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Position in bed is associated with left or right location in benign paroxysmal positional vertigo of the posterior semicircular canal.

PURPOSE
To determine if position during bedrest is related to the canal affected in posterior canal benign paroxysmal positional vertigo (BPPV).


MATERIALS AND METHODS
Fifty-five individuals with posterior canal BPPV were investigated. Diagnosis was established if a consistent clinical history was found with vertigo and induced positional nystagmus elicited on the Dix-Hallpike test (DHT). Preference for left or right position during bed rest was determined before performing the DHT. All patients were treated by a single particle repositioning procedure, and relapses were investigated at the seventh and 30 days posttreatment.


RESULTS
Forty-five individuals always slept on the same side (29 on the right, 16 on the left side), and 10 patients preferred to change sides during bed rest. Among those patients able to maintain a constant position during bed rest, 27 and 18 presented a positive DHT on the right and left sides, respectively. The canal affected was found to be significantly associated with side during bed rest (relative risk = 2.75; P = 0.01, Fisher exact test). DHT was negative in 86% of patients at 30 days. No differences were found between individuals who presented a constant position in bed and those who changed positions.


CONCLUSIONS
Lateral supine position during bed rest is associated with the canal affected in BPPV. We speculate that gravity might facilitate the deposition of particulate material on the posterior semicircular near the ampulla canal during bed rest.