Mal de debarquement
Mal de debarquement (or mal de débarquement) syndrome (MdDS, or common name disembarkment syndrome) is a neurological condition usually occurring after a cruise, aircraft flight, or other sustained motion event. The phrase "mal de débarquement" is French and translates to "illness of disembarkment". MdDS is typically diagnosed by a neurologist or an ear nose and throat specialist when a person reports a persistent rocking, swaying, or bobbing feeling (though they are not necessarily rocking). This usually follows a cruise or other motion experience. Because most vestibular testing proves to be negative, doctors may be baffled as they  attempt to diagnose the syndrome. A major diagnostic indicator is that most patients feel better while driving or riding in a car, i.e, while in passive motion. MdDS is unexplained by structural brain or inner ear pathology and most often corresponds with a motion trigger, although it can occur spontaneously. This differs from the very common condition of "land sickness" that most people feel for a short time after a motion event such as a boat cruise, aircraft ride, or even a treadmill routine which may only last minutes to a few hours. The syndrome has recently received increased attention  due to the number of people presenting with the condition, and more scientific research has commenced in determining what triggers MdDS and how to cure it. Symptoms. Common symptoms most frequently reported include a persistent sensation of motion usually described as rocking, swaying, or bobbing, disequilibrium with difficulty maintaining balance; it is seldom accompanied by a true spinning vertigo. Chronically fatigued, sufferers can become fatigued quickly with minimal exertion and some might experience neck and back pain. Other symptoms include the feeling of pressure in the brain, mostly around the frontal lobe area, headaches and/or migraine headaches, ophthalmodynia periodica (ice  pick stabbing headaches in the early stages of MdDs), ear pain, ear fullness and possibly tinnitus. Fluctuations in weather also affect sufferers, in particularly hot weather and barometric pressure changes. Many have photo-sensitivity and find it more difficult to walk in the dark as well as other sensitivities to strong smells including chemical smells. Cognitive impairment ("brain fog") includes an inability to recall words, short term memory loss, an inability to multi-task, misspelling and mispronunciation of words, difficulty in concentrating. Many MdDS sufferers report they are unable to use a computer for any length of time due to  the visual over-stimulation, and some are even unable to watch television. Symptoms can be increased by stress, lack of sleep, crowds, flickering lights, loud sounds, fast or sudden movements, enclosed areas and visual intolerance of busy patterns and scrolling movement. MdDS sufferers may have hypersomnia and can sleep up to 12 or more hours a day, depending on their symptom levels. Research reveals MdDS is not migraine-related and many sufferers have never had migraine symptoms prior to the onset of the disorder. However, for some MdDS sufferers there maybe have been a correlation between migraine and some pathophysiological  overlap or even some other precipitating illness. The condition may be masked by a return to motion such as in a car, train, plane, or boat; however, once the motion ceases, the symptoms rebound or return, often at much higher levels than when the journey first commenced. The symptoms of MdDS may be extremely debilitating and fluctuate high and low on a daily basis; it greatly affects the daily life and working capacity of sufferers with many having to relinquish work; it also limits most other daily and social activities. Sufferers can have low quality of life in both the  physical and emotional realms, comparable to people who have multiple sclerosis with many symptoms being of a similar nature. High levels of disequilibrium can contribute to suffers not being able to drive a car or walk far and this can create varying levels of anxiety in some or possibly depression due to the significant level of disability. Diagnosis. MdDS is diagnosed several ways, one being by the symptoms: in particular, the "constant rocking, swaying feeling" and the abatement of this feeling when in motion again and as a matter of exclusion. There are no definitive tests that confirm MdDS, only  tests that rule out other conditions. Tests include hearing and balance, and MdDS is generally diagnosed by either a neurologist or an ear, nose, and throat specialist. Treatment. There is no known cure for MdDS, as with most balance and gait disorders, some form of displacement exercise is thought helpful (for example walking, jogging, or bicycling but not on a treadmill or stationary bicycle). This has not been well-studied in MdDS. Medications that suppress the nerves and brain circuits involved in balance (for example, the benzodiazepine clonazepam) have been noted to help and can lower symptoms; however, it is  not a cure. It is not known whether a medication that suppresses symptoms prolongs symptom duration or not. Vestibular therapy has not proved to be effective in treating MdDS. Additional research is being undertaken into the neurological nature of this syndrome through imaging studies. Many sufferers of this syndrome have found relief by taking histamine blockers or antihistamines (Benadryl for instance). A single Benadryl gel tab at the beginning of the flight and at each 4-hour interval for longer flight. Epidemiology. The condition is thought to be under-reported in the medical literature. A study of 27 cases conducted  by Timothy C Hain in 1999 noted all but one patient to be female. The average age in this series was 49 years. This apparent gender disparity, however, may be due in part to the fact that the questionnaire which formed the basis of the study was circulated in a publication with a predominantly female reader base. Subsequent studies have produced conflicting results with regard to the gender distribution of MdDS. The trends in Hain's report have recently been supported by the MdDS Balance Disorder Foundation, in a study of over 100 individuals diagnosed with MdDS. The female:male  ratio was approximately 9:1; the average age of onset was 43–45 years. However, another recent study found that 44% of subjects who had experienced MdDS for 2 years or more were male, suggesting a more even distribution. It has been shown to occur in excursions of as little as 30 minutes though it has been unclear how long it takes for symptoms to occur. The most commonly reported inciting event was a prolonged ocean cruise (~45%); however, shorter boating excursions (~22%), aircraft travel (~15%), and automobile travel (~8%) have all been described. Mal de Débarquement syndrome has been noted as  far back to the times of Erasmus Darwin in 1796, and Irwin J A (1881) "The pathology of seasickness". Cases of MdDS have been reported in children as young as eight and in both genders. Men may have a more difficult time obtaining a diagnosis due to the disparity of women reported. When sailors and soldiers returned from World War II, the syndrome was reported at a higher rate in males Research. Repetitive transcranial magnetic stimulation. Despite MdDS causing significant disability, therapy for persistent MdDS remains virtually nonexistent. A pilot study has commenced utilizing repetitive transcranial magnetic stimulation (rTMS) this  being a method of neuromodulation in which a local magnetic field is applied over the scalp to induce an electric current in the cortical structures underlying the coil. Low-frequency rTMS (e1 Hz) induces local inhibition, whereas high frequency rTMS (Q5 Hz) induces local excitation. The TMS studies have proved to help in lowering the symptoms of MdDS if the treatment is ongoing; however, it is not a cure. Vestibulo-Ocular Reflex Research 2014. At least one clinical trial on readaptation of the vestibulo-ocular reflex undertaken by Dr Mingjia Dai from Mount Sinai Hospital in New York City produced  results for a significant percentage of patients who participated in the program. Dr Dai developed an intervention that provided improvement in symptoms for 70% of the patients in the clinical trial phase. The protocol involved a physical manipulation of the patient intended to readapt the vestibulo-ocular reflex. While the program was no longer in the research phase, Dai continued to accept patients. According to Dai, success was measured as a 50% reduction of symptoms. Recent research reveals a very small percentage of MdDS cases may be related to optokinetic nystagmus (OKN).