Unusual Locations of Benign Paroxysmal Positional Vertigo: Rare Entity or Regular Occurrence?

INTRODUCTION: According to the literature and our recent experience, even if patients present with symptoms strongly suggestive of benign paroxysmal positional vertigo (BPPV), the observed positional nystagmus does not always correspond to any previously described typical location. The aim of this multicentric study was to evaluate the frequency of both typical and less common forms of BPPV. MATERIAL AND METHODS: All consecutive patients presenting with BPPV in two hospitals between November 2016 and October 2017 were included. For each subject, answers to a standardized evaluation form and a recorded videonystagmoscopy were obtained by two otorhinolaryngologists. Appropriate diagnostic and therapeutic maneuvers were performed. RESULTS: A total of 532 patients were studied and 491 cases of typical BPPV were found: 370 cases of canalolithiasis of the posterior semicircular canal (SCC), 3 cases of canalolithiasis of the anterior SCC, 107 cases of canalolithiasis of the lateral SCC, and 11 cases of cupulolithiasis of the lateral SCC. Fourty one patients reported symptoms suggestive of BPPV with positional nystagmus that could correspond to unusual locations of otoconia in the SCC: 18 cases of canalolithiasis in the anterior ampulla of the lateral SCC, 16 cases of posterior short arm canalolithiasis, four cases of pseudo-spontaneous nystagmus in canalolithiasis of the lateral SCC, and three cases of canalolithiasis of the posterior third of SCC. DISCUSSION: Unusual BPPV accounted for almost 8% of BPPV treated in our clinics; it is paramount to know how to diagnose them, to carry out the appropriate therapeutic maneuvers and relieve these patients.