Benign paroxysmal positional vertigo of the anterior semicircular canal: atypical clinical findings and possible underlying mechanisms.

Anterior semicircular canal (ASC) lithiasis is uncommon and usually self-treated. In the rare cases when such patients seek medical advice, diagnosis requires careful consideration of the patient's symptoms and the clinical characteristics of the nystagmus triggered by the Dix-Hallpike (D-H) examination. In this study, two atypical cases of ASC benign paroxysmal positional vertigo (BPPV) are presented and the relevant literature is reviewed. Regardless of their unique symptoms, both participants in this study were diagnosed with lithiasis of the left ASC. The clinical manifestations of ASC BPPV may differ significantly from typical symptoms seen in the more common posterior semicircular canal BPPV. The possible mechanisms responsible for this intriguing variance, as well as guidelines for diagnosing the affected side, are discussed.