At the bedside

Diagnosis & criteria

MdDS is diagnosed from the history against defined criteria, with normal tests confirming there is nothing else to find. The art is recognising the pattern rather than ordering more investigations.

The Bárány Society criteria

In 2020 the Bárány Society published consensus diagnostic criteria for MdDS, requiring all of the core features below and exclusion of other causes.1 Tick the features present in your patient to see whether the picture meets the definition.

Bárány criteria checker

all 5 required

Oscillatory self-motionNon-spinning vertigo: a persistent perception of rocking, bobbing or swaying, present continuously or for most of the day.
Onset after passive motionSymptoms begin within 48 hours of the end of exposure to passive motion (a boat, plane, car or train) — or, in the non-motion-triggered form, without such a trigger.
Temporary relief by motionSymptoms are temporarily reduced by re-exposure to passive motion, e.g. while driving a car. This near-paradoxical feature is highly characteristic of MdDS.
Lasts > 48 hoursSymptoms persist for more than 48 hours, distinguishing the syndrome from the brief, self-limited 'sea legs' most people feel after a voyage.
Not better explained otherwiseNot better accounted for by another vestibular, neurological or medical disorder — vestibular and imaging tests are normal.

0 of 5 present — MdDS requires all criteria. Reconsider the differential for the missing features.

A teaching aid, not a diagnostic instrument. MdDS remains a clinical diagnosis of exclusion with normal vestibular and imaging tests; the criteria distinguish the syndrome from the brief, normal ‘sea legs’ nearly everyone feels after a voyage.

The role of testing

MdDS is a clinical diagnosis of exclusion: there is no confirmatory test. Audiometry, vestibular function tests (VNG/caloric, vHIT, VEMP) and MRI are normal — their purpose is to exclude peripheral and central mimics rather than to confirm MdDS.2 A clear history of motion-triggered onset with relief on re-exposure to motion and normal examination is the diagnosis.

Differential diagnosis

The two diagnoses most often confused with MdDS are the normal transient after-rocking of a voyage and PPPD. The discriminating questions are duration (>48 hours), and whether motion relieves (MdDS) or provokes (PPPD) the symptoms.

Distinguishing MdDS from its mimics
Condition	Distinguishing features
Transient mal de débarquement ('sea legs')	The normal, brief after-rocking that nearly everyone feels post-voyage; self-limited within hours to <48 h — not the syndrome
PPPD	Chronic non-spinning dizziness worsened by upright posture, motion and complex visual scenes — but NOT relieved by passive motion; often follows an acute vestibular event
Vestibular migraine	Episodic vertigo with migraine features; episodic rather than constant rocking; responds to migraine therapy
BPPV	Brief positional spinning vertigo with characteristic nystagmus on positional testing — not a constant rocking sensation
Vestibular neuritis / central lesion	Abnormal vestibular tests, nystagmus or other neurological signs — MdDS has normal examination and tests

Misdiagnosis is common — patients are frequently labelled with anxiety, PPPD or vestibular migraine before MdDS is recognised.3 A confidently taken history, anchored on the motion-relief paradox, is the most powerful diagnostic tool.

Key points

Diagnosis uses the 2020 Bárány Society criteria — all core features plus exclusion of other causes.
MdDS is a clinical diagnosis of exclusion; vestibular tests and imaging are normal.
Duration >48 h separates the syndrome from normal transient ‘sea legs’.
Motion relieves MdDS but provokes PPPD — the key discriminator.
Misdiagnosis is frequent; the history carries the diagnosis.