Effect of age and sex on maturation of sensory systems and balance control

Abstract

Maintenance of postural balance requires an active sensorimotor control system. Current data are limited and sometimes conflicting regarding the influence of the proprioceptive, visual, and vestibular afferent systems on posture control in children. This study investigated the development of sensory organization according to each sensory component in relation to age and sex. A total of 140 children (70 males, 70 females; mean age 10y [SD 4y]; age range 3y 5mo–16y 2mo) and 20 adults (10 males, 10 females; mean age 30y 6mo [SD 8y 4mo]; age range 17y 2mo–49y 1mo) were examined using the Sensory Organization Test. Participants were tested in three visual conditions (eyes open, blindfolded, and sway-referenced visual enclosure) while standing on either a fixed or a sway-referenced force platform. Mean equilibrium scores for the six balance conditions showed rapid increases and maturation ceiling levels for age-related development of the sensorimotor control system. Proprioceptive function seemed to mature at 3 to 4 years of age. Visual and vestibular afferent systems reached adult level at 15 to 16 years of age, revealing differences between young males and females. Characterizing balance impairments can contribute to the diagnostic evaluation of neuromotor disorders. Maintenance of postural balance requires an active sensori-motor control system. Afferent information from the propri-oceptive, visual, and vestibular systems, as well as from the cognitive system, is integrated and evaluated to generate motor responses that keep the body inside its limits of stability (Nashner et al. 1982, Black et al. 1983, Black 1985). In adults, the sensory systems are well organized and act in a context-specific way (Shumway-Cook and Woollacott 1985). In children, however, the sensory systems are not completely developed, although their anatomical structures are detectable and mature early in life (Ornitz 1983). The three afferent sen-sory systems (proprioceptive, visual, and vestibular) develop more slowly than the hierarchically lower automatic motor processes that mature early in childhood (Forssberg and Nashner 1982). Although there is limited data on the influence of proprio-ceptive, visual, and vestibular afferent systems on posture con-trol in children, several studies have been conducted on the development of sensory organization. Brandt et al. (1976) and Hirabayashi and Iwasaki (1995) reported that develop-ment and calibration of the three sensory subsystems occur sequentially. When evaluating the proprioceptive system, Riach and Hayes (1987) and Aust (1996) reported that the Romberg quotient, a measure of somotosensory function, increased to adult values by 9 to 11 or 12 years of age. In contrast, Hira-bayashi and Iwasaki (1995) found that maturation of the pro-prioceptive function occurred by approximately 3 to 4 years of age. The visual influence on standing stability is reported to be established at adult levels by the age of 15 years, whereas the vestibular system is still developing at that age (Hira-bayashi and Iwasaki 1995, Aust 1996). Investigations into standing stability in response to inter-sensory conflict have produced different results. Forssberg and Nashner (1982) reported that children younger than 7 years 6 months could not suppress the influence of sensory input providing inappropriate orientation information. Shumway-Cook and Woollacott (1985) suggested that 7-to 10-year-old children were able to resolve intersensory conflict like adults. In contrast, Peterka and Black (1990), Hirabayashi and Iwasaki (1995), and Cherng et al. (2001) found that optimal stance sta-bility was reached by the age of 15 years. Because data on maturation of the proprioceptive, visual, and vestibular functions are conflicting, this study aimed to compare the sensory organization of posture control in chil-dren and adolescents with that of adults. Analysis of posture mechanisms is necessary to produce standard values which, in turn, allow detection of pathological results in balance con-trol. This allows differentiation of neurological and ortho-paedic diagnoses. The significance of each sensory component was deter-mined using computerized dynamic posturography. Method The child participants were healthy children from kinder-garten and school, and in-patient children awaiting adeno-tomies or tonsilectomies. Apart from the underlying illness, the in-patient children were healthy. Information on the children was based on medical records and parent interview. Adult par-ticipants were healthy colleagues from the Department of Otorhinolaryngology, Innsbruck Medical University. A total of 140 children (70 males, 70 females; mean age 10y [SD 4y]; age range 3y 5mo–16y 2mo) and a reference group of 20 adults