Table 5.

Summary of the Literature and Recommendations for Use of NMES for Foot Drop, Plantar Spasticity, and Gait Improvement

Indication	Parameter Recommendations	Outcome Measures Demonstrating Benefit
Lower extremity foot drop; plantar (gastrocs) spasticity; gait re-education	Electrode placement: 1 electrode over the common peroneal nerve, the other over the MP of tib ant or both tib ant and peronei. Additional channel might be considered for gluteus medius stimulation Body and limb position: DFL against gravity during gait re-education or with patient sitting or standing (weight-shift Ex) NMES waveform: biphasic PC Frequency: 30–50 Hz to produce tetany68–75 Pulse duration: 300 μs72–76 Current amplitude: individual maximum tolerated to achieve ankle DFL (varying from neutral to max)72–78 Work–rest cycle: ON:OFF 5–10:6–30 s70,72,75,76 When using NMES as part of gait retraining, ON:OFF times are controlled by pressure-sensitive heel switch71,74,76 Treatment schedule: 30 min/d70–76 Session frequency: 5 d/wk71,72,74,75,78 over 3–4 wk70,72,73,75,78	Increase in muscle strength (torque, MMT)71,73,74 Increase in ankle DFL74 Increased EMG activity75 Decrease in ankle plantar flexor (gastrocs) spasticity (Barthel Index, modified Ashworth Scale, CSS)70,74,75 Increase in gait speed68,69,78 Improved LE function (F-M, Mass Gen Hosp, ambulation)68 Improvement in gait kinematics (symmetry, stride length)68,70,71,76 Improved balance (Berg Balance Scale)71
Rationale for recommended NMES protocol	NMES protocol for foot drop has been used by many research groups,70,73,74,77,78 and improvements in muscle strength and gait symmetry were achieved using a simple single-channel system that targets tib ant and peronei muscles of the affected leg. An additional channel was also added to stimulate plantar flexors (gastrocs) during stance phase.76 Chung and associates71 found that combining activation of ankle DFL during swing phase with activation of gluteus medius during stance phase produced greater gait symmetry, and the effort of walking was reduced.79 Pulse frequency of 30–50 Hz produces smooth muscle tetany. Higher pulse frequency was used to produce greater muscle force.77,78 Pulse duration of 300 μs and amplitude that produces comfortable but complete contraction of the ankle DFL and evertors can produce neutral foot position. ON:OFF times are determined most often by using a simple pressure-sensitive heel switch, which triggers the NMES signal at heel-off during swing phase. In this way, tib ant of the affected leg remains contracted during gait in a way that prevents foot drop. NMES has also been shown to improve muscle strength when applied with the patient in sitting or static standing to move the ankle through ROM in a cyclical manner without patient involvement. We recommend using NMES while patients are walking because it has been associated with a therapeutic benefit that persists after the NMES treatment ends.69 Treatment schedules of between 20 and 30 min per session are progressed as fatigue permits.70–76 Bakhtiary and Fatemy77 used a very short, 9-min session of NMES and showed significant improvements in DFL strength and ROM. Most protocols used NMES 3–5 times per wk for at least 3–4 wk.70,72,73,75,78 Longer treatment programmes given over 6–12 wk may be required.71,74,76 Patients who have sustained a stroke up to 18 mo before NMES have benefited from this therapy.71,74 Many devices have been developed in which NMES units are incorporated into a custom-fitted orthotic or brace for easy application by the patient for home use. Examples of these technologically advanced automated devices with in situ electrodes, portable gait-event detection devices (pressure sensor, accelerometers, EMG activity), or both include the Bioness,80 Odstock Dropped Foot stimulator,69 and WalkAide.81 PT involvement typically entails initial sessions to fit and adjust the device, followed by a 2 to 6 wk training period during which the patient adapts to and gradually increases the duration of daily use of NMES.
Physiological effect of NMES	Muscles affected by stroke have a higher proportion of fast-twitch, fatiguable fibre types on the paretic side.16 NMES can produce hypertrophy and increase force generation in muscles weakened by central nervous system infarct.71,73,77 Newsam and Baker19 showed increased motor unit recruitment in weakened muscles stimulated with NMES for 4 wk post-stroke. Stimulation of the LE dorsiflexor muscles can reduce spasticity in plantar flexors.74,75 Burridge and McLellan82 demonstrated that patients who had ankle plantar muscle spasticity were more likely to respond to NMES treatment protocol. Benefits produced by NMES to tib ant muscles are thought to be mediated through reciprocal inhibition. Reciprocal inhibition occurs through inhibitory interneurons in the spinal cord.83 Measures of surface EEG before and after 3 mo treatment including NMES applied to ankle dorsiflexors showed altered activation of the primary motor cortex affected by stroke.84 These cortical changes were associated with significant improvements in several measures of gait.
Critical review of research evidence	Of 11 RCTs that were reviewed, 9 reported positive effects of NMES on leg impairments, function, or both. Macdonell and colleagues72 reported that 4 wk of daily cyclical NMES applied for 20 min to affected ankle dorsiflexors in sitting (without patient involvement) did not improve leg spasticity (Barthel Index) or LE function (F-M). Patients in this study had very little voluntary muscle contraction and were within 6 wk of a stroke. The other study that did not detect a difference in gait kinematics, ankle movement, or stroke recovery also applied NMES in a cyclical fashion to patients who had no voluntary activation of the affected leg muscles.78 Cozean and colleagues76 found no association between time since stroke and study outcomes, whereas other studies have suggested that the sooner after stroke NMES is applied, the better the outcomes. Systematic review of this body of research has produced pooled effects that consistently favour NMES over conventional PT treatment (e.g., Bobath techniques) for muscle strength gains29,53,58 and faster speed of walking.85,86 Dickstein87 found increased walking speed after NMES; however, they concluded that none of the increases would have resulted in community ambulation, and therefore they suggested that using NMES was not warranted. A Cochrane review published in 2006 also did not find that NMES increased gait speed over control treatments.88 Conflicting results among the meta-analyses29,53,85,86,88 and SRs22,23,87 that have been published on this topic can be explained by the reviewers combining for analysis heterogeneous patient populations and a wide range of NMES protocols. Each of the large reviews included different sets of studies and excluded some of the controlled clinical trials included in the present review.22,23 A recent SR involving 33 studies found no conclusive evidence to suggest that more sophisticated and often expensive types of devices produce better outcomes than the simple protocols.89 This conclusion is similar to that of a subcommittee of the American Congress of Rehabilitation Medicine, which found insufficient evidence to support the use of electrical stimulation orthotic substitute devices over traditional ankle–foot orthosis without NMES.67

NMES=neuromuscular electrical stimulation; gastrocs=gastrocnemius muscle; MP=motor point; tib ant=tibialis anterior muscle; MMT=manual muscle testing; DFL=dorsiflexion; Ex=exercise; EMG=electromyography; CSS=Composite Spasticity Score; PC=pulsed current; LE=lower extremity; F-M= Fugl-Meyer Assessment; Mass Gen Hosp=Massachusetts General Hospital Functional Ambulation Class; ROM=range of motion; PT=physiotherapy/physical therapy; EEG=electroencephalogram; RCT=randomized controlled trial; SR=systematic review.