Motor Lateralization Provides a Foundation for Predicting and Treating Non-paretic Arm Motor Deficits in Stroke

Abstract

Brain lateralization is a ubiquitous feature of neural organization across the vertebrate spectrum. We have developed a model of motor lateralization that attributes different motor control processes to each cerebral hemisphere. This bilateral hemispheric model of motor control has successfully predicted hemisphere-specific motor control and motor learning deficits in the ipsilesional, or non-paretic, arm of patients with unilateral stroke. We now show across large number and range of stroke patients that these motor performance deficits in the non-paretic arm of stroke patients vary with both the side of the lesion, as well as with the severity of contralesional impairment. This last point can be functionally devastating for patients with severe contralesional paresis because for these individuals, performance of upper extremity activities of daily living depends primarily and often exclusively on ipsilesional arm function. We present a pilot study focused on improving the speed and coordination of ipsilesional arm function in a convenience sample of three stroke patients with severe contralesional impairment. Over a three-week period, patients received a total of nine 1.5 h sessions of training that included intense practice of virtual reality and real-life tasks. Our results indicated substantial improvements in ipsilesional arm movement kinematics, functional performance, and that these improvements carried over to improve functional independence. In addition, the contralesional arm improved in our measure of contralesional impairment, which was likely due to improved participation in activities of daily living. We discuss of our findings for physical rehabilitation.

Keywords: Bilateral hemispheric model; Contralesional; Dynamic dominance; Interlimb transfer; Ipsilesional; Jebsen-Taylor hand function test; Paresis; Rehabilitation.

Fig. 1

Multidirection reaching movements in patients with unilateral stroke (Schaefer et al. 2009b). a Reaching movements in the non-paretic arm of patients with left (LHD) and right (RHD) hemisphere damage. b Variance in hand positions during the initial trajectory phase (bottom ellipses), and in the final position (top ellipses) of the movement

Fig. 2

Data from 72 age and gender matched control participants (36 using the right arm, and 36 using the left arm), 22 LHD survivors, and 29 RHD survivors. Y-axis represents the Jebsen-Taylor Hand Function Test score. Data are normalized to control subjects’ dominant arm performance (100 %). X-axis stratified by hand (in the case of stroke survivors, this is always the non-paretic, ipsilesional arm), and severity of contralesional deficit

Fig. 3

Participants were positioned facing a horizontally positioned mirror that reflected the 55″ monitor. The arm was supported over a horizontal table top, positioned just below shoulder height (adjusted to each individual’s comfort), by an air-jet system, which reduced the effects of gravity and friction

Fig. 4

Timeline for the intervention—baseline period of 2 weeks, during which no intervention was done. Two baseline tests (Test 1 and Test 2) were given (2 weeks apart) prior to Non-Paretic arm training, and Test 3 was given immediately after the 3-week training period

Fig. 5

Participants were initially exposed to virtual reality games for 40 min, followed by real-life tasks for another 40 min

Fig. 6

Mean ± SE for clinical assessments

Fig. 7

Sample Handpaths prior to and following training, and associated measures (Mean ± SE) for the two pretests (test1, test2), and the post test (test3)