Persistent Spontaneous Nystagmus Following a Canalith Repositioning Procedure in Horizontal Semicircular Canal Benign Paroxysmal Positional Vertigo

Abstract

To our knowledge, this is the first report of a case that shows on video persistent nystagmus findings consistent with a canalith jam. We discuss a possible mechanism underlying this phenomenon.

Spontaneous Jamming of Horizontal Semicircular Canal Combined with Canalolithiasis of Contralateral Posterior Semicircular Canal

“…In this condition, a continuous alteration of hydrostatic pressure within the affected SC leads to a persistent deflection of the cupula towards the utricle or in the opposite direction. It results in spontaneous nystagmus regardless of head position changes, mimicking vestibular neuritis [3][4][5][6][7].…”

“…Canalith jam represents an uncommon subtype of BPPV in which canaliths are thought to aggregate plugging the canal lumen. In this condition, entrapped otoliths are assumed to exert either negative or positive pressure on the cupula, preventing dynamic responses of the affected SC by blocking endolymphatic flows, thus resulting in a persistent direction-fixed nystagmus regardless of head positions [3][4][5][6][7]. Canalith jam can occur either spontaneously or as a complication of canalith repositioning maneuvers (CRM) [3][4][5][6][7].…”

Horizontal semicircular canal jam: Two new cases and possible mechanisms

“…12 In each case in which vestibular function was reduced there was recovery within 30 days. 7,11,12 2 | CASE DESCRIPTIONS Here we present video evidence and description of two patients presenting with positional symptoms consistent with BPPV who also showed a peripheral, horizontal, unidirectional-fixed nystagmus irrespective of the head position suggesting canalith jam of the hSCC. In both cases, the canalith jam occurred spontaneously, presumably within the lumen of the hSCC.…”

“…An obstruction within the lumen has also been suggested to occur spontaneously or as a complication following a canalith repositioning maneuver . Hypothetically, the canalith jam may induce a prolonged utriculofugal deviation of the cupula from the horizontal semicircular (deflection away from the ampulla for an inhibitory stimulus) or a prolonged utriculopetal deviation of the cupula (deflection toward the ampulla for an excitatory stimulus) . Both would cause a nonfatiguing, spontaneous, horizontal nystagmus regardless of head position.…”

“…Persistent direction‐fixed, spontaneous nystagmus consistent with canalith jam of the hSCC can be associated with ipsilateral canal paresis based on caloric testing; the video head impulse test; and asymmetrical cervical and ocular vestibular evoked myogenic potentials . In each case in which vestibular function was reduced there was recovery within 30 days …”