Vestibular deficit and recovery in rare forms of benign paroxysmal positional vertigo with downbeat nystagmus

Purpose: The primary goals are to investigate the rate of vestibular deficit (VD) during the acute attack and to follow up on vestibular recovery (VR) after the resolution of BPPV in patients with rare forms of BPPV that cause downbeat nystagmus. Second, to determine the effects of VD on dizziness severity in patients with rare BPPV forms and to compare all the results with those of typical posterior canal BPPV. Methods: This prospective follow-up study included 23 patients (56.86 ± 12.21 years) with rare BPPV forms (5 anterior canal, 18 apogeotropic posterior canal) and 23 patients (50.75 ± 13.67 years) with typical posterior canal BPPV. Dix-Hallpike, McClure-Pagnini, Semont, and supine head-hanging diagnostic maneuvers were performed on all patients during the acute BPPV attack. All patients underwent an objective (vHIT and oVEMP) and subjective vestibular test (DHI) battery before the therapeutic maneuvers (Epley, Quick Liberatory Rotation, or Yacovino maneuvers). One month after complete resolution of BPPV, all vestibular evaluations were performed once again in both groups. Results: In patients with rare forms of BPPV, 30.43% had canal deficit and 43.38% had utricular deficit on the affected side during an acute BPPV attack (p = 0.009, p = 0.001), whereas no patients in the typical BPPV group had vestibular deficit (0%). One month after BPPV resolution, the canal deficit of 26.09% and the utricular deficit of 34.78% had completely recovered in the rare forms of BPPV group. The rare BPPV forms group reported experiencing a higher level of dizziness during the acute attack and more residual dizziness one month after resolution, compared to the typical BPPV group, despite the fact that there are no statistically significant differences in dizziness levels between the groups (p > 0.05). Conclusion: It is possible that a VD may be seen in some patients with rare forms of BPPV and may not fully recover. It should be kept in mind that rare forms of BPPV may cause persistent VD in some patients, even if BPPV is resolved. The patients with both rare forms of BPPV (much more) and typical BPPV forms may describe residual dizziness after the resolution of BPPV. Additionally, canal deficit is a significant predictor of dizziness severity in all patients with BPPV.