Alternating stimulation of synergistic muscles during functional electrical stimulation cycling improves endurance in persons with spinal cord injury

Therapeutic effects of functional electrical stimulation (FES) cycling for persons with spinal cord injury (SCI) are limited by high rates of muscular fatigue. FES-cycling performance limits and surface mechanomyography (MMG) of 12 persons with SCI were compared under two different stimulation protocols of the quadriceps muscles. One strategy used the standard “co-activation” protocol from the manufacturer of the FES cycle which involved intermittent simultaneous activation of the entire quadriceps muscle group for 400 ms. The other strategy was an “alternation” stimulation protocol which involved alternately stimulating the rectus femoris (RF) muscle for 100 ms and the vastus medialis (VM) and vastus lateralis (VL) muscles for 100 ms, with two sets with a 400 ms burst. Thus, during the alternation protocol, each of the muscle groups rested for two 100 ms “off” periods in each 400 ms burst. There was no difference in average cycling cadence (28 RPM) between the two protocols. The alternation stimulation protocol produced longer ride times and longer virtual distances traveled and used lower stimulation intensity levels with no differences in average MMG amplitudes compared to the co-activation protocol. These results demonstrate that FES-cycling performance can be enhanced by a synergistic muscle alternation stimulation strategy.     

Neurometric evaluation of the cortical somatosensory evoked potential in acute incomplete spinal cord injuries

The clinical application of evoked potentials has at times been criticized for its failure to provide an objective quantifiable assessment of the processing of sensory information and a reflection of nervous system integrity at least comparable in accuracy to other methods of assessment. The challenge is to quantify the SEP in a manner that accurately reflects the function of the somatosensory system.Therefore, neurometrics, an approach which emphasizes the transformation of the neurophysiological data to a common metric of relative probability by reference to normative standards and the classification of critical features of data by multivariate statistics, was employed.The 3-part study involved the evaluation of the diagnostic, prognostic and localization functions of the cortical tibial SEP in patients with incomplete spinal cord injuries. Two neurometric indices which correlated well with concurrent and future neurological status were developed. The distributions of influence of dorsal columns and spino-thalamic tracts on the SEP were established.     

Excessive reflexes in spinal cord injury triggered by electrical stimulation

Interaction of electrocutaneous stimulation with an impaired human motor control system may result in unstable reflex loops causing excessive spastic reactions. These contractions are usually excluded from analysis since the presence of spasm is one of the criteria commonly applied for discarding a contraction. They may, however, provide interesting information on the nature of spasticity. The dorsiflexor muscles of four SCI subjects were activated by means of surface electrical stimulation and the isometric ankle moment was measured. Short bursts of constant stimulation frequency at seven different frequencies (8, 12, 16, 20, 25, 33, 50 Hz) triggered spastic reactions in all subjects. The onset times of spastic activity during an electrically elicited contraction shortened with increased stimulation frequency. A stimulation burst may also have a spasticity reduction effect on a subsequent burst, indicating potential short term therapeutic effects of stimulation on spasticity in isometric conditions.     

Mechanisms of spinal cord electrical stimulation action on autonomic functions

The method of transcutaneous electrical stimulation of the spinal cord (ESSC) has recently begun to be actively used for both experimental studies of human motor functions and the rehabilitation of motor function in patients with spinal cord pathology. The spinal cord is the most important center of the regulation of vital functions, and ESSC affects as spinal locomotor networks as the visceral system too, which should be taken into account for the development of an improved method of rehabilitation and its use in experiments on healthy volunteers. We present a review of studies on the possible mechanisms of ESSC effects on the peripheral and cerebral circulation, cardiovascular, respiratory, excretory, and digestive systems of mammals.     

Electrical stimulation in multiple sclerosis. Comparison of transcutaneous electrical stimulation and epidural spinal cord stimulation

Forty-nine multiple sclerosis patients with bladder symptoms and/or walking disability were subjected to a therapeutic trial with electrical spinal cord stimulation and transcutaneous electrical stimulation, a second aim being to compare these two treatments. A clear subjective improvement in bladder symptoms was achieved in the majority of the cases, and this was substantiated by objective parameters. In a proportion of cases a more moderate improvement seems to have been achieved in a variety of symptoms. Transcutaneous electrical stimulation seems to be a useful selection procedure for later electrical spinal cord stimulation.     

Pulsed subcutaneous electrical stimulation in spinal cord injury: preliminary results

The treatment of long-term, stable para- and quadriplegics with pulsed electrical stimulation for pain control resulted in, anecdotally, a significant number of these individuals showing increased motor function as well as sensory awareness. This small pilot study was conducted in order to assess the hypothesis that pulsed electrical fields can effect diseased neurological function. Thirteen para- and quadriplegic subjects with 18 months of stable neurological signs and symptoms were exposed daily to pulsed electrical stimulation for a 6-month period and assessed for any improvement in motor function or sensory perception. The hypothesis is that pulsed electromagnetic fields can normalize viable but dysfunctional neuronal structures. Results were encouraging.     

Effects of transcutaneous electrical spinal cord stimulation on stepping patterns during walking

Effects of transcutaneous electrical spinal cord stimulation (tESCS) on the parameters of stepping movements in healthy subjects were investigated during two kinds of activity: walking on a moving treadmill belt (active treadmill) as well as pushing the treadmill belt by effort of the legs (passive treadmill). It was found that the total interference electromyogram (EMG) activity during stepping performance on a passive treadmill was 1.5–2 times higher than during stepping on an active treadmill. In addition, the amplitude of angular displacement of the hip joint and ankle was 2.5 times and 1.7 times higher, respectively, during passive vs. active treadmill, while the duration of stepping cycle decreased by 19%. Although the muscles were exposed to different load and the parameters of motion on the active and passive treadmill were different, tESCS caused an increase in the total EMG activity in 96% of cases both on the active and on the passive treadmill. In both cases, the stepping cycle period decreased by 4–43% in all subjects. These results suggest that tESCS can affect voluntary stepping patterns under conditions of different afferent control.     

Missed injuries of the spinal cord.

Damage to the spinal cord had not been recognised initially in 15 patients out of a consecutive series of 353 admitted over a decade to the National Spinal Injuries Centre with paralysis due to trauma to the cord. In some patients the missed diagnosis led to mismanagement and a greater neurological deficit. Missed injuries of the spinal cord are seen in patients with multiple injuries and head injuries and in those without any paralysis. Various radiological errors contribute to the failure to recognise the vertebral injury. In addition to causing severe disability to the victim these missed and mismanaged injuries of the spinal cord cost the National Health Service large sums in compensation. A careful evaluation of the history of each accident, with greater awareness of the potential of certain types of accidents to cause spinal cord injury, should reduce the incidence of missed injuries of the spinal cord.