|Image from Frontiers in Neurology|
Physical findings of mal de debarquement include body oscillations at 0.2 Hz, oscillating vertical nystagmus when the head was rolled from side-to-side, and unilateral rotation during the Fukuda stepping test (performed by marching in place with eyes closed for 30 seconds and noting any excessive turning suggestive of a vestibular imbalance).
Most people have some degree of mal de debarquement after a boat trip, but symptoms usually dissipate within hours of disembarking. For those who continue to suffer for weeks or longer, the traditional treatment include displacement exercises whereby vigorous physical exercise is performed while in motion (i.e., jogging on the street, but not on a treadmill).
However, this form of therapy did not always correct the internal sense of imbalance in patients as the underlying cause of this disorder was unknown until recently.
Recent research has elucidated that mal de debarquement is due to a maladaptation of the vestibulo-ocular reflex (VOR) to the roll of the head during rotation. As such, treatment is to readapt the VOR.
How does one "readapt" the VOR???
"After determination of the direction of the optokinetic stimulus and the rocking frequency, subjects were seated in a circular room (diameter, 6 ft) that had an optokinetic stimulator that projected 1.4° black and white stripes on the wall that filled the subject’s field of vision (image above). During treatment, the stripes were rotated at a constant velocity. Rotation of the drum elicited optokinetic nystagmus, and it also produced a sense of self-rotation (circular vection). The direction of the sensed rotation was opposite to that of the direction of rotation of the visual field. The subjects’ heads were rolled ±20° at their rocking frequency by the examiner while the subject watched the rotation of the stripes. A metronome tone directed the rocking frequency. The velocity of the optokinetic stimulus was initially 10°/s, but could be altered according to the subject’s response. Each session lasted for 3–5 min. Subjects were treated over 1 week. They had one to eight treatments per day for up to 5 days. When the severity of their MdDS was reduced by ≥50%, they were not necessarily treated further. " [link]
Basically the patient's "head is passively rolled at the rocking frequency while watching stripes moving to the left to act against the maladapted VOR component to the right. Using the diagram above, H is the velocity of the horizontal optokinetic stimulus; V is the component of the optokinetic stimulus in the head sagittal plane; P represents the maladapted vertical component; Head positions: A, on the left, B, in the center, and C, on the right. Arrows show the direction of the horizontal and vertical slow phase velocity." [link]Unfortunately, only major medical centers typically have the optokinetic stimulator to provide such treatment. (Our office does NOT have one.)
Another possible treatment more within reach by most medical practices is to treat it like a migraine headache with verapamil, nortriptyline, topiramate, or some combination thereof. According to one research paper, treatment with migraine medications resolved this syndrome in 73% of patients.
Readaptation of the vestibulo-ocular reflex relieves the mal de debarquement syndrome. Front. Neurol., 15 July 2014 | doi: 10.3389/fneur.2014.00124
Management of mal de debarquement syndrome as vestibular migraines. Laryngoscope. 2016 Oct 12. doi: 10.1002/lary.26299. [Epub ahead of print]