Management of Meige’s syndrome by facial and trigeminal nerve combing followed by transplantation of autologous adipose-derived mesenchymal stem cells: a prospective nonrandomized controlled study :Jin Zhu, Bei-Yao Gao, Xin Zhang, Cheng-Cheng Sun, Hua Zhao, Ming Chen, Yan Yuan, Ping Zhou, Yan-Li Luo, Dongsheng Xu, Shi-Ting Li, Brain Network and Modulation

RESEARCH ARTICLE
Year : 2022 | Volume : 1 | Issue : 1 | Page : 20--30

Management of Meige’s syndrome by facial and trigeminal nerve combing followed by transplantation of autologous adipose-derived mesenchymal stem cells: a prospective nonrandomized controlled study

Jin Zhu¹, Bei-Yao Gao², Xin Zhang¹, Cheng-Cheng Sun³, Hua Zhao¹, Ming Chen¹, Yan Yuan¹, Ping Zhou¹, Yan-Li Luo⁴, Dongsheng Xu⁵, Shi-Ting Li¹,
¹ Department of Neurosurgery, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
² Department of Rehabilitation Medicine, China-Japan Friendship Hospital, Beijing, China
³ Tongji University School of Medicine, Shanghai, China
⁴ Department of Psychological Medicine, Renji Hospital Affiliated to Shanghai Jiaotong University School of Medicine, Shanghai, China
⁵ School of Rehabilitation Science; Institute of Rehabilitation Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, China

Correspondence Address:
Dongsheng Xu
School of Rehabilitation Science; Institute of Rehabilitation Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai
China
Shi-Ting Li
Department of Neurosurgery, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai
China

Abstract

Increasing attention has recently been focused on reducing abnormal neuroexcitability in patients with Meige’s syndrome using nerve combing surgery. However, nerve injury caused by nerve combing is of critical concern. Animal studies have shown that stem cells can repair cranial nerves; autologous adipose-derived mesenchymal stem cells have been proved to be safe and effective in clinical trials. A total of 38 patients with Meige’s syndrome were enrolled in this prospective nonrandomized controlled study and divided into a non–stem cell group (n = 30) and a stem cell group (n = 8). Patients in the non-stem cell group underwent facial and trigeminal nerve combing only; patients in the stem cell group underwent adipose-derived mesenchymal stem cell implantation after facial and trigeminal nerve combing. A blepharospasm disability index score was used to evaluate effectiveness of the surgery, and a House–Brackmann grade was used to evaluate facial nerve injury. These data were recorded before the operation and at 7 days, 3 months, and 6 months after the operation. The overall improvement percentage of blepharospasm was 93% at 6-month follow-up in the non-stem cell group. A greater number of nerve combing events during the operation led to better outcomes but increased risk of facial paralysis. Patients in the stem cell group had better facial nerve function at the 6-month follow-up (House–Brackmann grade, P = 0.003) and better blepharospasm improvement at 3 and 6 months than those in the non–stem cell group (blepharospasm disability index score, P = 0.003 and P < 0.001, respectively). Cerebrospinal fluid protein analysis showed that levels of several cytokines were significantly increased after adipose-derived mesenchymal stem cell transplantation, including interleukin-6 (P < 0.01) and interferon gamma-induced protein 10 (P < 0.0001) and the growth factors insulin-like growth factor-1 (P < 0.0001), insulin-like growth factor-binding protein-1 (P < 0.0001), growth/differentiation factor-15 (P < 0.001), and angiopoietin-like 4 (P < 0.001). Facial and trigeminal nerve combing combined with adipose-derived mesenchymal stem cell transplantation is a safe and effective remedy to improve recovery from Meige’s syndrome.

How to cite this article:
Zhu J, Gao BY, Zhang X, Sun CC, Zhao H, Chen M, Yuan Y, Zhou P, Luo YL, Xu D, Li ST. Management of Meige’s syndrome by facial and trigeminal nerve combing followed by transplantation of autologous adipose-derived mesenchymal stem cells: a prospective nonrandomized controlled study.Brain Netw Modulation 2022;1:20-30

How to cite this URL:
Zhu J, Gao BY, Zhang X, Sun CC, Zhao H, Chen M, Yuan Y, Zhou P, Luo YL, Xu D, Li ST. Management of Meige’s syndrome by facial and trigeminal nerve combing followed by transplantation of autologous adipose-derived mesenchymal stem cells: a prospective nonrandomized controlled study. Brain Netw Modulation [serial online] 2022 [cited 2023 Dec 2 ];1:20-30
Available from: http://www.bnmjournal.com/text.asp?2022/1/1/20/340141

