Approximately 72% of individuals with stroke experience motor deficits in their affected lower limbs.1 The loss of motor control necessary for walking is one of the most devastating losses experienced by individuals poststroke.2 Accordingly, gait rehabilitation has become a key concern of physical therapists who treat individuals with stroke.3 Despite research demonstrating that with rehabilitation individuals poststroke are able to improve function even more than 12 months after a stroke,4 structured rehabilitation is generally ended within 3 months to 1 year in many parts of the world. Rather than allowing secondary disuse and maladaptive motor patterns to increase the disability that remains after discharge from rehabilitation, home-based rehabilitation programs are a way to provide ongoing treatment to improve (or at least maintain) functional performance.
Spasticity of the plantarflexor muscles is a common complication following stroke. Spasticity is defined as a velocity-dependent increase of tonic stretch reflexes with exaggerated tendon jerks, resulting from hyperexcitability of the stretch reflex.5 Transcutaneous electrical stimulation (TES) is a type of peripheral nerve stimulation that has been used for decades to relieve pain, particularly that of musculoskeletal origin. A previous study in our laboratory has shown that somatosensory stimulation in the form of TES applied over the peroneal nerve started to reduce plantarflexor spasticity and improve the peak voluntary torque generated by the ankle dorsiflexor in as little as 2 weeks.6 This placebo-controlled study demonstrated that the decrease in spasticity and increase in peak dorsiflexor torque were evident after TES but not after placebo stimulation. We have hypothesized that the possible mechanisms involved could be enhanced presynaptic inhibition of hyperactive stretch reflexes in the spastic ankle plantarflexors (as revealed by increased H-reflex inhibition during vibration), enhanced descending voluntary commands to the motor neurons of the paretic muscles, or decreased co-contraction of spastic plantarflexors during maximum voluntary dorsiflexion.6
Motor deficits aside, somatosensory deficits are usually associated with slower recovery of motor function in individuals poststroke.8 A likely explanation is that afferent inputs to the somatosensory cortex (S1) are required for acquiring motor skills.8 In animal studies, direct anatomical projections have been found from S1 to the motor, premotor, and parietal cortices,9 and these projections can modulate neuronal activity in the primary motor cortex (M1).10 The anatomical connections between S1 and M1 have been thought to provide the anatomical substrate through which electrical stimulation enhances motor cortex reorganization in humans.11
A previous study in our laboratory has shown that TES excites large diameter Aα afferent fibers.12 Since applying TES to the affected extremity excites afferent input projecting to S1,13 it might in turn facilitate motor output from M1 through the S1-to-M1 projection. We therefore hypothesized that the afferent input from somatosensory electrical stimulation combined with task-related training (TRT) might augment motor output more than TES or TRT alone. A randomized, placebo-controlled, clinical trial was designed to test the idea that TES to acupuncture points in the lower extremity, combined with TRT, could significantly reduce ankle spasticity, increase ankle muscle strength, and improve walking capacity compared with no treatment, TES alone, or placebo TES + TRT.14,15 The participants were individuals poststroke who were within 5 years of the stroke incident. As hypothesized, gains were observed in the TES + TRT group, and the gains were maintained even 4 weeks after treatment ended. However, detailed guidelines for conducting the home program including how to locate the acupoints and position the electrodes, how to progress the TRT program, and how to develop a safe environment for a home program for individuals with stroke have not been addressed in a comprehensive manner before.
The aim of this case study was to assist in translating our previous research findings into clinical practice. The objectives were 2-fold: (1) to examine the extent of improvement in motor impairments and walking function in a patient who had lived for 7 years with spastic hemiplegia due to stroke and (2) to describe and provide detailed guidelines for a home program of TES on acupoints, combined with TRT.
