[Vibratory test and head shaking test and caloric test: a series of 87 patients]

The purpose of this work was to study the complementary contribution of the vibratory test (VT), the head shaking test (HST) and the caloric test (CT) in patients with total or partial vestibular lesions. We investigated the usefulness of these three tests, particularly the high frequency VT, for multiple-frequency vestibular study.

The study cohort included 40 patients with total vestibular lesions (TVL) and 47 patients with partial vestibular lesions (PVL), the latter group including 21 patients with recent Menière disease, 15 with sudden-onset loss of vestibular function (SLVF), 5 with tumors of the cerebropontine angle, and six with diverse conditions. The HST protocol was 2 Hz stimulation (head speed greater than 180 degrees /s). The VT used an ABC 100 Hz vibrator operating at 0.8 mm and an S stimulator delivering frequencies between 30 and 115 Hz during 10 s stimulations. An LIVN-2 videoscope (biodigital France) and a 2D and 3D videonystagmograph (synapsis France) were used for the recordings. Mastoid stimulation was used for the VT.

For the 40 patients with TVL, the three tests (VT, CT, HST) were in agreement for all frequencies. The nystagmus produced by the VT demonstrated a horizontal component in 96% of the patients, a vertical component in 47%, and a rotational component in 30%. For the 47 patients with PVL, 9 of the 21 with Menière disease had a normal CT. Conversely, nystagmus was triggered by the HST in 10 and by the VT in 6. Nystagmus triggered by the VT and the HST was non-coherent with opposing direction in two-thirds of the patients. In certain cases, the VT demonstrated a variation in the direction of the nystagmus depending on the stimulation frequency, 30 or 100 Hz. Among the 15 patients with SLVF, the HST triggered nystagmus in only 5 and the VT in 14 (5 patients had nystagmus non-coherent with the side of the lesion). For the 5 patients with tumors of the cerebropontine angle (small neuroma or meningioma), the CT was negative in all 5, the HST was negative in 3, and the VT demonstrated lesional nystagmus in 4. Looking at the overall results, in the 47 patients with PVL (including 21 cases of Menière disease outside an acute phase) the CT demonstrated significant hypovalence in 70%, while the nystagmus demonstrated asymmetrical response in 44% when triggered by the HST and in 85% when triggered by the VT.

The VT is less invasive than the HST, particularly for elderly patients with osteoarthritis. It would be interesting in patients with bilateral tympanic perforation since the CT cannot be performed. It can reveal vestibular asymmetry. For unilateral partial vestibular lesions, the VT triggers nystagmus more often than the HST. It is particularly sensitive between acute episodes in patients with Menière disease. A discordance between the direction of the nystagmus triggered by the HST and the VT is particularly frequent in patients with labyrinthine hydropsis who exibit a normal CT. In certain cases of apparent bilateral areflexia to the CT for low frequencies, the VT can disclose vestibular asymmetry for high frequencies. The nystagmus triggered by the VT begins and ends with stimulation with little or no tiring. The nystagmus triggered by the HST occurs after the stimulation and depends on the frequency of the head shaking. Thus, the HST (2 Hz and its harmonics), the VT (100 Hz) and the CT (<0.01 Hz) all make significant contributions to multiple-frequency analysis of vestibular function, particularly useful in patients with partial vestibular lesions. These tests probably solicit cells with different topographies or different frequency sensitivities.