Vestibulo-ocular reflex involvement in childhood-onset multiple sclerosis

Evidence for the differential efficacy of yaw and pitch gaze stabilization mechanisms in people with multiple sclerosis

People with multiple sclerosis (PwMS) who report dizziness often have gaze instability due to vestibulo-ocular reflex (VOR) deficiencies and compensatory saccade (CS) abnormalities. Herein, we aimed to describe and compare the gaze stabilization mechanisms for yaw and pitch head movements in PwMS. Thirty-seven PwMS (27 female, mean ± SD age = 53.4 ± 12.4 years old, median [IQR] Expanded Disability Status Scale Score = 3.5, [1.0]. We analyzed video head impulse test results for VOR gain, CS frequency, CS latency, gaze position error (GPE) at impulse end, and GPE at 400 ms after impulse start. Discrepancies were found for median [IQR] VOR gain in yaw (0.92 [0.14]) versus pitch-up (0.71 [0.44], p < 0.001) and pitch-down (0.81 [0.44], p = 0.014]), CS latency in yaw (258.13 [76.8]) ms versus pitch-up (208.78 [65.97]) ms, p = 0.001] and pitch-down (132.17 [97.56] ms, p = 0.006), GPE at impulse end in yaw (1.15 [1.85] degs versus pitch-up (2.71 [3.9] degs, p < 0.001), and GPE at 400 ms in yaw (-0.25 [0.98] degs) versus pitch-up (1.53 [1.07] degs, p < 0.001) and pitch-down (1.12 [1.82] degs, p = 0.001). Compared with yaw (0.91 [0.75]), CS frequency was similar for pitch-up (1.03 [0.93], p = 0.999) but lower for pitch-down (0.65 [0.64], p = 0.023). GPE at 400 ms was similar for yaw and pitch-down (1.88 [2.76] degs, p = 0.400). We postulate that MS may have preferentially damaged the vertical VOR and saccade pathways in this cohort.

Video head impulse test in subacute and chronic stroke survivors: new perspectives for implementation of assessment in rehabilitation

INTRODUCTION

The Video Head Impulse Test (vHIT) is a safe and reliable assessment of peripheral vestibular function. Many studies tested its accuracy in clinical settings for differential diagnosis and quantification of the vestibulo-oculomotor reflex (VOR) in various disorders. However, the results of its application after lesions of the CNS are discordant and have never been studied in rehabilitation. This study aims to assess the VOR performance in a sample of stroke survivors.

METHODS

This is a cross-sectional study on 36 subacute and chronic stroke survivors; only persons with first-ever stroke and able to walk independently, even with supervision, were included. We performed VOR assessments for each semicircular canal by vHIT and balance assessments by the Berg Balance Scale and the MiniBESTest scale.

RESULTS

Two hundred and sixteen semicircular canals were assessed using the Head Impulse paradigm (in both the vertical and horizontal planes), while 72 semicircular canals were assessed using the Suppressed Head Impulse paradigm (horizontal plane). There was a high prevalence of participants with dysfunctional canals, particularly for the left anterior and right posterior canals, which were each prevalent in more than one-third of our sample. Furthermore, 16 persons showed an isolated canal dysfunction. The mean VOR gain for the vertical canals had confidence intervals out of the normal values (0.74-0.91 right anterior; 0.74-0.82 right posterior; 0.73-0.87 left anterior).

CONCLUSION

Our findings suggest that peripheral vestibular function may be impaired in people with stroke; a systematic assessment in a rehabilitation setting could allow a more personalized and patient-centred approach.

People with multiple sclerosis and unilateral peripheral vestibular loss demonstrate similar alterations in head and trunk turning kinematics compared to healthy controls

BACKGROUND

Individuals with peripheral vestibulopathy are known to have difficulty with volitional head turns. This leads to differences in head and body turning kinematics, compared to those without vestibular dysfunction. Multiple sclerosis (MS), a neuro-inflammatory disease affecting the central nervous system, can cause vestibular dysfunction (dizziness, unsteadiness, gaze instability). However, head and trunk turning kinematics in people with MS (PwMS) have not been assessed.