The patient was recruited through advertising and referral from a local stroke support network. The patient was a 61-year-old Chinese man with right-sided, spastic hemiplegia resulting from a stroke 7 years previously. He was right-handed. He could achieve 15° passive dorsiflexion in the affected ankle but showed moderate spasticity in the ankle plantarflexors with a Composite Spasticity Scale (CSS)16 score of 12 (of a maximum score of 16). He scored 9 (of a maximum score of 10) on the Abbreviated Mental Test.17 He had been a high school principal but had retired after the stroke. He was 175 cm (5 ft 9 in) tall and weighed 60.7 kg (134 lb) and was generally healthy apart from the hemiplegia.
Computed tomography revealed that the stroke was caused by an infarct in the area supplied by the left middle cerebral artery. The patient was medically and neurologically stable and took no medication aside from daily aspirin for stroke prophylaxis. He had been discharged from any rehabilitation services (including physical therapy and occupational therapy) 4 years 10 months before this program began. The patient was independent in activities of daily living and used a cane for ambulation. He claimed to exercise regularly, walking in the park for an hour every morning. He wore an ankle-foot orthosis to keep his ankle in a neutral position during walking. Before the treatment program began, the patient was informed about the objectives and details of the home program and of the outcome measures. He signed an informed consent form approved by the ethics committee of The Hong Kong Polytechnic University.
Prior to the intervention, the patient completed baseline testing that consisted of the following tests and measures. He wore his own comfortable footwear and his ankle-foot orthosis and used a single straight cane in all the walking tests.
Composite Spasticity Scale
Ankle plantarflexor was measured using the CCS, which was developed to measure ankle plantarflexor tone.6,16 It is an ordinal scale that combines the results of clinical assessment of (1) Achilles tendon jerks, (2) resistance to passive ankle dorsiflexion, and (3) the amount and duration of ankle clonus. All outcome measurements were performed by the same examiner. These 3 scores were then summed to generate the “total spasticity score.” A total score ranging from 1 to 6 is considered to represent “no spasticity,” 7 to 9 as “mild spasticity,” 10 to 12 as “moderate spasticity,” and 13 to 16 as “severe spasticity.”6,16
Peak Torques Generated During Maximum Isometric Voluntary Contraction of the Ankle Dorsiflexors and Plantarflexors
Ankle muscles was measured in terms of the peak torque generated in maximum isometric voluntary contraction of the ankle dorsiflexors and plantarflexors. Weakness after a stroke is typically measured by maximum isometric torque or force, and this measure has been shown to be a prognostic indicator.18 We measured peak torques by using a load cell mounted on a custom-built foot frame. The patient lay supine with the knee at approximately 50° of flexion and the ankle in a neutral position.19 He was encouraged to contract either the ankle dorsiflexors or the ankle plantarflexors “as hard as possible” for approximately 3 seconds and then relax. He performed 3 maximal contractions of each muscle, and the trial in which he produced the highest torque was selected for further statistical analyses.19
Gait speed has been shown to be a valid, reliable, and sensitive indicator of locomotor performance in patients after stroke.20 In this study, gait velocity was measured using a 4.6-m (15 ft) instrumented mat (GAITRite, CIR Systems Inc, Havertown, Pennsylvania).19 The patient walked at his normal speed, and the gait velocity was calculated by the GAITRite software (Version 2.2).
Six-Minute Walk Test
The Six-Minute Walk Test (6MWT) was originally developed to assess endurance in clinical population cardiorespiratory and cardiovascular disorders.21 The test has recently been validated for the measurement of exercise endurance after stroke.19 In this study, the test was conducted along a 33-m (108.2 ft) corridor, with markers at each end of the walkway. The patient was instructed to walk back and forth from one marker to the other, covering as much distance as he could during the allotted time of 6 minutes. The distance covered in 6 minutes was recorded to the nearest centimeter. The patient was allowed to stop and rest as needed.
Timed Up and Go Test
The Timed Up and Go (TUG) test is a simple, quick, and reliable functional mobility test that is commonly used to examine functional mobility in community-dwelling, frail older adults22 and individuals poststroke.19 The patient was required to stand up from a chair with armrests, walk 3 m, turn around, return to the chair, and sit down. The time taken to complete this task was measured in seconds with a stopwatch.
