Head-Shaking Nystagmus in Posterior Canal Benign Paroxysmal Positional Vertigo with Canalolithiasis
Journal of Clinical Medicine
There have been several studies about head-shaking nystagmus (HSN) in posterior canal benign paroxysmal positional vertigo (PC-BPPV). The purpose of the study was to determine the characteristics of HSN and its relationship with head-bending nystagmus (HBN) and lying-down nystagmus (LDN) in PC-BPPV and to suggest a possible pathomechanism of HSN based on these findings. Methods: During the study period, 992 patients with BPPV were initially enrolled. After excluding horizontal or anterior canal
... l or anterior canal BPPV, multiple canals involvement, secondary causes of BPPV, identifiable central nervous system (CNS) disorders, unidentifiable lesion side, or poor cooperation, 240 patients with unilateral PC-BPPV were enrolled. We assessed the frequency, pattern of HSN, and correlation with other induced nystagmus after positional maneuvers such as head bending, lying down, head-turning, and Dix-Hallpike test. Results: Approximately 32% of patients with PC-BPPV showed HSN. Among patients with HSN, approximately 61% of patients showed predominantly downbeat nystagmus, and two-third of them had a torsional component. The torsional component was mostly directed to the contralesional side. Horizontal nystagmus (36%) and upbeat nystagmus (3%) were also observed after head-shaking in PC-BPPV. The presence of HSN was significantly correlated with that of HBN in PC-BPPV (p = 0.00). The presence of a torsional component of HSN was also significantly correlated with that of HBN in PC- BPPV (p = 0.00). Discussion: Perverted HSN, a typical sign of central vestibulopathy, is common in posterior canal BPPV and related to HBN. For generating HSN in PC-BPPV, the otolithic movements related to the endolymph dynamics seem to be more important than the velocity storage mechanism.