Disease Patterns
PPPD
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Signature on CDP
The figure below shows the archetypal PPPD pattern across the six SOT conditions, MCT response, and ADT adaptation, compared against an age-matched normal reference.
In this module
- PPPD overview (Bárány Society criteria)Foundation · Trainee · Clinician
- Supportive CDP findingsTrainee · Clinician
- PPPD vs aphysiologic patternClinician
PPPD overview (Bárány Society criteria)
Persistent postural-perceptual dizziness (PPPD) is defined by Bárány Society 2017 criteria as three months or more of dizziness, unsteadiness, or non-spinning vertigo present on most days, exacerbated by upright posture, active or passive motion, and complex visual stimuli. The disorder is often triggered by a prior acute vestibular event (neuritis, BPPV, even a panic attack), and persists by maladaptive postural-control strategies.
PPPD is a clinical diagnosis. CDP, audiometry, MRI, and the rest of the workup are supportive — they document the absence of organic disease that would otherwise explain the symptoms — but they don't make the diagnosis. The criteria are symptom-based.
The disorder is common. Vestibular clinics commonly identify PPPD in 10–30% of chronic-dizziness referrals, depending on case mix. Many patients have been investigated extensively before the diagnosis is recognised; CDP plays a useful role in providing objective evidence consistent with the clinical picture.
Supportive CDP findings
The supportive CDP findings for PPPD are visual preference (elevated PREF ratio) and over-scaled MCT amplitudes. Either or both may be present; neither is required for the diagnosis.
Visual preference is the more specific finding — a PREF ratio above 1.0 in a patient with three months of dizziness and a normal structural workup is highly suggestive. The mechanism is hyper-reliance on visual cues: when vision becomes misleading (sway-referenced surround), the patient cannot disengage from it and sways with the false visual signal.
Over-scaled MCT amplitudes reflect anxious hypersensitivity. The patient over-corrects to small perturbations, producing larger sway than the perturbation warrants. This is non-specific (it can occur in any anxious patient) but supports the PPPD picture when present alongside visual preference.
PPPD vs aphysiologic pattern
PPPD and aphysiologic patterns can co-exist, and distinguishing them requires care. PPPD is a clinical diagnosis with supportive CDP findings; aphysiologic patterns are CDP signatures that don't fit any physiologically-plausible disease. A patient can have both.
When the CDP shows clear visual preference plus over-scaling but no Cevette inversion, the picture fits PPPD without aphysiologic features. The patient is genuinely impaired by maladaptive postural control.
When the CDP shows a Cevette inversion or other aphysiologic features in addition to PPPD-supportive findings, the interpretation is more nuanced. Aphysiologic features can arise from extreme effort variability in anxious patients, or from a separate functional overlay. The clinical picture, the patient's effort during testing, and the consistency with other findings should drive interpretation rather than the CDP alone.