All of the tests were administered in the laboratory of The Hong Kong Polytechnic University. The patient was assessed by one of the authors (S.S.M.N.) on 4 occasions: prior to the intervention, after 2 and 4 weeks of treatment, and at follow-up 4 weeks after the treatment was completed. The intervention was administered by another physical therapist who was blinded to the intervention. The reliability of all outcome measures used in this study had been demonstrated in a previous study of individuals with stroke.19 Intraclass correlation coefficients of 0.80 to 0.99 were shown in that study.
The intervention included 60 minutes of TES, followed by 60 minutes of TRT. The patient was required to conduct the program at home, 5 days a week for 4 weeks. The patient also attended 8 instruction sessions: 5 times in the first week, twice in the second week, and once in the third week. In the first instructional session, the patient learned how to use the equipment and how to perform the prescribed exercises. The subsequent sessions were to evaluate, modify, and progress the exercises as necessary. The instruction sessions helped to ensure that the patient followed the home program properly and allowed the physical therapist to progress the exercise level as necessary. The patient was instructed to record the time and duration of his daily home program sessions in a logbook. To ensure adherence to the treatment protocol, the physical therapist gave telephone reminders 3 times a week and checked daily the client's logbook at every instruction session.
Transcutaneous Electrical Stimulation
The patient received 60 minutes of TES (100 Hz, 0.2-ms square pulses, at 2-3 times the sensory threshold) from a portable transcutaneous electrical nerve stimulator (TENS; CEFAR Dumo 2.4 K, Cefar Medical Products AB, Lund, Sweden). The choice of TES parameters and intensity was based on the results of a previous study in our laboratory, showing that these parameters reduce plantarflexor spasticity.6 The intensity was set at 2 to 3 times sensory threshold, which activates the sensory afferents but generally elicits no visible muscle contraction. The electrodes were carefully positioned over the following 4 acupuncture points of the affected leg: ST 36 (acupoint Zusanli), LV 3 (acupoint Taichong), GB 34 (acupoint Yanglinquan), and UB 60 (acupoint Kunlun) (Figure 1).
These acupoints are commonly used in traditional Chinese medicine23 and have been used in previous studies to improve the motor function in individuals with stroke.14,15,24,25 ST 36 is 7 to 8 cm below the tibial tuberosity and on the lateral aspect of the tibialis anterior muscle. LV 3 is on the dorsum of the foot between the first and second metatarsal bones. GB 34 is on the anteroinferior aspect of the capitulum of the fibula. UB 60 is in the depressed area lateral to the tendon of the calcaneus, posterior to the lateral malleolus. The patient sat comfortably in a chair with a backrest while receiving electrical stimulation of the affected lower leg.
Task-Related Training Protocol
The task-related locomotor training program was modified from that recommended by Carr and Shepherd (Table 1).26 The program lasted 60 minutes per session. It included 40 minutes of 4 lower-limb task-specific strengthening exercises with wooden platforms 2.5 or 5 cm in height (Table 1), 10 minutes practicing transitional movement, and 10 minutes of gait training with rhythmic auditory cues generated by a metronome previously set according to the patient's walking pace (Table 1). The wooden platforms were used for loading exercises, stepping up and down exercises, and heel-lift exercises (Table 1). The patient was allowed to stop and rest as needed. All the exercises were checked by the physical therapist (and rechecked at the clinic visits) to ensure that the patient could perform the exercise program independently and safely at home.
Progression of the Exercises
The physical therapist progressed the lower-limb task-specific strengthening exercises by using a higher platform when the patient could perform the weight-bearing exercises 20 times without compensatory movement and by increasing the number of repetitions to be completed within 10 minutes. The patient was advised to increase the speed of exercises and decrease the rest time as tolerated in order to maximize the number of repetitions. The walking exercise was progressed by increasing speed.
