Abstract
BACKGROUND: Nystagmus (i.e., involuntary eye movement) provoked by the Dix-Hallpike test (DHT) is considered the gold standard for diagnosing posterior semicircular canal benign paroxysmal positional vertigo (psc-BPPV). However, robust evidence regarding this diagnostic maneuver's treatment efficacy is still lacking. This study aimed to investigate the parameters of positional nystagmus in the DHT as prognostic factors for unilateral psc-BPPV. METHODS: We reviewed 357 patients with unilateral psc-BPPV who underwent the computer-controlled canalith repositioning procedure (CCRP), which mimics the Epley maneuver. Additionally, positional nystagmus in the DHT was observed through a video-oculography. Patients were retrospectively divided into two groups according to resistance to the CCRP. Univariable and multivariable analyses were performed on age, gender, blood pressure, and nystagmus parameters of the affected side in the DHT in order to reveal associated factors causing resistance to the CCRP. RESULTS: With univariate and multivariate analysis, we observed a decrease in vertical time course during slow phase nystagmus on the affected side (odds ratio, OR 0.77, P=0.011 vs. OR 0.80, P=0.027). Moreover, an increased vertical velocity amplitude in the DHT during slow phase nystagmus (OR 3.16, P=0.029 vs. OR 2.96, P=0.035) remained an associated factor of maneuver resistance. CONCLUSIONS: Decreased canalith weight on the affected side was associated with resistance to the CCRP. This association corresponded to the observation that psc-BPPV patients with a decreased time course and increased velocity in the slow phase of recording nystagmus have a worse prognosis of their BPPV persisting after a single CCRP.