Functional reach and touch to evaluate perceptive impairment in diplegic cerebral palsy children

INTRODUCTION
In 30% of children with Diplegic Cerebral Palsy (CP), disability depends not only on motor aspects, but most of all on perceptual impairments. The Central Nervous System (CNS) cannot collect, elaborate and integrate redundant sensitive and sensorial information in order to obtain coherent representations of reality[1]. Clinical signs that are characteristic of the perceptive impairment consequent to( movement intolerance and to, fear of spaces) seem to be correlated with a visual-kinestesic conflict because of the incoherence between visual and proprioceptive information [1]. We suggest an experimental set up of Functional Reach and Touch (FRT) to establish the presence and to measure the intensity of the perceptive disease by varying the exposition of patients to the empty space.

METHODS
14 patients affected by Spastic Diplegia (SD) (aged 6-15 years) and 5 control subjects (aged 6-14 years) executed FRT while sitting on a height-adjustable chair (0.6 m – low; 1.0 m – high). Subjects were asked to stand steady for 10 seconds, and then, after hearing a whistle, to reach and touch a target (a ball with an accelerometer to sample the touching instant). A force plate under the chair acquired the Centre of Pressure (COP) trajectory. FRT was registered in 18 different positions/conditions, resulting from the combinations of: i) distance to target equal to 120% (near) and 150% (far) of the arm-length (from the acromion to the tip of the medium finger); ii) postero-omolateral (PO), antero-omolateral (AO) or antero-controlateral (AC) directions; iii) high or low chair; iv) presence/absence of perceptive facilitation ‘raised floor’ (highFAC): white sheet stretched at knee level (2.3x2.3m2) hiding the empty space.

RESULTS
All control subjects but one (who failed at high_far_AC) managed to have a positive outcome (target reached). Patients with SD had a positive outcome in 79% of the near, and in 48% of the far trials. Out of the 14 SD, 8 clinically showed the perceptive impairment[1] (perceptual). Only the 17% of these latter obtained a positive outcome far versus the 87% of the remaining 6 (motor). The estimate of the movement smoothness (Normalized Jerk Score – NJS[2]) applied to COP trajectory showed that the highFAC facilitates the performance in perceptuals in a more significant way than in motors. While in the high_far_AO, perceptual subjects worsened (NJS increment) of a factor equal to 24.0, motors of 5.3 and controls of 3.6 in comparison to the relative low trial, in the highFAC trials all the subjects showed similar results (NJS almost triplicated). The facilitation effect appeared also analyzing the Sway Area (SA)[3] during the first 10 s of static posture of all trials. In perceptual subjects a trend was observed: low=159 mm2/s, highFAC=203 mm2/s, high=244 mm2/s, while the effects were absent in controls and motors (about 40 mm2/s).

DISCUSSION
The experimental setup showed here represents a sensitive tool to detect the presence of the perceptive impairment in patients with SD. Although with high variability, results showed different behaviors in patients with motor disability compared to the perceptuals. The presence of perceptive facilitation ‘raised floor’ in the FRT trials yielded to an improvement of the performance only in the perceptual, as measured by movement smoothness during the task (NJS) and of the SA during the static posture. Further experiments and more detailed statistical analysis are needed to characterized the absence and the magnitude of the perceptive impairment in patients with SD in a exhaustive way.

BIBLIOGRAFY
[1] Ferrari A, Cioni G, Le forme spastiche della paralisi cerebrale infantile, Springer, Milano,2005.
[2] Chang JJ, et al., Clin Biomech 2005; 20: 381-3