Idiopathic Bilateral Vestibulopathy: Peripheral Vestibular Disorders and Their Repercussions

The goal of this exploratory study is to gain a better understanding of the symptomatology of idiopathic bilateral vestibulopathy (IBV) by characterising as precisely as possible the type and intensity of each patient's peripheral vestibular deficit, and to investigate the link between this symptomatology and some functions influenced by the vestibular system (i.e. cognitive, emotional, vegetative functions).

Bilateral vestibulopathy (BV) is defined as total or partial impairment of vestibular function on both sides, leading to chronic postural and visual instability. Idiopathic bilateral vestibulopathy (IBV) is a rare condition characterised by acquired BV of unknown aetiology. Although described more than thirty years ago, IBV remains a condition with imperfectly understood contours, mechanisms and consequences.

The peripheral vestibular system, located in the inner ear, is the main balance organ. Sensory information from the vestibular system is distributed to different brain structures, which perform a wide range of functions, such as maintaining stability of gaze and posture, controlling certain functions such as sleep, spatial memory and emotional processes, and perceiving movement, spatial orientation and self-image.

The most common symptoms of IBV are persistent postural instability, and, when moving the head and body, a reduction in visual acuity that can go as far as a sensation of instability of the visual environment. Patients also often report problems with orientation and spatial memory, poor body shape, sleep disorders, attentional problems, and anxiety or depression. Because little is known about this disease, diagnosis often comes late, after several years of various explorations and consultations with doctors and specialists.

Based on the observation that patients suffering from IBV have heterogeneous peripheral impairments, both qualitatively (type of sensory organ affected) and quantitatively (the impairment is more or less complete), and that the sometimes complex symptomatology is difficult to relate to the type of peripheral deficit, the aim of this project is to gain a better understanding of the symptomatology of IBV by evaluating certain functions that have recently been shown to be influenced by the vestibular system, and to relate this to the type and intensity of the peripheral deficit.

Hence, the main aim of this project is to study the link between symptomatology - both 'classic' (posturo-oculomotor) and cognitive, emotional and vegetative - and the type and intensity of vestibular disorder.

Eligibility Criteria:
Inclusion Criteria:

* Person over 18 years of age (male or female)
* Healthy volunteer (for participants in the control group) or a member of the French Association of the Idiopathic Bilateral Vestibulopathy (AFVBI) or a bilateral vestibulopathy carrier (for participants in the patient group).
* Person who has read the information sheet and given written informed consent to take part in the study.
* Person affiliated to a social security scheme

Exclusion Criteria:

* Declaration of illiteracy
* Declaration of dementia (Alzheimer's disease, vascular dementia)
* Any progressive neurological disease (brain tumour, epilepsy, migraine, stroke, sclerosis, myoclonus, chorea, neuropathy, muscular dystrophy, myotonic dystrophy, etc.)
* All progressive psychiatric conditions (psychosis, mood or anxiety disorders, etc.),
* Declaration of pathologies threatening short-term vital prognosis (cancer)
* Drug addiction, alcohol dependence or coffee abuse during the last 6 months
* Contraindications to MRI (in particular electronic or metallic implants, claustrophobia, etc.).
* For healthy volunteers: vestibular or auditory disorders.

In addition, the vulnerable persons referred to in articles L. 1121-5 to 8 and L. 1122-1-2 of the French Public Health Code are excluded from the study:

* Pregnant, breast-feeding or parturient women,
* Persons deprived of their liberty, hospitalised without consent or admitted to a health or social establishment for purposes other than research,
* Minors,
* Adults under legal protection or unable to express their consent,
* Persons in emergency situations who are unable to give their prior consent.