Deficient recovery response and adaptive feedback potential in dynamic gait stability in unilateral peripheral vestibular disorder patients.

Unilateral peripheral vestibular disorder (UPVD) causes deficient locomotor responses to novel environments due to a lack of accurate vestibular sensory information, increasing fall risk. This study aimed to examine recovery response (stability recovery actions) and adaptive feedback potential in dynamic stability of UPVD-patients and healthy control subjects during perturbed walking. 17 UPVD-patients (>6 months since onset) and 17 matched healthy control participants walked on a treadmill and were subjected to eight unexpected perturbations during the swing phase of the right leg. For each perturbation, the margin of stability (MS; state of body's centre of mass in relation to the base of support), was determined at touchdown of the perturbed leg and during the following six recovery steps. The first perturbation caused a reduced MS at touchdown for the perturbed leg compared to baseline, indicating an unstable position, with controls requiring five recovery steps to return to MS baseline and UPVD-patients not returning to baseline level within the analyzed six recovery steps. By the eighth perturbation, control subjects needed two steps, and UPVD-patients required three recovery steps, both thereby improving their recovery response with practice. However, MS at touchdown of the perturbed leg increased only for the controls after repeated perturbations, indicating adaptive feedback-driven locomotor improvements for the controls, but not for the UPVD-patients. We concluded that UPVD-patients have a diminished ability to control dynamic gait stability during unexpected perturbations, increasing their fall risk, and that vestibular dysfunction may inhibit the neuromotor system adapting the reactive motor response to perturbations

Visual and proprioceptive contributions to postural control of upright stance in unilateral vestibulopathy.

Preserving upright stance requires central integration of the sensory systems and appropriate motor output from the neuromuscular system to keep the centre of pressure (COP) within the base of support. Unilateral peripheral vestibular disorder (UPVD) causes diminished stance stability. The aim of this study was to determine the limits of stability and to examine the contribution of multiple sensory systems to upright standing in UPVD patients and healthy subjects. We hypothesized that closure of the eyes and Achilles tendon vibration during upright stance will augment the postural sway in UPVD patients more than in healthy subjects. Seventeen UPVD patients and 17 healthy subjects performed six tasks on a force plate: forwards and backwards leaning, to determine limits of stability, and upright standing with and without Achilles tendon vibration, each with eyes open and closed (with blackout glasses). The COP displacement of the patients was significantly greater in the vibration tasks than the controls and came closer to the posterior base of support boundary than the controls in all tasks. Achilles tendon vibration led to a distinctly more backward sway in both subject groups. Five of the patients could not complete the eyes closed with vibration task. Due to the greater reduction in stance stability when the proprioceptive, compared with the visual, sensory system was disturbed, we suggest that proprioception may be more important for maintaining upright stance than vision. UPVD patients, in particular, showed more difficulty in controlling postural stability in the posterior direction with visual and proprioceptive sensory disturbance

Influence of cervical spine stabilization via Stiff Neck on the postural system in healthy patients: compensation or decompensation of the postural system? (vol 267, pg 1623, 2010)

Functional and structural disorders of the cervical spine are often regarded as the cause of non-specific vertigo. Pathogenetically, disorders of proprioceptive connections between neck muscles and vestibular cores as well as the proprioceptors in the cervical facette joints are presumed. According to a study by Hulse and Ho (HNO 48:295-301, 1), after manual therapeutic intervention in patients with functional disorders of the cervical spine 50% of the probands stated a significant reduction of their vertigo. This was backed up in posturography, which documented an improvement in vestibulospinal reactions. To date, the effects of artificial as well as surgical stabilization of the cervical spine on the balance system have not been explored yet. In a first pilot study, we examined the influence of artificial stabilization of the cervical spine via cervical collar Stiff Neck, manufactured by Ambu/Perfit ACE] on the balance system of 20 healthy probands. For this purpose, a posturography (Balance Master Systems, Neuro-Com, Clackamas, OR, USA) was applied to 20 healthy probands (10 males, 10 females) with a mean age of 35 years who had no prior spine pathology. Posturography was analyzed under static and dynamic test situations with and without Stiff Neck cervical collar. The results were compared statistically to the Wilcoxon test. In the static test situation of the modified clinical test of sensory interaction on balance, a significantly improved standing stability occurred. In none of the dynamic tests did fixation of the cervical spine by Stiff Neck cuff lead to a measurable impairment of the movement coordination. All probands felt subjectively more stable when wearing the Stiff Neck. In healthy probands, a fixation of the cervical spine leads to a stabilization of the postural balance situation. This fixation seems to be helpful in compensating the malfunction of other components of balance information. In a next step, this same model of analysis is applied to patients with cervical instability. Standing stability and movement coordination before and after cervical fusion are being explored