RESEARCH QUESTION

Will PwMS, demonstrate head and body kinematics alterations similar to individuals with a peripheral dysfunction compared to vestibular healthy individuals?

METHODS

Eleven individuals with a recent vestibular schwannoma resection (VSR), fourteen PwMS, and 10 healthy control (HC) participants were fitted with head and trunk worn inertial measurement units (IMUs) and performed walking and turning tasks. Head and trunk peak turning speed and amplitude were extracted. Regression models controlling for gait speed were fit per outcome with post hoc corrections applied to significant models.

RESULTS

Yaw plane head turn speed and amplitude were significantly less in the VSR group compared to HC. Pitch plane head turn amplitude was significantly smaller in PwMS compared to HC (p = 0.04), however pitch plane speed did not differ between the groups. There was no difference between PwMS and the VSR group in yaw or pitch plane speed and amplitude. Both PwMS and the VSR group turned significantly slower than HC during the 180d body turn as measured at the head and trunk (head speed model p = 0.009 and <0.001; trunk speed model p < 0.001 for both groups) however the MS and VSR groups did not differ from each other.

SIGNIFICANCE

Turning kinematics while walking in PwMS are altered compared to HC and are similar to individuals with unilateral vestibular hypofunction. Centrally mediated vestibular dysfunction in PwMS may alter movement kinematics and should be considered during examination and treatment.

Unique compensatory oculomotor behavior in people living with multiple sclerosis

INTRODUCTION

Globally, there are 3 million people living with multiple sclerosis (PLW-MS). A large proportion of PLW-MS have abnormal vestibular function tests that suggest central vestibular lesions. Yet, data regarding vestibular-ocular control in PLW-MS is limited. Thus, we aimed to further characterize compensatory saccade (CS) behavior in PLW-MS.

METHODS

We analyzed video head impulse data from four groups of six age- and sex-matched adults: people living with mild MS (PLW-mild-MS, people living with moderate MS (PLW-moderate-MS), people living with unilateral vestibular deafferentation (PLW-UVD), and healthy controls (HC).

RESULTS

PLW-moderate-MS had lower lateral canal vestibulo-ocular reflex (VOR) gain bilaterally compared to PLW-mild MS (p < 0.001), HC (p < 0.001), and PLW-UVD (p < 0.001). CS frequency was higher for impulses towards the less affected side in PLW-moderate-MS versus the more (p = 0.01) and less (p < 0.001) affected sides in PLW-mild-MS. CS latency was shorter (p < 0.001) and CS peak velocity was lower (p < 0.001) with impulses towards the more affected side versus the less affected side in PLW-moderate-MS. However, CS peak velocity with impulses towards each side was similar in PLW-mild-MS (p = 0.12). Gaze position error (GPE) was larger after impulses towards the more affected side versus the less affected side in PLW-moderate-MS (p < 0.001) and PLW-mild-MS (p < 0.001). MS-related disability was moderately associated with VOR gain (p < 0.001) and GPE (p < 0.001). Additionally, we identified micro-saccades and position correcting saccades that were uniquely employed by PLW-MS as compensatory gaze stabilizing strategies.

CONCLUSIONS

In PLW-MS, the characteristics of compensatory oculomotor behavior depend on the extent of residual VOR gain.

Greater Disability Is Associated with Worse Vestibular and Compensatory Oculomotor Functions in People Living with Multiple Sclerosis

Globally, there are nearly three million people living with multiple sclerosis (PLW-MS). Many PLW-MS experience vertigo and have signs of vestibular dysfunction, e.g., low vestibulo-ocular reflex (VOR) gains or the presence of compensatory saccades (CSs), on video head impulse testing (vHIT). We examined whether the vestibular function and compensatory oculomotor behaviors in PLW-MS differed based on the level of MS-related disability. The VOR gain, CS frequency and latency, and gaze position error (GPE) were calculated from the individual traces obtained during six-canal vHIT for 37 PLW-MS (mean age 53.4 ± 12.4 years-old, 28 females) with vertigo and/or an imbalance. The subjects were grouped by their Expanded Disability Status Scale (EDSS) scores: PLW-min-MS (EDSS = 1.0-2.5, n = 8), PLW-mild-MS (EDSS = 3.0-4.5, n = 23), and PLW-moderate-MS (EDSS = 5.0-6.0, n = 6). The between-group differences were assessed with Kruskal-Wallis tests. The VOR gains for most of the canals were higher for PLW-min-MS compared to PLW-mild- and mod-MS, respectively. CS occurred less often in PLW-min-MS versus PLW-mild- and mod-MS, respectively. No clear trend in CS latency was found. The GPE was often lower for PLW-min-MS compared to PLW-mild- and mod-MS, respectively. Thus, our data demonstrate that worse VOR and compensatory oculomotor functions are associated with a greater MS-related disability. PLW-MS may benefit from personalized vestibular physical therapy.

