Episodic Vestibular Syndrome with Hyperventilation-Induced Downbeat Nystagmus

Triggered saccadic oscillations: case series and review of the literature

Saccadic oscillations (SOs) mostly occur spontaneously, but can be occasionally triggered by various stimuli. To determine clinical characteristics and underlying mechanisms of triggered SOs, we analyzed the clinical features and quantitative eye-movement recordings of six new patients and 10 patients in the literature who exhibited with triggered SOs. Eleven of the 16 patients (69%) had a lesion involving cerebellum and/or brainstem such as cerebellar degeneration, cerebellitis, or cerebellar infarction. The other causes were vestibular migraine (n = 2), multiple sclerosis (n = 1), Krabbe disease (n = 1), and idiopathic (n = 1). Vestibular stimulation was the most common trigger (n = 11, 69%), followed by removal of visual fixation (n = 4, 25%), hyperventilation (n = 1), light (n = 1), and blink (n = 1). The types of triggered SOs were varied which included ocular flutter (n = 13), opsoclonus (n = 3), vertical SOs (n = 2), and macrosaccadic oscillations (n = 1). Three patients exhibited downbeat nystagmus either before (n = 1) or after (n = 2) the onset of SOs. The frequency of triggered SOs ranged from 4 to 15 Hz, and oscillations with smaller amplitudes had higher frequencies and smaller peak velocities. SOs can be triggered by the modulation of unstable saccadic neural networks through vestibular and visual inputs in lesions of the brainstem and cerebellum.

Etiologic distribution of dizziness/vertigo in a neurological outpatient clinic according to the criteria of the international classification of vestibular disorders: a single-center study

OBJECTIVE

The study aimed to determine the etiological characteristics of patients with dizziness/vertigo attending a neurological clinic according to the criteria of the International Classification of Vestibular Disorders (ICVD), hoping to provide a valuable reference for clinicians to diagnose and treat dizziness/vertigo.

METHOD

A total of 638 consecutive patients with a chief complaint of dizziness/vertigo who attended the vertigo clinic of our neurology department from January 2019 to January 2020 were included. Clinical data of patients, including baseline data, medical history, neurological, neuro-otological, and auxiliary examination results were collected. The etiologic distribution of dizziness/vertigo was determined by analyzing the diagnoses of patients.

RESULTS

Of the 638 patients with dizziness/vertigo, 38.8% were males, 61.2% were females, with a male: female ratio of 1:1.58 and a mean age of 52.9 ± 16.9 years. Benign paroxysmal positional vertigo (BPPV) was the most common cause of dizziness/vertigo in both female (38.9%) and male patients (25.5%). Subgroup analysis based on sex showed that vestibular migraine (VM) and probable autoimmune inner ear disease (p-AIED) were more prevalent in female patients (10.7% and 3.8%, respectively), while vascular vertigo/dizziness was more common in male patients (10.1%). Subgroup analysis based on age showed that the most common diseases were VM in patients aged 0-30 years (27.4%), BPPV in patients aged 31-60 years (27.1%) and 61-100 years (46.0%). Episodic vestibular syndrome (EVS) was the most commonly observed, accounting for up to 60.6% (389/638) of all patients, and the most common diagnoses were BPPV (55.3%, 215/389), VM (15.2%, 59/389), primary unilateral peripheral vestibular dysfunction (p-UPVD) of unknown etiology (11.8%, 46/389), p-AIED (4.4%, 17/389), and vascular vertigo/dizziness (2.8%, 11/389) in these patients. Chronic vestibular syndrome (CVS) was found in 14.0% (90/638) of the patients, and the most common diagnoses were persistent postural-perceptual dizziness (PPPD, 35.6%, 32/90), psychogenic dizziness (18.9%, 17/90), p-UPVD of unknown etiology (15.6%, 14/90), vascular vertigo/dizziness (15.6%, 14/90), and bilateral vestibulopathy (7.8%, 7/90). Acute vestibular syndrome (AVS) was observed in 8.4% (54/638) of the patients, and the most common diagnoses were p-UPVD of unknown etiology (31.5%, 17/54), vestibular neuritis (24.1%, 13/54), probable labyrinthine apoplexy (16.7%, 9/54), stroke (13.0%, 7/54), and psychogenic dizziness (11.1%, 6/54). 16.4% (105/638) of the patients were found to have other disorders, including 15.2% (16/105) of patients with internal diseases, and 84.8% (89/105) of patients with unknown causes. In terms of localization diagnosis, 56.1%, 17.0%, 10.0%, and 16.4% of the patients were diagnosed with peripheral vestibular disorder, central vestibular disorder, psychiatric and functional vestibular disorders, and other disorders, respectively.

