Stroke is a major cerebral vascular disease, which is characterized by the sudden onset of neurological symptoms due to abnormalities in the cerebral circulation, with clinical signs persisting for more than 24 hours [1]. It is the second most common cause of death worldwide, with broad ranges of prevalence and severity [2,3].

Spasticity, a sequela of stroke, refers to abnormal muscle tension that also occurs in upper motor neuron syndrome and is marked by a velocity-dependent increase in resistance against passive elongation [4]. This spasticity may impede the rehabilitation of stroke patients by causing contracture or pain in the muscles and joints. Moreover, impairment of voluntary motor functions adversely affects the ability to perform activities of daily living (ADLs) and causes a significant decline in quality of life [5].

The treatments for spasticity include i) physiotherapy, including maintaining proper posture, joint exercises, stretching, and electrical stimulation; ii) pharmacological approaches, including drug therapy using tizanidine/baclofen and botulinum toxin injections; iii) surgical intervention. However, achieving a complete recovery from spasticity is challenging. Thus, several types of clinical trials are needed to formulate treatments that can address the various adverse effects and limitations of each currently available treatment modality [6].

Spasticity is a symptom that does not improve easily, meaning it is necessary to find a more effective treatment method for affected patients. Recently, there has been a growing effort to improve the effectiveness of treatments by using electroacupuncture to increase the overall treatment rate of stroke spasticity [7]. However, clear evidence of the effectiveness of electroacupuncture in the treatment of spasticity is not currently available since the research has predominantly involved small-scale studies with varying outcomes, thereby lacking rigorous research designs. Therefore, there is a need for clinical trials that apply uniform standards and procedures concerning therapeutic stimulation points, duration, and intensity [8]. The present study aimed to investigate changes in upper limb spasticity (ULS) of stroke patients after applying constant and regular electroacupuncture therapy (EAT) at specific therapeutic stimulation points, EAT duration, and EAT intensity.

1. Study design and participants

This was a prospective, single-arm, pre- and post-analytical study that was conducted between June 2018 and December 2018. It was designed without a control group to assess the results after treatment in a hospitalized treatment environment, while a licensed Korean medical doctor conducted the acupuncture. This study was designed and reported according to the Revised Standards for Reporting Interventions in Clinical Trials of Acupuncture (STRICTA), thereby extending the CONSORT statement [9] to ensure replicability. The study protocol, including the informed consent form, was approved by the Institutional Review Board of the Korean National Rehabilitation Center (approval No. NRC-2018-01-007). Moreover, the study protocol was registered with the Clinical Research Information Service (CRIS) for the Republic of Korea (identification No. KCT000 2968).

A total of 30 patients with post-stroke ULS (PT-ULS) were included in the present study (Fig. 1). Patients hospitalized in the Korean National Rehabilitation Center were recruited consecutively through advertisements in the hospital. Each patient provided written informed consent before participation.

Figure 1. Flow diagram of the study process.

During the study period, all participants were treated with conventional rehabilitative treatment, including physical therapy, occupational therapy, and heat–electromechanical therapy (heat pack, interferential current therapy [ICT]). Physical therapy and occupational therapy were conducted twice daily for 30 min per session, for a total of 10 sessions per week. Additionally, heat–electromechanical therapy (heat pack, ICT) was conducted once daily for 15 min per session, for a total of 5 sessions per week. All participants were allowed to take muscle relaxants and analgesic medicine if prescribed by the rehabilitation medical doctors. EAT was considered an additional treatment.

The inclusion criteria were as follows: (1) adults aged ≥ 19 years; (2) patients diagnosed with stroke based on evidence of hemorrhage and/or cerebral infarction on computed tomography (CT) or magnetic resonance imaging (MRI); (3) patients who had suffered a stroke in the previous 2 years; (4) patients with PT-ULS corresponding to grade 1 or higher on the modified Ashworth scale (MAS); (5) patients who did not undergo nerve block or other surgical interventions to reduce spasticity; (6) patients who submitted a signed informed consent form.

The exclusion criteria were as follows: (1) patients with severe cardiovascular, liver, kidney, hematopoietic, or endocrine disease; (2) patients with acute or chronic infectious disease or autoimmune disease; (3) patients with a history of serious psychiatric illness (such as schizophrenia) or history of medication use for a psychiatric disorder; (4) patients who could not be accurately evaluated due to cognitive impairment; (5) patients who indicated phobia or hypersensitivity to acupuncture in the questionnaire survey; (6) patients with a history of disorders involving blood coagulation; (7) patients treated with warfarin and with an international normalized ratio (INR) score of ≥ 3; (8) patients who were unable to provide accurate responses due to communication issues; or (9) patients unfit to participate in the study as determined by the principal investigator or sub-investigators.