At the outset, the patient was encouraged to steady himself by holding onto firm furniture with his unaffected arm while exercising. He was encouraged to reduce the support as soon as possible in order to minimize the use of compensatory strategies. A physical therapist supervised the patient during the instruction sessions to ensure that he performed the exercise appropriately. Exercise endurance was monitored through the 16-point Borg Rate of Perceived Exertion (RPE).27 The patient was encouraged to work at a level between 11 and 13 (fairly light to somewhat hard). He was instructed to terminate the exercise if he experienced any chest pain or any musculoskeletal pain or discomfort. Technique and the importance of responding to day-to-day fluctuations in health, energy, and mood were constantly emphasized as essential for injury prevention and for gaining optimal benefit. To avoid a sudden sharp rise in blood pressure due to holding the breath during exercise, the patient was asked to count out loud during exercise.
Following weeks 2 and 4, outcome measures were assessed (Table 2). The patient's CSS score had decreased by 4 levels, from 13 of 16 at baseline to 9 of 16 at week 4, with improvements in all 3 subscale tasks. At week 4, peak dorsiflexion and plantarflexion torques had improved by 62.9% and 36.4%, respectively. Gait velocity and distance covered in the 6MWT also improved at week 4 by 30% and 25.9%, respectively, when compared with the baseline values. The patient's TUG time was reduced by 23.7%. The same measurements were again repeated 4 weeks after the treatment had ended, and the gains observed at week 4 had all been maintained.
The outcomes show that a custom-designed, home-based exercise program of somatosensory electrical stimulation over 4 acupoints combined with TRT can be beneficial even 7 years after stroke. Four weeks of treatment reduced this patient's impairment, reducing plantarflexor spasticity and increasing his ankle dorsi- and plantarflexor strength. In functional terms, the program increased both his gait velocity and his walking endurance and improved the upright functional mobility as indicated by decreased time to perform the TUG. Note that these improvements were achieved through a program performed mostly at the patient's own home, without compromising his safety. The treatment adherence was excellent, with not a single missed treatment session noted. The well-structured instruction sessions, regular telephone reminders, the daily logbook, and the clear explanation of the rationale for the study and the assessment measures might have contributed to the patient's adherence to the protocol.
The patient was in the habit of exercising on a regular basis, in the form of a walk in the park for 1 hour every morning. Since the patient did not change his other activities during the intervention, the changes seen might be assumed to result from the intervention. However, the individual contributions of the TES and TRT components remain to be determined. Furthermore, results from a single case study cannot delineate possible contribution of this patient's active life style (vs others who are sedentary) to the benefits of the current training protocol.
Our previous study showed that TES applied over the peroneal nerve was effective both in reducing plantarflexor spasticity and in improving the peak torque generated by the ankle dorsiflexors starting from week 2.6 Mechanisms underlying the improvements after electrical stimulation could be due to decreased co-contraction of the spastic plantarflexors, enhanced presynaptic inhibition of hyperactive stretch reflexes in the spastic ankle plantarflexors, and/or possible disinhibition of descending voluntary commands through the motor neurons of the paretic muscles. Alternatively, applying somatosensory electrical stimulation over these 4 acupuncture points might have increased afferent input to the sensorimotor cortex. This could have in turn enhanced the output from M1, thereby improving motor function through the aforementioned mechanisms.
In the ancient book of acupuncture, Ling Shu23 stated that all the organs ascend to the eye, which communicates with many meridians, constituting a system called “Eye System” that ascends to the vertex, enters the brain, and then surfaces at the nape. Besides entering the brain, the Eye System interconnects with many meridians around the eyes (including UB, ST, GB, and LV). Stimulation of acupuncture points that interconnect with the Eye System is expected to facilitate recovery in stroke patients.23 In one of our previous studies,6 TES was applied to the peroneal nerve whereas in this case study (as in 2 related randomized trials14, 15), the TES as applied over acupuncture points. The acupuncture points chosen were on the anterolateral aspect of the lower limb in locations that were in near to the nerves, and the TES protocol might therefore have excited nerve segments. The case study format does not allow us to draw conclusions about the comparative benefits to these different stimulation sites. Identifying the most effective stimulation site warrants further study.
