E. Byron Marsolais

Restoration of key grip and release in the C6 tetraplegic patient through functional electrical stimulation

Electrical stimulation of selected paralyzed forearm and hand muscles in C6 spinal cord injury patients provides control of lateral pinch (key grip) and release. The movement augments tenodesis grip or the grip achieved through tendon transfer procedures. Chronically indwelling percutaneous coiled wire electrodes were implanted with hypodermic needles into thenar (adductor pollicis and/or opponens pollicis), finger flexor (flexor digitorum superficialis and profundus), and thumb extensor (extensor pollicis longus) muscles. The strength of contraction is controlled by changing the stimulus pulse width and frequency, which determine the number of active muscle fibers and their rate of activation, respectively. Finger flexor activation always precedes thumb adduction /opposition to provide a stable platform for lateral pinch; release is provided by stimulation of the thumb extensor. The patient controls the timing and the strength of the contraction from a single control signal. This control signal is a myoelectric signal (MES) from a muscle which retains voluntary function, e.g., sternocleidomastoid. Electrical activity from the muscle is processed (rectified and averaged) and used to activate the stimulator. Each command to control the muscle is proportional in time, i.e., once a lower threshold bound is exceeded with the MES, the command increases (or decreases) linearly until the MES falls below threshold again. A zero level MES maintains the stimulus; exceeding the upper bound reverses the direction of stimulus change or deactivates stimulation if the level is held long enough. Five subjects have been involved in the development of this system for periods of up to 2 years, and three are presently involved in its evaluation. The function the electrical stimulation provides has been beneficial in performing tonic tasks such as eating and writing.

A Randomized Controlled Trial of Functional Neuromuscular Stimulation in Chronic Stroke Subjects

Background and Purpose— Conventional therapies fail to restore normal gait to many patients after stroke. The study purpose was to test response to coordination exercise, overground gait training, and weight-supported treadmill training, both with and without functional neuromuscular stimulation (FNS) using intramuscular (IM) electrodes (FNS-IM). Methods— In a randomized controlled trial, 32 subjects (>1 year after stroke) were assigned to 1 of 2 groups: FNS-IM or No-FNS. Inclusion criteria included ability to walk independently but inability to execute a normal swing or stance phase. All subjects were treated 4 times per week for 12 weeks. The primary outcome measure, obtained by a blinded evaluator, was gait component execution, according to the Tinetti gait scale. Secondary measures were coordination, balance, and 6-minute walking distance. Results— Before treatment, there were no significant differences between the 2 groups for age, time since stroke, stroke severity, and each study measure. FNS-IM produced a statistically significant greater gain versus No-FNS for gait component execution (P=0.003; parameter estimate 2.9; 95% CI, 1.2 to 4.6) and knee flexion coordination (P=0.049). Conclusion— FNS-IM can have a significant advantage versus No-FNS in improving gait components and knee flexion coordination after stroke.

Implanted functional neuromuscular stimulation systems for individuals with cervical spinal cord injuries: Clinical case reports

OBJECTIVE To determine the feasibility of providing the ability to stand and to facilitate the performance of standing transfers to individuals with cervical-level spinal cord injuries via functional neuromuscular stimulation (FNS). The applicability of implantable technology to this population was investigated, and the characteristics of the potential system users were explored. The effects of FNS on the effort and assistance required to stand and complete standing transfers were examined. SETTING Institutional rehabilitation practice. DESIGN Nonrandomized controlled trial. PATIENTS Twenty-four individuals with low cervical spinal cord injuries were evaluated for inclusion in a program of lower extremity FNS, four of whom received the intervention. INTERVENTION Chronically indwelling percutaneous intramuscular electrodes were used to exercise the hip, knee, and trunk extensors and develop activation patterns to produce standing function. These temporary systems were then replaced with silicone-enclosed helical wire electrodes suitable for eventual use with an eight-channel implantable receiver/stimulator. MAIN OUTCOME MEASURES Full sensory and motor evaluations were performed and physical contraindications to stimulation were catalogued. For active subjects, American Spinal Injury Association Total Motor Scores with and without FNS were recorded, along with quadriceps strength and ability to complete exercise, standing, controlled sitting, and standing transfer maneuvers. Performances of implanted electrodes were determined by the stability of recruitment properties, impedances or surface potentials, and serial radiographs. RESULTS Motor scores increased an average of nine points with stimulation over baseline volitional values. With FNS, all four volunteers were able to exercise, stand, and sit independently or with minimal assistance. Although they required varying degrees of assistance with the pivot phase of the transfer maneuver, all were able to raise and lower their body weight independently with stimulation and to use the system to facilitate standing transfers. One participant received the implantable receiver/stimulator, which remains operational at follow-up more than 3 years later. CONCLUSION FNS can provide the ability to exercise, stand, and transfer to individuals with tetraplegia, even in the presence of medical complications and upper extremity impairment. FNS facilitates standing transfers by eliminating the heavy lifting usually required by a caregiver, thus decreasing the effort and assistance necessary to gain access to places impossible to approach with conventional sliding transfers.

