Postural Instability in Subjects With Usher Syndrome

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.

Vestibular phenotype‐genotype correlation in a cohort of 90 patients with Usher syndrome

“…We confirm previous reports identifying an overall aging effect on postural stability 32 . Our posturography data further support and expand upon observations by Caldani et al 17 that patients with Usher syndrome have reduced postural stability that results from deficits in visual and vestibular contributions to balance.…”

“…These findings have implications for personalized and targeted counseling and (re)habilitation of postural stability and balance in patients with Usher syndrome. This study also extends knowledge of postural stability in USH1 and USH2, which has been previously limited to one study in a genetically confirmed population, 17 and supplements the comprehensive report of variable SOT findings in USH3 39 …”

“…Each Usher syndrome gene is associated with one of the three clinical types. However, there are some reported examples of atypical RP, 10 auditory or vestibular manifestations in patients with variants in genes associated with Usher type I 11‐17 and type II 18‐24 . Some disparity exists because of previous technological limitations in clinical assessment.…”

Usher syndrome and Nebulin‐associated myopathy in a single patient due to variants in MYO7A and NEB

“…Segregation studies, by Sanger sequencing, confirmed the presence of this pathogenic variant in heterozygosity in both parents, and the absence in the heathy sister (Figure 3). Although the kyphosis presented by our proband could be, at least partially, explained by the vestibular impairment, the other musculoskeletal complaints are not associated with Usher syndrome 34 . NEB pathogenic variants are implicated in the nemaline myopathy type 2 (NEM2, OMIM#256030), mainly characterized by early‐onset muscle weakness, predominately in proximal limb muscles with a high variability, ranging from mild to severe 35 .…”

Vestibular impact of Friedreich ataxia in early onset patients

“…Indeed, preserved low frequency canal function can be observed in some peripherical inner ear diseases with selective canal impairment (reduced middle and high frequency canal function with normal low frequency canal function -e.i. Usher type I syndrome) [44].…”