Vestibular syncope: clinical characteristics and mechanism

Abstract

Background and Objectives: Vestibular syncope is a condition in which vertigo-induced hemodynamic changes cause syncope. This study investigated the clinical and laboratory findings of vestibular syncope and tried to refine our knowledge of the mechanism underlying this newly recognized entity. Methods: This study retrospectively analyzed 53 patients (33 women, median age = 63 years [interquartile range = 54-71 years]) with vestibular syncope from January 2017 to December 2021. To explain the mechanism of vestibular syncope, we incorporated a velocity-storage model into the dual reflex pathways comprising the vestibulo-sympathetic reflex and baroreflex and predicted the cardiovascular responses. Results: Twenty (37.7%) patients had multiple episodes of vestibular syncope, and seven (13.2%) had potentially life-threatening injuries. Meniere's disease (20.8%) and benign paroxysmal positional vertigo (9.4%) were the most common underlying vestibular disorders. Abnormal vestibular function tests included impaired cervical vestibular-evoked myogenic potentials (57.5%) and positive head impulse tests (31.0%). Orthostatic hypotension was found in 19.5% of patients. Dyslipidemia (30.2%) and hypertension (28.3%) were common medical comorbidities. The dual reflex pathways incorporating the function of the velocity-storage circuit in the brainstem and cerebellum suggest that vestibular syncope is a neurally mediated reflex syncope associated with a sudden hemodynamic change during vertigo. This change can be arterial hypertension triggered by a false downward inertial cue, as suggested previously, or hypotension driven by a false upward inertial cue. Conclusions: Vestibular syncope is associated with various vestibular disorders and requires careful evaluation and intervention to prevent recurrent falls and significant injuries.

The role of otolith reflexes in orthostatic intolerance

“…Other authors have speculated that it may not be altered end organ performance per se that contributes to otolithautonomic dysregulation, but alterations in the velocity storage mechanism within the brainstem and cerebellum [8]. Work by Kwon and colleagues [14] has described "vestibular syncope"-the time-locked relationship between vertigo episode and syncopal event-in a variety of clinical presentations. Interestingly, orthostatic blood pressure measurements were generally insensitive to identifying patients at risk, suggesting that altered vestibular reflexes may provide a trigger for these symptoms by influencing underlying cardiovascular-autonomic performance.…”

Periodic vertigo and downbeat nystagmus while supine: Dysfunction of Purkinje cells coding gravity

“…We tested our hypothesis by simulating a velocity‐storage model introduced elsewhere 1,13–15 . We postulated that a lesion would impair the connections between the tilt‐coding and translation‐coding cells.…”

Vestibular syncope

“…In about 62% of cases, the primary vestibular disorders causing vertigo attacks could not be identified. However, among the known causes, Meniere's disease was the most common cause, followed by benign paroxysmal positional vertigo [12 ▪▪ ]. These observations suggest that vestibular syncope can occur in association with various vestibular disorders causing intense vertigo attacks and increase the risk of falls.…”

“…VS, velocity-storage; BP, blood pressure. The figure was modified from the ones in the previous publication [11 ▪▪ ,12 ▪▪ ].…”

“…Therefore, malfunction of the vestibular system can disturb the cardiovascular function and lead to syncope [8–10]. Indeed, some patients with vestibular disorders develop syncope in a close temporal relationship with their vertigo attacks, thereby giving birth to the concept of vestibular syncope [11 ▪▪ ,12 ▪▪ ]. Since dizziness is one of the cardinal prodrome and postdrome of syncope, however, the diagnosis of vestibular syncope is often challenging.…”