What is the diagnosis and treatment for a patient experiencing a sensation of being in a car while remaining still, potentially indicating a neurological or psychiatric condition?

Mal de Débarquement Syndrome (MdDS)

The sensation of being in a car while remaining still most likely represents Mal de Débarquement Syndrome (MdDS), a neurological condition characterized by persistent perception of motion (rocking, swaying, or bobbing) that typically follows prolonged exposure to passive motion such as car travel, and requires symptomatic management as no definitive cure exists.

Clinical Presentation and Diagnosis

MdDS presents as a persistent illusion of motion that paradoxically improves with actual movement (such as riding in a car) and worsens when stationary. This distinguishes it from other vestibular disorders:

• The sensation typically begins after disembarking from prolonged passive motion exposure (car, boat, plane, train) 1
• Symptoms are relieved by re-exposure to motion and worsen when still—the opposite pattern of most vestibular disorders 2
• Unlike BPPV, MdDS does not cause brief episodes triggered by specific head positions, but rather continuous symptoms 2, 3
• There is no associated hearing loss, which helps differentiate from Meniere's disease 3
• No loss of consciousness occurs, distinguishing it from syncope 2

Key Differential Diagnoses to Exclude

Benign Paroxysmal Positional Vertigo (BPPV)

• BPPV causes brief episodes (typically <1 minute) of vertigo triggered by specific head movements, not continuous motion sensation 2, 3
• Dix-Hallpike maneuver provokes characteristic nystagmus in BPPV but would be negative in MdDS 2
• BPPV accounts for 85-95% of peripheral vestibular disorders but has distinct episodic rather than continuous presentation 3

Vestibular Migraine

• Requires episodes lasting 5 minutes to 72 hours with associated migraine features (headache, photophobia, phonophobia) 2
• Has a lifetime prevalence of 3.2% and accounts for 14% of vertigo cases 2, 3
• Distinguished by necessary migraine components not typically present in MdDS 2

Central Neurological Causes (Red Flags)

Immediate neurological evaluation is warranted if any of the following are present:

• Downbeating nystagmus without torsional component on examination 2, 3
• Direction-changing nystagmus without head position changes 2
• Associated neurological signs: dysarthria, dysmetria, dysphagia, sensory/motor deficits 2
• Sudden onset (suggesting cerebellar or brainstem stroke, which presents in 10% of cases mimicking peripheral vestibular disorders) 2, 3
• Baseline nystagmus without provocative maneuvers 2

Psychiatric Considerations

• Post-traumatic stress following motor vehicle accidents can cause persistent sensation of movement, occurring in 39-53% of MVA victims 1, 4
• However, psychiatric causes typically include other trauma-related symptoms (intrusive memories, avoidance, hyperarousal) 4

Management Approach

Initial Assessment

Perform targeted history focusing on:

• Temporal relationship to passive motion exposure (car, boat, plane travel) 1
• Pattern of symptom relief with re-exposure to motion 2
• Absence of episodic vertigo, hearing loss, or loss of consciousness 2, 3
• Screen for red flag neurological symptoms requiring urgent evaluation 2, 3

Treatment Strategy

Symptomatic management is the mainstay, as no definitive cure exists:

• Vestibular rehabilitation therapy may provide benefit for adaptation, though evidence is limited for MdDS specifically 2
• Reassurance about the benign nature and typical self-limited course (though some cases persist) 2
• Avoidance of vestibular suppressants (meclizine, benzodiazepines) which may delay central compensation 2

Modifying Factors Requiring Assessment

Evaluate for factors that increase fall risk and functional impairment:

• Impaired mobility or balance (12-fold increased fall risk with dizziness symptoms) 2, 3
• Age >65 years (one in three falls annually in this population) 2, 3
• CNS disorders or lack of home support 2
• Occupational hazards if symptoms affect work safety 2

Driving and Safety Considerations

Address driving safety explicitly:

• The sensation itself does not cause loss of consciousness and poses lower risk than syncope 2
• However, distraction from persistent symptoms may impair driving performance 2
• Risk stratification should consider symptom severity, frequency, and presence of prodromal warning 2
• For persistent disabling symptoms, temporary driving restrictions may be warranted until adaptation occurs 2

Common Pitfalls to Avoid

• Do not dismiss as anxiety without thorough vestibular assessment, as psychiatric symptoms may be secondary to the distressing physical sensation 1, 4
• Do not perform unnecessary vestibular testing if history is classic for MdDS, as standard vestibular tests are typically normal 2
• Do not prescribe vestibular suppressants chronically, as they impede central compensation 2
• Do not miss central causes: any atypical features warrant neuroimaging and neurology consultation 2, 3