Many patients complain of hemiplegic shoulder pain following stroke. Here, the
effectiveness of pulsed radiofrequency stimulation of the suprascapular nerve is
compared with intra-articular corticosteroid injection for chronic hemiplegic
shoulder pain following stroke. This single-center, prospective, randomized
controlled study included 20 patients with hemiplegic shoulder pain after stroke,
randomly assigned to the pulsed radiofrequency and intra-articular corticosteroid
injection treatment groups (n = 10 in each). Hemiplegic shoulder pain
severity was measured by numeric rating scale and passive shoulder range motion
was assessed at baseline and one and two months after each procedure. Compared to
the baseline numeric rating scale scores, post-treatment scores decreased
significantly in both groups (p
Following stroke many patients experience different types of pain syndrome [1, 2]. Among these, hemiplegic shoulder pain (HSP) is one of the most frequent [3, 4]. Although their etiology is unclear, adhesive capsulitis, subacromial bursitis, shoulder subluxation and spasticity are known to be associated with the development of HSP . HSP resolves in most cases within six months, but approximately 20% of patients experience debilitating and persistent shoulder pain . Persistent HSP may hinder functional recovery after stroke, decrease quality of life and lead to emotional problems, such as depression and anxiety .
Generally, clinicians employ range of motion (ROM) exercises, oral medications and other modalities of therapy to control HSP . However, despite this, HSP persists in many patients. For the treatment of persistent HSP, unresponsive to conventional modes of therapy, intra-articular corticosteroid injection (ICI) into the shoulder joint is widely used, but its palliative effect has only a relatively short duration . Furthermore, corticosteroids may have adverse effects, including allergic reactions, flushing, hyperglycemia, menstrual disturbances and adrenal suppression [9, 10]. Suprascapular nerve block (SSNB) is another option for relieving HSP [11, 12]. The suprascapular nerve (SSN) originates from the ventral rami of the C4, C5 and C6 spinal nerves and emerges from the upper trunk of the brachial plexus. It provides 70% of the sensory innervation of the shoulder joint . Thus, blockage of pain transmission through the SSN provides effective control of HSP. However, the efficacy of SSNB varies with the study population and depends on the therapeutic modality with which it is compared . Moreover, the effect of SSNB may also be limited due to the short duration of action of local anesthetic agents.
Pulsed radiofrequency (PRF) was introduced by Sluijter in 1997 . Many previous studies have reported its safety and effectiveness in alleviating pain. In this procedure, an electrical field is generated around the targeted nerves or tissues, but these structures are not damaged by this stimulation. Conventional radiofrequency provides continuous electrical simulation to the targeted nerves or tissues and ablates these structures due to the high temperatures around the radiofrequency needle tip [16, 17, 18, 19]. However, PRF only provides electrical stimulation for brief durations between prolonged resting phases. Therefore, it does not produce heat sufficient to damage surrounding structures . The primary mechanism of PRF is modulation of pain signals by the generated electrical field . Several previous studies have reported that PRF can be effective in controlling various types of pain, such as neuralgia, muscle pain and joint pain [9, 22, 23]. Additionally, recent studies have shown that PRF of the SSN may effectively manage shoulder pain [24, 25, 26, 27]. However, the effect of PRF stimulation of the SSN in the management of HSP after stroke remains undetermined.
Therefore, this study, investigated whether PRF stimulation of the SSN could effectively reduce shoulder pain and increase the shoulder ROM in patients with HSP following chronic stroke. Furthermore, the effectiveness of PRF and ICI was compared in these patients.
20 consecutive stroke patients were prospectively recruited, including 13 men
and 7 women, mean age 58.0
Written informed consent was obtained from all subjects. The study protocol was
approved by the Institutional Review Board of Yeungnam University Hospital
(2017-02-011). The sample size was based on the findings of a previous study
. The reduction in the NRS score after treatment (PRF of the SSN vs.
lidocaine injection) was 1.50
Subjects were allocated (by random number table) to receive either PRF stimulation of the SSN (PRF group) or ICI administration in the shoulder joint (ICI group) (Fig. 1). An experienced clinician performed the assigned procedure once for each subject under ultrasound (US) guidance. All patients underwent rehabilitation therapy (Monday to Friday: 2.5 h/day; Saturday: 1 h/day).
Study flow diagram for pulsed radiofrequency and intra-articular corticosteroid injection groups. Abbreviations: ROM, range of motion; NRS, numeric rating scale; PRF, pulsed radiofrequency; ICI, intra-articular corticosteroid injection.
