Novel Assessment of the Paretic Upper Limb and Bimanual Coordination after Stroke

Abstract

Unimanual and bimanual upper limb impairments are often present after stroke and the neurophysiological mechanisms underlying bimanual coordination are not completely understood. This thesis had three separate aims. The first aim was to develop and provide preliminary evidence for an assessment that could categorise unimanual upper limb outcome after stroke quickly and remotely. The second aim was to use transcranial magnetic stimulation (TMS) to study the neurophysiological mechanisms mediating different forms of bimanual coordination in healthy adults. The final aim was to develop and use a novel behavioural assessment of coordination during bimanual task performance to evaluate bimanual coordination impairments and recovery after stroke.

Action Research Arm Test scores obtained in-person from 333 participants at three months post-stroke were retrospectively analysed to produce three assessments for quickly categorising upper limb outcome after stroke, called the Fast Outcome Categorisation after Stroke (FOCUS) assessments. The overall accuracy of one FOCUS assessment for categorising upper limb outcome when performed remotely during a videocall was 88.5% at three months after stroke (n = 26), 96.3% at six months after stroke (n = 27), and 78.4% at the chronic stage after stroke (n = 37).

One neurophysiological study used TMS and motor evoked potentials to assess corticomotor excitability (CME) and two measures of interhemispheric inhibition (IHI) in 20 healthy adults while they performed tasks with different bimanual coordination requirements. IHI was similar between tasks, but CME was higher during asymmetric movements than symmetric movements. This was the first study to measure CME and IHI during bimanually-active dynamic tasks requiring different forms of bimanual coordination.

The Bimanual Coordination After Stroke Scale (BCASS) is a novel behavioural assessment of coordination during bimanual task performance after stroke. In one study, preliminary evidence from 30 participants with chronic stroke found the BCASS was sensitive, valid, and reliable. In another study, the BCASS was used to measure initial impairments and recovery of bimanual coordination in 56 participants from one week after stroke to six months after stroke. Bimanual coordination plateaued at three months after stroke alongside unimanual upper limb motor recovery. The initial impairments and time course of bimanual coordination recovery depended on movement symmetry and goal conceptualisation of the BCASS tasks.

This thesis developed the novel BCASS and FOCUS assessments for evaluating function of the upper limbs after stroke, while also furthering our understanding of the neurophysiological mechanisms underlying bimanual coordination. These original contributions can facilitate future upper limb research after stroke.