Treatments of Mal de Debarquement Syndrome (MdDS) by Habituation of Velocity Storage
Condition: Mal de Debarquement Syndrome (MdDS)
MeSH terms: Syndrome
Study type: Interventional

Summary: 
      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.
    

Detailed description: 
      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.
    

Intervention name(s): re-adaptation of the vestibulo-ocular reflex; Habituation of velocity storage of the vestibulo-ocular reflex
Intervention type(s): Device; Device
Intervention description(s): 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.
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: 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.
Masking: Single (Participant)
Primary purpose: Treatment
Keywords: Mal de Debarquement Syndrome; Motion Sickness; body rocking; body swaying; Habituation of velocity storage