Disease Patterns
BPPV
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Signature on CDP
The figure below shows the archetypal BPPV pattern across the six SOT conditions, MCT response, and ADT adaptation, compared against an age-matched normal reference.
In this module
- BPPV and CDPFoundation · Trainee · Clinician
- Findings between attacksFoundation · Trainee · Clinician
- After successful repositioningTrainee · Clinician
BPPV and CDP
Benign paroxysmal positional vertigo presents with brief (typically less than 60 seconds) episodes of spinning vertigo provoked by specific head positions, most commonly rolling over in bed, looking up, or bending forward. The Dix-Hallpike manoeuvre reliably elicits the diagnostic nystagmus pattern.
BPPV is the most common cause of vertigo in clinical practice. Posterior canal involvement accounts for about 85% of cases; horizontal canal BPPV is less common but harder to recognise; anterior canal BPPV is rare.
CDP is essentially irrelevant to BPPV diagnosis. The test challenges quiet stance, not head position, and BPPV is provoked specifically by head movement. A normal CDP in a patient with positional vertigo does not exclude BPPV — the Dix-Hallpike does that work.
Findings between attacks
Between BPPV attacks, CDP is typically normal or near-normal. The disorder doesn't affect the quiet-stance machinery; even during a symptomatic period, a patient tested when not actively dizzy will usually have a normal or near-normal SOT.
A patient with BPPV and an abnormal CDP usually has something else going on too — concomitant peripheral vestibulopathy, fear-avoidance behaviour, or an unrelated cause of imbalance. BPPV alone does not explain abnormal CDP findings.
This is why BPPV is the classic example of a vestibular diagnosis that requires the right test. Positional testing (Dix-Hallpike, supine roll) is diagnostic; CDP is unhelpful here.
After successful repositioning
After a successful canalith-repositioning manoeuvre (Epley, Semont, BBQ roll depending on canal involved), the diagnostic positional nystagmus disappears and the patient's symptoms resolve. CDP, which was likely normal already, remains normal.
Persistent imbalance after successful BPPV treatment is not uncommon and is sometimes called 'residual dizziness' or 'sub-objective postural instability'. It typically resolves over days to weeks, may benefit from a brief course of vestibular rehabilitation, and rarely requires further investigation.
If imbalance persists for weeks after successful treatment, look for co-existing causes: PPPD overlay, concomitant peripheral vestibulopathy, or central pathology. A CDP at this point can be useful — not for the BPPV itself, but for whatever else might be contributing.