The exact cause of MdDS is not well understood. Several theories have been proposed, including the possibility that it is a disorder related to the brain's ability to adapt to changes in balance. MdDS usually occurs after spending time on a boat and the symptoms occur when returning to solid ground, producing a sensation called "sea legs". When on a boat, the brain is continuously affected by the movement of the waves in different directions, such as rolling, rocking, bobbing, pitching and rocking movements. The brain adapts to this movement through a reflex called the vestibulo-ocular reflex (VOR) to maintain stable vision when the head is in motion. In people with MdDS, there may be an inability to restore the normal balance after being exposed to movement, resulting in the persistent sensation of movement.
MdDS occurs when the balance of the body is disturbed due to problems with the two types of vestibular receptors, the otoliths and the semicircular canals. These receptors send information to the brain about the position of the head in relation to space and gravity.
In the case of MdDS, there is an inability to properly integrate these receptors into the balance system, along with problems in the cerebellum (cerebellum) that normally helps to adapt the reflexes. In order for our eyes to focus on our surroundings when we move our heads, cooperation between the balance and visual systems is essential. When the alignment of the vestibulo-ocular reflex is not working properly in MdDS, the sensation of movement occurs. Restoring proper alignment of this reflex is key to resolving the condition.
Research shows that it is possible to teach the body to readapt, which can alleviate the symptoms of MdDS. A 2014 study entitled "Readaptation of the vestibulo-ocular reflex relieves the Mal de Débarquement syndrome" proposed a treatment method that focused on correcting the maladaptation of the vestibulo-ocular reflex in MdDS. The treatment involved the use of a special visual stimulation called optokinetic stimuli (OKN) along with movements of the head in the direction the patient perceived they were moving. The aim was to help the body re-adapt the reflex correctly and reduce the perception of their own movement. Of the 24 participants in the study, 17 (70%) became symptom-free after the treatment and remained so for up to four months afterwards. We use this particular treatment in the clinic, along with other therapies.