Is backward disequilibrium in the elderly caused by an abnormal perception of verticality? A pilot study.
OBJECTIVE
We hypothesised that backward disequilibrium (BD), defined by a posterior position of the centre of mass with respect to the base of support, could be caused by a backward tilt in the perception of verticality.


METHODS
The relationship between BD, the perception of verticality, and the history of falls in 25 subjects aged 84.5+/-7.4 years was analysed. An original ordinal scale, the BD scale (BDS), was used to quantify BD. Postural (PV) and haptic verticals (HV) were measured in sagittal plane.


RESULTS
BDS scores closely correlated with the number of falls (r = 0.81, p =10(-5)). The more the PV was tilted backward, the greater the BDS scores (r = -0.95, p<10(-6)), with a huge backward tilt of about 15 degrees in 4 subjects with severe BD. In these subjects, the tilt in perception of verticality was transmodal since a severe backward HV tilt was also found.


CONCLUSIONS
This transmodality suggested high-order cognitive disruption in the construction of the subjective vertical used in postural control by subjects showing BD, which confirmed our hypothesis.


CONCLUSIONS
This study clearly shows that perception and action with respect to gravity are closely related and brings a new insight about fall mechanisms in the elderly.
Manckoundia
Patrick
P
INSERM/ERIT-M 0207 Motricité-Plasticité, Université de Bourgogne, Dijon, France. patrick.manckoundia@chu-dijon.fr
Mourey
France
F
Pfitzenmeyer
Pierre
P
Van Hoecke
Jacques
J
Pérennou
Dominic
D
D000058:Accidental Falls; D000369:Aged, 80 and over; D015577:Geriatric Assessment; D006801:Humans; D010865:Pilot Projects; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D012720:Severity of Illness Index; D015837:Vestibular Diseases / Q000209:etiology*; D014724:Vestibular Function Tests; D014796:Visual Perception / Q000502:physiology*