Bilateral Vestibulopathy, Healthy Volunteers, Reflex, Abnormal
Conditions
Keywords
Saccadic Eye Movements, Bilateral Vestibulopathy, Bilateral Vestibular Hypofunction
Brief summary
Patients with chronic bilateral vestibular hypofunction may suffer from a visual instability during head movement called oscillopsia. Visual consequence of vestibular deficit can lead to a severe impairment of their quality of life. However, correcting saccades during rapid head movement, called covert-saccades, have been more recently identified. These saccades, which occur during the head movement in patients with vestibular hypofunction, present a very short latency. They could compensate for the lack of vestibular-ocular reflex and greatly decrease oscillopsia and visual impairment. The triggering of these covert-saccade is still not known. They could be of visual origin but the short latency is unusual. The objective of this study is to evaluate the potential role of visual trigger in 12 patients with chronic bilateral areflexia, using different visuo-vestibular conditions. The latency of simple visually guided saccades will also be tested in the group of patients and a group of 12 healthy controls.
Interventions
OTHERCovert Saccades and Virtual Reality
During this intervention, patients will undergo head impulse testing while wearing virtual reality Headsets. During the head impulse tests the visual information will be modified in order to create a conflict between head rotation and rotation of the visual scene. Recording of head and eye movement will be done during these head impulses in order to verify if visual information modifies compensatory eye movements during head impulses.
OTHERActives versus passives Head Impulses
Patients will undergo classic passive head rotation as well as active head rotation in order to compare latencies of covert saccades in both conditions.
OTHERVisually guided saccades
Patients as well as healthy control subjects will undergo testing of visually guided saccades in different conditions (step, gap, overlap) in order to compare latencies of covert saccades between both groups.
Sponsors
Hospices Civils de Lyon
Study design
Allocation
NON_RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to 90 Years
Healthy volunteers
Yes
Inclusion criteria
* For all : * Age from 18 to 90 * Understanding of the experimental instructions * Informed Consent * For Patients : Bilateral vestibular hypofunction with regards to the criteria of the of the Barany Society A. Chronic vestibular syndrome with at least three of the following symptoms 1. Postural imbalance 2. Unsteadiness of gait 3. Movement-induced blurred vision or oscillopsia during walking or quick head/body movements 4. Worsening of postural imbalance or unsteadiness of gait in darkness and/or on uneven ground B. No symptoms while sitting or lying down under static conditions C. Bilaterally reduced or absent angular VOR function documented by * bilaterally pathological horizontal angular VOR gain \< 0.6, measured by the video-HIT5or scleral-coil technique and/or * reduced caloric response (sum of bithermal max. peak SPV on each side \< 6°/sec7)and/or * reduced horizontal angular VOR gain \< 0.1 upon sinusoidal stimulation on a rotatorychair (0.1 Hz, Vmax = 50°/sec). D. Not better accounted for by another disease \* For Healthy control No ENT or neurological disorders
Exclusion criteria
* Corrected Visual Acuity lower than 5/10 * Other conditions leading to oscillopsia or ataxia * Oculomotor palsy, ocular instability in primary position * Treatment that may affect ocular motility (psychotropes) * Cervical rachis pathology with instability * Cochlear Implants * Non-stabilized medical disease * Pregnant women * Patients under tutelage * Patient without social security
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Latency of covert-saccades | Day 1 | Latency of covert saccades correspond to the time between the beginning of head impulse and the initiation of the first covert-saccade |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Frequency of covert-saccades | Day 1 | Frequency of covert saccades corresponds to the total amount of covert-saccades divided by the total amount of head impulse tests multiplied by 100. |
| Velocity of covert-saccades | day 1 | Velocity of covert saccades correspond to the maximal velocity of the first covert-saccade |
| Amplitude of covert-saccades | Day 1 | Amplitude of covert saccades correspond to amplitude of the first covert-saccade |
| Latency of visually-guided saccades | Day 1 | Latency of visually guided saccades correspond to the time between the appearance of target and the initiation of the first saccade |
Countries
France
Outcome results
None listed