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

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.