Clinical manifestations

Presentation and course

Symptoms of mal de debarquement include sensations of rocking, swaying, swinging, unsteadiness, and disequilibrium. For example, Groen reported, "the former passenger feels himself rising and rolling when in the hotel bed on shore" (33).

In general, no associated audiologic, vestibular, or vegetative symptoms are present (ie, tinnitus, hearing loss, hyperacusis, aural fullness, vertigo, nausea, vomiting, or headache). In reports where additional symptoms are described, patients were recruited from populations of "dizzy" patients (35; 17), and it is difficult to be sure that these subjects did not have other coincident audiovestibular or headache disorders (30). However, it is not surprising that the sensation of chronic rocking dizziness associated with mal de debarquement syndrome may cause or aggravate headaches in susceptible individuals (17; 01). In addition, patients with vestibular migraine may be more susceptible to developing mal de debarquement (63), and they may be more disabled than individuals with mal de debarquement who do not have vestibular migraine, in terms of severity of dizziness, job impact, and number of symptoms (06).

Some cases develop mal de debarquement after relatively short voyages of several hours (54; 21; 49). Most cases begin immediately on returning to land, but up to 25% may develop within 6 hours of disembarkation (32; 31; 21); occasional cases reportedly may not begin for several days after disembarkation (31). Mal de debarquement can also occur following other means of conveyance, such as car, train, air, or space travel. Duration is usually less than 24 hours (32; 31), but some may gradually resolve over a few days (33; 31; 21). A few patients have difficulty driving until the symptoms subside (31).

A small minority of patients may develop persistent symptoms, sometimes lasting more than 5 years (15; 12; 13). Persistent mal de debarquement appears more common in middle-aged women (10; 45; 35; 34; 08; 15; 12). Some patients with persistent symptoms develop spontaneous episodes of mal de debarquement-like symptoms after the initial mal de debarquement episode (15). Migraine is more common for those who develop spontaneous recurrences. In one study, nearly all patients suffering from mal de debarquement had a personal or family history of migraine headaches or signs or symptoms suggestive of atypical migraine (29).

Self-reported mal de debarquement syndrome is associated with high levels of depression, anxiety-related disorders, history of substance use disorders, and illness intrusiveness (04; 57). Mal de debarquement-related disability is associated with the severity of depression, anxiety, and neuroticism but not with the severity of mal de debarquement (57).

Neurologic examination is generally normal in both mal de debarquement and persistent mal de debarquement (45; 60; 15; 12; 61; 62), except possibly for some hesitancy in performing tests of balance (10) or some mild unsteadiness with ambulation. However, reported physical findings in some patients have included body oscillation at 0.2 Hz, oscillating vertical nystagmus when the head is rolled from side to side in darkness and unilateral rotation during the Fukuda stepping test (24). Symptoms may improve with the return to a ship (10; 31) or with reexposure to other passive motion (15).

Prognosis and complications

Most cases resolve spontaneously. However, middle-aged women seem to be particularly likely to experience protracted symptoms following an ocean cruise, with persistence of symptoms for many years (10; 54; 45; 35; 34; 60; 15; 12). Most mal de debarquement episodes lasting longer than 3 days resolve within a year, but the probability of resolution declines each year (18). Mal de debarquement dramatically impacts quality of life and imposes a considerable economic burden on affected patients (44).

Clinical vignette

Case 1. A 29-year-old man noted 2 days of mild but persistent dizziness and disequilibrium, which began immediately following disembarkation from a 2-week sailing trip. One night, in the middle of the trip, he experienced moderate sea sickness (without vomiting) when in the ship cabin at a mooring during a nocturnal tropical storm. Symptoms following disembarkation included mild disequilibrium when standing and walking and a rocking or swaying sensation when standing, sitting, or supine. Past history was unremarkable, and there was no associated vertigo, oscillopsia, hearing loss, hyperacusis, tinnitus, aural fullness, otalgia, nausea, vomiting, headache, or paresthesias. Symptoms gradually resolved without treatment.

Case 2. A 61-year-old woman noted 5 months of persistent imbalance and rocking sensations following a 7-day houseboat cruise. Other passengers had similar symptoms that resolved within a few days, whereas her symptoms persisted. Her symptoms were exacerbated by riding in an elevator as well as by heights. Examination was not reported (10).

Biological basis

Etiology and pathogenesis

The etiology of mal de debarquement is unknown (61; 62). It may result from an aberrant adaptive response to passive motion (41), defective or delayed readaptation or recalibration of vestibular pathways following cessation of motion (31; 45), or “pseudo-hallucinations” from vestibular memory, ie, stored vestibular information from the hippocampus (49). Individuals susceptible to mal de debarquement have a relatively greater dependence on the somatosensory system than the vestibular or visual systems for maintenance of balance (55).

