Mal de Débarquement Syndrome

Definition and epidemiology

Mal de débarquement (French for ‘sickness of disembarkation’) syndrome (MdDS) is defined by non-spinning vertigo that begins after exposure to passive motion has ended and is present continuously or for most of the day. People feel as if they are rocking, bobbing or swaying, and the symptoms ease temporarily when passive motion resumes, for example when driving. Triggers include boat, air, car and train travel, as well as swaying buildings or platforms. In criteria published in 2020, the Bárány Society divided the syndrome by duration into MdDS in evolution, transient MdDS and persistent MdDS (Cha et al., 2020).

A rocking sensation lasting less than 48 hours after leaving a boat is common, regarded as normal, and affects men and women equally. Once symptoms last beyond 48 hours, and especially beyond a month, the picture shifts sharply towards women, who make up 75-100% of these cases. Onset is most often between 40 and 49 years, and cases from age 12 into the 70s have been reported. Population frequency is unknown, but at one tertiary neurotology clinic 1.3% of patients seen over five years were diagnosed with MdDS, compared with 8.6% diagnosed with Ménière’s disease (Cha et al., 2020). In a series of 64 patients, 75% were women and the mean age at the first episode was 39 years (Cha et al., 2008).

Symptoms and signs

The main complaint is a sensation of rocking, bobbing or swaying, often described as ‘feeling as if I am still on the boat’. Spinning vertigo is not expected. A clear reduction of symptoms while driving or riding in a vehicle is a core feature of the diagnosis (Cha et al., 2020). In some patients the body has been shown to oscillate at about 0.2 Hz (Dai et al., 2014). Neurological examination, electronystagmography (ENG) and brain MRI are normal in most patients (Cha et al., 2008).

Under the Bárány criteria, the syndrome is called ‘in evolution’ while symptoms are ongoing and the observation period is under a month, ‘transient’ if symptoms resolve within a month, and ‘persistent’ if they last more than a month (Cha et al., 2020). In one series, 51% of 104 episodes lasted over a month, 18% over a year and 11% over five years. Episodes may recur with new journeys, and in some patients later episodes occur without any motion exposure even though the first was triggered by travel (Cha et al., 2008). A similar oscillating sensation that begins without any passive motion has not been classified by the Bárány committee and is referred to in the literature as ‘spontaneous’ or ‘atypical’ MdDS (Cha et al., 2020).

Causes and risk factors

The mechanism is not fully understood (Van Ombergen et al., 2016). One leading explanation is that during time in a moving environment the vestibulo-ocular reflex (VOR) and the brain’s spatial orientation system adapt to the motion; after the journey the adaptation fails to reverse, so the person continues to perceive motion on stable ground. On this view the VOR has adapted inappropriately to head roll during rotation, and readapting it can relieve the symptoms (Dai et al., 2014). Neuroimaging studies have reported changes in brain metabolism and network connectivity, but these methods are not used for clinical diagnosis (Cha et al., 2020).

The strongest known risk factors are female sex and middle age. The link with migraine is notable: in one series, migraine was present in 73% of patients who later had spontaneous episodes, compared with 22% of those who did not (Cha et al., 2008). Even so, more than half of people with MdDS never meet criteria for migraine, and the two can coexist (Cha et al., 2020). Sea travel is the commonest trigger (Van Ombergen et al., 2016); evidence on how journey length or sea conditions affect risk is limited.

Audiological and clinical assessment

The diagnosis rests entirely on the clinical history; there is no pathognomonic examination, laboratory or imaging finding. The Bárány Society criteria are (Cha et al., 2020):

• A. Non-spinning vertigo with an oscillatory quality (rocking, bobbing, swaying), present continuously or for most of the day.
• B. Onset within 48 hours after the end of exposure to passive motion.
• C. Temporary reduction of symptoms with renewed exposure to passive motion (e.g. driving).
• D. Symptoms lasting more than 48 hours; by duration, MdDS in evolution (observation under a month), transient (resolving within a month) or persistent (lasting more than a month).
• E. Not better accounted for by another disease or disorder.

Audiological and vestibular testing serves to exclude other diagnoses. With a typical history the yield is very low, and incidental findings can mislead (Cha et al., 2020):

• Pure-tone and speech audiometry, tympanometry and acoustic reflexes: no findings are expected in MdDS; new hearing loss is an atypical feature that needs further investigation.
• Vestibular tests (video head impulse test, caloric testing, VEMPs, videonystagmography): usually normal. Direction-changing positional nystagmus in darkness has been reported, but it is non-specific and also occurs in people without MdDS.
• MRI and CT: low yield; requested when there are atypical features such as eye movement abnormalities or neurological signs.

The conditions most often confused with MdDS are Persistent Postural-Perceptual Dizziness (PPPD), vestibular migraine and motion sickness. The key distinctions are when symptoms begin and whether passive motion relieves them (Cha et al., 2020). For a general overview, see an introduction to vertigo and balance disorders.

Treatment and audiological rehabilitation

There is no evidence-based standard treatment; published studies are small and mostly uncontrolled, and placebo-controlled randomised trials are needed (Van Ombergen et al., 2016). In the transient form symptoms often settle on their own, and explaining that the condition is benign and common is important. The choice of medication and other treatments rests with the doctor.

The most studied approach is a visual-vestibular protocol aimed at readapting the VOR. The patient rolls the head from side to side while watching a rotating visual stimulus that fills the whole visual field (an optokinetic stimulus). In the first series of 24 patients, about 70% had complete or substantial improvement lasting about a year on average, while six relapsed (Dai et al., 2014). In a follow-up study of 141 patients, marked improvement after one week was seen in 78% of the classic (travel-triggered) form and 48% of the spontaneous form; improvement was maintained at one year in 52% and 48% respectively, and complete remission occurred in 27% and 19% (Dai et al., 2017). As these studies had no control group, the results should be interpreted with caution.

In a pilot study of repetitive transcranial magnetic stimulation (rTMS) over the dorsolateral prefrontal cortex, ten patients showed short-term improvement; there was no sham condition, and longer symptom duration predicted a poorer response (Cha et al., 2013). The summary table of the Bárány document lists SSRI and SNRI antidepressants and benzodiazepines among treatments with a reported response, and physical therapy and psychotherapy among those without (Cha et al., 2020); the efficacy of these drugs has not been shown in randomised trials.

The audiologist’s contribution is to recognise the typical history, explain to the patient that vestibular test results may well be normal, avoid unnecessary repeat testing, and refer the patient to a doctor familiar with the syndrome.

Impact on quality of life and advice

Persistent MdDS can markedly affect work, study and social life because of a rocking sensation that lasts all day. Patients describe difficulty concentrating, fatigue and the sense of not being understood because the condition is invisible. Feeling better while driving may seem paradoxical but is typical of the syndrome, and explaining this to the patient reduces anxiety. Long-lasting symptoms can lead to anxiety and depressive symptoms, in which case psychological support should be considered.

Practical advice: note the journey that triggered the symptoms, how long they have lasted and what makes them better or worse, and share this with your doctor. If you are planning another boat trip or flight, discuss the chance of recurrence with your doctor beforehand. While symptoms persist, take care on stairs, at heights and in crowded places where you feel less secure. Knowing that the condition is benign and that many people improve with time or treatment can make it easier to return to normal activity.