Looking At The Literature

While FES has been around for some time, the research into the affect of electrical stimulation on denervated muscle is not as extensive as we thought and as such a definitive ‘body of proof’ for its use is not present. The following table provides a summary of some of the literature to date and we encourage you to interpret the findings with an objective mind set.

Study	Purpose	Parameters	Findings
S1: Kern, H., Boncompagni, S., Rossini, K., Mayr, W., Fano, G., Zanin, ME., Podhorska-okolow, M., Protasi, F. & Carraro, U. (2004). Long-Term Denervation in Humans Causes Degeneration of Both Contractile and Excitation- Contraction Coupling Apparatus, Which Is Reversible by Functional Electrical Stimulation (FES): A Role for Myofiber Regeneration? Journal of Neuropathology and Experimental Neurology, 63(9): 919-931 S2: Kern, H., Salmons, S., Mayr, W., Rossini, K. & Carraro, U. (2005). Recovery of Long Term Denervated Human Muscles Induced by Electrical Stimulation. Muscle Nerve, 31: 98-101 S3: Modlin, M., Forstner, C., Hofer, C., Mayr, W., Ritcher, W., Cararro, U., Protasi, F. & Kern, H. (2005). Electrical Stimulation of Denervated Muscles: First Results of a Clinical Study. Artificial Organs 29(3): 203-206	S1: Investigated the effect of electrostimulation on long term denervated muscle as a consequence of SCI and the structural changes that occur after FES (myofiber regeneration). S2: Investigated the effects of an intense electrical stimulation program on denervated quadriceps muscle as a result of a traumatic cauda equine lesion at T12. Commencing program 18 months post incident, with a one subject focus, looking at changes in muscle fibre size, excitability and force generating capacity. S3: Evaluated the effects of electrical stimulation on denervated muscles in people with spinal cord injuries.  All patients had either a cauda or conus lesions and had been suffering complete denervation of the quadriceps femoris muscle for at least 6-12 months.	S1, S2, S3 all collected data from the same study, consisted of 4 phases throughout study. Phase 1: Initial 1-3 months. Biphasic stimulation impulses, very long duration and high intensity. Muscle twitch was elicited by impulses lasting 150 to 200ms with amplitudes up to ±200 mA. Stimulation frequency was slightly less than 2Hz. Duration:  15 min/day (4 secs on2 sec off) Frequency: 5 days/ week. Electrodes made of conductive silicone rubber were used for surface stimulation. Phase 2: After 3-6 months Previous high pulse intervals were shortened to 50ms and then to 40ms to achieve a higher stimulation frequency. Phase 3: After 4-6 months.  the protocol was changed to a tetanic pattern (40ms pulse and 10ms  pause) delivered at 20Hz for 2s “on and 2s “off”, twice a day 3 times a day. Phase 4: Repeats were increased to 15-30 reps per set, 2min rest and 6-8 sets twice a day. Force training sessions were implemented. Force training sessions were also introduced with tetanic contractions against 70-80% of maximum load, 8-12 repetitions, 4-6 sets with a 2 minute rest once a day.	S1: Post electrical stimulation program the size of the myofibril increased, adipocytes were absent and collagen was present in normal amounts. They concluded that FES training could reverse muscle fibre degeneration. S2: After 26 months of  stimulation the subjects quadriceps muscles had increased in size and resembled those of a healthy sedentary individual (Muscle cross-sectional areas increased from 36.0 cm2 to 57.9cm2 (right) and from 36.1cm2 to 52.4cm2 (left). The intense stimulation regime also produced increases in excitability and force generating capacity of the muscles. S3: After one year of electrical stimulation a marked increase in CSA of the quadriceps muscle (mean: +29.74%) and also the hamstrings was observed. They concluded that appropriate electrical stimulation protocol can reverse the structural and functional changes that occur in denervated muscle. Moreover they concluded that it is possible to increase muscle mass and decrease the changes due to interrupted nerve supply, therefore reducing secondary problems.
Cakmak, A. (2004). Electrical Stimulation of Denervated Muscles. Disability and Rehabilitation26(7): 432-433	An ongoing study of the effectiveness of electrical stimulation on denervated muscle in  a man who suffered a pelvic ‘open book’ fracture, lumbosacral plexus avulsion and right lower extremity paralysis.	No parameters were specified	After 3 years of rehabilitation Cakmak concluded that electrical stimulation for denervated muscle be continued
Kern, H., Carraro, U., Adami, N., Biral, D., Hofer, C., Forstner, C., Modlin, M., Vogelauer, M., Pond, A., Boncompagni, S., Paolini, C., Mayr, W., Protasi, F. & Zampieri, S. (2010). Home-Based Functional Electrical Stimulation Rescues Permanently Denervated Muscles in Paraplegic Patients With Complete Lower Motor Neuron Lesion. Neurorehabilitation and Neural Repair, 24(8): 709-721	Investigation into the effect of home based functional electrical stimulation (h-bFES) to confirm a previous studies findings that h-bFES can rescue long term denervated muscle in patients with complete conus/cauda equina lesions. Muscle mass, force, and structure were determined before and after 2 years of h-bFES.	Stimulation therapy consisted of 4 combined programs 1: Biphasic stimulation impulses of very long duration(120-150 ms, 60-75 ms per phase) at high intensity (up to ±80 V and up to ±250 mA). 2,3&4: A combination of twitch and tetanic stimulation in consecutive sessions with a duration of up to 30min for each group of muscles (thigh, lower leg, glutes).	Post 2 year treatment there was a 35% CSA increase of the quadriceps muscle, an increase in the mean diameter of muscle fibres (16.6 ± 14.3 to 29.1 ± 23.3 mm), and a 1187% increase in force output during electrical stimulation from 0.8 ± 1.3 to 10.3 ± 8.1 N m (P < .001). Concluded that h-bFES of denervated muscle is an effective home therapy.
Gigo-Benato, D., Russo, T. L., Geuna, S., Domingues, N. R. S. R., Salvina, T. F., & Parizotto, N. A., (2010). Electrical stimulation impairs early functional recovery and accentuates skeletal muscle atrophy after sciatic nerve crush injury in rats. Nerve and Muscle 41(5), 685 – 693.	Examined the neuromuscular recovery in rats after a peripheral nerve lesion through the use of functional electrical stimulation, and to determine the functional rehabilitation of denervated muscle.	No parameters were specified. Electrical stimulation was applied to the tibialis anterior for six sessions following the crush injury to the sciatic nerve.	The results of this study did not support the use of electrical stimulation for denervated muscle as it was documented that electrical stimulation caused an increase in muscle atrophy.



