Parkinson’s disease (PD) is a progressive neurodegenerative condition characterized by the degeneration of dopaminergic neurons in the substantia nigra of the midbrain. Its key motor symptoms include slowness of movement (bradykinesia), resting tremor (4–6 Hz), muscular rigidity, and impairments in postural reflexes. Non-motor symptoms, including autonomic dysfunction, sensory abnormalities, psychiatric conditions, cognitive decline, sleep disturbances, and impulse control issues, are also prevalent [1].

The worldwide prevalence of PD is reported to be 1.51 per 1,000 individuals. Studies have indicated that men are more frequently affected than woman. The prevalence shows a marked increase with advancing age, with 9.34 per 1,000 individuals aged ≥ 60 years diagnosed with PD. Particularly between 2010 and 2023, the prevalence of PD surged to 3.81 per 1,000 individuals [2]. In Korea, the prevalence of PD is also showing an upward trend. According to the National Health Insurance Service data, the number of patients treated for PD increased from 96,764 in 2016 to 111,312 in 2020, reflecting an increase of 14,548 patients (15.0%) over 4 years, with an average annual growth rate of 3.6% [3].

The primary treatment for PD is the administration of levodopa, a dopamine precursor. However, the prolonged use of levodopa have side effects, including the “wear-off” effect and dyskinesia, with approximately 50% of patients experiencing these issues after 5 years of treatment and nearly 80% after 10 years. Given these limitations, many patients turn to complementary therapies, with acupuncture and moxibustion treatments being widely employed [4].

Acupuncture and moxibustion treatments for PD primarily focus on improving gait disturbances, such as freezing of gait, through the stimulation of acupuncture points associated with the spine and joints. More recently, bee venom therapy and herbal acupuncture have gained traction, with these therapies contributing to the functional recovery and enhanced quality of life of patients with PD. One significant point of interest is research showing that combining the anti-Parkinson’s drug Madopar with acupuncture treatment leads to better improvements in assessment scores, such as the Unified Parkinson Disease Rating Scale (UPDRS), as compared with the use of Madopar alone. This indicates that an integrative medical approach, combining Western medicine and traditional Korean treatments, may enhance the efficacy of the PD treatment [5].

Scalp acupuncture is a specialized form of segmented acupuncture therapy that integrates the theories of traditional Korean medicine with Western medicine’s neurological and functional theories of the cerebral cortex. This therapeutic modality involves stimulating specific areas on the scalp to treat a range of conditions. It has been clinically applied to central nervous system disorders, psychiatric disorders, pain management, and sensory abnormalities [6].

Studies on scalp acupuncture as a treatment for PD have been continuously progressing. Although it remains challenging to conclusively determine its effectiveness based on existing research, the potential benefits of scalp acupuncture are increasingly recognized. Notably, scalp acupuncture shows promise as a complementary option for patients who developed side effects from conventional PD medications or who do not respond to conventional treatments. Moreover, animal studies have indicated that scalp acupuncture may offer neuroprotective effects, including anti-inflammatory actions and maintenance of action potentials, suggesting a beneficial influence on the neurological conditions [7].

A 2011 investigation [8] focused solely on research studies conducted within China, and a 2022 study [4] identified only two papers related to scalp acupuncture. Although a 2023 study [9] broadened the search scope to include both CNKI and PubMed, it limited its analysis to only examining the current research trends. Despite the widespread clinical application of scalp acupuncture, there remains a notable lack of standardized guidelines and scientific evidence that practitioners can reliably referred to and implement. In particular, there has been no systematic analysis of specific treatment parameters, including needle specifications, insertion methods, and manipulation techniques, making it challenging to ensure consistency and reproducibility of the clinical outcomes.

In light of this, the present study aimed to comprehensively analyze the most recent domestic and international research trends on scalp acupuncture as treatment for PD and to evaluate its efficacy through a systematic review and meta-analysis. Specifically, we sought to establish standardized methodologies for scalp acupuncture and develop concrete treatment protocols that can be practically implemented in clinical settings. Our research study will help establish clinical evidence for scalp acupuncture in PD treatment while providing guidance for future clinical applications and research directions.

1. Literature search

A thorough search was performed across nine databases, including international (PubMed, EMBASE, and CENTRAL), Chinese (CNKI), and domestic databases (KISS, RISS, KMBASE, OASIS, and ScienceOn). The search took place on July 3, 2024, with no limitations on the publication date (Appendix 1).