Full Text

Introduction

Meige’s syndrome, named after French neurologist Henry Meige, is a benign functional syndrome characterized by bilaterally involuntary movement of eyelids and facial muscles. The prevalence of Meige’s syndrome is approximately 100 cases per 100,000. Meige’s syndrome is currently considered an extrapyramidal disease; it commonly occurs in older female patients, and is often clinically misdiagnosed as hemifacial spasm, senile ptosis, or myasthenia gravis (Pandey and Sharma, 2017). At present, treatments that have been used include clonazepam, trihexyphenidyl, diazepam, and baclofen; botulinum toxin type A injection (Jankovic and Orman, 1987; Czyz et al., 2013); periorbital muscle resection; and deep brain stimulation (Ostrem et al., 2007; Reese et al., 2011; Hao et al., 2020); however, the effects of these nonsurgical treatments are unsatisfactory.

To our knowledge, our study is the first to involve cranial nerve surgery using facial and trigeminal nerve combing, based on the hyperexcitability of the blink-reflex circuit. Postoperatively, the symptoms of involuntary movement of facial muscles were significantly alleviated. However, some degree of facial paralysis and numbness occurred because of secondary facial nerve injuries, which seems to be the major concern for this novel surgical technique (Zhang et al., 2017).

Reducing the abnormal excitability of the cranial nerves through a surgical approach has recently received increasing attention (Zhang et al., 2017). However, nerve injury associated with surgery is of critical concern, and nerve injury recovery in previous studies was limited when treating with hormones (Adour et al., 1972; Lejeune et al., 2002).

Animal studies showed that stem cells can repair cranial nerves (Mazo et al., 2008; Shiba et al., 2016). Currently, autologous adipose-derived mesenchymal stem cells (Ad-MSCs) are becoming safe and effective cell resources for several diseases in clinical trials (Kølle et al., 2013; Wen et al., 2014). Still, this promising treatment has not yet been used for treatment of human cranial nerves. In this prospective study, we delivered Ad-MSCs directly to the facial and trigeminal nerves intraoperatively after nerve combing.

Subjects and Methods

Study design and objective

Thirty-eight patients with Meige’s syndrome who sought treatment in Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China, were enrolled in this nonrandomized controlled trial from April 2016 to April 2018. The patients were divided into two treatment groups based on their own choices after consultation with doctors. Patients in the non-stem cell group (NSC group) chose nerve combing only, while patients in the stem cell group (SC group) underwent Ad-MSC treatment as well as nerve combing. All patients were followed up for a minimum period of 6 months. The objective of this study was to evaluate the effectiveness of facial and trigeminal nerve combing and autologous Ad-MSC transplantation for the treatment of patients with Meige’s syndrome.

The study design and consent form were reviewed and approved by the Institutional Review Board of Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (approval No. XHEC-C-2016-015-2) on June 1, 2016 (Additional file 1 [SUPPORTING:1]), and registered at ClinicalTrials.gov (identifier NCT02853942) on August 3, 2016. The study was conducted in accordance with the Declaration of Helsinki. This study follows the Transparent Reporting of Evaluations with Nonrandomized Designs (TREND) statement (Additional file 2 [SUPPORTING:2]) (Des Jarlais et al., 2004).

The evaluators, monitors, and data analysts were blinded to the grouping information, whereas participants and those administering the interventions were not blinded to study condition assignments. To minimize bias, participants and investigators were unaware of assignment information until the enrollment was completed, and participants did not know the grouping information before completing treatment. Objectively identifiable metrics were used to avoid evaluation bias, and standard operating practices were used to reduce implementation bias.

Sample size calculation

After preliminary observation, it was found that the effective rate of nerve combing was 70%, and the effective rate of combination therapy was 90%. At α = 0.05 and β = 0.1, a sample size of at least 113 was needed. The natural progression of Meige’s syndrome is highly variable, as are the measures of its outcome, so we were not able to exactly match the number of patients in the two groups.

Inclusion and exclusion criteria

Participants with Meige’s syndrome were eligible if they met the following criteria: (1) met the diagnostic criteria described by Pakkenberg et al. (1987); (2) participants or their parents provided written informed consent for nerve combing; and (3) participants or their parents who accepted the Ad-MSC–transplantation therapy provided additional written informed consent. Participants were excluded if they were diagnosed with facial paralysis.