Figure 5 - Comparison of light microscopy taken of a denervated quadriceps femoris muscle beofre (left) and after (right) electrical stimulation training (Kern et al, 2004).



For further interest in the use of FES with OTHER nerve injuries/pathologies the following references are a good source of further information.

Everaert, D.G., Thompson, A.K., Chong, S.L. & Stein, R.B. (2010) Does Functional Electrical Stimulation for Foot Drop Strengthen Corticospinal Connections? Neurorehabilitation and Neural Repair, 24 (2), 168– 177.

Paul, L., Rafferty, D., Young, S., Miller, L., Mattison P. & McFadyen, A. (2008). The effect of functional electrical stimulation on the physiological cost of gait in people with multiple sclerosis. Multiple Sclerosis, 14: 954–961

Stein, R.B., Everaert, D.G., Thompson, A.K., Chong, S.L., Whittaker, M., Robertson, J. & Kuether, G. (2010). Long-Term Therapeutic and Orthotic Effects of a Foot Drop Stimulator on Walking Performance in Progressive and Nonprogressive Neurological Disorders. Neurorehabilitation and Neural Repair 24(2) 152– 167.

Thompson, A.K., Estabrooks, K.L., Chong S. & Stein, R.B. (2009). Spinal reflexes in ankle flexor and extensor muscles after chronic central nervous system lesions and functional electrical stimulation, Neurorehabilitation and Neural Repair.  23 (2), 133-142