2. Literature selection and exclusion criteria

The present study exclusively focused on randomized controlled trials (RCTs) involving patients with PD. Case reports, cross-sectional studies, pilot studies, feasibility studies, simple reviews, and mechanistic or experimental research were excluded. The inclusion criteria were as follows: participants diagnosed with PD, without restrictions on age, gender, or disease progression. The intervention in the treatment group was restricted to scalp acupuncture, excluding other modalities, such as electroacupuncture, dry needling, herbal acupuncture, and auricular acupuncture. Studies were included if the treatment group received scalp acupuncture alongside other interventions, such as general acupuncture or medication, provided that these interventions were identical in the control group, thereby ensuring a valid comparison of the scalp acupuncture’s effects. However, studies were excluded if additional interventions, besides scalp or general acupuncture, were applied exclusively to the treatment group.

3. Literature screening and data extraction

The studies were chosen in accordance with the inclusion and exclusion criteria. After removing duplicates, the titles and abstracts were screened to identify relevant studies. Full-text articles were then analyzed to extract key information, including the basic characteristics of the treatment and control groups, scalp acupuncture areas, acupuncture points, intervention methods and duration, evaluation indicators, and outcomes.

4. Risk of Bias assessment method

The assessment of bias risk in the selected RCTs was conducted using Cochrane’s Risk of Bias (RoB) tool. The evaluation examined the following seven domains: random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective outcome reporting, and other biases. The RoB was classified into the following three categories: “high risk,” “low risk,” and “unclear risk.”

The RoB assessment was performed independently by two reviewers (JO, JK). If the two reviewers failed to reach a consensus, the final decision was made after consultation with a third reviewer (JL).

5. Data synthesis and analysis method

Meta-analysis was performed using Review Manager 5.3 (Cochrane Collaboration) on studies where the outcome measures allowed for a quantitative synthesis. For continuous variables, the generic inverse variance estimation method was applied to calculate the mean difference (MD) and 95% confidence intervals (CIs) under a fixed-effect model. Study heterogeneity was assessed using the I² statistic, with values interpreted as follows: ≤ 25% indicating low heterogeneity, 50% as moderate, and ≥ 75% as high heterogeneity [10].

The assessment of publication bias using a funnel plot was not conducted in the present study. When < 10 studies are included in a meta-analysis, the test lacks sufficient statistical power, making it challenging to differentiate between random variation and true asymmetry. As a result, the funnel plot evaluation was not performed in this meta-analysis.

1. Literature selection

A total of 110 studies were identified through the search process. The breakdown by database is as follows: 18 studies from PubMed, 35 from Embase, 7 from CENTRAL, 39 from CNKI, 2 from KISS, 1 from RISS, 2 from KMBASE, 3 from OASIS, and 3 from ScienceOn. After eliminating 29 duplicates, 81 studies remained. Titles and abstracts were reviewed, resulting in the exclusion of 64 studies that did not meet the criteria for participants, interventions, or study design during the first screening. Full-text reviews were conducted on the remaining studies, with two studies further excluded as they showed inconsistencies with the criteria. In total, 15 studies were selected, of which seven were included in the meta-analysis (Fig. 1, Tables 1, 2) [11-25].

Figure 1. Flow diagram of the study selection process of this review.

Table 1 . Comparative analysis of treatment efficacy between scalp acupuncture combined with Western medicine versus Western medicine alone in Parkinson’s disease: a systematic review of 15 randomized controlled trials including patient demographics, intervention methods, treatment duration, and clinical outcomes based on UPDRS scores and quality of life measures from 2004 to 2023.