Sea (or space) travel presents the vestibular, visual, and proprioceptive systems with a series of unnatural and unpredictable movements of varying amplitude in a variety of planes (pitch, yaw, and roll), producing various sensory conflicts (56; 58; 05). In contrast, terrestrial travel generally is associated with much more regular and predictable movements without simultaneous shifts in different planes. The normal short-term multisensory adaptive response to sea travel and ship motion is recognized in the expression "getting one's sea legs." Postural sway excursion and variability increase in individuals with minimal offshore experience after disembarking (05). Sensory reorganization difficulties maintaining an upright posture in challenging sensory conditions depends on vestibular and somatosensory inputs (05), the cerebellar flocculus, and the vestibular nuclei (58). Once this multisensory adaptive process, what some have called developing a new “internal model,” has occurred, post-voyage movements on land are awkward until a similar compensatory readaptation or recalibration to the conditions on land occurs. This period of readaptation is what is experienced as mal de debarquement. For unknown reasons, some patients apparently have difficulty with this readaptation process and experience persistent mal de debarquement.

The caudal aspect of the parabrachial nucleus contains neurons that are responsive to periodic rotational stimulation and modulated with respect to head orientation (gravity) during constant velocity off-vertical axis rotation (46). The caudal vestibulo-recipient parabrachial nucleus may help detect anomalies in control of postural stability during locomotion and may also be involved with the malaise associated with mal de debarquement (46).

Voxel-based morphometry in 28 individuals with mal de debarquement syndrome and 18 age-, sex-, and handedness-matched controls identified grey matter volume differences between cases and controls, and among cases, as a function of illness duration (16). Differences were identified in visual-vestibular processing areas, somatosensory network structures, and a structure within the central executive network (ie, the dorsolateral prefrontal cortex).

In another study, 18F-FDG PET showed relative hypermetabolism in the occipital and prefrontal cortices and hypometabolism in the vestibulocerebellum (nodulus and uvula) among those with mal de debarquement syndrome (compared to those who were unaffected) (39). Analysis of functional connectivity of the significant regions in the PET scans revealed decreased connectivity between the prefrontal cortex and visual processing areas in the mal de debarquement group. Resting-state functional connectivities were significantly decreased between the vestibular regions of the flocculus, superior temporal gyrus, and parietal operculum and the visual association areas of the middle occipital gyrus, fusiform gyrus, and cuneus in participants with mal de debarquement syndrome (39).

Based on experiments in monkeys exposed to continuous rotation in darkness, coupled with side-to-side roll, Dai and colleagues reproduced some of the features of human mal de debarquement syndrome (25; 20). Through further experiments, these investigators linked alterations in the velocity storage integrator with development of mal de debarquement syndrome (20).

The basis for the female preponderance of cases is unclear, but a potential relation has been proposed between gonadal hormone fluctuations and symptom aggravation in the motion-triggered group (51).

Epidemiology

Mal de debarquement is common following sea voyages and may occur in up to 73% to 86% of subjects (32; 31; 03), even among professional seamen (03). Occurrence appears to be related to sea sickness susceptibility but not to experience at sea (32), although some authors have also indicated that mal de debarquement is more common with initial sea voyages and less common and severe with subsequent voyages (31; 21). Prolonged sea voyages and rough sea conditions may be risk factors for mal de debarquement (10; 32). Women are more susceptible than men to both sea sickness and mal de debarquement (35; 28; 61; 62).

Relatively little epidemiologic information is available on persistent mal de debarquement, which appears to be relatively uncommon (32; 31; 30); it appears to be much more common in women than men (10; 54; 45; 35; 34; 60).

Prevention

Some anecdotal information suggests that small doses of benzodiazepines (eg, clonazepam, diazepam, or lorazepam) can be helpful prophylactically, particularly for those with a history of mal de debarquement; patients may want to consider this as an option when planning another trip involving the previously precipitating motion (eg, a cruise).

Differential diagnosis

The diagnosis of mal de debarquement is usually straightforward and is largely based on the history and a normal examination.

Mal de debarquement is distinct from motion sickness because subjects experience symptoms following termination of motion rather than during the period of motion, and subjects with mal de debarquement do not commonly have associated nausea, vomiting, diaphoresis, or headache.

Mal de debarquement has some similarities to the phobic postural vertigo syndrome: in mal de debarquement, a period of motion exposure induces a persistent sensorimotor derangement, whereas in phobic postural vertigo, a self-limited organic vestibular disorder induces a persistent psychophysiologic derangement characterized by anxiety, dependent or avoidant behavior, and nonrotational dizziness, with fluctuating unsteadiness, and postural and gait instability (09). In some patients, mal de debarquement may also induce or exacerbate anxiety disorders (08).

