Postural responses without versus with acute external cervical spine fixation: a comparative study in healthy subjects and patients with acute unilateral vestibular loss

Effect of simulated acute bilateral severe conductive hearing loss on static balance function in healthy subjects: a prospective observational pilot study

PURPOSE

Maintaining static balance is a process coordinated by central integration of visual, vestibular and somatosensory information. Whether or not hearing and spatial acoustic information contributes to the maintenance of static postural balance is unclear.

METHODS

A prospective observational pilot study was performed. Twenty-five normal hearing adults (68% female; 19-31 years) underwent a computerized dynamic posturography test battery including the Sensory Organization Test (SOT), the Motor Control Test (MCT), and the Adaptation Test (ADT). The balance tests were performed two times, in a randomized sequence without or with acute hearing loss. Earplugs (sound insulation 37 dB) or headphones with white noise (sound volume 75 dB) induced the conductive hearing loss. Hence, all participants passed through four sequences of the balance test battery. A repeated-measures analysis of variance (ANOVA) was used to analyze the results.

RESULTS

The ANOVA revealed no difference for any SOT and ADT subtest without hearing loss and simulated hearing loss (either earplugs or headphones; all p > 0.05). The ANOVA showed no longer latencies with simulated hearing loss compared to no hearing loss in both experiments with one exception: the reaction of the right foot during large forward translation was longer with hearing loss than without hearing loss in both experiments (p = 0.025).

CONCLUSIONS

Overall, a simulated acute conductive bilateral moderate or severe hearing loss did not disturb the static balance function in normal hearing younger adults in this first small pilot study.

Regular physical activity reduces the effects of Achilles tendon vibration on postural control for older women

The aim was to determine in what extent physical activity influences postural control when visual, vestibular, and/or proprioceptive systems are disrupted. Two groups of healthy older women: an active group (74.0 ± 3.8 years) who practiced physical activities and a sedentary group (74.7 ± 6.3 years) who did not, underwent 12 postural conditions consisted in altering information emanating from sensory systems by means of sensory manipulations (i.e., eyes closed, cervical collar, tendon vibration, electromyostimulation, galvanic vestibular stimulation, foam surface). The center of foot pressure velocity was recorded on a force platform. Results indicate that the sensory manipulations altered postural control. The sedentary group was more disturbed than the active group by the use of tendon vibration. There was no clear difference between the two groups in the other conditions. This study suggests that the practice of physical activities is beneficial as a means of limiting the effects of tendon vibration on postural control through a better use of the not manipulated sensory systems and/or a more efficient reweighting to proprioceptive information from regions unaffected by the tendon vibration.

Discrepancy in the involution of the different neural loops with age

The purpose of the study was to compare the effects of sensory manipulations on postural control for subjects of different ages. A young group of subjects (n = 17; 20.0 ± 1.3 years) and an old group of subjects (n = 17; 74.7 ± 6.3 years) were compared in 14 postural conditions [2 reference conditions and 12 sensory manipulation conditions: eyes closed, cervical collar, tendon vibration, electromyostimulation, galvanic vestibular stimulation (2 designs), foam surface] on a force platform. Spatio-temporal parameters of the center of foot pressure displacement were analyzed. When vestibular or proprioceptive afferences were manipulated, the old group was more disturbed than the young group. In addition, when myo-articular proprioceptive afferences were the only non-manipulated information source, the old group was also more disturbed than the young group. Hence, the inability to correctly interpret proprioceptive information and/or the impairment of myo-articular information would appear to be the major factor causing postural control deterioration. Moreover, concerning the vestibular system, it may be that aging alters the central integration of vestibular afferences. These results suggest that aging differently affects the functional ability of the different neural loops in postural control.