The importance of the bow and lean test as an initial positional test for diagnosing BPPV

This study aimed to evaluate the diagnostic potential of nystagmus direction observed during bow and lean tests (BLTs) in patients with posterior canal canalolithiasis BPPV (P-BPPV), lateral canal canalolithiasis BPPV (Lca-BPPV), and lateral canal cupulolithiasis BPPV (Lcu-BPPV).

A total of 62 patients (40 women, 22 men; aged 24-70 years) with clinically suspected BPPV were enrolled. Diagnoses included 39 cases of P-BPPV, 15 of Lca-BPPV, and 8 of Lcu-BPPV. Each participant underwent the Dix-Hallpike Test (DH), Head Roll Test (HRT), and bow and lean tests for diagnostic assessment. The primary outcome was the presence and direction of nystagmus during BLTs, in relation to BPPV subtype.

Nystagmus was detected in 77.4% of subjects during the bow test and in 46.8% during the lean test. A statistically significant difference was found in nystagmus direction across BPPV subtypes (p < 0.05). Right-beating horizontal nystagmus during the bow test was significantly more frequent in right-sided Lca-BPPV. Right down-beating torsional nystagmus during the bow test occurred exclusively in left P-BPPV, while left down-beating torsional nystagmus was seen only in right P-BPPV. Right up-beating torsional nystagmus was significantly associated with right P-BPPV, and left up-beating torsional nystagmus with left P-BPPV (p < 0.05).

In P-BPPV, DH-induced nystagmus direction was opposite in the bow position but matched in the lean position. These findings underscore the diagnostic value of BLTs, particularly the bow test, in identifying the affected canal in posterior and lateral canal BPPV.