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March 2003


The FNS Project

By Janis J. Daly, PhD, MSPT


(Left) A patient uses the FNS-IM system during ambulation on a treadmill. (Right) The FNS-IM system simulator, battery belt, and finger switch.
Conventional rehabilitation is not capable of restoring normal, safe gait to many stroke survivors. Although several clinical techniques are available, none are sufficient to return many stroke patients to a normal walking pattern.1 Some researchers have investigated potential rehabilitation techniques for improving gait and motor function. Recently researched techniques include partial-weight-supported (body in a sling) walking on a treadmill,2 EMG biofeedback,3,4 auditory feedback,5 sensory retraining,6 and block of the tibial nerve to decrease equinovarus and to diagnose contracture versus spasticity differentially.7

Functional neuromuscular stimulation (FNS) is a promising technique that can directly activate muscles and produce normal joint movements. Furthermore, it can be modulated to assist or cue remaining volitional movements. FNS has been the focus of research studies for more than 30 years for stroke rehabilitation. Gains in impairment and mobility have been reported.1,9,8

FNS addresses unique problems in stroke patients. Many stroke patients are older adults who do not respond well to conventional exercise and gait training programs. Older adults need slower-paced exercise sessions and can benefit from motivation enhancement.10-14 Advantages of FNS are: 1) it can activate muscles without overexertion; 2) FNS provides visual and kinesthetic evidence of muscle contraction, which enhances motivation; 3) patients can exercise using FNS in an individually paced session, independent of the therapist.

However, multi-channel FNS systems for gait training that have used surface electrodes were reported to have had prohibitive obstacles preventing their routine use, including discomfort of the stimulus at levels required to produce joint movement; inordinate time required for locating multiple motor points and donning multiple pairs of electrodes; inability to stimulate deeper muscles; and inconsistent muscle response from day to day. The positioning of electrodes posed a great problem for hemiplegic patients and was sometimes prohibitively complex.9,16-17

Because of the promising potential of FNS and the obstacles presented by surface FNS systems, our team designed and tested an eight-channel FNS system using intramuscular electrodes (FNS-IM). The FNS-IM system was tested for its potential as an intervention for motor learning and gait training for patients in the acute and chronic phases following stroke.

BACKGROUND

The FNS-IM system is comprised of eight implanted electrodes and associated lead wires that exit the skin. The stimulating portion of the electrode is a fine wire less than a centimeter in length, and the patient does not feel the electrode or lead wires beneath the skin or on the surface. When the patient is not using the system, the lead wires are coiled and contained in a small connector affixed to the thigh. The patient can bathe, swim, and engage in other activities. At the close of the rehabilitation protocol, the electrodes are removed using local anesthesia.

During use, the lead wires are connected to an individualized stimulator worn on the patient’s belt. The patient’s stimulator is customized and programmed by the therapist to contain stimulation patterns that are comfortable and therapeutically targeted to strengthen and condition the paretic muscles. Additional stimulation patterns are designed by the therapist to retrain coordination of movement patterns and gait. The therapist progresses the patient by adapting the FNS-IM patterns to use with progressively more challenging motor tasks. As the patient regains volitional movement control, the level and frequency of FNS-IM system use are gradually reduced. The patient learns to operate the system independently and uses it for a home exercise program.

The FNS-IM system was designed to address the previously reported difficulties of surface FNS systems. The system’s performance was studied for 17 patients who used a total of 124 intramuscular electrodes. FNS-IM was provided for a total of 1,413.8 electrode months. During this time, there were no instances of infection. There was a 99% survival rate of the electrodes at the end of the planned treatment protocols (6 months or more); 93% of the electrodes delivered a good muscle response throughout the protocols. Nine electrodes moved from the motor point during the protocol and their use was then discontinued. The stimulus was set at comfortable levels throughout the protocol, and the stimulus produced movement about the joint. The FNS-IM system had the following advantages: accurate placement of electrodes; good muscle selectivity; consistency of muscle activation; comfortable stimulus; and practical donning time for either the patient (less than 5 minutes) or the therapist.18