Preoperative neurophysiological evaluation

All patients underwent detailed neurophysiological assessments before the operation, including blink reflection (Berardelli et al., 1985), brain stem trigeminal evoked potentials, and spontaneous free electromyography (fEMG). For blink reflection, the patient opened their eyes slightly, and the stimulating electrodes were placed on the supraorbital notch and supraorbital foramen. The recording electrodes were placed on the lower eyelid and lateral orbital margin, respectively. The ground electrode was placed on the ear or cheek. Stimulation was performed with a square pulse at intervals of 0.1–1.0 ms, and the stimulus was gradually increased to reach a maximum of 20 mA (Nicolet® Endeavor™ CR 16 channel desktop intraoperative monitoring system, MFI Medical Equipment Inc., San Diego, CA, USA). For brain stem trigeminal evoked potential, a neurophysiological monitor (Medtronic 4 channel desktop IOM system, Medtronic, Minneapolis, MN, USA) was used to deliver a square-wave stimulation with a frequency of 10 Hz and a wave width of 0.04 ms. The filter setting was 100 Hz–2 kHz. The stimulation intensity increased from 0.1 mA to the waveform that could be Z extracted. The first branch of the trigeminal nerve was stimulated; then the needle electrode was placed at the supraorbital foramen, and the scalp was recorded from C3-FPz and C4-FPz. For fEMG, the recording electrode was placed in the orbicularis oculi muscle without stimulation, and the spontaneous free electromyography was recorded [Figure 1].{Figure 1}

Operative procedure

For the NSC group [Figure 2]A, each patient was placed in a lateral decubitus position and underwent a standard suboccipital retrosigmoid craniotomy. The dura mater was exposed inferior and posterior to the junction of the transverse and sigmoid sinuses. A curved incision was made on the dura mater, the dura was turned over and suspended toward the sigmoid sinus, the cerebellum was gently retracted, and the cerebrospinal fluid (CSF) was evacuated. The dissection of the nerve was continued until the whole intracranial segment of the VII nerve was exposed. The neurovascular relationship was carefully evaluated to identify the vessel in contact with the facial nerve. Any involved vessels were separated from the VII nerve. Meanwhile, a knife blade (Bausch & Lomb Inc., Laval, Canada) was inserted vertically into the cisternal segment of the facial nerve. The facial nerve was combed several times along the nerve fibers, until the amplitude of the fEMG decreased by 30–50% [Figure 2]B. The trigeminal nerve was subsequently combed using the same method (Additional Video 1).{Figure 2}

[MULTIMEDIA:1]

Preparation of autologous Ad-MSCs

Adipocytes were extracted from patients’ abdomens 15 days before the operation and cultured by a stem cell company (Juwei Cell Co., Ltd., Xiamen, China) (Zuk et al., 2002). After culturing for 8 days, the proliferation and morphology of Ad-MSCs were analyzed using optical microscopy (CFI60 Optical System, Nikon Corporation, Tokyo, Japan). Cell counting, flow cytometry, and bacterial endotoxin tests were conducted. When the number of Ad-MSCs reached 3 × 108, each patient was scheduled for their operation [Figure 3]A and [Figure 3]B.{Figure 3}

For the SC group, an additional step was added, following the facial and trigeminal nerve combing procedure. The cisternal segment of the facial nerve was encapsulated in Gelfoam (Pfizer, New York City, NY, USA) , and Ad-MSCs (1 × 108/mL) in 2 mL solution were injected into the cerebellopontine angle around the cisternal segment of the facial nerve [Figure 3]C. Finally, the dura mater was closed with sutures in a watertight pattern. The operation process for nerve combing and Ad-MSC transplantation is shown in Additional Video 1.

Postoperative follow-up

The blepharospasm disability index (BSDI) score (Jankovic et al., 2009) and the House–Brackmann (HB) grade (Vrabec et al., 2009) were obtained at four time points: before the operation, and 7 days, 3 months, and 6 months after the operation. The BSDI score was used to measure theimpairment of specific activities of daily living due to blepharospasm. The lower the score, the worse the quality of daily living. The HB grade was used to evaluate facial nerve injury. The HB grade divides the degree of facial paralysis into six grades from mild to severe. Grade I represent normal facial movements in all parts and grade VI represents complete facial paralysis. The workflow of this research is shown in [Figure 3]D.

