In 1964, further histological studies showed evidence of ruptures of Reissner’s membrane, one of the membranous divisions between the potassium-rich endolymph and the perilymph of the cochlea. The ensuing ‘rupture theory’ proposed that the acute mixing of potassium-rich endolymph with perilymph leads to transient hair cell dysfunction within the cochlear and vestibular end organs, resulting in the attacks seen in Ménière’s disease. On the basis of this theory, many different forms of surgery to alter the function of the endolymphatic system were designed, with the aim of preventing pressure build up within the inner ear and minimising the membrane ruptures implicated in attacks of Ménière’s disease.
As the understanding of the complex physiology of the inner ear evolved and the outcomes of various surgical and medical treatments for Ménière’s disease were reviewed, it seemed less likely that the rupture theory could explain the attacks of vertigo and fluctuating hearing loss. Contemporary understanding of the radial and longitudinal endolymph flow patterns in the healthy and diseased cochlea led to a theory in 1991 that Ménière’s disease is caused by episodic disturbances of endolymph formation and resorption.5 The theory encompasses current anatomical, physiological and pathophysiological knowledge about the functions of the cochlear and balance system. It also explains the stages of Ménière’s disease, including the occurrence of drop attacks late in the disease, and the responses to various treatments, particularly surgery to the endolymphatic system.
Although no single theory of Ménière’s causation is accepted by all workers in this field, a more contemporary concept of the disease is that it represents a failure of the complex inner ear homeostasis caused by any of a range of pathologies. The symptoms during an attack can be more usefully viewed as a syndrome than as a single disease entity. The inner ear changes leading to symptoms may be caused by a range of abnormalities (Figure 1). They include autoimmune diseases (Cogan’s syndrome and systemic lupus erythematosus), congenital rubella and other viral infections (possibly herpes simplex) of the inner ear (viral labyrinthitis), syphilis, chronic ear disease, acoustic neuroma, trauma, allergy and hormonal changes with the menstrual cycle. In most patients the cause is unknown.
In the vast majority of cases, Ménière’s disease can be diagnosed on the basis of an accurate history that looks for the AAO diagnostic criteria, and a few relevant tests to exclude differential causes of recurrent vertigo.2 Clinical examination of patients with Ménière’s disease often finds no abnormalities or at most shows evidence of a unilateral sensorineural hearing loss (or bilateral asymmetrical hearing loss in the case of bilateral disease). Clinical tests of balance such as Romberg’s test (standing feet together with eyes closed) and Unterberger’s stepping test (walking on the spot with eyes closed) may show only a mild disturbance of balance. This is because most patients are examined only between attacks, long after their symptoms have resolved. If there are associated persisting neurological signs (cranial nerve palsies or nystagmus) then other intracranial pathologies need to be considered.
In the few cases where patients have been observed during an acute attack, clinical examination has varying results. In general, patients appear quite unwell because of the unpleasant sensation of vertigo. They may be sweaty and pale, unable to stand up safely, nauseated and violently vomiting. There may be horizontal nystagmus that changes direction as the attack progresses. Following an attack, patients are left with a sense of ‘hangover’ for a day or two before recovering to normal function.
Pure tone audiogram
The most useful investigation for diagnosing Ménière’s disease is a standard pure tone audiogram. In classical Ménière’s disease, this may show varying degrees of sensorineural hearing loss. Most commonly the hearing loss affects low tones, although other patterns are also seen (Figure 2).