Study	Participant (E/C; age, diagnosis duration, H&Y)	E treatment	Intervention (n)	Control (n)	Outcome measure
Xu and Liu [11]	70.62 ± 10.34/71.28 ± 11.16, 5.53 ± 1.27/6.02 ± 1.09, N/A	SA (chorea and tremor control area, motor area)	A (60): SA + RM + WM (Dodopazine) Period: 1 month	B (60): WM (Dodopazine) Period: 1 month	1) UPDRSIII (p < 0.05) 2) PDQ-39 (p < 0.05) 3) BBS (p < 0.05) 4) BI (p < 0.05) 5) CSI (p < 0.05) 6) TER (p < 0.05)
Huang et al. [12]	62.11 ± 6.01/61.71 ± 6.56/62.57 ± 5.96, 45.74 ± 17.23/44.20 ± 20.53/45.80 ± 23.13, 1–4	SA (chorea and tremor control area) + GA (GV20, EX-HN1)	A (35): SA + WM B (35): shallow acupuncture group + WM C (35): combined group + WM Period: 2 months	N/A	1) UPDRSIII (p < 0.01) 2) PSQI (p < 0.01) 3) TER (p < 0.01)
Jia et al. [13]	67.68 ± 10.51/68.82 ± 11.96, 7.59 ± 3.63/8.23 ± 3.24, 1–4	SA (MS6, MS8, MS9, MS14) + GA (GV20, EX-HN1, GV14, GB20, PC6, LI4, BL18, BL23, GB34, ST36, ST40, SP6, KI3, LR3)	A (33): SA + GA + WM (Levodopa) Period: 2 months	B (33): WM (Levodopa) Period: 2 months	1) Total UPDRS (p < 0.05) 2) UPDRSIII (p < 0.05) 3) MDRSPD (p < 0.05) 4) TER (p < 0.05)
Hong et al. [14]	64 ± 5/63 ± 6, 3.5 ± 1.3/3.6 ± 1.2, 1–3	SA (motor area, balance area, chorea and tremor control area)	A (26): SA + WM + VR RM Period: 2 months	B (26): WM + VR RM Period: 2 months	1) UPDRSIII 2) TUGT 3) TER 4) Gait parameter
Zhang et al. [15]	61.8 ± 4.6/62.2 ± 4.3, 4.84 ± 1.53/4.58 ± 1.68, 1–2.5	SA (chorea and tremor control area) + GA (GV20, EX-HN1, GB20)	A (43): SA + GA + WM (Madopar) Period: 2 months	B (43): WM (Madopar) Period: 2 months	1) PDQ-39 2) HAMD 3) HAMA 4) NMSS 5) PDSS 6) SCOPA-AUT
Liu and Bai [16]	65 ± 7/67 ± 7, 7.500 ± 3.277/7.333 ± 3.397, 2–5	SA (chorea and tremor control area)	A (30): SA + needling Huatuo Jiaji points Period: 1 month	B (30): GA Period: 1 month	1) Total UPDRS (p < 0.01) 2) WEBSTER (p < 0.01) 3) TER (p < 0.01)
Wang et al. [17]	64.12 ± 3.00/63.84 ± 2.62, 6.35 ± 2.13/5.42 ± 3.14, N/A	SA (chorea and tremor control area) + GA (EX-HN1, GB20, LI4, LR3, KI3)	A (29): SA (for 3 hours) + GA + WM + RM (during needle retention) Period: 2 months	B (29): SA (for 30 minutes) + GA + WM + RM (after needle retention) Period: 2 months	1) UPDRSIII (p < 0.05) 2) ADL (p < 0.05) 3) TER (p < 0.05)
Liu et al. [18]	64.68 ± 7.32/63.78 ± 7.51, 5.87 ± 2.54/5.66 ± 2.78, N/A	SA (chorea and tremor control area)	A (53): SA + GA + WM (Carbidopa) Period: 3 months	B (53): WM (Carbidopa) Period: 3 months	1) Total UPDRS (p < 0.05) 2) PDQ-39 (p < 0.05) 3) TER (p < 0.05)
Liu et al. [19]	57 ± 9/58 ± 9, 2.42 ± 1.00/2.33 ± 0.90, N/A	SA (chorea and tremor control area)	A (30): SA + WM (Madopar) Period: 3 months	B (30): WM (Madopar) Period: 3 months	1) WEBSTER (p < 0.05) 2) TER (p < 0.05)
Suo et al. [20]	67.2 ± 5.6/ 66.8 ± 5.8, N/A, N/A	SA (chorea and tremor control area) + GA (GB20)	A (35): SA + WM (Madopar) Period: 1 month	B (35): WM (Madopar) Period: 1 month	1) Total UPDRS (p < 0.01)2) WEBSTER (p < 0.01)
Huang et al. [21]	61 ± 8/59 ± 9, 5.38 ± 3.22/5.47 ± 3.18, N/A	SA (motor area, balance area)	A (20): SA + WM (Madopar) Period: 1 month	B (20): WM (Madopar) Period: 1 month	1) Total UPDRS (p < 0.001) 2) PSQI (p < 0.001) 3) TER (p < 0.001)
Gu et al. [22]	66 ± 8/70 ± 8, 4.44 ± 3.32/4.56 ± 3.11, N/A	SA (motor area) + GA (GB20, LI4, LI11, LR3, KI3, GB34)	A (23): SA + GA + WM (Madopar) Period: 3 months	B (25): WM (Madopar) Period: 3 months	1) Total UPDRS (p < 0.05) 2) UPDRSI-IV (p < 0.05) 3) TER (p < 0.05)
Huang et al. [23]	65.60 ± 3.78/60.80 ± 3.63, 5.40 ± 1.75/6.40 ± 2.14, 2.18 ± 0.26/2.04 ± 0.30	SA (MS4, MS6, MS8, MS9, MS14)	A (15): SA + WM (Madopar) Period: 5 weeks	B (15): WM (Madopar) Period: 5 weeks	1) Total UPDRS (p < 0.05) 2) rCBF (p < 0.05)
Jiang et al. [24]	65.60 ± 3.78/60.80 ± 3.63, 5.40 ± 1.75/6.40 ± 2.14, 2.20 ± 0.34/2.00 ± 0.32	SA (MS4, MS6, MS8, MS9, MS14)	A (15): SA + WM (Madopar) Period: 6 weeks	B (15): WM (Madopar) Period: 6 weeks	1) WEBSTER (p < 0.05) 2) TER (p < 0.05)
Yang and Chen [25]	64.3/66.1, 3.6/4.8, N/A	SA (motor area, leg motor and sensory area, chorea and tremor control area)	A (30): SA + WM (Madopar) Period: 3 months	B (30): WM (Madopar) Period: 3 months	1) WEBSTER (p < 0.05) 2) TER (p < 0.05)