Antibody arrays

We collected CSF samples from one patient in the NSC group and seven patients in the SC group during the operation and 3 days after the operation via lumbar puncture. The antibody arrays (GSH-GF-1 for growth factors, GSH-ANG-1000 for angiogenic factors, and GSH-CHE-1 for chemokines) were designed and manufactured by RayBiotech Life Inc. (Peachtree Corners, GA, USA). The antibody array experiments were performed by Wayen Biotechnology (Shanghai, China) in accordance with the established protocol. In brief, fivefold-diluted CSF was hybridized with the slides overnight at 4°C. Then, a cocktail of biotinylated antibodies was added to detect the bound cytokines. The signals were visualized using a fluorescent dye conjugated with AlexaFluor 555-conjugated anti-guinea pig IgG (5 μg/mL, Thermo Fisher Scientific, Waltham, MA, USA, Cat # A-21435, RRID: AB_2535856), detected using an Axon GenePix 4000B microarray scanner (Molecular Devices LLC, San Jose, CA, USA), and analyzed using GenePix Pro 6.0 software (Molecular Devices LLC).

Efficacy outcomes

The primary efficacy outcome was percentage improvement of the BSDI scores and HB grades from baseline to 6 months postoperation. Secondary efficacy outcomes included cytokine levels measured in the CSF during the operation and 3 days after the operation and the neurophysiological assessments of blink reflection, brain stem trigeminal evoked potentials, and spontaneous free electromyography, which were assessed before the operation, during the operation, and 7 days after the operation.

Statistical analysis

Data were analyzed using Microsoft Excel, and statistical analysis was performed using SPSS version 22 (IBM, Armonk, NY, USA). Continuous variables were presented as mean ± standard deviation (SD) or median (interquartile range), and categorical variables were presented as frequencies. We compared differences between the groups for changes from baseline for BSDI score and HB grade using the Kruskal–Wallis test. The statistical correlations between fEMG amplitude reduction rate, HB grade, BSDI score, and nerve combing times were estimated as appropriate for each variable. The statistical significance was determined by the Spearman correlation coefficient. Two-tailed P-values of less than 0.05 were considered to indicate statistical significance.

Data from the antibody arrays were acquired using the BeadArray Reader (Illumina, Inc., San Diego, CA, USA) and evaluated using the BeadStudio Application (Illumina, Inc.), developed by Genergy Bio (Shanghai, China). Gene set enrichment analysis and Gene Ontology analyses were used to detect changes in biological processes, cellular components, and molecular function. Pathway analysis was conducted based on the Kyoto Encyclopedia of Genes and Genomes database (Kanehisa and Goto, 2000; Kanehisa, 2019, 2021). Protein-protein interaction was analyzed using the STRING database (Szklarczyk et al., 2015) and Cytoscape software (Shannon et al., 2003) supported by the National Resource for Network Biology.

Results

Participants

A total of 38 cases of Meige’s syndrome were recruited. Thirty patients, consisting of 6 men and 24 women aged from 47 to 72 years (mean 60.1 ± 8.1 years), underwent facial and trigeminal nerve combing only (NSC group). Eight patients, consisting of two men and six women aged from 53 to 69 years (mean 62.1 ± 5.6 years), underwent facial and trigeminal nerve combing followed by autologous Ad-MSC transplantation (SC group).

Hyperexcitability of the blink reflex circuit in patients with Meige’s syndrome

In the blink reflex circuit, the trigeminal nerve is afferent and the facial nerve is efferent [Figure 1]A. The brain stem trigeminal evoked potential waveform was induced by low threshold stimulation (0.6 mA), which proved the hyperexcitability of the afferent pathway of the blink reflex circuit [Figure 1]B. The abnormally enhanced waveforms recorded by fEMG demonstrated the hyperexcitability of the afferent pathway of the blink reflex circuit [Figure 1]C. The blink reflex has two components: an early R1 response and a late R2 response. The R1 response is usually present ipsilateral to the side being stimulated, whereas the R2 response is typically present bilaterally [Figure 1]D.