The procedure was conducted from behind the patient by a physician with the
patient in an upright position. A US device (LOGIQ P6, General Electric, Republic
of Korea) with an 11-MHz linear probe was used to guide injection administration.
During PRF stimulation and ICI administration, the hand on the side of the
injection could be placed on the contralateral shoulder. For PRF stimulation, the
US probe was placed just above and parallel to the scapular spine. The
supraspinatus muscle and scapular notch were visualized on the US images. The SSN
was seen as a hyperechoic structure in the scapular notch, 3–4 cm below the
transverse scapular ligament. A 22-gauge, 10-cm cannula with a 10-mm active tip
(Cosman RF Cannula, CC10522, Cosman Medical, Burlington, MA, USA) was inserted
towards the scapular notch using a medial-to-lateral approach (Fig. 2). An
electrode was connected to the PRF needle. When the patient reported paresthesia
during sensory stimulation (50 Hz, 1 ms pulse width,
Ultrasound image of suprascapular nerve with linear ultrasound probe. Abbreviations: TM, trapezius muscle; SM, supraspinatus muscle; SN (arrow head), suprascapular nerve; arrow, pulsed radiofrequency needle pathway.
Patients were assessed prior to the study (baseline) and at one and two months
after the procedure. The same investigator, blinded to the therapeutic
intervention, assessed the clinical outcomes before and during follow-up. The
intensity of pain in the affected shoulder was assessed using the NRS. Passive
shoulder joint ROM was investigated using a goniometer. Shoulder flexion,
abduction and external and internal rotations were assessed with the patients in
a supine position. Degree of shoulder flexion and abduction was measured with the
elbow in extension and ROM of external and internal rotations evaluated with the
elbow at 90
Change in NRS score was measured as the difference between the pre-treatment
score and the score at each time point during post-treatment follow-up. Change in
NRS (%) was calculated as “((pre-treatment score - score after
Data were analyzed using Statistical Product and Service Solutions software
(SPSS, version 22.0, IBM Corporation, Armonk, NY, USA). Intergroup comparison of
the demographic data and the rate of successful pain relief employed the
Mann–Whitney U-test and Fisher’s exact test, respectively. A normality test
employed the Kolmogorov–Smirnov test. Repeated measure one-factor analysis was
used to evaluate changes in the NRS scores in the PRF and ICI groups. A repeated
measure two-factor analysis was used to compare the changes between the groups
over time. Multiple comparisons were obtained using the Bonferroni correction.
The level of statistical significance was set at p
All enrolled subjects completed the study and no adverse events were observed in
either group. There were no significant differences in the demographic
characteristics between the two groups (p
|PRF group||ICI group||p-value|
|(n = 10)||(n = 10)|
|Sex (Male : Female), n||6:4||7:3||0.648|
|Affected hemisphere (Right : Left), n||6:4||4:6||0.656|
|Months from onset||13.1
|Stroke type (infarct : hemorrhage), n||7:3||4:6||0.648|
|Initial passive ROM of shoulder, degree|
|Values are given as mean |
Abbreviations: PRF, pulsed radiofrequency; ICI, intra-articular corticosteroid injection; NRS, numeric rating scale; ROM, range of motion; MBC, modified Brunnstrom classification (scores range from 1 to 6; higher scores indicate better hand function); FAC, Functional Ambulation Category (scores range from 0 to 5; higher scores indicate better walking ability); MMSE, Mini-Mental State Examination.
The intragroup analysis showed that the NRS scores differed significantly over
time in both the groups (PRF group: p = 0.009; ICI group: p
Changes in the numeric rating scale scores.
Compared to the pre-treatment NRS scores, both groups showed a significant
decrease in the scores at one and two months after treatment. However, the NRS scores
were significantly lower in the ICI group than in the PRF group at one and two months
after the procedure.
Abbreviations: NRS, numeric rating scale; PRF, pulsed radiofrequency; ICI,
intra-articular corticosteroid injection.
Changes in the passive shoulder joint range of motion
In the PRF group, a significant increase in the shoulder ROM was observed in
flexion, abduction, and external rotation at one and two months after PRF. In the ICI
group, a significant increase was found in all ROM measurements at one and two months
after ICI administration. In the intergroup comparison, all ROM measurements were
significantly higher in the ICI group than in the PRF group.
Abbreviations: ROM, range of motion; PRF, pulsed radiofrequency; ICI,
intra-articular corticosteroid injection.