UPDRS, Unified Parkinson Disease Rating Scale; E, experimental group; C, control group; H&Y, Hoehn and Yahr scale; SA, scalp acupuncture; RM, rehabilitation; WM, Western medicine; PDQ-39, Parkinson Disease Questionnaire-39; BBS, Berg Balance Scale; BI, Barthel Index; CSI, Composite Spasticity Index; TER, total effective rate; GA, general acupuncture; PSQI, Pittsburgh Sleep Quality Index; MDRSPD, Motor-Dysfunction Rating Scale for Parkinson Disease; VR, virtual reality; TUGT, Timed Up & Go Test; HAMD, Hamilton Depression Scale; HAMA, Hamilton Anxiety Rating Scale; NMSS, Non-Motor Symptoms Scale; PDSS, Parkinson Disease Sleep Scale; SCOPA-AUT, Scale for Outcomes in Parkinson Disease for Autonomic Symptoms; WEBSTER, Webster scale; ADL, activities of daily living; rCBF, regional cerebral blood flow; N/A, not available..

Table 2 . Comprehensive analysis of scalp acupuncture technical parameters and manipulation methods in Parkinson’s disease treatment: a systematic review of 15 randomized controlled trials (2004–2023) including detailed specifications for needle types, insertion angles, manipulation techniques, retention times, and electroacupuncture.

Study	Needle specification (mm)	Insertion angle (°)	Depth (mm)	Manipulation technique	Retention time (min)	Electroacupuncture
Xu and Liu [11]	0.35 × 25	15	10.0	N/A	N/A	N/A
Huang et al. [12]	0.30 × 40	30	23.0	1) Rapid insertion 2) Flat needling 3) Quick twirling for 2 min	30	Used (2 mA, 25 Hz, continuous wave)
Jia et al. [13]	0.30 × 40	30	30.0	1) Twirling at 200 times/min 2) Duration: 1 min 3) Repeated three times every 10 min	30	N/A
Hong et al. [14]	0.25 × 30	N/A	20.0	1) Twirling at 200 times/min 2) 2 min per point	30	N/A
Zhang et al. [15]	0.30 × 40	30	30.5	1) Twirling at 180 times/min 2) 1 min per point	N/A	Used (2 Hz, dense wave)
Liu and Bai [16]	0.30 × 40	15	10.0	1) Reinforcing–reducing method	40	N/A
Wang et al. [17]	N/A	30	N/A	1) Twirling at 200 times/min 2) 1 min per point	N/A	N/A
Liu et al. [18]	0.34 × 40	30	30.0	1) Twirling at 200 times/min 2) 1 min per point	N/A	N/A
Liu et al. [19]	0.35 × 40	N/A	N/A	N/A	60	N/A
Suo et al. [20]	0.35 × 50	15	38.0	1) Twirling at 200 times/min 2) 1 min per point	N/A	Used (wave type N/A)
Huang et al. [21]	0.40 × 15	Vertical	To periosteum	1) Twirling at 160 times/min 2) Gradually increasing the stimulation	30	N/A
Gu et al. [22]	N/A	N/A	N/A	N/A	N/A	Used (2 Hz, continuous wave)
Huang et al. [23]	N/A	N/A	N/A	N/A	N/A	Used (100 Hz, 2–4 mA)
Jiang et al. [24]	N/A	Oblique	To galea aponeurotica	1) Quick small-amplitude twirling	N/A	Used (patient tolerance)
Yang and Chen [25]	0.35 × 40	30	2/3 of the scalp	1) Twirling 2–3 times/s 2) Once every 10 min	30	N/A

N/A, not available..

