Ms. W, aged 35 years, experienced an intense sensation of rocking after spending five days on a houseboat. The sensation was present in all body positions but was most noticeable when she was upright and walking.
She had no history of similar motion exposure and had previously taken ocean cruises without difficulty. There was no fluctuation of hearing, tinnitus, ear pressure, or spinning vertigo (either spontaneously or positional).
Ms. W was otherwise healthy and had no history of such neurologic conditions as migraine. She had taken no motion sickness medication before or during the cruise. The patient did not seek medical attention, and her symptoms improved slowly over two months without treatment.
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One year later, Ms. W went on another cruise and had a recurrence of symptoms. Physical examination showed normal tympanic membranes, no cranial nerve abnormalities, and no spontaneous nystagmus; the rest of the neurologic examination was normal, as was a hearing test. Although the patient felt as if she were rocking back and forth, Rhomberg and gait testing were normal. Dix-Hallpike testing for benign paroxysmal positional vertigo (BPPV) was unremarkable.
Ms. W underwent vestibular testing that included videonystagmography, rotational chair testing and computed dynamic posturography. A discussion of these tests is beyond the scope of this case presentation, but all results were normal.
Specifically, there was no evidence of a reduced vestibular response on caloric testing, and Ms. W’s balance on the swaying posturography test was also within normal limits. An MRI of the head and a neurologic consultation showed no evidence of a specific central abnormality.
The differential diagnosis included BPPV, Ménière disease, recurrent vestibular neuritis, and migraine, but the patient’s symptoms and test results pointed toward none of these. A tentative diagnosis was made of mal de debarquement (MDD). Neither treatment with such vestibular suppressant medications as meclizine (Dramamine) and diazepam (Valium) nor vestibular rehabilitation physical therapy was helpful.
As had happened previously, Ms. W’s symptoms gradually resolved over a two- to three-month period. A recommendation was made to avoid situations involving similar types of motion.
1. Analysis
Balance function is a complex system involving input from vision, somatosensory, cervical, and vestibular sensors to the central nervous system, which instantaneously orients the body in space. Common causes of unsteadiness or dizziness include viral labyrinthitis or neuritis, BPPV, Ménière disease, migraine, and disequilibrium of aging (sometimes referred to as “multisensory deficit syndrome”).
Patients with such abnormalities in the vestibular system as BPPV or Ménière disease usually present with a sense of spinning or whirling vertigo, whereas a somatosensory abnormality like peripheral neuropathy causes unsteadiness.
Disequilibrium of aging is the most common abnormality causing unsteadiness and is marked by a sense of imbalance caused by gradual deterioration of central and peripheral sensory function. Individuals with disequilibrium of aging notice their symptoms almost exclusively when they are ambulating.
However, the less well-known syndrome of MDD, consisting of a feeling of rocking, swaying, unsteadiness, and disequilibrium after exposure to motion, should also be considered.1-6 MDD (or “sickness of disembarkment”) has been defined as the inappropriate sensation of movement after exposure to motion and it is most commonly felt after a long sea voyage.
MDD can also occur after traveling by any means of transportation, including an automobile or an airplane.7 The condition may also be associated with space flight, waterbeds, flight-simulator training, helmet-mounted virtual movement, and rotating rooms.1
For most people, the sense of movement duplicates the inciting motion. For example, patients with MDD after an ocean cruise may feel as if they are still rocking back and forth like the boat on the waves. This feeling may last hours, weeks, or in rare cases, years.3,6
Symptoms may be improved or alleviated by a return to the precipitating mode of transportation. Patients who experience a rocking sensation after a cruise may feel quite normal once they are back onboard a ship, or even with such other motion as riding in an automobile.6 This temporary symptom relief leads some patients to jokingly request a prescription for a cruise.1
Short-term MDD can be a common occurrence. For example, most cruise passengers initially feel unsteady when the ship is rocked by ocean waves. Within a short period (typically one or two days), they adapt to the ship’s motion. After the cruise ends and they return to shore, passengers may temporarily feel a rocking sensation that usually lasts just minutes to hours.