In the intergroup analysis, changes in the NRS scores and all ROM measurements
differed significantly over time between the two groups (p
Pain relief (pain improvement
This study investigated the effectiveness of PRF of the SSN in alleviating pain
and compared it with ICI treatment in patients with HSP after chronic stroke. The
severity of pain measured by NRS was significantly reduced at one and two months
after both interventions. However, the NRS scores were significantly lower in the
ICI group than in the PRF group at one and two months post-treatment.
Furthermore, only two out of ten patients (20%) who underwent PRF had
successful pain relief (
The mechanism of action of PRF of the SSN has not yet been clearly identified. However, based on previous studies, some mechanisms can be suggested. Cosman et al.  reported that pain reduction after PRF stimulation was correlated with the long-term depression of synaptic transmission following low-frequency electrical stimulation of neurons by PRF. Therefore, the PRF of the SSN seems to inhibit the transfer of nociceptive stimuli from the shoulder joint. Additionally, Hagiwara  reported that when the electromagnetic field produced by PRF stimulates the peripheral nerves, excitatory C-fibers are inhibited and activity of the descending serotonergic and noradrenergic pain inhibitory pathways is enhanced. The effectiveness of ICI in this study is consistent with the findings of several previous studies on HSP [5, 30, 31]. Here, the potent anti-inflammatory effect of corticosteroids seemed to have reduced the shoulder pain and increased the extensibility of the shoulder joint capsule in the ICI group . It is believed that the outcome of ICI was better than that of PRF because the corticosteroid injection was administered at the origin of pain. In contrast, PRF controlled the shoulder pain indirectly by acting on the SSN. Despite the superior effect of the ICI, its potential adverse effects should be considered [9, 10]. Therefore, PRF treatment of the SSN may be a helpful therapeutic modality in the management of HSP, especially in patients contraindicated for or who experience significant side effects with corticosteroid injections. Furthermore, US was used to guide the PRF needle when approaching the SSN. US not only increases the safety and accuracy of the procedure, but also diagnoses shoulder disorders accurately [32, 33].
Several previous studies have demonstrated the efficacy of PRF treatment of the SSN for shoulder pain due to rotator cuff pathology or adhesive capsulitis. However, to the author’s knowledge, only one study has evaluated the effectiveness of PRF stimulation of the SSN in HSP after stroke [24, 25, 26, 27]. In 2018, Picelli et al.  retrospectively evaluated the effect of PRF of the SSN in six chronic stroke patients with HSP. They reported that the intensity of shoulder pain evaluated using the visual analog scale was significantly reduced and the shoulder ROM significantly improved with PRF, with a sustained effect for at least four months. The present study is the first prospective randomized controlled study to compare the effectiveness of PRF and ICI in HSP after chronic stroke. However, its limitations should be considered. First, there was no investigation of the long-term effects of the therapy beyond two months. Second, patients were not blinded to the treatment they received. Third, the study did not include a placebo group. Finally, the mechanisms causing HSP, such as soft tissue problems, motor impairment and neural factors, were neither considered nor evaluated.
Results indicate that the effectiveness of PRF of the SSN in pain reduction, as evaluated by NRS score, was minimal in patients with HSP after stroke. Although NRS scores were significantly reduced following PRF, only 20% of patients experienced successful pain reduction. In contrast, there was a greater decrease in the severity of pain after ICI, and 70% of patients experienced successful pain reduction. Furthermore, improvement in the shoulder ROM was greater with ICI than with PRF. Therefore, it is suggested that ICI may more effectively control HSP in patients with stroke than PRF of the SSN. However, in patients at a risk of complications with corticosteroids, PRF of the SSN may be a reasonable clinical option.
HSP, hemiplegic shoulder pain; ROM, range of motion; SSNB, suprascapular nerve block; SSN, suprascapular nerve; PRF, pulsed radiofrequency; ICI, intra-articular corticosteroid injection; NRS, numeric rating scale; US, ultrasound.
THK and MCC conceived and designed the experiments; THK and MCC performed the experiments; THK and MCC analyzed the data; THK and MCC contributed reagents and materials; THK and MCC wrote the paper.
Informed consent was obtained from all the participants. The Institutional Review Board of Yeungnam University Hospital approved this study (code 2017-02-011).
This study was supported by a National Research Foundation of Korea Grant funded by the Korean government (Grant no. NRF-2021R1A2C1013073).
The authors declare no conflict of interest.