The feasibility of using FNS-IM to treat eight patients in the acute phase of stroke (3 weeks to 3 months from stroke onset) was investigated. The day after electrode placement, all patients had the same ambulatory status, as prior to the procedure. Only 1 day of rehabilitation or normal activity was compromised by the electrode placement procedure. The patients responded well to FNS-IM in addition to their prescribed conventional therapy. Feasibility of the FNS-IM system use was demonstrated. Following the combination of conventional treatment + FNS-IM, there were significant gains, according to comparisons made using the Wilcoxon signed rank test. There were gains in: Functional Independence Measure (FIM) score (P = .0159); muscle strength (77% of treated muscles improved); Fugl-Meyer Coordination Scale (P = 0.014); Tinetti Balance (P = 0.022); and Gait Scales (P = 0.029). The patients responded positively to the use of the system, reporting that it was practical, comfortable, and easy to use. Within 1 to 3 weeks, patients were able to don the system independently and use the stimulator for an individualized home exercise program. Patients were satisfied with the technology and believed that any inconveniences were inconsequential.19 The therapists believed that the FNS-IM system was useful during rehabilitation for exercise and gait training as follows: muscle strengthening (100% of patients); muscle endurance (88% of patients); coordination training (88%); gait training (88%); stair climbing (59%).19

FNS-IM FOR CHRONIC STROKE

The system was tested in patients in the chronic phase following stroke, in order to control for spontaneous recovery that can occur during that phase. Six patients with chronic stroke (1 to 4 years after stroke) were enrolled. They received conventional rehabilitation twice weekly for 3 months, including the use of surface electrical stimulation for treating paralyzed muscles and other gait training techniques. Following 3 months of conventional treatment, patients received the FNS-IM system and were treated twice weekly. Their treatment included FNS-IM for exercise and gait training.

STUDY OUTCOMES

Outcome measures included strength of individual muscles, coordination,20,21 and gait characteristics. All outcome measurements were made with the FNS-IM system turned off, so that volitional motor control could be assessed. During the conventional treatment, there were some improvements; however, the improvements generally plateaued below normal performance.22 Following the conventional rehabilitation, patients were treated with FNS-IM. Table 1 shows impairment gains achieved by these six patients during the FNS-IM treatment phase, beyond those obtained in the conventional phase of treatment. For example, ankle strength improved for three of six patients during the FNS-IM treatment, beyond that obtained during conventional rehabilitation. Three to four patients improved in muscle strength for ankle dorsiflexors, knee flexors, and knee extensors. Five patients improved in coordination of ankle flexion, knee flexion, and knee extension.23-24


Table 1. Gains of strength and coordination for chronic stroke patients following FNS-IM, beyond gains attained with 3 months of conventional treatment.

Table 2 shows gains in volitional gait achieved during the FNS-IM treatment phase, beyond those obtained in the conventional phase of treatment. All six patients improved in dorsiflexion at heel strike. Five improved in knee flexion at toe-off, peak swing knee flexion, peak swing dorsiflexion, knee extension at heel strike, and mid-stance knee control. There were a number of functional gains for patients including: resolution of wheelchair dependence, resumption of leisure activities, and resumption of social activities.22-24 The FNS-IM system was feasible to use and produced benefits for patients in the chronic phase of stroke regarding strength, coordination, gait pattern, and function. Compared to surface-stimulation systems, the FNS-IM system produced more specific muscle contraction, more consistent responses from day to day, more comfortable response at a therapeutic level, and significantly improved gait patterns.


Table 2. Gains of volitional gait for chronic stroke patients following FNS-IM, beyond gains attained with 3 months of conventional treatment.

Janis J. Daly, PhD, MSPT, is associate professor, Department of Neurology, Case Western Reserve University School of Medicine, Cleveland, and research scientist, Research Service, Cleveland Louis Stokes VA Medical Center. Research supported by the Department of Veterans Affairs, Office of Rehabilitation Research and Development, Grant #B1705R.

REFERENCES
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  19. 19. Daly JJ, Ruff RL, Haycook KL, Strasshofer B, Marsolais EB, Dobo L. Feasibility of gait training for acute stroke patients using FNS with implanted electrodes. J Neurol Sci. 2000;179(S1-2):103-107.
  20. 20. Fugl-Meyer AR, Jaasko L, Layman I, Olsson S, Steglind S. Post stroke hemiplegic patient. Scand J Rehabil Med. 1975; 7(13):31.
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  22. 22. Daly JJ, Ruff RL, Osman S, Scheiner A. Electrically induced recovery of volitional gait components for older stroke patients. Am J Phys Med Rehabil. 2000;79: 349-360.
  23. 23. Daly JJ, Barnickle K, Kobetic R, Marsolais EB. Electrically induced gait changes post stroke, using an FNS system with intramuscular electrodes and multiple channels. Journal of Neurologi Rehabilitation. 1993;7:17-24-25.
  24. 24. Daly JJ, Ruff RL, Osman S, Bieri CL. The response of prolonged flaccid paralysis to FNS, rehabilitation techniques. Disabil Rehabil. 2000;22:565-573.

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