Functional and Gait Assessment in Children and Adolescents Affected by Friedreich's Ataxia: A One-Year Longitudinal Study

Abstract

Friedreich's ataxia is the most common autosomal recessive form of neurodegenerative ataxia. We present a longitudinal study on the gait pattern of children and adolescents affected by Friedreich's ataxia using Gait Analysis and the Scale for the Assessment and Rating of Ataxia (SARA). We assessed the spectrum of changes over 12 months of the gait characteristics and the relationship between clinical and instrumental evaluations. We enrolled 11 genetically confirmed patients affected by Friedreich's ataxia in this study together with 13 normally developing age-matched subjects. Eight patients completed a 12-month follow-up under the same protocol. By comparing the gait parameters of Friedreich's ataxia with the control group, we found significant differences for some relevant indexes. In particular, the increased knee and ankle extension in stance revealed a peculiar biomechanical pattern, which correlated reliably with SARA Total, Gait and Sitting scores. The knee pattern showed its consistency also at the follow-up: Knee extension increased from 6.8±3.5° to -0.5±3.7° and was significantly correlated with the SARA total score. This feature anticipated the loss of the locomotor function in two patients. In conclusion, our findings demonstrate that the selective and segmental analysis of kinetic/kinematic features of ataxic gait, in particular the behavior of the knee, provides sensitive measures to detect specific longitudinal and functional alterations, more than the SARA scale, which however has proved to be a reliable and practical assessment tool. Functional outcomes measures integrated by instrumental evaluation increase their sensitivity, reliability and suitability for the follow-up of the disease progression and for the application in clinical trials and in rehabilitative programs.

Fig 1. Kinetic/Kinematics parameters.

The figure shows the time series of the variables examined in the paper. In the horizontal axis is represented the time normalized respect to the duration of the gait cycle (from the hell contact to the floor to the ipsilateral succeeding hell contact). The arrows indicate the peak values here studied. The black line represents the mean values of the baseline of the patient with FRDA, while the gray band represents the standard deviation of the control group. In the first row are represented in degree the flexion and extension rotation of the hip, the knee and the ankle, from left to right respectively. In the second and third rows are represented joints moment and power, respectively, normalized respect to body wheight. In the four row is represented the hip ab-adduction and the angle of the internal end external rotation of the foot.

Fig 2. Ankle, hip and knee rotational co-variation during a complete gait cycle.

The figure depicts the angles of hip, knee and ankle during the gait cycle on 3D plot, that is, the angle values on vertical axes of Fig 1 for hip, knee and ankle was bring back, respectively on x, y and z axes, in this figure. This figure represents the lower limb joint co-variation during the gait cycle. Solid line represents the mean values of controls, dotted line the baseline of FRDA, and dashed line the FRDA follow-up. Dark gray arrows indicate the foot landing, that is, the gait cycle start. White arrows indicate the beginning of the swing phase. The large light gray arrow represents the gait pattern progressive deterioration towards ankle and knee extension moving from the dotted to the dashed curves in patients with FRDA (see S1 Fig for a 3D animation of the graph).