Associations Between Bipedal Stance Stability and Locomotor Stability Following a Trip in Unilateral Vestibulopathy

Posturography is used to assess balance in clinical settings, but its relationship to gait stability is unclear. We assessed if dynamic gait stability is associated with standing balance in 12 patients with unilateral vestibulopathy. Participants were unexpectedly tripped during treadmill walking and the change in the margin of stability (MoSchange) and base of support (BoSchange) relative to nonperturbed walking was calculated for the perturbed and first recovery steps. The center of pressure (COP) path during 30-s stance with eyes open and closed, and the distance between the most anterior point of the COP and the anterior BoS boundary during forward leaning (ADist), were assessed using a force plate. Pearson correlations were conducted between the static and dynamic variables. The perturbation caused a large decrease in the BoS, leading to a decrease in MoS. One of 12 correlations was significant (MoSchange at the perturbed step and ADist; r = -.595, P = .041; nonsignificant correlations: .068 ≤ P ≤ .995). The results suggest that different control mechanisms may be involved in stance and gait stability, as a consistent relationship was not found. Therefore, posturography may be of limited use in predicting stability in dynamic situations

Deficient recovery response and adaptive feedback potential in dynamic gait stability in unilateral peripheral vestibular disorder patients

Unilateral peripheral vestibular disorder (UPVD) causes deficient locomotor responses to novel environments due to a lack of accurate vestibular sensory information, increasing fall risk. This study aimed to examine recovery response (stability recovery actions) and adaptive feedback potential in dynamic stability of UPVD-patients and healthy control subjects during perturbed walking. 17 UPVD-patients (>6 months since onset) and 17 matched healthy control participants walked on a treadmill and were subjected to eight unexpected perturbations during the swing phase of the right leg. For each perturbation, the margin of stability (MS; state of body's centre of mass in relation to the base of support), was determined at touchdown of the perturbed leg and during the following six recovery steps. The first perturbation caused a reduced MS at touchdown for the perturbed leg compared to baseline, indicating an unstable position, with controls requiring five recovery steps to return to MS baseline and UPVD-patients not returning to baseline level within the analyzed six recovery steps. By the eighth perturbation, control subjects needed two steps, and UPVD-patients required three recovery steps, both thereby improving their recovery response with practice. However, MS at touchdown of the perturbed leg increased only for the controls after repeated perturbations, indicating adaptive feedback-driven locomotor improvements for the controls, but not for the UPVD-patients. We concluded that UPVD-patients have a diminished ability to control dynamic gait stability during unexpected perturbations, increasing their fall risk, and that vestibular dysfunction may inhibit the neuromotor system adapting the reactive motor response to perturbations

Sound levels in nursery schools

Introduction. Children and teenagers often suffer from hearing loss because of exposure to sound levels above 100 dB generated by toys, portable music players and stereo equipment in discotheques. Even in nursery schools and schools, considerable noise levels are produced by children's voices. Methods. Sound levels were measured in a nursery school in Cologne in four different rooms, each with 22 children aged between 3 and 6 years and two teachers. Sound dosimeters detected sound levels in each room for 5 days of the week. These were positioned in the room above the playing children as well as near the teachers' ears. The same measurements were repeated after the children had been instructed about noise and possible noise damage. In addition, the children were now able watch the noise lights, an instrument resembling traffic lights which translated the sound levels actually measured in their room into optical signals. A questionnaire containing 13 questions about noise and sensitivity to noise was distributed to 35 teachers at nursery schools in the Cologne municipal area. Results. Mean sound levels of an 8-h/day measuring period (L-eq) were 80.1 +/- 2.3 dB(A) near the ear of the teacher and 70.87 +/- 2.5 dB(A) measured in the room. The maximal sound level for 1 s, L-max dB(A), was 112.55 +/- 2.3 dB(A) near the ear and 103.77 +/- 8.1 dB(A) in the room. After the children had learned about noise and were able to check the sound level they produced with the help of the noise lights, a tendency towards a reduction of sound levels in the room and near the teachers'ears could be seen. An evaluation of the questionnaire revealed the high physical strain and emotional stress the teachers were subjected to due to noise. Conclusions. Children and teachers in nursery schools are subjected to high sound levels. Therefore, the education and early sensitization of children to noise in order to prevent prospective hearing damage, e.g. using the noise light, should be set as a goal. Soundproofing measures are also possible. Further investigations to assess the effects of these measures are planned