CONCLUSION

(1) Dizziness/vertigo was more common in females, which was frequently caused by damage to the vestibular system. Non-vestibular or unknown etiologies were also seen in some patients; (2) VM was more prevalent in women than in men, vascular vertigo/dizziness was more commonly observed in men; (3) EVS was more common in patients with dizziness/vertigo. The most common causes of dizziness/vertigo were peripheral vestibular disorders in patients with AVS and EVS, PPPD and psychogenic dizziness in patients with CVS. The most common causes were BPPV and p-UPVD of unknown etiology in patients with a peripheral vestibular disorder, VM and vascular vertigo/dizziness in patients with central vestibular disorder, PPPD and psychogenic dizziness in patients with psychiatric and functional vestibular disorders.

Vestibular paroxysmia: clinical characteristics and long-term course

In 2016, the Bárány Society defined new diagnostic criteria for the neurovascular compression syndrome of the eighth nerve, called “vestibular paroxysmia” (VP), differentiating between definite (dVP) and probable (pVP) forms. The aim of this study was (1) to describe clinical symptoms and laboratory findings in a well-diagnosed large patient cohort according to those criteria, and (2) to evaluate the long-term course over years in dVP. We identified 146 patients (73 dVP, 73 pVP) from our tertiary dizziness center registry. Data of structured history-taking, clinical neurological, neuro-ophthalmological/-otological examinations as well as MRI imaging were extracted for analyses. Overall, attack frequency ranged between 5 and 30 attacks per day; spinning vertigo was the most frequent type. In two-thirds of patients, attacks occurred spontaneously; in one-quarter, they were triggered by head movements. The majority (approximately 70%) reported no accompanying symptoms; in those with symptoms, mild unilateral cochlear symptoms prevailed. One-third of patients initially showed hyperventilation-induced nystagmus without specific direction, and a deviation of the subjective visual vertical between 3° and 6°. Complete loss of peripheral vestibular function was never evident. dVP and pVP significantly differed concerning the vertigo type, e.g., spinning vertigo was more frequent in dVP. Fortunately, three-quarters of dVP patients remained attack-free during follow-up (mean 4.8 years, standardized questionnaire), more than half of them even without any medication. Patients with ongoing attacks showed significantly higher attack frequency at baseline, but reported persistent frequency reduction. Overall, the long-term prognosis of VP appears favorable, not necessarily requiring ongoing treatment.

Discordant vestibulo-ocular reflex function according to the frequency and mode of stimulation

This study aimed to determine the incidence, pattern, and etiology of dissociated vestibulo-ocular reflex (VOR) function according to the stimulus frequency in dizzy patients. We retrospectively evaluated the results of bithermal caloric tests and video-head impulse tests (vHITs) in 1022 patients with dizziness or vertigo between July 2016 and April 2021. Patients were classified into concordant group (normal or abnormal results on both tests) and discordant group (dissociated results between two tests). Of 1022 patients, discordant group had 159 (16%), comprising abnormal horizontal vHITs with normal caloric responses (n = 36, 23%) and abnormal caloric tests with normal horizontal vHITs (n = 123, 77%). The former group showed similar frequency of peripheral (44%) and central (42%) causes, and more common involvement of bilateral horizontal semicircular canals in central than peripheral causes (86.7 vs 37.5%, p = 0.005). The most common peripheral causes were Meniere's disease and chronic vestibular neuritis, while central causes were variable, but mainly affecting the cerebellum. In the latter group, peripheral causes were common (67%), with the main etiologies being Meniere's disease and vestibular neuritis, whereas central causes were found in only 5%. The degree of canal paresis did not differ significantly between patients with central and peripheral causes. Discordant VOR function according to the stimulus frequency was not uncommon in dizzy patients. Specific patterns of VOR dissociation according to the disease etiologies may offer insight into underlying pathophysiology.