Posterior semicircular canal benign paroxysmal positional vertigo should be diagnosed and confirmed with a positive Dix-Hallpike test, and only then should a particle repositioning maneuver be performed. If a patient with positional vertigo has a Dix-Hallpike test that is repeatedly negative or results in atypical nystagmus, less common BPPV variants or central positional vertigo should be considered.
Sources:
Hilton MP, et al. The Epley (canalith repositioning) manoeuvre for benign paroxysmal positional vertigo. Cochrane Database Syst Rev. 2014 Dec 8;12:CD003162. PMID: 25485940.