Upper and Lower Motoneuron Lesions in Tetraplegia - Diagnostic and Therapeutic Implications of Electrical Stimulation

Abstract

The overall objective of this thesis was to improve outcomes and predictability of the treatment of upper extremity function in patients with cervical spinal cord injury and tetraplegia by advancing the diagnostic and therapeutic tools employed in upper and lower motor neuron lesions. An overview is presented of the current knowledge about the principles of electrical stimulation and its usefulness and proven effects on the upper limb. Initially a technique was developed to map the topographic distribution of the motor points of extensor and flexor forearm muscles in able-persons. The mapping system for selected muscles on the dorsal and palmar aspect of the forearm led to remarkable findings when electrical stimulation was applied to patients with cervical spinal cord injuries. One of the main findings was that flexors are noticeably more often denervated than extensors due to lower motoneuron lesions. The findings may explain the clinical observation of better functional outcome after surgical nerve transfer to extensors compared to relatively disappointing results after nerve transfer to the flexors. The continuation of the research project was an interventional study to investigate the possibility to increase the thickness and to influence the structure in denervated forearm and hand muscles by direct electrical muscle stimulation. The case series report showed that this was possible. A reasonable interpretation is that the viability of the motor end-plate pool can be maintained through direct electrical muscle stimulation and that it is likely that an early onset of stimulation improves the conditions for successful reinnervation after nerve transfer. In addition, the time between spinal cord injury and nerve transfer may be prolonged without impairing the outcome. In order to identify the effect of electrical stimulation on neuromodulation it was analysed how robotic-controlled exercises combined with functional electrical stimulation could increase the voluntary strength of movements in people with spinal cord injury. The only available system for robotically controlled training is adapted to the lower limbs and therefore this study was performed on the lower extremities. The combination of electrical stimulation and robot-controlled, voluntary initiated training increased the recruitment of motor units and muscle strength in the legs.