Correlations between efficacy, facial nerve function, and number of nerve combing events

In the NSC group, the total number of facial nerve combing events ranged from 7 to 24 for each patient. One week after operation, the amplitude of fEMG decreased by 31% and 75% in patients with the least number of nerve combing events (7 events) and the most nerve combing events (21 events), respectively [Figure 2]C. In addition, Spearman correlation test analyses showed a positive correlation between the number of nerve combing events and intraoperative fEMG amplitude reduction rate (r = 0.5167, P = 0.004; [Figure 2]D) and a positive correlation between the number of nerve combing events and HB grade one week after the operation (r = 0.7594, P < 0.001; [Figure 2]E). However, a greater number of nerve combing events was associated with greater facial nerve injury. More importantly, the BSDI score decreased as nerve combing events increased (r = −0.4584, P = 0.01; [Figure 2]F), indicating that better surgical outcomes resulted from more nerve combing events.

Safety evaluation of autologous Ad-MSC transplantation

There were no significant abnormalities in CSF analysis, immune function, and biochemical parameters in all eight patients in the SC group. No severe complications, such as intracranial infection, CSF leakage, seizures, disturbance of consciousness, and coma, occurred in any patients. All patients were discharged 8 days after the operation.

Efficacy and facial nerve function after facial and trigeminal nerve combing with autologous Ad-MSC transplantation

We classified the outcomes of all 38 patients into improvement and nonimprovement based on their BSDI scores. The criterion for improvement was when the BSDI score increased by at least one point. After the operation, BSDI scores were reduced in all 38 patients; 93% of patients in the NSC group and 100% of patients in the SC group had further improvement at the 6-month follow-up visit [Figure 3]E. Patients in the SC group had a better outcome than patients in the NSC group, beginning from 3 months postoperation (P = 0.02). The SC group had less facial paralysis (P = 0.03) according to the HB grade compared with the NSC group 6-months postoperation [Table 1].{Table 1}

Comparison of proteins in CSF between preoperation and postoperation in the stem cell group

After facial and trigeminal nerve combing, we collected CSF preoperation and 3 days postoperation from eight patients in two groups (one from the NSC group and seven from the SC group), and then we analyzed the customized antibody arrays. A heatmap of 117 detected cytokines was generated to illustrate the distinguishable protein expression profiles of the samples [Figure 5]A. Interleukin-6 and interferon gamma-induced protein 10 were highly expressed in the SC group in the early stage postoperation [Figure 5]B. Preoperation and postoperation results in the SC group were further analyzed to clarify the combined influence of nerve combing and autologous Ad-MSC transplantation. Of these proteins, 28 were upregulated and 6 were downregulated [Figure 5]C. A series of pathways are involved in angiogenesis and cytokine production, including the epidermal growth factor receptor signaling pathway and the hypoxia inducible factor 1 signaling pathway [Figure 5]D and [Figure 5]E. The proteins involved in these pathways were analyzed for protein–protein interaction. Based on the log fold change and betweenness centrality index values for network nodes, interleukin-4, interleukin-6, interleukin-8, interleukin-10, interleukin-1B, transforming growth factor beta 1, and epidermal growth factor were revealed to be important upregulated hub genes. These selected protein–protein interaction hubs with novel connectivity exhibited potentially critical biological insights [Figure 5]F. A scatterplot was drawn according to the expression values of the two groups of samples. The signal values of insulin-like growth factor-1, insulin-like growth factor–binding protein-1, growth/differentiation factor-15, and angiopoietin-like 4 were significantly increased (P < 0.01, P < 0.001, P < 0.001, and P = 0.005, respectively) in CSF after autologous Ad-MSC injection compared with the values preoperation, which were consistent with each patient’s clinical response [Figure 5]G.{Figure 4}{Figure 5}

Discussion

While the pathogenesis of Meige’s syndrome is unclear (LeDoux, 2009; Pandey and Sharma, 2017), patients with Meige’s syndrome share similar clinical manifestations. They all show varying degrees of eyelid and facial muscle twitching, blinking difficulties, and frequent facial involuntary movements. In this study, we found that the brain stem trigeminal evoked potential waveform was commonly induced by lower threshold stimulation, and we observed abnormally enhanced waveforms recorded by fEMG, suggesting that abnormal hyperexcitability of the blink-reflex circuit existed in patients with Meige’s syndrome. On the basis of this observation, our team developed a new surgical approach that we termed facial and trigeminal nerve combing. In the 30 patients who underwent this procedure alone, the surgical approach not only reduced the hyperexcitability of the blink-reflex circuit but also led to better clinical outcomes than deep brain stimulation treatment, with 38% to 72% improvement after nerve combing (Ostrem et al., 2007; Reese et al., 2011).

