Downbeat nystagmus becomes attenuated during walking compared to standing

Abstract

Downbeat nystagmus (DBN) is a common form of acquired fixation nystagmus related to vestibulo-cerebellar impairments and associated with impaired vision and postural imbalance. DBN intensity becomes modulated by various factors such as gaze direction, head position, daytime, and resting conditions. Further evidence suggests that locomotion attenuates postural symptoms in DBN. Here, we examined whether walking might analogously influence ocular-motor deficits in DBN. Gaze stabilization mechanisms and nystagmus frequency were examined in 10 patients with DBN and 10 age-matched healthy controls with visual fixation during standing vs. walking on a motorized treadmill. Despite their central ocular-motor deficits, linear and angular gaze stabilization in the vertical plane were functional during walking in DBN patients and comparable to controls. Notably, nystagmus frequency in patients was considerably reduced during walking compared to standing (p < 0.001). The frequency of remaining nystagmus during walking was further modulated in a manner that depended on the specific phase of the gait cycle (p = 0.015). These attenuating effects on nystagmus intensity during walking suggest that ocular-motor control disturbances are selectively suppressed during locomotion in DBN. This suppression is potentially mediated by locomotor efference copies that have been shown to selectively govern gaze stabilization during stereotyped locomotion in animal models.

Roles for cerebellum and subsumption architecture in central pattern generation

“…3). The recent reports of activity-dependent suppression of vestibular balance control (Dietrich et al 2020), and down-beat nystagmus attenuation during walking would align with this view (Dietrich et al 2022). Direct evidence for the coordination of gaze behaviours and walking have been shown in cats (Zubair et al 2019), who argue that "gaze-stride coordination arises as a part of the whole-body locomotor synergy, which includes the limbs, body, head, and eyes.…”

Downbeat nystagmus: a clinical and pathophysiological review

“…In addition, is typical of the DBS a peculiar gait disturbance characterized by a reduced step speed, a shorter swing phase, and a longer double-support stance phase (114) due to impaired sensorimotor integration caused by the vestibular-cerebellar lesion. Notably, DBN frequency and postural imbalance were significantly reduced during walking compared to standing (p < 0.001), and the frequency of nystagmus during walking was further modulated in a manner that depended on the specific phase of the gait cycle (p = 0.015) (115). The attenuation of DBN symptoms may result directly from the locomotor activity itself, reflecting selective central and/or peripheral suppression of sensory feedback during locomotion.…”

Vestibulo-Ocular Reflex Suppression: Clinical Relevance and Assessment in the Digital Age

“…An increased velocity gain in the suppressed state could indicate that the person cannot keep a fixed target in the centre of the field of vision (even unintentionally). It is known from other forms of nystagmus that the frequency of nystagmus, which also results from the slow phase, is variable and can provide information about the severity of the disease [36,37]. Furthermore, increased variability of this velocity gain (Fig.…”