2. Intervention

EAT consisted of a total of 12 sessions over 4 weeks. Disposable, single-use, sterilized, stainless-steel needles (Dongbang Acupuncture Inc., Seoul, Korea; length 40 mm, diameter 0.3 mm) were inserted to a depth of 15-20 mm to elicit needle sensation (De qi). After applying acupuncture therapy at four acupoints on the affected arm (LI11, LI10, LI4, and TE5; Fig. 2), electrostimulation (60 Hz) was applied for 20 min (Supplementary Material).

Figure 2. Acupoints in the experimental group.

3. Outcome measurements

MAS, which is a scoring method commonly used to measure spasticity in clinical practice, was used as the primary outcome. The method uses a grade between 0 and 4 to record the resistance felt by the evaluator during passive movements in the joint being evaluated. The joints on the affected side of the patient indicate their clinical muscle tension. After sufficiently relaxing the subject’s muscles, the resistance felt by applying a manual joint exercise, which flexes as quickly as possible, is subjectively evaluated and classified [10].

The Fugl–Meyer assessment for the upper extremity (FMA-UE) was implemented as the secondary outcome and is a tool that quantitatively evaluates the degree of functional recovery in stroke patients based on the post-stroke motor function recovery phase. It is divided into upper and lower limb function evaluations; however, the present study evaluated only criteria corresponding to the upper limb. The evaluation of the upper extremity motor function comprised a total of 18 items, including shoulders, elbows, and forearms, 12 items for wrists and hands, and 3 for upper extremity coordination, with the highest score of 66 points. Each item is scored on a three-point scale (0 = cannot be performed, 1 = can be partially performed, and 2 = perfectly performed) [11]. Sanford et al. [12] reported the reliability of the FMA-UE upper limb motor function evaluation as 0.96. Outcomes (MAS and FMA-UE) were measured at three points: before therapy, after 6 sessions, and after 12 sessions.

4. Statistical analysis

The results were analyzed using SPSS 21.0 (IBM Corp., Armonk, NY, USA). Demographic data are presented as descriptive statistics (mean, standard deviation, frequency, and percentage). Pre-, mid-, and post-treatment analyses of the MAS and FMA-UE results were performed using one-way repeated measure analysis of variance (ANOVA). A value of p < 0.05 was considered statistically significant. Missing data in dropouts were replaced using the last-observation-carried-forward method.

1. Demographic data

The study population consisted of 30 participants (21 men and 9 women) with a mean age of 53.8 ± 15.2 years. There were 23 patients with brain infarction and seven with brain hemorrhage (Table 1). The mean duration from disease onset was 30.3 ± 16.6 weeks.

Data are presented as mean ± standard deviation or percentage (%)..

&md=tbl&idx=1' data-target="#file-modal"">Table 1

Demographic data.

Characteristic	Subjects (N = 30)
Age (years)	53.8 ± 15.2
Sex (N/%)
Male	21 (70.0)
Female	9 (30.0)
Stroke type (N/%)
Infarction	23 (76.7)
Hemorrhage	7 (23.3)
Onset (weeks)	30.3 ± 16.6

Data are presented as mean ± standard deviation or percentage (%)..

2. Outcomes

One-way repeated measure ANOVA was performed to identify the effect of EAT on post-stroke ULS. A total of three measured values were compared in this study: pre-, mid-, and post-treatment.

1) Primary outcomes

Table 2 shows the comparison of each evaluation results for the MAS, which was used as an evaluation for post-stroke spasticity. The MAS results were significant for the elbow, although only depending on the evaluation period (p < 0.001), while the mean values decreased in the order of pre- (1.83 ± 0.08), mid- (1.53 ± 0.09), and post-treatment (1.33 ± 0.09). In addition, the Bonferroni post-hoc test found significant differences in the measured values at each evaluation period, meaning EAT effectively relieved post-stroke elbow spasticity. The MAS results for the wrist were also significant depending on the evaluation period (p < 0.01), while the means decreased in the order of pre- (2.03 ± 0.09), mid- (2.00 ± 0.10), and post-treatment (1.73 ± 0.08). In addition, the Bonferroni post-hoc test showed significant differences between pre–post and mid–post measured values, indicating EAT effectively relieved post-stroke wrist spasticity (Table 2).