A previous study demonstrated that although nerve combing without neurovascular decompression is a safe and effective treatment for trigeminal neuralgia, a majority of patients treated with nerve combing experienced some degree of facial numbness (Yang and Wang, 2019). Our study also found that facial muscle spasms were relieved with an increased number of nerve combing events, but the risk of facial nerve injury also increased. Thus, attenuation of the neural side effects from facial and trigeminal nerve combing becomes a critical challenge. Usually, a decrease of fEMG amplitude of 30% to 50% during the operation is an effective and safe range when combined with fEMG monitoring throughout the operation. Nonetheless, it is not easy to achieve a decrease in fEMG amplitude by nerve combing. In fact, there was greater than 50% amplitude reduction in 40% (15/38) of patients who had one more nerve combing event; these patients had varying degrees of recovery after the operation.

Autologous Ad-MSCs were accepted as relatively safe cell resources to repair tissue injury. Many studies have suggested that paracrine factors of Ad-MSCs play multiple roles in the microenvironment of the injured nerve, including promoting growth, antiapoptosis, anti-inflammation, and angiogenesis (Rodríguez Sánchez et al., 2019; Albayrak et al., 2020; Llewellyn et al., 2021). Former studies showed that Ad-MSCs exert paracrine functions by secreting higher levels of interleukin-6, interferon gamma-induced protein 10, and other cytokines and chemokines for immune regulation and tissue repair (Faulkner et al., 2013; Nepali et al., 2018). The results of the eight patients who received autologous Ad-MSC transplantation showed that the effectiveness of the operation and the recovery of facial nerve injury were both significantly improved compared with the effectiveness of the operation and the recovery of facial nerve injury in the NSC group; this suggests that facial and trigeminal nerve combing combined with Ad-MSC transplantation is a safer treatment option for Meige’s syndrome than nerve combing alone.

The antibody array showed altered expression of important cytokines and growth factors 3 days after transplantation of Ad-MSCs. Higher expression of interferon gamma-induced protein 10 and interleukin-6 in the SC group 3 days after operation probably induced earlier-stage inflammatory reactions for necrotic tissue clearance (Tilg et al., 1994; Broeren et al., 2016). Furthermore, high levels of growth factors (insulin-like growth factor-1, insulin-like growth factor-binding protein-1, growth/differentiation factor-15, and angiopoietin-like 4) suggest that stem cells might promote the nerve repair process from day 3 (Chen et al., 2006; Kempf et al., 2006; Gealekman et al., 2008). Protein-protein interactions and biological functions of the most highly expressed growth factors also indicated that inflammation and tissue repair were activated after Ad-MSC transplantation. This treatment strategy may be further optimized with a greater understanding of the mechanism.

The limitations of our study include a lack of randomized allocation of patients to the two groups, relatively small sample size, an imbalance in the number of patients between the two groups, and possible recall bias. Further laboratory and multicenter clinical investigations are required to evaluate the potential mechanisms and confirm the clinical value of combination therapy for the treatment of Meige’s syndrome.

In conclusion, our study demonstrates that facial and trigeminal nerve combing is an effective option for treatment of patients with Meige’s syndrome; combination with autologous Ad-MSC transplantation is beneficial for recovery of secondary facial injury. A randomized controlled trial with a large sample size and longer follow-up period is warranted.

Author contributions

JZ, STL, DX conceived and designed the study. All authors in Xinhua Hospital were involved in data collection. XZ did the lumbar puncture and YY was responsible for the neurophysiological monitoring. XZ, BYG, ZC analysed and interpreted the data. JZ, BYG, XZ, HZ wrote the initial draft of the report, and MC, BYG created the initial drafts of the figures and tables. All authors were involved in further development, review, and approval of the report.

Conflicts of interest

There are no conflicts of interest.

Editor note: DX is an Editorial Board member of Brain Network and Modulation. He was blinded from reviewing or making decisions on the manuscript. The article was subject to the journal’s standard procedures, with peer review handled independently of this Editorial Board member and his research group.

Availability of data and materials

All data generated or analyzed during this study are included in this published article and its supplementary information files.

Open access statement

This is an open access journal, and articles are distributed under the terms of the Creative Commons AttributionNonCommercial-ShareAlike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms.[36]

Additional files

Additional file 1: Hospital ethics approval (Chinese).

Additional file 2: TREND checklist.

Additional Video 1: Video of Trigeminal nerve and facial nerve combing operation.

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