Functional Electrical Stimulation
FES is a system that consists of a stimulator that sends out electrical impulses and a set of electrodes that administer the impulses to the muscle or nerve. The electrodes are typically placed on the skin, close to the affected limb. However, systems that use invasive, implanted electrodes are also in use. In the case of the non-invasive systems, electrodes are placed on the skin and then connected to a stimulator (both wired and wireless systems exist) worn around the waist, arm or leg.3 Surface systems enjoy the benefits of being non-invasive and relatively inexpensive. However, difficulties may arise with this kind of system because repeated placement of the electrodes in the appropriate locations requires skill and patience. Furthermore, as the electricity must pass through pain receptors in the skin, the subject could experience some pain. It might also be hard to activate deep muscles and to achieve isolated contractions. Additionally, the amount of wires and devices that one must wear can feel bulky and impractical.4
Invasive systems come in two kinds. The less invasive ‘percutaneous’ system involves implanting the electrodes by inserting them through the skin into the muscles using a hypodermic needle. The electrode leads exit the skin and are, like the surface system, connected to external stimulation equipment. As the leads must pass through the skin, they are very fine and therefore not as durable as other leads. The more invasive 'fully-implanted' system involves implanting the stimulator in the body, eliminating the need for outside wiring. As the leads do not need to go through the skin, they can be more robust and therefore more durable. The stimulator is typically implanted in the chest or abdomen.5
Possible benefits of Functional Electrical Stimulation for stroke
FES can be used as part of treatment for a number of complications associated with hemiplegia (severe weakness on one side of the body) and to improve movement in both lower and upper limbs. Two positive effects of FES treatment for stroke are quite well established by medical research. First, therapy involving FES can increase muscle strength.6 Second, such treatment improves gait symmetry. In particular, FES is used for treating ‘foot-drop’, a condition that involves significant weakness in the ankle and toe that makes it impossible to move the foot upwards at the ankle joint.7
A very recent study of FES for foot-drop used a surface system containing a stimulator unit (kept in a pocket or strapped to the patient’s waist), two electrodes and a mechanical heel switch in an insole under the heel to trigger the stimulator. The system works as follows:
'When the heel is off the ground, during swing phase of gait cycle, the stimulation is switched ON; the stimulator then transmits an electrical current to stimulate the ankle dorsiflexors or the common peroneal nerve to prevent foot drop and achieves a toe clearance from ground to mimic normal voluntary gait movement […]. When the heel comes into contact with the floor again during stance phase of gait cycle, the stimulation is switched OFF. This ON/ OFF pattern of stimulation can help to minimize muscle fatigue by giving time for the target muscle to rest.'8
The study concluded that FES was beneficial but the effects were not permanent. The patient would have to continue using the FES system, or lose the positive effects. Researchers stated that FES,
'combined with conventional rehabilitation program improves the walking ability and enhances the motor recovery functions when compared with conventional rehabilitation program alone and thus may more effectively manage foot-drop caused by the stroke. Thus the FES therapy may have the potential to be used with individuals with stroke in their daily lives as an assistive technique. We assume that within normal rehabilitation conditions, it would be necessary for people to continue FES themselves at home.'9
A study on upper limb disability after stroke suggests that FES can be a beneficial treatment. The study found that both wrist grip strength and the range of joint movement improved with the treatment. However, when the treatment stopped, the benefits did not seem to be maintained.10 Other research supports the view that FES is useful for reducing or preventing shoulder ‘subluxation’ (partial dislocation of the arm at the shoulder joint caused by extreme muscle weakness around the shoulder or spastic muscles).11 A recent pilot study has further suggested that FES can be used to treat ‘plantarflexor spacisity’, also known as ‘spastic foot’, in stroke patients.12
Arguments against using Functional Electrical Stimulation for stroke
While FES appears to be relatively safe, the electric shock can feel unpleasant and some might experience it as intolerably so.13 Regarding research on the benefits of FES, it can be hard to test the actual benefits of the treatment in the setting of a conventional medical test because it is difficult to construct a proper test group. As FES involves administering electric shocks to the patient, it is not easy to introduce a placebo. One way around this could be to tell the patients that they might or might not feel the electrical stimulation.14
- Chuck Reisling tells how he uses a home operated FES system called ‘Neuromove’ to treat weakness in his left hand following a stroke. In 'A Rehab Revolution' by Emily Springer. Stroke Connection Magazine, September/October 2004, p.21-2
Notes and references
- Peckham PH, Knutson JS, 'Functional Electrical Stimulation for Neuromuscular Applications'. In Annual Review of Biomedical Engineering, 2005, vol. 7, pp. 327- 60, p. 328
- See Hankey GJ, Pomeroy VM, King LM, Pollock A, Baily-Hallam A, Langhorne P, 'Electrostimulation for Promoting Recovery of Movement or Functional Ability After Stroke: Systematic Review and Meta-Analysis'. In Stroke, 2006, vol. 37, pp. 2441-2.
- Peckham PH, Knutson JS, 2005: 331
- Peckham PH, Knutson JS, 2005: 332
- Peckham PH, Knutson JS, 2005: 332
- Glanz M, Klawansky S, Stason W, Berkey C, Chalmers TC 'Functional Electrostimulation in Poststroke Rehabilitation: A Meta-Analysis of the Randomized Controlled Trials'. In Archives of physical medicine and rehabilitation, 1996, vol. 77(6), pp. 549-53. They state that their meta-analysis shows that 'pooling from randomized trials supports FES as promoting recovery of muscle strength after stroke. This effect is statistically significant. There is a reasonable likelihood of clinical significance as well.' (p. 549) They do, however, express concern over the quality of some of the studies included in the meta-analysis. (p. 551-2)
- FES has been considered as a possible treatment for foot-drop since the early 1960s. See Liberson WT, Holmquist HJ, Scott D, Dow M, 'Functional electrotherapy stimulation of the peroneal nerve synchronized with the swing phase of gait of hemiparetic patients'. In Archives of physical medicine and rehabilitation, 1961, vol. 42, pp. 101–105.
- Sabut KK, Sikdar C, Mondal R, Kumar R, Mahadevappa M, 'Restoration of gait and motor recovery by functional electrical stimulation therapy in persons with stroke'. In Disability and Rehabilitation, 2010, vol. 32(19), pp. 1594–1603, p. 1596
- Sabut KK, Sikdar C, Mondal R, Kumar R, Mahadevappa M, 2010: 1601-2
- Powell P, Pandyan D, Granat M, Cameron M, Stott DJ, 'Electrical Stimulation of Wrist Extensors in Poststroke Hemiplegia'. In Stroke, 1999, vol. 31, pp. 1384-9
- Linn SL, Granat MH, Lees KR, 'Prevention of Shoulder Subluxation After Stroke With Electrical Stimulation'. In Stroke, 1999, vol. 30, pp. 963-8
- Cheng JS, Yang YR, Cheng SJ, Lin PY, Wang RY, 'Effects of Combining Electric Stimulation With Active Ankle Dorsiflexion While standing on a Rocker Board: A Pilot Study for Subjects With Spastic Foot After Stroke'. In Archives of physical medicine and rehabilitation, 2010, vol. 91(4), pp. 505-12.
- “The drawback is some survivors can’t tolerate the sensation,” says Dr. Richard Harvey. Stroke Connection Magazine, September/October 2004, p. 22.
- Yan T, Hui-Chan WEI, Li LSW, 'Functional Electrical Stimulation Improves Motor Recovery of the Lower Extremity and Walking Ability of Subjects With First Acute Stroke: A Randomized Placebo-Controlled Trial'. In Stroke, vol. 36, pp. 80-5.