Diagnostic approach

In the case of bilateral vestibulopathy, there are no auditory signs, headaches, or neurovegetative signs. There is also no vertigo in the usual sense. There may be attacks of vertigo during the onset of the disease, but in the stabilized, chronic state, there is rather no more vertigo, no more rotatory signs, because both vestibules are affected, without asymmetry. However, instability persists.
Thus, the doctors consulted think it is a neurological problem rather than a pathology responsible for vertigo, which explains the wandering and the delay in diagnosis by an average of 2 to 5 years. It is not easy to imagine, in the collective medical unconscious, that a vestibular deficit will not cause vertigo.
The main concern of the general practitioner or ENT during the first consultation is to think of an inner ear disease, a vestibular deficit in front of a set of instability and oscillopsias (visual blurring that appears as soon as you move your head - see Symptoms page)..

Clinical tests

Before instrumental measurements are done, diagnosis is primarily clinical. It is based on the coexistence of symptoms (balance disorder, chronic visual instability with oscillopsias, and altered sense of orientation) with the feature that balance disorder resulting from bilateral vestibular deficit is persistent and markedly accentuated in the dark. The great difficulty of maintaining equilibrium on irregular soil in the penumbra is always present in bilateral vestibular deficit and this symptom should lead to vestibular evaluation.

The basic physical examination shall include at least tests for walking, balancing and assessment of gaze stability when the head is moving:

• Standard walking in a straight line on a stable plane in a normally lit environment does not present difficulties for the patient with bilateral vestibulopathy, but performance degrades when asked to walk with eyes closed, in combination with head movements or feet on a line.
• Balancing while standing, feet together, eyes open, or even closed, is possible on a flat and stable support, but not on an unstable support (tray on half a ball, foam support, etc.).
• The simple and quick exercise of reading during head movements will show the difficulty in stabilizing the gaze.

Bilateral vestibular deficits have to be confirmed by objective testing

There are three main tests that confirm the diagnosis of bilateral vestibular deficit: the "Video Head Impulse Test" (VHIT), the caloric vestibular test and the rotatory vestibular test.

• The "Video Head Impulse Test" (VHIT)

This test involves recording eye movements during brief examiner-induced head rotations at speeds of 50 to 300 degrees per second. Normally, the eyes remain in place, staring at the visual target, regardless of head movements.
In the case of bilateral vestibular deficit, the eyes go with the movement of the head and return to the visual target a fraction of a second later..

• The caloric vestibular test

It is performed on a patient lying down with his head raised by 30°. Sending water into the ears at different temperatures (30°C and 44°C) creates fluid movements in the external semicircular canals. This test allows you to evaluate one side and then the other separately. It normally triggers a little vertigo and nystagmus (eye movements) that can be seen under video glasses. The response is weak in the case of vestibulopathy.

• Rotatory vestibular test (rotating chair)

It is performed on a patient sitting in a rotating chair wearing videonystagmography (VNG) glasses in the dark. The VNG records, via an infrared camera embedded in a mask, the spontaneous eye movements.
This recording allows, through computer analysis, a quantification of the speed and amplitude of eye movements in the presence or absence of external stimuli.
The chair is caused to swing sideways by 90° and nystagmus are triggered. They are observable, recordable, measurable.
In vestibular deficits, the person does not even sense the chair is moving, nor is there an eye response

But there are other complementary tests.