Most Commonly Affected Canal in BPPV
The posterior semicircular canal is by far the most commonly affected canal in BPPV, accounting for 85-95% of all cases. 1, 2
Canal Distribution in BPPV
The distribution of semicircular canal involvement follows a clear hierarchy:
- Posterior canal: 85-95% of all BPPV cases 1, 2, 3
- Lateral (horizontal) canal: 5-15% of cases 1, 2, 3
- Anterior (superior) canal: 1-3% of cases, making it the rarest variant 3, 4, 5
Why the Posterior Canal is Most Affected
The posterior semicircular canal's predominance is explained by its anatomical position:
- Gravity-dependent positioning: When lying supine, the posterior canal occupies the most gravity-dependent position, making it the natural collection point for dislodged otoconia 2
- Anatomical vulnerability: The posterior canal's orientation relative to the utricle facilitates migration of free-floating calcium carbonate crystals (otoconia) from the utricle into this canal 1, 2
Clinical Implications
Diagnostic Approach
- Start with the Dix-Hallpike maneuver to diagnose posterior canal BPPV, as this will identify the vast majority (85-95%) of cases 1, 6
- Perform the supine roll test if the Dix-Hallpike is negative but clinical suspicion remains high, to evaluate for lateral canal BPPV 1, 6
- The sensitivity of the Dix-Hallpike maneuver is 82% with specificity of 71% for posterior canal BPPV 1, 6
Common Pitfall
- Do not skip the supine roll test in patients with negative Dix-Hallpike but classic BPPV symptoms, as lateral canal BPPV (10-15% of cases) is frequently missed when clinicians fail to perform this additional maneuver 1, 6, 3
- A negative Dix-Hallpike does not rule out BPPV—it may indicate lateral canal involvement or require repeat testing 1
Treatment Success
- Canalith repositioning procedures are highly effective for posterior canal BPPV, with success rates of 70-90% after initial treatment and 90-98% with repeated maneuvers 1, 7
- The mechanical nature of posterior canal BPPV (free-floating particles in a gravity-dependent canal) explains why repositioning maneuvers work so effectively 2