At the bedside

Differential diagnosis

BPPV is usually obvious, but positional vertigo has impostors — some benign, one dangerous. The episode duration, the triggers, the presence of cochlear symptoms, and the behaviour of the nystagmus separate them.

Episode duration is the first discriminator. BPPV is measured in seconds; Ménière’s and migraine in minutes to hours; neuritis is continuous over days. Central positional vertigo is variable or persistent and carries red flags — pair a suspicious duration with non-fatiguing nystagmus or neurological signs and image rather than reposition.

Distinguishing BPPV from its mimics
Diagnosis	Episode duration	Trigger	Cochlear symptoms	Key clue
BPPV	< 1 min	Positional (lying, rolling, looking up)	None	Latency + fatigability; canal-specific nystagmus on positional testing
Vestibular migraine	Minutes–hours	Variable, sometimes positional	Usually none	Migraine features (headache, photophobia, aura); no reproducible fatigable nystagmus
Ménière's disease	20 min–hours	Spontaneous	Fluctuating low-frequency loss, tinnitus, fullness	Cochlear symptoms with the vertigo
Vestibular neuritis	Days (continuous)	Not positional	None	Acute prolonged vertigo; abnormal head impulse; unidirectional spontaneous nystagmus
Central positional vertigo	Variable / persistent	Positional	None	No latency, non-fatiguing, pure downbeat or direction-changing; neurological signs

The benign mimics

Vestibular migraine can be positional, but episodes run minutes to hours and usually carry migrainous features; its positional vertigo lacks the reproducible, fatigable nystagmus of BPPV. Ménière’s disease is set apart by its cochlear triad (fluctuating hearing loss, tinnitus, fullness) and longer episodes — though BPPV can coexist with it. Vestibular neuritis causes acute, continuous vertigo over days with an abnormal head impulse and is not positional; BPPV may follow it in recovery.

The dangerous mimic — central positional vertigo

Cerebellar and brainstem lesions — infarction, demyelination, tumour — can mimic positional vertigo. The distinguishing features are mechanical opposites of BPPV: nystagmus with no latency, that does not fatigue, often pure downbeat or direction-changing, and frequently lacking the torsional component of posterior-canal BPPV.1,2

Red flags that mandate MRI (diffusion-weighted) and referral: atypical or non-fatiguing nystagmus; persistent imbalance; associated cranial-nerve, cerebellar or long-tract signs (diplopia, dysarthria, limb ataxia, facial numbness); and failure to respond to a correctly performed repositioning manoeuvre.3