Diagnostic workup

History and physical examination are usually sufficient; no diagnostic tests are required. However, largely because of physician unfamiliarity with this disorder, diagnosis is often delayed (44; 61; 48), and an average of 19 clinical visits is needed for patients to obtain a diagnosis (44).

Electronystagmography or video-oculography, including caloric testing, is generally normal when performed in cases of persistent mal de debarquement but may show abnormal tracking or direction-changing positional nystagmus (10; 54; 45; 39); the latter findings are nonlocalizing and of questionable significance, particularly because they may be present in approximately 10% of normal subjects (42). The video head impulse test, ocular and cervical vestibular-evoked myogenic potentials, rotatory testing, audiograms, brainstem auditory evoked responses, and cerebral imaging are also normal (or show incidental findings) (10; 54; 45; 39).

Diagnostic guidelines have been proposed for persistent mal de debarquement syndrome (61; 62):

Management

Most cases with mal de debarquement resolve spontaneously over hours to days, and no further treatment beyond reassurance is necessary for the occasional patient who seeks medical care.

Chronic mal de debarquement has fluctuations that are both innate and driven by environmental stressors (14). Consequently, the therapeutic strategy is to provide counseling to manage expectations, identify and manage behavioral and lifestyle factors that exacerbate symptoms, employ cognitive-behavioral therapy, and utilize anxiolytic medications and SSRI/SNRI antidepressants as necessary to manage anxiety (11; 18; 53; 14).

For patients with more persistent or disabling symptoms, improvement in patient-reported outcomes has been reported with several different modalities, including pharmacologic management with neurotropic drugs, vestibular rehabilitation, and neuromodulating stimulation (40).

Benzodiazepines and SSRI/SNRI antidepressants have had anecdotal success with persistent mal de debarquement (54; 35; 11; 18), but because discontinuation of benzodiazepines may cause symptom exacerbation, these should be employed cautiously and for a limited time (54). Amitriptyline has also been reported to help assist recovery of persistent mal de debarquement (54). Neither meclizine nor transdermal scopolamine has been helpful for persistent mal de debarquement (10; 54; 35).

Formal vestibular rehabilitation has had limited success in this disorder (35) and, in some cases, may produce a short-term exacerbation of symptoms before long-term improvement (54). Nevertheless, patients should be encouraged to avoid inactivity and, thus, actively participate in activities that may enhance readaptation such as walking (10; 54; 45). “Sensory reweighting,” using vestibular, somatosensory, and visual challenges twice a week over a 10-week period, has been reported to be helpful in a single case (43).

Management of mal de debarquement as vestibular migraine may improve patients' symptoms and increase their quality of life. In one study, 11 of 15 patients (73%) responded well to management with a vestibular migraine protocol, which included lifestyle changes, as well as pharmacotherapy with verapamil, nortriptyline, topiramate, or some combination, whereas, in comparison, a retrospective control group of 17 patients demonstrated a lower rate of improvement when treated with vestibular rehabilitation and physical therapy (29).

Dai and colleagues reported that “readaptation” of the vestibulo-ocular reflex produced either a cure or a substantial improvement in 70% of 24 subjects with persistent mal de debarquement syndrome for a period of approximately 1 year on average (26; 24). On the premise that maladapted rocking sensations and the associated physical symptoms could be diminished or eliminated by readapting the vestibulo-ocular reflex, subjects were treated by rolling the head from side to side while watching a rotating full-field stimulus. In a later study, Dai and colleagues reported the outcomes of 141 patients (122 females and 19 males) whose heads were rolled while watching a rotating full-field visual surround (23). Significant improvement was defined as a reduction in symptom severity by more than 50%. No objective measures were used during follow-up because of the wide geographic distribution of the patients. The treatment group consisted of 120 classic and 21 spontaneous mal de debarquement patients. The initial rate of significant improvement after a week of treatment was 78% in classic patients and 48% in spontaneous patients. One year later, significant improvement was maintained in 52% of classic and 48% of spontaneous subjects. There was complete remission of symptoms in 27% (32) of the classic and 19% (4) of the spontaneous patients. These results have been supported by a sham-controlled trial (50). This treatment paradigm has been replicated in a virtual reality environment, successfully resolving symptoms in two visits in a single case study (37).

Special considerations

Pregnancy

Chronic mal de debarquement syndrome symptoms may improve during pregnancy (52). Although a hormonal basis has been suggested, this remains speculative.