Balance sensory organization in children with profound hearing loss and cochlear implants

Abstract

(1) To determine the feasibility of the use of a modified postural control test under altered sensory conditions in children over 8 years of age, and (2) to assess how deaf children use sensory information for postural control when they have normal or abnormal vestibular responses, and if hearing input from a unilateral cochlear implant, changes their postural behavior. We selected 36 children, 8 to 11 years of age, with congenital or early-acquired profound sensorineural hearing loss, 13 of them with unilateral cochlear implantation and 22 normal-hearing children. The Postural Control (PC) test consists of a force platform with 2 stimulation paradigm conditions: (1) standing on the platform with opened eyes; (2) standing on foam placed on the force platform with closed eyes. Implanted children were tested with the implant turn on and turn off in this condition, in order to evaluate eventual change in the postural control parameters when they have hearing habilitation. The body center of pressure distribution area (COP) and the body sway velocity (SV) were the parameter to evaluate the postural control. Deaf children were classified into two groups according with the vestibular responses: group A (n=28) Children with normal vestibular rotary responses; group B (n=8) children with hypoactive responses. Children in group A had diagnoses of syndromic and non-syndromic hereditary deafness, and children in group B had inner ear malformations, post-meningitis deafness, and one child had non-syndromic hereditary deafness with hypoactive vestibular response. In condition 1, when vestibular, somatosensory and visual information were enabled, the COP and SV values did not show any statistically significant differences between groups A, B and control. In condition 2, when visual information was removed and the somatosensory input strongly modified by standing on the foam, group B showed significant higher COP and SV values than groups A and control (p<0.05). In addition, the scalograms by wavelets of children in group B had higher amplitudes increasing the sway frequencies contents up to 3 Hz, not allowing them to maintain the up right stance in similar stimulation than in condition. Implanted children of the group A and B with the implant turn on, in the condition 2, did not show any significant difference in the SV, comparing when they had the implanted turn off. Group A p=0.395 and group B p=0.465 (Wilcoxon ranked test). These findings allow us to confirm that this postural test can be performed in children over 8 years old. Also our results suggest that deaf children with associated hypoactive vestibular responses included in our study, despite the etiology of the deafness, primarily use visual and somatosensory information to maintain their postural control. Hearing habilitation with a unilateral cochlear implant has no effect on the observed sensory organization strategy.