Compensatory saccades differ between those with vestibular hypofunction and multiple sclerosis pointing to unique roles for peripheral and central vestibular inputs

Individuals with peripheral or central vestibular dysfunction recruit compensatory saccades (CSs) in response to high acceleration, yaw head impulses. Although CSs have been shown to be an effective strategy for reducing gaze position error (GPE) in individuals with peripheral hypofunction, for individuals with central vestibular dysfunction, the effectiveness of CS is unknown. The purpose of our study was to compare the effectiveness of CS, defined as the ability to compensate for head velocity and eye position errors, between persons with central and peripheral vestibular dysfunction. We compared oculomotor responses during video head impulse testing between individuals with unilateral peripheral vestibular deafferentation, a disorder of the peripheral vestibular afferents, and individuals with multiple sclerosis, a condition affecting the central vestibular pathways. We hypothesized that relative to individuals with peripheral lesions, individuals with central dysfunction would recruit CSs that were delayed and inappropriately scaled to head velocity and GPE. We show that CSs recruited by persons with central vestibular pathology were not uniformly deficient but instead were of a sufficient velocity to compensate for reductions in VOR gain. Compared to those with peripheral vestibular lesions, individuals with central pathology also recruited earlier covert CS with amplitudes that were better corrected for GPE. Conversely, those with central lesions showed greater variability in the amplitude of overt CS relative to GPE. These data point to a unique role for peripheral and central vestibular inputs in the recruitment of CS and suggest that covert CSs are an effective oculomotor strategy for individuals with multiple sclerosis.NEW & NOTEWORTHY Compensatory saccades (CSs) are recruited by individuals with unilateral vestibular deafferentation (UVD) to compensate for an impaired vestibulo-ocular reflex (VOR). The effectiveness of CS in multiple sclerosis (MS), a central vestibular impairment, is unknown. We show that in UVD and in MS, covert CSs compensate for reduced VOR gain and minimize gaze position error (GPE), yet in >50% of individuals with MS, overt CS worsened GPE, suggesting unique roles for peripheral and central vestibular inputs.

Cervical vestibular evoked myogenic potentials and video head impulse test studies: alternative methods for detecting brainstem involvement in multiple sclerosis

BACKGROUND

Brainstem involvement (BSI) has been reported as a major predictive factor for future disability in Multiple Sclerosis (MS).

AIMS/OBJECTIVES

To evaluate whether Cervical Vestibular Evoked Myogenic Potentials (cVEMPs) and Video Head Impulse Test (vHIT) can be used to detect demyelinating lesions in vestibular pathways in MS.

MATERIAL AND METHODS

Fifty three people with MS and 40 controls were evaluated with Dizziness Handicap Inventory (DHI), vHIT and cVEMP.

RESULTS

The median value of DHI in MS group was significantly higher than controls (p<.001). According to vHIT results, while the results of horizontal canal vestibulo-ocular reflex gain in group with brain stem involvement (gBSI (+)) were significantly different from both controls and group without brain stem involvement (gBSI (-)) (p= .036 and .024, respectively), results of gBSI (-) were similar with controls (p= .858). When cVEMP results were examined, mean P1 wave latency in gBSI (+) was significantly longer than controls (p= .002), but difference between gBSI (-) and controls and gBSI (+) was not statistically significant (p= .104 and .279, respectively).

CONCLUSIONS AND SIGNIFICANCE

vHIT and cVEMP can be used in diagnosis and follow-up of people with MS without demyelinating brainstem lesions on MRI.