Patient Positioning — From Seated to Supine Head-Hanging
Patient moves quickly from seated to supine with head turned 45° and extended.
- 45°: Head turn angle (toward tested ear)
- 20°: Head extension (below horizontal)
- Fast: Maneuver speed (brisk single motion)
- 30–60s: Hold duration (observe eyes throughout)
Setup and hand placement
Examiner supports the head during the rapid positional change.
Target canal orientation
Turn aligns posterior canal plane with gravity for debris movement.
Latency Period Before Nystagmus Onset
A short delay separates positioning from visible nystagmus.
- 2–10s: Typical latency (canalith transit time)
- <20s: Max latency BPPV (longer suggests central cause)
- Vertigo: Symptom onset (often precedes visible beat)
- No latency: Central red flag (immediate onset atypical)
Why latency occurs
Free-floating otoconia need time to move and deflect the cupula.
Clinical significance
Presence of latency helps distinguish peripheral from central vertigo.
Characteristic Rotatory Nystagmus Pattern
Torsional, upbeating nystagmus toward the undermost (affected) ear.
- Torsional: Nystagmus type (geotropic upbeat pattern)
- <60s: Duration (transient, self-limiting)
- Toward floor: Fast-phase direction (top pole beats down)
- ~10–15s: Peak intensity time (after onset)
Beat morphology
Slow drift followed by rapid corrective fast-phase saccade.
Canal-specific signature
Posterior canal produces this torsional-vertical combination pattern.
Fatigability With Repeated Testing
Repeating the maneuver on the same side reduces the nystagmus response.
- ~50%: 2nd trial intensity (of initial response)
- <20%: 3rd trial intensity (often barely visible)
- Debris dispersal: Mechanism (fewer particles displaced)
- Confirms: Clinical use (peripheral canalithiasis)
Repeated-trial decline
Each successive maneuver produces a weaker, shorter response.
Distinguishing feature
Fatigability is typical of BPPV, unlike central positional nystagmus.
Positive Test Confirming Posterior Canal BPPV
Latency, torsional nystagmus, and fatigability together confirm diagnosis.
- High: Diagnostic accuracy (classic triad present)
- Posterior: Affected canal (most common BPPV type)
- Epley maneuver: Next step (canalith repositioning)
- Favorable: Prognosis (often resolves with treatment)
Diagnostic criteria met
Latency plus rotatory nystagmus plus fatigability equals positive test.
A positive Dix-Hallpike test supports posterior canal BPPV diagnosis.
Treatment pathway
Positive result guides canalith repositioning treatment selection.