Exploring the Link Between Motor Functions and the Relative Use of the More Affected Arm in Adults with Cerebral Palsy

Abstract

Individuals with hemiparetic cerebral palsy (CP) exhibit reduced use of their more affected (MA) arm, yet the factors that influence its use during activities of daily living remain elusive. The objectives of this study were to describe the relative use of the MA arm during an ecological task, examine its relationship with the level of impairment, and investigate its association with performance in various unilateral and bilateral tasks.

Methods: Participants took part in two sessions comprising robotic assessments and clinical assessments of motor functions, as well as accelerometry measurement during kitchen tasks. Four variables were derived from accelerometry data. Stepwise regression analyses were used to identify the best contributors to the accelerometry variables among robotic and clinical assessments.

Results: Nineteen adults with CP (34.3 years old ± 11.5; MACS I = 7, II = 6, III = 6) were included. The Use Ratio measured during the kitchen tasks ranged between 0.10 and 0.63. The best predictors of all accelerometry metrics were two bilateral assessments (r² = 0.23-0.64).

Conclusions: The importance of assessing bilateral tasks was reaffirmed by the key role played by two bilateral tasks in determining the relative use of the MA arm. The results support the use of intensity-based accelerometry metrics to measure MA arm use.

Keywords: accelerometry; activities of daily living; bimanual coordination; cerebral palsy; motor function; upper extremity.

Figure 1

(A) Experimental setup for the Kinarm Exoskeleton Lab and (B) workspace representation of the Object Hit, Ball on Bar, and Visually Guided Reaching tasks.

Figure 2

Experimental setup for the accelerometry assessment. (A). Participant wearing one accelerometer at each wrist while setting the table. (B). Accelerometer used for the assessment including a representation of the x-, y-, and z-axes.

Figure 3

Histograms showing the distribution of results for each assessment. Robotic assessments are displayed within a grey square. The red line indicates the cutoff for normative data when available, with the direction of the arrow pointing toward the presence of impairments.

Figure 4

Distribution of upper limb use intensity for representative subjects across levels of impairment. The x-axis represents the Magnitude Ratio, i.e., the relative contribution of each upper extremity in terms of intensity. A negative value represents a larger use of the MA arm while a positive value represents a larger use of the LA arm. A value of 0 means that both arms are used equally. The column of data at −7 represents unilateral movement of the LA arm, and the column of data at 7 represents unilateral movements of the MA arm. The y-axis represents the intensity of bilateral use (Bilateral Magnitude). The color scale represents the frequency at which each combination happened, ranging from blue (less frequently) to red (more frequently). MACS = Manual Ability Classification Scale.