Functional Neuroimaging and Transcranial Magnetic Stimulation in Mal de Debarquem

DESCRIPTION (provided by applicant): Mal de debarquement syndrome (MdDS) is a balance disorder in which patients develop a persistent internal sense of movement after a prolonged period of passive motion exposure. This is classically described as landsickness occurring after boat rides. Patients describe a hallucination of movement such as rocking and bobbing even though they are not physically moving. This disorder is thought to be due to a primary problem of brain adaptation as testing of inner ear function and structural brain imaging is always normal. However, it is unknown which parts of the brain control this adaptation. Most cases of mal de debarquement only last a few hours, but there are many people who experience the symptoms for months or years, leading to significant morbidity. The term MdDS is generally reserved for patients who experience symptoms for at least one month. A large case series of patients with MdDS showed that the majority of these patients develop profound sensitivity to visual motion, a symptom which only occurs during their MdDS attacks and may be a key component of this syndrome. Therefore, investigating brain areas that respond to both visual and vestibular stimuli may reveal differences between patients with MdDS and normal controls. If there are differences in such areas, the activity may be modulated externally with repetitive transcranial magnetic stimulation (rTMS). Though still in the experimental phases, rTMS has been used in the treatment of many disorders characterized by maladaptive responses, most notably major depression, chronic pain, and tinnitus. Studies on tinnitus show that there is an area of heightened baseline activity in the auditory cortex and that this activity can be dampened with rTMS. The proposed studies in this grant will first assess differences in the ability to detect visual motion in a computer based motion detection task. The threshold values determined on this task will be used as stimulation parameters in an fMRI paradigm which seeks to activate brain areas that detect visual motion. The main area that will be activated is motion sensitive area MT+/V5 which receives both visual and vestibular information. MT+/V5 will serve as a target in a sham-controlled 1Hz rTMS treatment design. We hope to reveal functional differences in brain activity in MdDS and to be able to introduce a new modality of treatment for this currently incurable disorder. PUBLIC HEALTH RELEVANCE: Mal de Debarquement Syndrome (MdDS) is an under-recognized disorder of balance control occurring after passive motion exposure such as on cruises, airplane or long car rides. It leads to significant morbidity and remains without a cure or knowledge about basic pathophysiology. Because the disorder is one of a phantom perception of self-motion and there is clinical evidence that visual motion processing may be affected, we hypothesize that brain areas that process both visual and vestibular information may be affected. If differences in the performance of psychophysical tasks that assess visual motion perception and in brain activation patterns in functional neuroimaging can be seen, then areas of differential activation may be targets for therapy with transcranial magnetic stimulation (TMS). The application of TMS to MdDS is proposed as a novel therapy for this disorder following the same rationale as other disorders of maladaptive cortical reorganization.