2. Qualitative analysis of included literature

For the characteristics of the study participants, the 15 studies that were ultimately selected were all RCTs, with the number of participants in each study varying between 30 and 120. In total, 991 participants were included across the studies. The participants’ average age ranged from 57.50 to 70.95 years.

For the interventions, scalp acupuncture was the main intervention in all treatment groups. Among the 15 studies, seven combined scalp acupuncture with Western medicine; of these, three studies involved only scalp acupuncture and Western medicine and four studies combined scalp acupuncture, general acupuncture, and Western medicine. Furthermore, three studies implemented a combination of scalp acupuncture, Western medicine, and rehabilitation therapy. In the control groups, 11 studies involved only Western medicine, such as Madopar or Levodopa, and one study combined Western medicine with rehabilitation therapy.

For the scalp acupuncture areas and treatment methods, scalp acupuncture was administered according to either Jiao’s or standard scalp acupuncture techniques. Among the studies, 12 employed Jiao’s scalp acupuncture, whereas three used the standard scalp acupuncture approach. In Jiao’s method, the most frequently used area was the “Chorea and Tremor Control Area,” which was applied in 10 studies. The “Motor Area” was used in five studies, and the “Balance Area," “Voluntary Movement Area," and “Leg Motor and Sensory Area” were each applied in one study. In the standard scalp acupuncture technique, the most frequently used areas were “MS6,” “MS8,” “MS9,” and “MS14,” each applied in three studies, with “MS4” being used in two studies. The most commonly used body acupuncture point was “GB20,” featured in five studies, followed by “EX-HN1" in four studies and “GV20” in three studies. The other points used included “LI4,” “LR3,” “KI3,” and “GB34.” The analysis of specific treatment methods revealed that, among the 15 studies, nine provided needle specifications. Of these, seven studies adopted a standard needle diameter of 0.30–0.35 mm and a length of 40 mm. Notably, Huang et al. [21] used shorter needles (0.40 × 15 mm), whereas Suo et al. [20] employed longer needles (0.35 × 50 mm). The insertion angles were reported in 10 studies, with six studies using a 30° angle and three studies employing a 15° angle. Interestingly, Huang et al. [21] uniquely adopted a vertical insertion method, whereas Jiang et al. [24] used an oblique insertion technique. The insertion depth was mentioned in 11 studies, with 20–30 mm being the most common range in five studies. Some studies used anatomical landmarks for depth determination, including insertion to the periosteum [21] or to the galea aponeurotica [24]. The manipulation techniques were detailed in 12 studies. High-frequency rotation (160–200 rotations per minute) was predominantly used, with five studies specifically employing 200 rotations per minute. Zhang et al. [15] used 180 rotations per minute, whereas Huang et al. [21] applied 160 rotations per minute. The duration of manipulation was typically 1–2 minutes per point, although Jia et al. [13] and Yang and Chen [25] implemented repeated stimulations at 10-minute intervals. The needle retention time was specified in eight studies, with 30 minutes being the most common (five studies). Liu and Bai [16] used 40 minutes, whereas Liu et al. [19] employed 60 minutes. Electroacupuncture was utilized in six studies, with Huang et al. [12], Gu et al. [22], and Zhang et al. [15] using low-frequency stimulation (2–25 Hz), whereas Huang et al. [23] employed high-frequency stimulation (100 Hz). The current intensity was typically set within the 2–4 mA range.

In the assessment tools, the most frequently used assessment tool was the total effective rate, which was employed in 13 out of 15 studies. The total UPDRS was applied in seven studies, UPDRS III in six studies, the Webster scale in five studies, Parkinson Disease Questionnaire-39 (PDQ-39) in three studies, and Pittsburgh Sleep Quality Index in two studies. To assess balance and gait, the Berg Balance Scale, Timed Up & Go Test, and gait parameters were employed. The Hamilton Depression Scale and Hamilton Anxiety Scale were used to assess the symptoms of depression and anxiety. The Parkinson Disease Sleep Scale was applied for sleep-related assessments. For the daily activities, the Activities of Daily Living and Barthel Index were used. Additionally, the Composite Spasticity Index, Motor-Dysfunction Rating Scale for Parkinson Disease, Non-Motor Symptoms Scale, Scale for Outcomes in Parkinson Disease for Autonomic Symptoms, and Regional Cerebral Blood Flow were employed in various studies.

