Describe Meniere disease with its clinical features and management.

Nature and Pathology

• The pathological hallmark is endolymphatic hydrops — distension of the endolymphatic system, demonstrated at post-mortem as ballooning of Reissner membrane and the saccule
• The mechanism is failure of endolymph homeostasis: either over-production by the stria vascularis or, more probably, under-absorption by the endolymphatic sac.

Clinical Features

• The classical tetrad — and the diagnosis requires the combination, not any single element:
• 1. Vertigo — episodic, rotatory, lasting 20 minutes to several hours (by definition at least 20 minutes and less than 12 hours), with severe nausea and vomiting and prostration. Attacks under 20 minutes suggest something else, and attacks lasting days are not Meniere
• 2. Fluctuating sensorineural hearing loss — initially low-frequency and reversible, recovering between attacks, which is highly characteristic; later becoming flat and permanent as the disease progresses

Investigation and Management

• Pure tone audiometry shows a low-frequency (rising) sensorineural loss early, becoming flat later; and serial audiograms document the fluctuation.
• Other tests — electrocochleography, with a raised SP/AP ratio supporting hydrops; caloric testing, showing reduced response on the affected side; glycerol dehydration test, historically used, in which hearing improves after an osmotic agent; and MRI with delayed gadolinium, which can now demonstrate hydrops directly
• MRI of the internal acoustic meatus is mandatory to exclude acoustic neuroma.
• Exclude syphilis, autoimmune disease and thyroid dysfunction where the picture is atypical or bilateral
• Management of the acute attack — bed rest in a quiet darkened room; vestibular sedatives (prochlorperazine, cinnarizine) and antiemetics, given parenterally if vomiting; and reassurance.
• Long-term medical management — salt restriction (under 2 g sodium daily) with avoidance of caffeine, alcohol and tobacco, which is the foundation and is frequently the only treatment needed; betahistine, widely used, which is thought to improve cochlear microcirculation, though the evidence is contested; and diuretics (hydrochlorothiazide with amiloride, or acetazolamide)
• Treat coexisting migraine, which is common and may be driving much of the symptom burden
• Vestibular rehabilitation between attacks, and a hearing aid for the established loss
• Intratympanic therapy where medical treatment fails:
• Intratympanic steroid (dexamethasone) — non-destructive and hearing-preserving, and therefore the first intratympanic step, particularly where hearing is still useful
• Intratympanic gentamicin — a chemical labyrinthectomy.
• Surgery — endolymphatic sac decompression or shunt.
• The principle governing all destructive treatment is that Meniere disease becomes bilateral in up to a third — so destroying one labyrinth may leave the patient without vestibular function at all if the other ear later becomes involved. This must be weighed and discussed
• Counsel about driving, working at heights and swimming, and about the unpredictability of attacks, which is often the most disabling aspect of the disease
• Attacks under twenty minutes are not Meniere, and attacks lasting days are not either; the duration is part of the definition
• The low-frequency loss recovers early on, which is what makes serial audiograms the most useful investigation
• Aural fullness gives the patient warning, and many learn to recognise an attack building an hour beforehand
• Tumarkin drop attacks cause serious injury and are an indication for definitive treatment rather than further medical trials
• MRI is mandatory to exclude acoustic neuroma, which can present with an identical picture
• Salt restriction is the foundation and is frequently the only treatment needed, though compliance is the difficulty
• Treat coexisting migraine, which is strongly associated and may be driving much of the symptom burden
• Intratympanic steroid is hearing-preserving and is therefore the first intratympanic step where hearing remains useful
• Gentamicin is more vestibulotoxic than cochleotoxic, which is the principle exploited by chemical labyrinthectomy
• Labyrinthectomy destroys hearing and is reserved for an ear with no useful hearing left to lose