Right hemisphere in visual regulation of complex equilibrium: the female ballet dancers' experience.

OBJECTIVE: To analyse the interaction between visual restrictions and somatosensory disturbances on unipedal control equilibrium with or without classical dance training. METHODS: The support (computerized force platform) was disturbed during roll and pitch sways in association with restriction of the left and right visual hemifields (selective nasal and temporal hemiretina goggles). The effect of training by comparing spontaneous dynamic equilibrium (spectral analysis of body sways) between 14 healthy female right-sided untrained and expert dancers was assessed. The foot of the supporting leg was placed on the unstable platform center in the same way for all the participants. RESULTS: In pitch sways, analysis of variance showed that, regardless of the supporting leg used, dancers oscillated significantly less than untrained participants (p<0.01). Furthermore, all participants were significantly less stable in pitch sways if the left visual field was occluded (p<0.001). However, in roll sways, equilibrium was disturbed by covering the eyes only in dancers (p<0.001). CONCLUSION: When classical dancers' feet were in an unusual position during the experimental task (a somatosensory constraint for them but not for untrained participants), dancers shifted their spatial reference frame from somesthetic to visual cues. The elimination of this visual reference may have created imbalance, indicating that right hemispheric visual dominance is particularly useful for postural control in complex equilibrium conditions.

Relationship between dynamic balance and self-reported handicap in patients who have unilateral peripheral vestibular loss.

OBJECTIVE: The purpose of this study was to investigate whether Dizziness Handicap Inventory (DHI) score is related to postural performance as assessed by dynamic posturography. STUDY DESIGN: Retrospective study. SETTING: Outpatient in a tertiary referral center. PATIENTS: Ninety-two complete unilateral vestibular loss patients, categorized into 3 groups according to the postlesion stage: 1 to 2 months (n = 32; age, 47.6 +/- 10.7 yr), 4 to 7 months (n= 23; 47.1 +/- 8.37 yr), and 1 year and older (n = 37; 49.2 +/- 9.5 yr). MAIN OUTCOME MEASURES: Dizziness Handicap Inventory and dynamic balance measured with a seesaw platform moving either in the anterior-posterior or in the mediolateral direction. RESULTS: The mean DHI score was 25.8 +/- 18.7 and the range was 0 to 68. Dizziness Handicap Inventory scores did not differ significantly between the different unilateral vestibular loss groups studied. No difference was detected between the groups for the 3 subscores (emotional, functional, and physical), except that the older-than-1-year group had a significantly higher physical score than the 2 others. No correlation was found between DHI scores and postural indicators for either direction of the platform. However, patients unable to maintain balance when the seesaw platform moved in the mediolateral direction had significantly higher DHI scores than those who did not fall. CONCLUSION: Even if they are not directly related, we suggest that DHI and dynamic posturography are complementary approaches for appreciating the vestibular compensation process and are thus useful for postoperative counseling for vestibular loss patients.

Relationship Between Dynamic Balance and Self-Reported Handicap in Patients Who Have Unilateral Peripheral Vestibular Loss.

OBJECTIVE:: The purpose of this study was to investigate whether Dizziness Handicap Inventory (DHI) score is related to postural performance as assessed by dynamic posturography. STUDY DESIGN:: Retrospective study. SETTING:: Outpatient in a tertiary referral center. PATIENTS:: Ninety-two complete unilateral vestibular loss patients, categorized into 3 groups according to the postlesion stage: 1 to 2 months (n = 32; age, 47.6 +/- 10.7 yr), 4 to 7 months (n= 23; 47.1 +/- 8.37 yr), and 1 year and older (n = 37; 49.2 +/- 9.5 yr). MAIN OUTCOME MEASURES:: Dizziness Handicap Inventory and dynamic balance measured with a seesaw platform moving either in the anterior-posterior or in the mediolateral direction. RESULTS:: The mean DHI score was 25.8 +/- 18.7 and the range was 0 to 68. Dizziness Handicap Inventory scores did not differ significantly between the different unilateral vestibular loss groups studied. No difference was detected between the groups for the 3 subscores (emotional, functional, and physical), except that the older-than-1-year group had a significantly higher physical score than the 2 others. No correlation was found between DHI scores and postural indicators for either direction of the platform. However, patients unable to maintain balance when the seesaw platform moved in the mediolateral direction had significantly higher DHI scores than those who did not fall. CONCLUSION:: Even if they are not directly related, we suggest that DHI and dynamic posturography are complementary approaches for appreciating the vestibular compensation process and are thus useful for postoperative counseling for vestibular loss patients.

Does footedness or hemispheric visual asymmetry influence centre of pressure displacements?

To isolate the footedness contribution from the hemispheric visual asymmetry contribution to the upright postural control, seven right and six left-footed healthy women were asked to balance on each unipodal stance on an unstable platform for each visual hemispaces. We compared lateral deviations of the centre of pressure when balancing on the left leg and on the right leg in three visual conditions: normal and restricted to each hemifields. Whatever the visual conditions, left-footers displaced the centre of pressure towards the outside of the supporting foot, whereas right-footers displaced it towards the right side for the two feet. Postural control appears to be regulated differently between the two groups of footedness. For left-footers it should be more based upon the perception of the centre of body mass and for right-footers upon the asymmetrical utilization of head receptors.