The TRT program was intended to incorporate specificity of training principles by targeting muscles known to be relevant to gait performance. Ankle plantarflexor muscle strength has been shown to be important in regulating gait speed because it generates much of the energy required to move the limb forward during push-off.28 As the TRT involved strengthening of the ankle dorsiflexors and plantarflexors, improvements in dorsiflexor and plantarflexor peak torque and gait velocity are consistent with our expectations. Gait velocity improved by approximately 30% after 4 weeks of TES + TRT. This is higher than the 13% reported in a previous study4 after 4 weeks of gait training in patients with chronic stroke.
The physiological mechanisms underlying strength gains in individuals with stroke is an area that warrants further study. Transcutaneous electrical stimulation has been shown to reduce plantarflexor spasticity,6 and a previous study in our laboratory has shown that plantarflexor spasticity is inversely correlated with dorsiflexor strength.29 Therefore, the decrease in plantarflexor spasticity in this patient could have contributed to the increase in his dorsiflexor strength. Furthermore, it is possible that reducing spasticity with TES enabled the patient to exert greater effort during the TRT that followed, thus contributing to greater improvement in motor function. The mechanism underlying the observed improvements in muscle strength may be multifactorial and may involve the enhancement of descending voluntary commands to the paretic muscles,30 reduction in agonist-antagonist co-contraction,6,30 and/or reorganization of synapses and cortical representation following repetitive practice of functional tasks.31
The improvement in gait velocity was clinically important. The subject was classified as a least-limited community walker (50-80 cm/s) before treatment.32 After 4 weeks of training, his mean gait velocity approached the value for the community walkers (≥80 cm/s) who are thought to be independent in all home and moderate community activities.32 The improvement in the distance covered during the 6MWT was 25.8%. Such an improvement is comparable with the 28% gain found in a randomized, controlled trial after 4 weeks of gait training.15 However, 6MWT results are influenced not only by neuromuscular function and peripheral muscle strength but also by other factors such as motivation and cardiorespiratory fitness. Nonetheless, improvements in the distance covered have important practical significance. After reviewing a series of clinical trials, Mayo and colleagues33 concluded that the increased distance covered in the 6MWT was the only significant predictor of integration into the community among stroke survivors.
After 4 weeks of performing the home program, the patient's TUG times had decreased by 23.7%, from 24.5 to 18.7 seconds. Such an improvement is clinically meaningful, as Podsiadlo and Richardson22 have found that older adults who were able to complete the TUG task in less than 20 seconds were independent in transfer tasks involved in their activities of daily living. Worthy of note is that the patient's TUG time remained below 20 seconds (at 18.8 seconds) even 4 weeks after the program had ended, indicating a useful carryover effect.
In this case study, the patient was asked to practice TRT after 60 minutes of electrical stimulation. Increased motor-evoked potentials in the tibialis anterior are known to persist for at least 110 minutes, following 30 minutes of low-frequency electrical stimulation (1 Hz) over the common peroneal nerve.34 The acupuncture points chosen were on the anterolateral aspect of the lower limb and, as noted earlier, the TES protocol might have excited segments of the peroneal nerve. It is hypothesized that TES is likely to offer the greatest benefit whereas the cortical excitability is higher, that is, when TRT practice follows electrical stimulation. Whether practicing TRT during electrical stimulation would have additional beneficial effects on functional recovery may be a fruitful topic for further study.
This case study has detailed a home-based program directed at improving the motor performance of a patient with chronic stroke of 7 years duration. After 4 weeks of treatment, this individual had significantly decreased plantarflexor spasticity and increased ankle muscle strength, as well as increased gait velocity, walking endurance, and functional mobility. An important finding is that all the gains in motor performance were maintained at 4 weeks after all treatment had ended. We acknowledge that the results from a single case study cannot be generalized to all individuals with stroke. However, this case study may be of particular value to clinicians, as it details a home-based protocol combining TES with TRT, and shows how it improved locomotor function in an individual who had long-standing chronic stroke.
The authors thank the Community Rehabilitation Network of Hong Kong's Society for Rehabilitation for assistance in recruiting subjects. The study was supported by the Development of Niche Areas Funding to Centre for East-meets-West in Rehabilitation Sciences.
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