Treatments of Mal de Debarquement Syndrome (MdDS) by Habituation of Velocity Storage

Mal de Debarquement Syndrome (MdDS) is an under-recognized but nevertheless common balance disorder, which in most cases occurs after exposure to prolonged passive motion. The current treatment approaches focus on reducing symptoms, but they can be retriggered. This project aims to shift the focus of MdDS treatment to permanently eliminating the symptom trigger while also minimizing symptoms.

Mal de Debarquement Syndrome (MdDS) is an under-recognized but nevertheless common balance disorder, primarily manifested by constant self-motion sensations consisting of rocking/swaying or gravitational pull of the body, which are accompanied by fatigue, migraine, hypersensitivity to light/noise/crowds, visually induced dizziness, and cognitive dysfunctions. As the name implies ("disembarkation sickness"), in most cases MdDS occurs after exposure to prolonged passive motion, specified as motion-triggered (MT) MdDS. However, the symptoms of MdDS can also occur without a motion trigger, termed as spontaneous MdDS. MdDS is debilitating and entails various mental health issues, such as suicidal thoughts, depression, and anxiety. Treatments for this disorder are still limited, as the specific underlying pathophysiology remains unclear. Recently, the team developed the first treatment method that can safely and effectively ease MdDS symptoms in the majority of patients via readaptation of the vestibulo-ocular reflex (VOR). The hypothesis underlying this treatment is that MdDS is caused by maladaptation of the functional component of the VOR called velocity storage, whose readaptation can be stimulated by exposure to whole-field visual motion coupled with head tilts. Over the past several years, more than 500 patients from around the world have been treated with this method. The success rate immediately after this treatment is 75% for MT MdDS, but some patients report return of symptoms after subsequent flights or prolonged car rides. Thus, the effectiveness of the current MdDS treatment protocol can depend on a serious practical limitation of needing to permanently avoid transportation. Building on the previous hypothesis of velocity storage maladaptation, the study team currently hypothesizes that another method, based on the reduction (habituation) of the velocity storage, can also resolve MdDS symptoms. Velocity storage can be greatly habituated within 4-5 days using a protocol previously developed in the study team's laboratory to reduce susceptibility to motion sickness. Preliminary data support the application of this protocol to MdDS. Moreover, since animal-based research suggests that velocity storage habituation is permanently retained, the study team further hypothesizes that this new treatment method yields robust long-term outcomes. In this project, 50 MT MdDS patients with otherwise normal vestibular and neurological functions will be randomly assigned into two groups, one to be treated by velocity storage habituation and the other by readaptation. Patients will be followed up for 6 months. Based on the preliminary data, the study team expects both groups to yield similar initial success rates for symptom improvement. However, the study team expects the group undergoing the habituation protocol to better retain the initial treatment impact in the long term. This project will significantly impact the MdDS treatment practice. The current approach focuses on reducing symptoms, but they can be retriggered by another prolonged exposure to passive motion. The habituation approach on the other hand focuses on permanently minimizing the symptom trigger while also minimizing symptoms. This project will also increase the current understanding of recurrent MdDS.

Mal de Debarquement Syndrome, Motion Sickness, body rocking, body swaying, Habituation of velocity storage

In this project, 50 motion triggered MdDS patients with otherwise normal vestibular and neurological functions will be randomly assigned into two groups, one to be treated by velocity storage habituation and the other by readaptation. Patients will be followed up for 6 months. Based on the preliminary data, we expect both groups to yield similar initial success rates for symptom improvement.

Treatment by re-adaptation of the vestibulo-ocular reflex (VOR) for participants with motion triggered MdDS

The VOR will be readapted by activating velocity storage with full-field optokinetic motion at 5°/s in a set direction while the head is oscillated with a set frequency and direction. The readaptation training will be conducted in repeated modules, each lasting for 1-5 min. The expected duration of daily sessions varies from 30 to 90 min. A day's session will be terminated if patient no longer feel symptoms of MdDS.