3. Quantitative synthesis and results analysis (meta-analysis)

A meta-analysis was performed on studies comparing the combined effects of scalp acupuncture and Western medicine with Western medicine-only treatment for PD. Among the 15 relevant studies, seven that utilized UPDRS as an assessment tool were quantitatively synthesized and analyzed.

Eight studies were excluded from the quantitative synthesis due to the differences in outcome measures (two studies used the Webster scale [19,25], one study used PDQ-39 [15]), variations in intervention methods (one study combined scalp acupuncture, Western medicine, and rehabilitation therapy [11]; one study compared scalp acupuncture, shallow acupuncture, and Western medicine [12]; one study compared scalp acupuncture, Western medicine, and rehabilitation therapy with Western medicine and rehabilitation therapy [14]), and differences in the control group design (one study compared scalp acupuncture with general acupuncture [16]; one study introduced variables for needle retention time and rehabilitation timing in scalp acupuncture [17]).

For the treatment efficacy of combined scalp acupuncture and Western medicine using UPDRS, a meta-analysis was performed on seven studies [13,18,20-24], comparing the treatment group receiving both scalp acupuncture and Western medicine with the control group receiving only Western medicine. Across the seven RCTs involving a total of 390 participants, the analysis revealed that the group receiving both scalp acupuncture and Western medicine showed significantly greater improvement in UPDRS scores than the group treated with Western medicine alone (MD 7.61; 95% CI: 6.69–8.53; p < 0.00001, I² = 98.9%) (Fig. 2).

Figure 2. Comparison of the UPDRS scores between the patients receiving additional scalp acupuncture treatment (scalp acupuncture + medication) and those receiving medication only (Western medicine treatment). SA, scalp acupuncture; WM, Western medicine; SD, standard deviation; CI, confidence interval; GA, general acupuncture; UPDRS, Unified Parkinson Disease Rating Scale.

The results of the subgroup analysis, based on four studies [20,21,23,24] that combined only scalp acupuncture and Western medicine, showed that among the 170 participants, the group receiving both treatments had significantly better UPDRS scores than the Western medicine-only group (MD 5.29; 95% CI: 4.25–6.32; p < 0.00001, I² = 11%).

Altogether, 220 participants were analyzed across three studies [13,18,22], comparing the treatment group receiving scalp acupuncture, general acupuncture, and Western medicine with the control group receiving only Western medicine. The results demonstrated that the group receiving scalp acupuncture, general acupuncture, and Western medicine showed a significantly greater improvement in UPDRS scores as compared with the Western medicine-only group (MD 16.56; 95% CI: 14.53–18.59; p < 0.00001, I² = 87%).

For the assessment of RoB, in random sequence generation, four studies were judged as “Low,” two studies [22,24] as “Unclear,” and one study [21] as “High.” For allocation concealment, six studies were judged as “Unclear,” and one study [13] was judged as “Low.” In the blinding of participants and personnel, all seven studies were judged as “High.” In the blinding of the outcome assessment, all seven studies were judged as “High.” In the incomplete outcome data, all seven studies were judged as “Low.” In selective reporting, one study [13] was judged as “Low,” and six studies were judged as “Unclear.” In the other sources of bias, all seven studies were judged as “Low” (Fig. 3).

Figure 3. Risk of Bias (RoB) summary and graph. Review authors’ judgments on each RoB item for each included study are presented as percentages across all included studies.

Scalp acupuncture therapy is a technique that integrates acupuncture with Western medicine’s cortical function theory, stimulating specific areas of the scalp for therapeutic purposes. It began in 1969 when Jiao Shunfa, in Shanxi Province, China, observed that stimulating the scalp based on the brain’s gyri produced significant therapeutic effects on cerebrovascular diseases. Jiao’s scalp acupuncture was founded on acupuncture and cortical localization theories, and it empirically established 14 scalp stimulation areas using standard lines on the scalp [26]. Standard scalp acupuncture, approved by the World Health Organization International Standard Acupuncture Nomenclature Committee in November 1989, involves inserting the needles into the corresponding areas of the scalp to enhance the motor and sensory functions [27].

