Using 100 Hz Mastoid Vibration in Apogeotropic Posterior Semicircular Canal Benign Paroxysmal Positional Vertigo: Diagnostic and Therapeutic Implications in a Retrospective Case-Control Study.

Background: Positional torsional downbeating nystagmus elicited during diagnostic maneuvers for posterior semicircular canal benign paroxysmal positional vertigo (PSC-BPPV) may indicate either ipsilateral apogeotropic PSC-BPPV or contralateral anterior canal BPPV, making differential diagnosis challenging. This retrospective study evaluated whether ipsilateral 100 Hz mastoid vibration could facilitate conversion to a geotropic nystagmus pattern, thereby supporting both diagnosis and treatment. Materials and Methods: Ten patients with apogeotropic PSC-BPPV underwent standard diagnostic and therapeutic maneuvers combined with ipsilateral 100 Hz mastoid vibration. The primary outcome was the rate of nystagmus geotropization. Secondary outcomes included the number of repositioning maneuvers required to achieve complete symptom resolution. Outcomes were compared with those of two control groups: one consisting of patients with apogeotropic PSC-BPPV treated without mastoid vibration and another consisting of patients with typical PSC-BPPV treated using standard repositioning maneuvers alone. Results: Mastoid vibration induced geotropization in 7 out of 10 patients (70%). The mean number of liberatory maneuvers required for symptom resolution was lower in vibration-responsive patients than in vibration-non-responsive patients (1.7 ± 0.49 vs. 3.0 ± 1.41;). Compared with patients with apogeotropic PSC-BPPV treated without mastoid vibration, vibration-responsive patients required significantly fewer maneuvers (2.1 ± 0.87 vs. 2.9 ± 0.74; p = 0.036). No significant difference was observed when compared with patients with typical PSC-BPPV (2.1 ± 0.87 vs. 2.1 ± 0.52; p = 0.82). Conclusions: Mastoid vibration may represent a useful adjunctive tool in the management of apogeotropic PSC-BPPV by facilitating conversion to the typical geotropic pattern. This conversion may provide useful diagnostic information, and potentially reduce the number of repositioning maneuvers required to achieve symptom resolution.