Characterization of the electrically excited flexion withdrawal response used in restoration of locomotion in spinal cord injured paraplegics

Granat, Malcolm; Smith, Alex; Phillips, G.F.; Kirkwood, C.A.; Barnett, Roger W.; Andrews, B.J.

doi:10.1109/iembs.1988.94897

Cited by 5 publications

(2 citation statements)

References 3 publications

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“…Latencies of triggered spasm in the order of several hundreds of milliseconds have been shown for flexion withdrawal reflexes elicited via stimulation of the common peroneal nerve (Granat et al, 1988). The same authors reported that stimulation at higher frequencies tended to reduce latencies.…”

Section: Discussionmentioning

confidence: 88%

Excessive Reflexes in Spinal Cord Injury Triggered by Electrical Stimulation

Mela¹,

Veltink²,

Huijing³

2001

apab

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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. Keywords: Surface electrical stimulation, spasticity, reflexes, isometric contractions, spinal cord injury, human dorsiflexor muscles. IntroductionElectrical stimulation has been proposed for many years as a promising rehabilitation technique to artificially activate muscles which are not anymore under voluntary control following spinal cord injuries.One of the possible applications of functional electrical stimulation is the restoration of mobility (Franken et al., 1994;Kilgore et al., 1997;Veltink & Donaldson, 1998;Taylor et al., 1999). Despite considerable research effort devoted to the implementation of such technique into useful systems, FES has not been accepted as a clinical aid to restore mobility.Among many problems researchers have been trying to solve, ranging from the lack of selectivity of excitation to the non-linearity and time-dependence of skeletal muscle's properties (Prochazka, 1993), spastic hyperreflexia has been an important factor limiting the success of FES (Kralj & Bajd, 1989). In a retrospective study, Barolat and Mainam (1987) showed that 97% of the SCI individuals of their study experienced spasms, 72% exhibited spasms within six months after the injury with a peak in severity within 12 months. Even if narrow inclusion criteria are followed during the recruitment of SCI subjects for experimental investigations, the selected subjects will most likely express muscle spasm at different levels. The spastic activity may be manifested as severe short bursts of forceful muscle contractions or less forceful but frequent contractions. These contractions occur spontaneously, but are likely to be triggered by tactile or nociceptive afferents (Schmit et al., 2000).Electrical stimulation of peripheral nerves interferes with the physiological control system. During electrically elicited contractions, such interference is manifested as a minor contribution to muscle activation for able bodied subjects due to the combined effect of orhodromic sensory and antidromic motor excitation of peripher...

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Section: Discussionmentioning

confidence: 88%

Excessive Reflexes in Spinal Cord Injury Triggered by Electrical Stimulation

Mela¹,

Veltink²,

Huijing³

2001

apab

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show abstract

“…Latencies of triggered spasms on the order of several hundreds of milliseconds have been shown for flexion withdrawal reflexes elicited by stimulation of the common peroneal nerve [6]. It is likely that the spastic contractions (Figs 1, 2A, 3A) investigated in the current study involved flexion withdrawal reflexes that were elicited by excitation of the cutaneous afferent nerve fibers.…”

Section: Sensory Motor Fiber Selectivity Of Mfacmentioning

confidence: 59%

FES-propelled cycling of SCI subjects with highly spastic leg musculature

Szecsi¹,

Schiller²

2009

NRE

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Background: The presence of spasms precludes the use of artificial electrical activation of the muscles to restore mobility. The prospect of using an electrical stimulus that produces motor activation without causing unwanted reflex activation in patients with high levels of spasticity is an appealing one. Objective: The purpose of the study was to determine the efficacy of modulated middle frequency alternating current (MFAC) muscle stimulation compared to the conventional method of standard low frequency rectangular pulse (LFRP) stimulation used in cycling of persons with spinal cord injury (SCI) and pronounced spasticity. Methods: To evaluate cycling-relevant differences between stimulation modes, 13 subjects with SCI (ASIA-A), 11 of them with strong spasticity, underwent isometric and cycling measurements using both 20 Hz LFRP and 4 KHz modulated with 50 Hz MFAC. The isometric long-lasting reflex torque response in the quadriceps and hamstrings muscles, and the dynamic work during 1000 sec of ergometric cycling as well as the number of involuntary stops caused by hyperreflexia were recorded. Results: The long-lasting reflex torque response was significantly lower when using MFAC than with LFRP stimulation. During MFAC stimulation work generated was on average 374% higher (p = 0.002) and the number of involuntary stops was on average 32% lower (p < 0.001) than during standard LFRP stimulation-propelled cycling. Conclusion: These findings suggest that MFAC-stimulated cycling of strongly spastic SCI subjects is more effective in terms of generated isometric torque and power than stimulation with LFRP. Thus, more health benefits, e.g., cardiovascular and muscular training and spasticity-decreasing effects, can be expected faster using MFAC instead of LFRP in stimulation-propelled cycling.

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