Recovery of Coordinated Gait: Randomized Controlled Stroke Trial of Functional Electrical Stimulation (FES) Versus No FES, With Weight-Supported Treadmill and Over-Ground Training

Background. No single intervention restores the coordinated components of gait after stroke. Objective. The authors tested the multimodal Gait Training Protocol, with or without functional electrical stimulation (FES), to improve volitional walking (without FES) in patients with persistent (>6 months) dyscoordinated gait. Methods. A total of 53 subjects were stratified and randomly allocated to either FES with intramuscular (IM) electrodes (FES-IM) or No-FES. Both groups received 1.5-hour training sessions 4 times a week for 12 weeks of coordination exercises, body weight–supported treadmill training (BWSTT), and over-ground walking, provided with FES-IM or No-FES. The primary outcome was the Gait Assessment and Intervention Tool (G.A.I.T.) of coordinated movement components, with secondary measures, including manual muscle testing, isolated leg movements (Fugl-Meyer scale), 6-Minute Walk Test, and Locomotion/Mobility subscale of the Functional Independence Measure (FIM). Results. No baseline differences in subject characteristics and measures were found. The G.A.I.T. showed an additive advantage with FES-IM versus No-FES (parameter statistic 1.10; P = .045, 95% CI = 0.023-2.179) at the end of training. For both FES-IM and No-FES, a within-group, pre/posttreatment gain was present for all measures (P < .05), and a continued benefit from mid- to posttreatment (P < .05) was present. For FES-IM, recovered coordinated gait persisted at 6-month follow-up but not for No-FES. Conclusion. Improved gait coordination and function were produced by the multimodal Gait Training Protocol. FES-IM added significant gains that were maintained for 6 months after the completion of training.

Response of sagittal plane gait kinematics to weight-supported treadmill training and functional neuromuscular stimulation following stroke

After stroke, persistent gait deficits cause debilitating falls and poor functional mobility. Gait restoration can preclude these outcomes. Sixteen subjects (>12 months poststroke) were randomized to two gait training groups. Group 1 received 12 weeks of treatment, 4 times a week, 90 min per session, including 30 min strengthening and coordination, 30 min over-ground gait training, and 30 min weight-supported treadmill training. Group 2 received the same treatment, but also used functional neuromuscular stimulation (FNS) with intramuscular (IM) electrodes (FNS-IM) for each aspect of treatment. Outcome measures were kinematics of gait swing phase. Both groups showed no significant pre-/posttreatment gains in peak swing hip flexion. Group 1 (no FNS) had no significant gains in other gait components at posttreatment or at follow-up. Group 2 (FNS-IM) had significant gains in peak swing knee flexion and mid-swing ankle dorsiflexion (p < 0.05) that were maintained for 6 months.

Orthoses and Electrical Stimulation for Walking in Complete Paraplegia

Orthotic systems, orthoses combined with functional neuromuscular stimulation (FNS), and FNS systems alone, are compared for their safety, function, and ease of use as walking systems for people with complete paraplegia. Despite the safety and joint protection offered by orthoses, the majority of paraplegics with lesions above the T-1 2 level discard braces at the termination of the rehabilitation period. Reasons include the limited function provided, poor cosmetic appearance, and high energy cost of use. Conventional bracing has been combined with FNS to facilitate the swing phase of gait, but the disadvantages of braces are still present; the advantage of slightly reduced energy cost with FNS is offset by the drawback of increased complexity. Trials of both surface and percutaneous FNS systems have demonstrated that FNS walking for paraplegics is feasible in the research environment. While pure FNS systems eliminate the disadvantages of bracing, they have the requirements of complex electrode application in the case of surface systems, or care of electrode skin sites and connections in the case of percutaneous systems. Additional problems of FNS systems are a high energy cost and lack of trunk and hip stability, requiring the use of a walker. The authors are addressing these problems through the development of closed-loop control of stimulation to utilize muscles in more normal on/off cycles and in the development of totally implanted systems to increase reliability and convenience.

Feasibility of gait training for acute stroke patients using FNS with implanted electrodes

Following stroke, many patients do not regain a normal, safe gait pattern even after receiving conventional physical therapy. One promising technique is functional neuromuscular stimulation (FNS) with intramuscular (IM) electrodes (FNS-IM). Five subjects were admitted into the study at 3 weeks to 3 months following the stroke. For each subject, electrodes were placed intramuscularly at the motor point of up to seven lower extremity paretic muscles. Subjects were treated for 6 months, twice weekly with FNS-IM for exercise and gait training. The stimulator and software provided individualized stimulation patterns, with flexible stimulus parameters and activation timings of multiple muscles. Outcome measures were active joint movement, coordination (Fugl-Meyer scale), balance (Tinetti scale), gait (Tinetti scale), activities of daily living (functional independence measure), and therapist and subject satisfaction (survey instrument). Subjects tolerated well the placement of IM electrodes with no adverse effects, and subjects lost no conventional rehabilitation time. Therapists and subjects were satisfied with the FNS-IM system as a rehabilitation tool. Post treatment, subjects demonstrated improvements in impairment and disability in active joint movement, coordination, balance, gait and activities of daily living. Considered together with prior research for chronic stroke subjects, this research suggests that FNS-IM can be successfully and efficaciously utilized for gait training for those with acute stroke.