MAS = modified Ashworth Scale..

*p < 0.05, **p < 0.01, ***p < 0.001..

&md=tbl&idx=2' data-target="#file-modal"">Table 2

Results of modified Ashworth scale (MAS) assessment.

Variable	Time	n	Mean ± SE	p-value	Significant difference	p-value (by Bonferroni test)
MAS (elbow)	Pre-test	30	1.83 ± 0.08	0.000***	Pre-test vs. Mid-test	0.004**
	Mid-test	30	1.53 ± 0.09		Mid-test vs. Post-test	0.035*
	Post-test	30	1.33 ± 0.09		Pre-test vs. Post-test	0.000***
MAS (wrist)	Pre-test	30	2.03 ± 0.09	0.007**	Pre-test vs. Mid-test	0.980
	Mid-test	30	2.00 ± 0.10		Mid-test vs. Post-test	0.009**
	Post-test	30	1.73 ± 0.08		Pre-test vs. Post-test	0.004**

MAS = modified Ashworth Scale..

*p < 0.05, **p < 0.01, ***p < 0.001..

2) Secondary outcomes

Table 3 shows the comparison of each evaluation results for the FMA-UE, which was used as an evaluation for post-stroke upper limb function. The FMA-UE results were significant depending on the evaluation period (p < 0.001), while the means increased in the order of pre- (20.27 ± 2.56), mid- (21.90 ± 2.71), and post-treatment (24.13 ± 2.81). In addition, the Bonferroni post-hoc test found significant differences in the measured values at each evaluation period, thereby showing that EAT was effective for post-stroke upper limb functional recovery (Table 3).

FMA-UE = Fugl–Meyer assessment for the upper extremity..

***p < 0.001..

&md=tbl&idx=3' data-target="#file-modal"">Table 3

Results of Fugl–Meyer assessment for the upper extremity (FMA-UE) assessment.

Variable	Time	n	Mean ± SE	p-value	Significant difference	p-value (by Bonferroni test)
FMA-UE	Pre-test	30	20.27 ± 2.56	0.000***	Pre-test vs. Mid-test	0.000***
	Mid-test	30	21.90 ± 2.71		Mid-test vs. Post-test	0.000***
	Post-test	30	24.13 ± 2.81		Pre-test vs. Post-test	0.000***

FMA-UE = Fugl–Meyer assessment for the upper extremity..

***p < 0.001..

3) Adverse events

There were no adverse events associated with EAT.

This study aimed to investigate the changes in the ULS of stroke patients after applying constant and regular EAT at the therapeutic stimulation points, in addition to investigating the EAT duration and intensity. Spasticity is a symptom that does not improve easily, meaning it is essential to identify a more effective treatment method for patients. Here, the use of EAT decreased ULS and improved functional recovery at the elbow and wrist.

Spasticity is one of the most common symptoms in stroke patients and is a form of upper motor neuron syndrome caused by a brain injury. It is a motor neuron disorder that is characterized by a velocity-dependent increase in the tonic-stretch reflex, along with hyperactive deep tendon and hyperactive tendon reflexes, which are caused by an exaggeration of the stretch reflex [4]. The mechanism underlying spasticity involves increased excitatory synaptic inputs, decreased inhibitory synaptic inputs, and increased motor nerve excitation due to changes in the electrical characteristics of the nerves [13,14]. Spasticity also involves changes in the degree of muscle stiffness or stretch reflexes, which influence spasticity depending on the time of onset [15].

Pharmacological therapy with antispastic drugs can be used to medically treat generalized spasticity. At the same time, botulinum toxin, phenol, or alcohol injection may be the optimal approach for localized spasticity. However, if these treatments are not effective, then, surgical intervention or baclofen pump implantation may be alternatives, although the limitations and possible adverse effects that are associated with each procedure must first be considered [16].

Electroacupuncture, which is used in Korean medicine, creates a synergistic effect of both acupoint stimulation and electrostimulation by applying stimulation directly to the human skin [17]. The technique allows electrostimulation to be continuously applied to a specific body part, while the amount of stimulation can be controlled objectively [18]. Moreover, adverse effects are reduced by applying the stimulation locally [19].

