The contribution of reorganised motor pathways to recovery of arm and hand function after stroke

Turton, Ailie Jean (1996). The contribution of reorganised motor pathways to recovery of arm and hand function after stroke. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000e132

Abstract

Stroke often disrupts the descending motor pathways controlling the upper limb with severe consequences for patients' hand function. Although some recover they are often slow and clumsy when using the affected hand. The mechanism underlying recovery is an unsettled question. Transcranial magnetic stimulation (TMS) was used to determine the changes in the connectivity and function of the corticospinal tract (CST) that are associated with improved motor performance in the recovering arm and hand. The study comprised four parts:

1. Task dependency of responses to TMS in recovered stroke patients.

Eight patients, who had recovered some degree of hand function were tested for task dependence of short-latency EMG responses to TMS. Normal subjects were also tested.

2. Longitudinal investigation of recovery of voluntary movement of arm and hand after stroke.

The relationship between the recovery of hand and arm function in a group of acute stroke patients (n=21) and the presence of short latency contralateral and ipsilateral EMG responses to TMS in four different upper limb muscles was investigated.

3. Ipsilateral responses in normal subjects.

The results of the longitudinal study prompted further investigation of the presence of ipsilateral responses in proximal and distal muscles in fifteen normal subjects.

4. The contribution of CS input to production of force in proximal and distal upper limb muscles.

Because patients did not always have responses to TMS in recovered proximal muscles, two further studies were carried out to clarify the contribution of CS input to production of force in proximal and distal upper limb muscles. First, the effect of voluntary contraction on response amplitudes in deltoid, biceps and ID1 were compared. Second, the effect of increasing stimulus intensity on recruitment of low threshold motor units was assessed for deltoid and ID1. In addition the change in response amplitude with increasing voluntary activity in the affected and unaffected shoulder muscles of three patients were compared.