Postural Instability in Subjects With Usher Syndrome.

Simona Caldani,Thierry Van Den Abbeele,Maud Tisné,Sylvette Wiener-Vacher,Maria Pia Bucci,Isabelle Audo

doi:10.3389/fneur.2019.00830

Simona Caldani, Thierry Van Den Abbeele + Show 4 more

Open Access

https://doi.org/10.3389/fneur.2019.00830

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Abstract

This study investigated postural performances and vestibular impairment in Usher patients. The three groups studied were: 11 patients with Usher type I (with visual and vestibular impairment), 14 patients with Usher type II (with only visual impairment), and 14 healthy control subjects. Postural stability was measured with a Framiral Multitest Equilibre platform with three visual conditions: eyes open (EO), eyes closed (EC), and vision disturbed by optokinetic stimulation (OPT), and two different postural conditions: stable or unstable platform. The surface and mean velocity of the center of pressure displacement (CoP) were measured and a postural instability index (PII) was calculated. Usher type I and II patients were more unstable than control subjects, but only for the unstable platform. Patients with Usher type I (with severe vestibular impairment) were also significantly more unstable than patients with Usher type II (with normal vestibular function) on the unstable platform. The severity of the vestibular impairment was correlated with the surface of the CoP displacement. We suggest that poor postural control of Usher patients is due to the abnormalities in their visual and, when defective, vestibular inputs. Measurements of postural stability on an unstable platform can distinguish type I from type II Usher patients. We emphasize the importance of multisensory evaluation in these patients to guide development of personalized visuo-vestibular rehabilitation techniques to improve their postural stability and improve their quality of life.

Highlights

Maintaining stable posture is necessary for performing many daily tasks [1]
Analysis of covariance (ANCOVA) found a significant interaction between Posture and Group [F(2, 38) = 22.82; p < 0.0001]; Bonferroni test showed that Usher type I had a larger surface of center of pressure displacement (CoP) only on unstable platform when compared to CTR and to Usher type II
Usher type II had a larger surface of CoP when compared to CTR (p < 0.02)

Summary

Introduction

Maintaining stable posture is necessary for performing many daily tasks [1]. Postural control corresponds to a complex neurological function that relies on sensory inputs that are conveyed by the visual, proprioceptive, and vestibular systems [2]. In the literature there are three different types of Usher syndrome: type I, with profound hearing loss, congenital vestibular dysfunction, and different degrees of RP, is diagnosed during the first decade of life. Type II Usher syndrome is characterized by hearing loss, normal vestibular function, and RP of varying degree. This is often diagnosed during the second or third decade of life. Usher type III, with progressive deafness and/or vestibular disorders, is usually diagnosed in the first decade of life [5]. These patients face progressive multisensory handicaps that lead to loss of balance control and motor independence

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