A new variant of posterior canal-benign paroxysmal positional vertigo-canalolithiasis.

Objective: The characteristics of typical posterior canal-benign paroxysmal positional vertigo-canalolithiasis (P-BPPV-Can) are well known. We found 10 patients with a new variant of P-BPPV-Can: Reverse (Rev)-P-BPPV-Can. The characteristics and pathophysiology of Rev-P-BPPV-Can are discussed.

Methods: For 4 years and 9 months, 10 patients with Rev-P-BPPV-Can (9 women and 1 man; mean age: 73 years) visited our clinic. Within the same period, 268 patients with unilateral typical P-BPPV-Can were treated. During the Dix-Hallpike and Epley maneuvers, nystagmus was recorded using an infrared charge-coupled device camera mounted on a pair of spectacles.

Results: The patients exhibited entirely opposite direction of nystagmus from typical P-BPPV-Can in both the Dix-Hallpike head position and upright sitting position. The patients had typical characteristics of nystagmus due to canalolithiasis, such as latency, duration of <1 min, linear-torsional nystagmus, and fatigability. Rev-P-BPPV-Can appeared after the Epley maneuver for typical P-BPPV-Can; in other patients, Rev-P-BPPV-Can changed to typical P-BPPV-Can. The affected sides of Rev-P-BPPV-Can were decided by those of typical P-BPPV-Can.

Conclusion: Canalolithiasis in the non-ampullary distal portion of the posterior semicircular canal may be a potential pathophysiology of Rev-P-BPPV-Can. The Epley maneuver has little effect for treating Rev-P-BPPV-Can, but spontaneous transition to typical P-BPPV-Can or spontaneous recovery is expected.