The central (velocity storage) time constant will be reduced by inducing cancellation of two velocity storage-mediated responses: OKN and the VOR. Sinusoidal rotation at 0.017 Hz (1 revolution/min) in darkness advances the slow phase eye velocity of the VOR by 32º. In contrast, the OKN at this frequency has no phase advancement. Thus, to counteract the VOR by OKN, the optokinetic stimulus should be set to 32º phase advance the out of phased head rotation stimulus. Since the conflict stimulus is expected to be overwhelming to patients at higher chair velocities, subjects will be first trained with a 10°/s stimulus. In a previous study, no complaints were reported when subjects were tested at such low velocities. Preliminary testing show signs of symptom improvement when the peak velocity reached 30°/s to 40°/s.

The severity of subjective symptoms will be assessed with self-report on a scale 0-10, where 0 is no symptom and 10 is the most difficult sensation of that symptom that patient can imagine. Higher score indicates more symptoms. Among these symptoms are: brain fog, head pressure, fullness of ear, heavy head, headache, nausea, blurry vision, fatigue, sensitivity to fluorescent lights, scrolling of computer screen, sensitivity to smell, sensitivity to noise, walking on trampoline, sensation of gravitational pull up or down. Subjects will be trained to estimate the level of symptoms to minimize inconsistency.

The severity of subjective symptoms will be assessed with self-report on a scale 0-10, where 0 is no symptom and 10 is the most difficult sensation of that symptom that patient can imagine. Higher score indicates more symptoms. Among these symptoms are: brain fog, head pressure, fullness of ear, heavy head, headache, nausea, blurry vision, fatigue, sensitivity to fluorescent lights, scrolling of computer screen, sensitivity to smell, sensitivity to noise, walking on trampoline, sensation of gravitational pull up or down. Subjects will be trained to estimate the level of symptoms to minimize inconsistency.

The severity of subjective symptoms will be assessed with self-report on a scale 0-10, where 0 is no symptom and 10 is the most difficult sensation of that symptom that patient can imagine. Higher score indicates more symptoms. Among these symptoms are: brain fog, head pressure, fullness of ear, heavy head, headache, nausea, blurry vision, fatigue, sensitivity to fluorescent lights, scrolling of computer screen, sensitivity to smell, sensitivity to noise, walking on trampoline, sensation of gravitational pull up or down. Subjects will be trained to estimate the level of symptoms to minimize inconsistency.

Static posturography will be obtained with a specifically designed computer program for a Wii board (Nintendo). The displacement of center of pressure (COP) over a 1 min period will be measured, and the root mean square of the postural displacement will be computed to compare the postural stability before and after the treatment. The total trajectory length (maximum excursion) of the COP deviation over 20 s will also be computed. Postural stability will be obtained with the subject standing with the feet 30 cm apart and eyes either open or closed. The sensation of body bobbing will be assessed by asking the patient to move the wrist up/down to imitate the internal sensation of bobbing and measuring the movement frequency with an accelerometer attached to the wrist. Presence of gravitational pull in sideway, forward or backward directions will be objectively measured with static posturography.

Visual Vertigo Analogue Scale. There are 9 separate visual analogue scales to rate intensity of visual vertigo provoking situation. Each scale is on a 0-10 cm line. Higher score represents more dizziness.

Visual Vertigo Analogue Scale. There are 9 separate visual analogue scales to rate intensity of visual vertigo provoking situation. Each scale is on a 0-10 cm line. Higher score represents more dizziness.

Visual Vertigo Analogue Scale. There are 9 separate visual analogue scales to rate intensity of visual vertigo provoking situation. Each scale is on a 0-10 cm line. Higher score represents more dizziness.

Physical, emotional, and functional disability related to MdDS will be assessed with DHI. DHI is a 25-item self report questionnaire, total score range from 0 to 100, with higher score indicating more perceived disability.

Physical, emotional, and functional disability related to MdDS will be assessed with DHI. DHI is a 25-item self report questionnaire, total score range from 0 to 100, with higher score indicating more perceived disability.

Physical, emotional, and functional disability related to MdDS will be assessed with DHI. DHI is a 25-item self report questionnaire, total score range from 0 to 100, with higher score indicating more perceived disability.

Inclusion Criteria: - Age 18-78. Exclusion Criteria: - Patient with serious spinal, neck and legs injuries will be excluded, since postural ability is essential for both treatments.

Individual participant data that underlie the results reported in this article, after deidentification (text, tables, figures, and appendices).

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