Impaired central innervation of intrinsic trunk muscles after stroke

Stroke and traumatic brain injury may cause an impaired central control of intrinsic trunk muscles following by deficits in activities of daily living. However, there is no established non-invasive electrophysiological evaluation of this central-nervous dysfunction. We introduced a new neurophysiologic methodology to determine this alteration of the central innervation of trunk muscles to optimize rehabilitation strategies.

Therefore, we investigated 30 patients after stroke. All patients suffered from hemisyndrome. We performed a complete measurement of the myoelectrical activity with surface electrodes of paraspinal muscles during dynamic and static tasks 3 weeks and 6 months, respectively, after acute stroke. A group of healthy volunteers served as controls. The acquired EMG parameters are analysed with respect to their spatial and temporal characteristics. This longitudinal study design allowed a correlation between the changes of central-nervous control and both time course and effectiveness of rehabilitation processes.

We found 3 weeks after stroke during dynamic tasks an increase of muscle activity of the non-hemiparetic side, in contrast to static tasks. 6 months after stroke no differences in muscle activity between the paretic and non-paretic side could be determined during static tasks, possibly due to training effects or neurogenic changes. However, a decrease of the muscle activation pattern and gait cycle changes was found during dynamic tasks.

Our results suggest an impairment of the activation pattern of paraspinal muscles after stroke in a time and task dependent manner indicating alterations and adaptive changes (i.e. neural plasticity) of different motor subsystems. This may lead to specific and target-oriented recommendations for the rehabilitation process to further optimize treatment strategies.