Application of tetra-ataxiametric posturography in clinical and developmental diagnosis.

Tetra-ataxiametric posturography is based on the measurement and computerized elaboration of electronic signals emitted by four footplates, one for each heel and toe, respectively. These are sensitive to vertical pressure produced by a subject standing straight but in various positions (feet parallel, in tandem, eyes closed, on pads, etc.). The method yields additional parameters not obtained by the traditional monoplate stabilometers, namely, weight-distribution patterns and correlations among six combinations of paired outputs from the two heels, two toes, heel/toe of each foot, and the two diagonals (tetra-ataxiametric synchronisations). Comparing age-matched learning disabled, mentally retarded, autistic, and hearing impaired (with and without labyrinthine hypofunction) with normal children, significant and clinically meaningful differences were detected between the tetra-ataxiametric measures of stability, interaction between Fourier Spectral Power Ranges of body sway, weight distributions, and synchronisations of toe parts. The same parameters correlated significantly with cognitive school readiness in normal populations. While the stability and spectral quotients show significant developmental changes, weight distribution and toe synchronisations are stable from 5 years onwards. The method is suitable for young subjects and attractive to children who may ordinarily be reluctant to cooperate, such as the autistic ones. The equipment is portable and tests can be conveniently carried out in a child's familiar educational setting.