then is too high, suddenly falls and gives the following clinical panorama:

• a repeated spontaneous series of severe rotatory vertigos with a duration of between 15 minutes and 6 hours (although generally lasting one to two hours),
• severe neuro-vegetative signs, such as nausea and vomiting during the crisis,
• imbalance during the crisis,
• fluctuating homolateral loss of hearing, especially pre-crisis, that is reversible in cases of patients recently diagnosed with Ménière’s; this becomes chronic and we often observe a “bell curve” using audiometry with hearing loss of bass tones
• tinnitus with ringing in the ears, especially pre-crisis.

Upon examination ... we often find "Nothing" at the early stages (recently diagnosed with Ménière’s); and therefore, diagnosis is based on clinical signs.
During pre-crisis, the pressure is high and often there is hypovalency with homolateral ocular drift.
Conversely, during and especially after the crisis, a spontaneous nystagmus appears beating to the side of the lesion.
Between crises, the search for a spontaneous nystagmus using VNS can give us an indicator of the state of the pressure of the offending labyrinth.

How it evolves is completely random with regard to the number and the severity of the dizzy episodes, and auditory dysfunction becomes more severe and longer lasting. However, crises are less frequent and the syndrome includes an almost permanent sense of imbalance.
Hydrops does the equivalent of the pressure syndrome without interruption of the membranous vestibule, and is therefore crisis free. We move from subnormal to above normal pressure and vice-versa, and occasionally this can happen several times a day!

Treatment is through medication, comprising Betahistine as a basic treatment together with sedatives, anti-vertigo medication such as Tanganil via I.V., as well as antiemetics if there are major vertigo attacks.
Often patients do not respond to, or respond badly to this first line of medication. They must therefore turn to vestibular rehabilitation, which should only be carried out by vestibular therapist with a great deal of experience in this field.
Nothing of course can be done about the endolymphatic pressure: the success of the therapy is based on the impression of only having slight discomfort in stead of major vertigo attacks experienced in the past.
Treatment is long term and often there are no less than fifty sessions over the course of the first year in order to ensure results. The alternative is surgery, which justifies the initial choice of VR.

Three surgeries are advocated:

• the instillation of transtympanic Gentamicin (although strictly speaking this is not a surgery), although it sometimes increases auditory disorders, such as hearing loss, but almost always leads to a drop off in vertigo after one or two instillation sessions.
• Vestibular rehabilitation is used in pre- and especially post-surgery.
• the decompression of the endolymphatic sac often gives good results but hardly has any affect on hearing; although there are sometimes relapses after a crisis-free period of two to five years.
• Vestibular rehabilitation is therefore carried out post-surgery.
• vestibular neurectomy, namely cutting the afferent nerve supply, is guaranteed to eliminate the vestibular syndrome.

It is often carried out using the retrosygmoid approach.
This major surgery has reached such a level of expertise that generally speaking, both hearing and the facial nerve are unaffected (through electrical and pressure monitoring during surgery).

Vestibular rehabilitation should therefore always be carried out post-surgery.