Motor control and emerging therapies for improving mobility in patients with spasticity

Treatment of spasticity has traditionally been targeted at reducing stretch reflex activity and muscle tone. However, these spasticity indicators and the actual movement disorder following a spinal or supraspinal lesion have been found to be unrelated. Increased muscle tone could be considered secondary and adaptive to a primary disorder and necessary for the continuing support of the body during locomotion. It is evident that antispastic medication is necessary for patients who experience severe pain and discomfort associated with increased muscle tone during rest. However, most therapies currently prescribed are directed at reducing excitation or increasing inhibition and may potentially interfere with voluntary movement. Impairment of walking may be due to a lack of descending input and a reduction in the afferent input to the spinal neuronal circuits. The result is reduced muscle strength, decreased physiological modulation of reflexes and muscle activity as well as cocontraction of agonist and antagonist muscles. Future therapeutic approaches aiming to assist ambulation in mobile spastic patients should focus on the treatment of these aspects in order to improve a patient’s movement ability. Emerging therapies include robot-assisted treadmill training, repetitive electrical stimulation, paired associative stimulation (PAS) and H-reflex conditioning which may provide a new approach for restoring motor function in the spastic patient population.