Serial audiograms recorded at intervals during the progression of Ménière’s disease may show fluctuations in the degree of hearing loss. In the earliest stages of Ménière’s disease, an audiogram (typically recorded after the attack has abated) usually appears normal. As the disease progresses, the hearing loss becomes more marked with some degree of hearing loss persisting between attacks (middle stages of the disease). Later in the disease course, the hearing loss becomes permanent and nonfluctuating.
Vestibular function tests and electrocochleography
Vestibular function tests are highly specialised tests of the balance system and are particularly useful in evaluating patients whose cases are unusual, for example with an atypical clinical history or bilateral disease.6 Vestibular testing is mandatory before considering interventions that involve permanent ablation of vestibular function (e.g. surgery, labyrinthectomy or vestibular nerve division). Vestibular function tests are best ordered and interpreted by a specialist (a neurologist or ear nose and throat surgeon) with experience in managing otological conditions.
An electrocochleogram, which records the hair cell responses to sound, may also be useful in confirming the diagnosis of Ménière’s disease in atypical cases.6
Imaging studies such as MRI and CT scans are useful in excluding acoustic neuromas (Figure 3) and other intracranial pathologies that disturb balance and hearing (e.g. acoustic tumours, hydrocephalus and multiple sclerosis). At current diagnostic resolutions, MRI imaging has no specific findings to indicate the presence of endolymphatic hydrops. However, there have been recent advances in MRI imaging using intratympanic injections of gadolinium contrast material, which have demonstrated dilation of the endolymph compartments in some patients with advanced Ménière’s disease (Figure 4).7 Further refinements of these imaging techniques may allow a more definite diagnosis in patients with Ménière-type symptoms, and strengthen the evidence base for the many treatments available for patients with Ménière’s disease.
General haematological and biochemistry tests show no specific abnormalities in Ménière’s disease but are useful in evaluating patients for other causes of imbalance. A full blood count may show anaemia. Renal function tests are important for patients who may require treatment with diuretics as part of their overall management.
Patients with disturbances of balance are extremely common in general practice, with many of the underlying causes being nonvestibular (Box 2). The key to evaluating the differential diagnosis of disturbed balance lies in obtaining an accurate history of the balance problem and associated symptoms (e.g. hearing loss, tinnitus and a feeling of aural fullness). Descriptions such as light-headedness, disorientation and floating are likely to have nonvestibular causes, whereas a history of vertigo (a true sense of movement, spinning, rocking or tilting) is highly likely to be due to a disturbance of the vestibular system, including Ménière’s disease.
Further clues in the history, such as the duration of the vertigo, its frequency (rate of recurrence), positional elements, and the association of hearing loss, tinnitus and aural fullness, allow Ménière’s disease to be distinguished from other vestibular causes of vertigo such as BPPV, vestibular neuritis and cerebellar haemorrhage.6 Vestibular migraine can mimic early Ménière’s disease but can usually be distinguished by its response to antimigraine medication (see below).