A key observation from the study results is the importance of considering both the methods and mechanisms of scalp acupuncture in treating PD. Most studies employed Jiao’s scalp acupuncture, targeting the “Chorea and Tremor Control Area” and “Motor Area,” along with the standard scalp acupuncture points “MS6,” “MS8,” and “MS14.” These areas are of particular anatomical and physiological significance.

Jiao’s scalp acupuncture’s “Chorea and Tremor Control Area” is situated at the front of the precentral gyrus in the frontal lobe, which is closely linked to the Motor Area of the cerebral cortex. Recent functional magnetic resonance imaging (fMRI) studies have revealed that this region is part of the cerebellar-thalamic-cortical circuit, playing a critical role in controlling tremor symptoms in PD patients. By modulating the activation patterns of the motor cortex, this area helps to improve the motor function and enhance the individual’s abilities to perform activities of daily living. Furthermore, this area has been shown to play a role not only in simple motor execution but also in the cognitive control of movement, such as motor planning and learning. These findings reinforce the potential of Jiao’s scalp acupuncture’s “Chorea and Tremor Control Area” to improve both motor and cognitive functions in PD patients [28].

The “Motor Area” is situated in the anterior central convolution of the cerebral cortex in the frontal lobe, which is closely associated with the motor cortex. This region has been widely utilized in the rehabilitation of patients with various types of paralysis, and fMRI studies have confirmed its efficacy in regulating motor control. Moreover, previous studies have shown that this area is closely linked to the brain activation responses seen in motor dysfunction in stroke patients. These findings further underscore the critical role of the “Motor Area” in the recovery and regulation of motor function [29].

According to Zhao et al. [30], the “Chorea and Tremor Control Area” and “Motor Area,” located in the frontal, temporal, and occipital lobes, directly activate and modulate the specific functional areas of the cerebral cortex. This effect not only is merely localized but also shows extensive therapeutic effects across various motor disorders. This indicates that scalp acupuncture exerts a complex influence on multiple brain regions, leading to improvements in motor function.

In standard scalp acupuncture, “MS6” (the posterior oblique parietal–temporal line) corresponds to the “Precentral Gyrus” [31], which is linked to the primary motor cortex responsible for motor symptoms in PD. “MS8” (lateral line I of the vertex) is associated with the lumbar, leg, and foot regions and is used to treat conditions, such as paralysis, numbness, and pain. “MS14” (the lower lateral line of the occipital scalp) relates to the Balance Area and is utilized in the treatment of balance disorders, which are frequent clinical motor dysfunctions seen in PD [32].

In summary, Jiao’s scalp acupuncture’s “Chorea and Tremor Control Area” and “Motor Area,” as well as the standard scalp acupuncture points “MS6,” “MS8,” and “MS14,” correspond to cerebral regions closely linked to PD. These areas are involved in motor control, tremor alleviation, and balance regulation, which are the central symptoms of PD. fMRI studies have demonstrated that the stimulation of these areas activates and modulates specific functional regions of the cerebral cortex. The treatment areas identified in this study could serve as valuable targets for future high-quality clinical research. The common patterns in the treatment methods identified in this study may serve as practical guidelines for clinical application. A standardized protocol could include the use of needles with a diameter of 0.30–0.35 mm and a length of 40 mm, inserted at a 30° angle, with high-frequency manipulation of 160–200 rotations per minute, and a retention time of 30 minutes. When electroacupuncture is employed, low-frequency stimulation (2–25 Hz) is recommended. Notably, the use of anatomical landmarks for determining the insertion depth appears to facilitate more precise and safe needle application.

The present meta-analysis demonstrated that combining scalp acupuncture with Western medicine resulted in therapeutic benefits on the UPDRS as compared with treatment with Western medicine alone (MD 7.61; 95% CI: 6.69–8.53; p < 0.00001, I² = 98.9%). However, the subgroup analysis showed differences in treatment efficacy between the group receiving both scalp acupuncture and general acupuncture and the group receiving scalp acupuncture alone. It is important to consider that the scalp acupuncture-only group underwent treatment for approximately 1 month, whereas the group receiving both scalp acupuncture and general acupuncture underwent treatment for 2–3 months. This indicates a potential difference in the treatment dosage, which must be accounted for. Going forward, high-quality clinical research should continue to investigate the optimal form and dosage to ensure efficient and effective acupuncture treatments.

