9.OTOLITHIC EVOKED POTENTIALS TESTS
9.OTOLITHIC EVOKED POTENTIALS TESTS
These new tests to explore the inner ear are essential for diagnosing the cause of the problem. They test the functionality of receptors so far unexplored, which may explain the symptoms mentioned by the patient.
1. Cervical evoked myogenic potentials induced by high level sound (cVEMP 100 Db Hl) stimuli in the cervical muscles stimuli (or sacculo-spinal-induced otolithic evoked potentials)
Clicking sounds or short tone bursts of 100 dB are delivered on one side using a helmet at a frequency of 5 Hz, and cervical myogenic evoked potentials are received on the same side in both sternocleidomastoid (SCM) muscles using surface electrodes placed on the upper third of these two muscles.
The early waves are comprised of a first positive wave after 10 ms (P13 wave) followed by a negative wave after 19 ms (N23 wave).
These waves demonstrate the correct functioning of a labyrinth receptor, the saccule and saccular nerve, a branch of the vestibular nerve (inferior branch).
2. Ocular evoked myogenic potentials induced by high level sound stimuli (oVEMP or utriculo-ocular-induced otolithic evoked potentials)
Strong sounds are delivered in each ear and the evoked potentials are collected using surface electrodes on the extraocular motor muscles on the opposite side (n1-p1 waves). Bone conductive stimulation using a 4810 vibrator at Fz or at the mastoid evoked also n1-p1 potentials and may be useful in case of bo bilateral response due to decreased sensitivity of this test with age.
This new test serves to assess the functioning of the utricle and utricular nerve, comprising the superior vestibular nerve.
Method
Surface electrodes (like ECG dots) will be applied to the skin directly underlying your lower eyelids and over your neck muscles. You may be asked to look upwards or to elevate your head 45 degrees above horizontal. You will be asked to listen to clicking noises through headphones. Alternately, vibration pulses will be delivered over your forehead at 3 pulses per second. The recordings taken from your neck muscles or eye muscles give us useful information about your gravity sensors.
Preparation. None
Time taken: 10 minutes