Fluctuating Posterior Canal Function in Benign Paroxysmal Positional Vertigo Depending on How and Where Otoconia Are Disposed

Abstract

Objective: Though fluctuations in vestibular function represent a common finding in Menière's disease, we describe how benign paroxysmal positional vertigo (BPPV) may result in fluctuations of vestibulo-ocular reflex for the involved canal depending on the disposition of otoliths. Patient: A 54-year-old woman suffering from refractory posterior canal (PC)-BPPV resulting in fluctuating PC function. Interventions: Diagnostic evaluation and rehabilitative treatment for BPPV involving the affected PC. Main Outcome Measures: Video-Frenzel and video-head impulse test (vHIT) findings before and after canalith repositioning procedures for PC-BPPV. Results: BPPV involving the nonampullary arm of right PC was diagnosed based on presenting positional downbeat nystagmus and selective right PC hypofunction at the vHIT. During physical treatment, nystagmus first became positional paroxysmal upbeat likely due to a shift of debris into the ampullary arm of the canal, then turned to spontaneous downbeat nystagmus consistently with a plug effect exerted by particles entrapped within the nonampullary arm of PC and finally receded proving an otoliths fall within the utriculus. Simultaneously, vHIT documented fluctuations for right PC vestibulo-ocular reflex gain as it first increased to normal values, then severely declined and finally normalized, respectively. High-resolution computed tomography scan detected ipsilateral superior canal dehiscence. Conclusions: In accordance with recently reported vHIT findings in different types of BPPV, fluctuation of PC function could be likely explained by the effect of particles on cupular dynamic responses depending on the portion of the canal gradually involved. Superior canal dehiscence may have played a role facilitating otoliths mobilization by reducing labyrinthine impedance.

Spontaneous Upbeat Nystagmus and Selective Anterior Semicircular Canal Hypofunction on Video Head Impulse Test: A New Variant of Canalith Jam?

“…It results in a persistent deflection (either utriculofugal or utriculopetal) of the cupula and in a blockage of endolymphatic flows between the clot and the cupula itself, generating spontaneous nystagmus [5][6][7]. While CJ involving the horizontal canal has demonstrated to result in spontaneous nystagmus mimicking an acute vestibular loss [6][7][8], it has already been reported how PSC-CJ could generate spontaneous DBN overlapping central oculomotor disorders [9][10][11]. In both cases, a reversible isolated hypofunction for the affected canal on video-HIT has demonstrated to represent a key data in the differential diagnosis [6,[9][10][11].…”

“…While CJ involving the horizontal canal has demonstrated to result in spontaneous nystagmus mimicking an acute vestibular loss [6][7][8], it has already been reported how PSC-CJ could generate spontaneous DBN overlapping central oculomotor disorders [9][10][11]. In both cases, a reversible isolated hypofunction for the affected canal on video-HIT has demonstrated to represent a key data in the differential diagnosis [6,[9][10][11]. In fact, according to the pathomechanism assumed for CJ, as the cupula of the affected canal is supposed to be persistently bent either in excitatory or inhibitory direction, dynamic responses of the ampullary receptor would be markedly impaired, leading to a canal "pseudo-hyporeflexia" [5][6][7][9][10][11].…”

Atypical Positional Vertigo: Definition, Causes, and Mechanisms

“…Persistent spontaneous nystagmus has been described in lateral and posterior canal BPPV [ 19 , 20 , 21 , 22 ]. It is not influenced by gravity and does not change direction with maneuvers: this differentiates it from pseudospontaneous nystagmus, which changes with movements in the sagittal and horizontal planes.…”

Recovery of Regular Daily Physical Activities Prevents Residual Dizziness after Canalith Repositioning Procedures

“…The diagnosis of BPPV concerning the affected ear and the involved canal and arm is commonly made by performing positioning tests, also known as diagnostic maneuvers. The tests work by gravity and inertial/centrifugal forces, which bend the affected SC cupula and move the free-floating debris [ 1 , 2 , 3 , 7 ]. Several maneuvers have been proposed to properly diagnose each BPPV variant by moving the patient’s head along the plane of the examined SC [ 1 , 2 , 3 ].…”

“…The tests work by gravity and inertial/centrifugal forces, which bend the affected SC cupula and move the free-floating debris [1][2][3]7]. Several maneuvers have been proposed to properly diagnose each BPPV variant by moving the patient's head along the plane of the examined SC [1][2][3].…”