In the data analysis, it was identified that Liu et al.’s study [18] introduced heterogeneity into the research. Upon reviewing the data, it was noted that the pre-treatment UPDRS scores in Liu et al.’s study [18] (88.72 and 87.86 for the treatment and control groups, respectively) were markedly higher than the averages from the other two studies (52.83 and 51.43 for the treatment and control groups, respectively). This disparity is likely responsible for the heterogeneity observed in the quantitative evaluation of the effect size. Given that UPDRS scores are indicative of PD severity [33], it is plausible that the participants in Liu et al.’s study [18] had more advanced PD symptoms as compared to those in the other studies. Shulman et al. [34] has reported that a UPDRS total score of 52, compared with 88, reflects a clinically significant difference in disease severity. This difference corresponds to approximately a 40–50% disparity on the Schwab and England Activities of Daily Living Scale and an approximate difference of 1.5 to 2.0 stages on the Hoehn and Yahr scale. Moreover, this 36-point difference exceeds more than twice the “large clinically important difference” of 17.1 points as defined by the study. This suggests that a total UPDRS score of 52, as compared to 88, markedly reflects different stages of PD progression and substantial differences in daily living capabilities [34]. Despite the treatment duration and methods being similar across the studies, Liu et al.’s study [18] demonstrated a greater treatment effect. This result warrants further confirmation through additional research in the future.

The limitations of the present study should be interpreted within the context of its primary objective, i.e., establishing standardized clinical guidelines for scalp acupuncture treatment in patients with PD. Although our meta-analysis demonstrated significant therapeutic benefits when combining scalp acupuncture with Western medicine, several methodological limitations warrant further consideration. Most notably, the predominance of Chinese studies and the limited number of participants (15 studies with 991 total participants) restrict the generalizability of our findings. The use of the total UPDRS score as the sole evaluation metric limited our ability to assess scalp acupuncture’s differential effects on various motor and non-motor symptoms of PD [34]. Additionally, most studies evaluated only the short-term effects within 3 months, which, as Maetzler et al. [35] noted, inadequately addresses PD’s progressive nature. Although Yeo et al. [36] demonstrated that GB34 stimulation activates neural responses in the PD-related brain regions, providing scientific evidence for combined scalp and body acupuncture therapies, the diversity in treatment protocols made it challenging to definitively evaluate this integrative approach.

However, these limitations should be reinterpreted in light of the study’s fundamental purpose. Despite the widespread clinical application of scalp acupuncture, practitioners lack standardized guidelines and scientific evidence for practical implementation. Our study aimed to move beyond mere efficacy verification to establish concrete, standardized scalp acupuncture protocols for clinical practice. The consistent patterns observed across the analyzed studies in terms of needle specifications, insertion methods, and stimulation areas serve to bridge this critical gap. Unlike previous studies that focused primarily on proving the treatment efficacy, our research provides practitioners with specific technical guidelines. For instance, we recommend the use of needles of 0.30–0.35 mm × 40 mm specifications, inserted at a 30° angle, with high-frequency (160–200 rotations per minute) and low-frequency (2–25 Hz) manipulation of electroacupuncture when applicable. Our meta-analysis confirmed the significant therapeutic benefits of combining scalp acupuncture with conventional medication use, supported by the neurological mechanisms identified through the fMRI studies. This enables a differentiated clinical approach based on disease progression and symptom characteristics, focusing on the “Chorea and Tremor Control Area” for patients with predominant motor symptoms in the early stages, while considering a comprehensive approach combining the “Motor Area” with body acupuncture for advanced cases.

Future research should focus on large-scale multicenter trials using these standardized protocols, with extended follow-up periods and more comprehensive evaluation metrics. Despite the abovementioned limitations, the present study contributes significantly to the field by providing practical guidelines for clinicians in implementing scalp acupuncture as PD treatment, thereby establishing a foundation for its broader clinical application.

A systematic review and meta-analysis were conducted to assess the efficacy of scalp acupuncture in treating patients with PD. Our study results showed significant improvements in the UPDRS scores in the group receiving a combination of scalp acupuncture and Western medicine. However, due to the limited number of studies included, it a definitive conclusion on the effect of acupuncture in the actual clinical field could not be made. More high-quality RCT studies are needed to widely evaluate the efficacy of scalp acupuncture treatment for PD.

Conceptualization: JO, JUK. Data curation: JO. Formal analysis: JO, JK, JL. Funding acquisition: JUK. Investigation: JK, JL. Methodology: THY, BYS. Project administration: THY, BYS. Resources: JK, JL. Software: YC. Supervision: THY, YC, JUK. Validation: BYS, JUK. Visualization: JO, YC. Writing – original draft: JO. Writing – review & editing: YC, JUK.

The authors have no conflicts of interest to declare.

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2021R1A2C1012846).

This research did not involve any human or animal experiment.