The frequency of the electrical stimulation can be divided into three categories based on frequency range: low (< 10 Hz), middle (10-100 Hz), and high (> 100 Hz). Studies on the antispastic effect of EAT in stroke patients with spasticity used mid-frequency stimulation (50-100 Hz) and found that EAT temporarily reduced spasticity caused by stroke; when it was repeatedly applied, a reduction in spasticity was maintained [20]. Thus, we used mid-frequency stimulation (60 Hz) in the present study.

It has been proposed that electroacupuncture alters neurotransmitter production and reduces spinal motor neuron excitability, thereby reducing muscle spasticity [20]. Electrostimulation can help induce muscle contractions and generate functional movements by electrically stimulating muscles that are difficult to control voluntarily [21].

Despite reports on the effects of acupuncture on post-stroke spasticity, such effects have not been clearly identified because present studies have been small-scale with varying results and contained insufficiently rigorous research designs, thereby indicating the need for clinical trials that apply uniform standards and procedures concerning therapeutic stimulation points, duration, and intensity [8].

In the present study, 12 sessions of EAT were performed over 4 weeks on 30 patients with PS-ULS. After applying acupuncture therapy at four acupoints on the affected arm (LI11, LI10, LI4, and TE5), electrostimulation (60 Hz) was applied for 20 min. Pre- and post-treatment analyses were performed on the changes in the outcome variables—MAS and FMA-UE.

Significant improvements were observed in the MAS assessment results in the elbow at 2 and 4 weeks after the start of EAT, compared to the baseline, while significant improvement was found in the wrist MAS only at 4 weeks after the start of EAT, compared to the baseline. EAT treatment decreased ULS at the elbow and wrist since a reduction in muscle tone may be related to EAT stimulation at the affected muscle.

The FMA-UE assessment results also showed significant differences in the FMA-UE at 2 and 4 weeks after starting EAT compared to the baseline. Changes in the motor function of the upper extremities may be related to a reduction in spasticity since a reduction in muscle tone resulted in upper extremity functional improvement.

It has been demonstrated that the minimal clinically important differences (MCID) in the average MAS of the effect sizes 0.5 and 0.8 and standard deviations for the upper extremity muscles were 0.48 and 0.76 [22]. Further, the MCID of the FMA-UE, which is represented as a change in score of ≥ 5 points, was defined as a favorable response in a previous report [23]. Changes in the present study could not achieve MCID; however, we expect the effect size to be greater when participants are treated long-term and with a higher frequency of EAT treatment sessions.

The limitations of this study included the following: (1) the EAT effects could not be clearly identified due to the lack of a control group and any potential treatment with an oral medication affecting the subject spasticity; (2) the study population was small, with relatively few clinical cases; (3) the long-term effects of EAT could not be determined due to the lack of follow-up assessments. Therefore, the results should not be extrapolated to other populations.

Based on the findings of the present study, the following are needed in the future: (1) comparative studies on the effects of EAT with a randomized controlled group applying sham acupuncture to solve potential confounding factors (effect modifiers); (2) studies on the therapeutic effects of EAT with groups of subjects categorized by the degree of spasticity; (3) expanded studies with larger study populations; (4) studies with follow-up evaluations to determine the long-term effects of EAT; (5) studies on the effectiveness of various stimulation factors, to assess how much EAT treatment is necessary to achieve optimal outcomes.

EAT decreased ULS and improved functional recovery at the elbow and wrist. Larger-scale and more rigorous clinical trials are needed in the future to verify the efficacy of EAT.

This research was supported by a grant (18-C-03) by the Korea National Rehabilitation Center and a grant from the Rehabilitation Research & Development Support Program (#NRCRSP-22TB02), National Rehabilitation Center, Ministry of Health & Welfare, Korea.

Supplementary data to this article can be found online at https://doi.org/10.51507/j.jams.2023.16.6.248.

This study was funded by a grant (18-C-03) by the Korea National Rehabilitation Center. Also, this work was supported by a grant from the Rehabilitation Research & Development Support Program (#NRCRSP-22TB02) by the Korea National Rehabilitation Center. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.

SML conceived the trial together with CHS, JSL, GEL, EJG, and EJK. SML drafted the manuscript and the design of study with CHS and EJK. CHS, JSL, and GEL conducted the acupuncture treatments. EJG evaluated the assessment tools and performed data analysis. EJK were involved in the diagnoses. SML prepared the manuscript with CHS and EJG. JSL, GEL, and EJK reviewed the manuscript. All authors read and approved the final manuscript.

The data supporting this study’s findings are available from the corresponding author upon reasonable request.

The authors declare no conflict of interest.