A 2020 study by Choo et al analysed patients who showed vertical nystagmus during the 'Bow and Lean Test' (BLT). They found that this type of nystagmus may indicate the presence of “hidden” posterior semicircular canal BPPV (PSC-BPPV), which can cause lingering vertigo symptoms even after treatment. So, if you see PSC patients with ongoing vertigo, be sure to check BLT.
Note: this test does not exclude central vertigo.

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