Treatment of Frey Syndrome with Botulinum Toxin-A: A Practical Approach from Minor's Test to Injection

Introduction

Frey's syndrome, described by Lucy Frey in 1923, is a unique condition characterized by sweating, flushing, and reddening as a direct response to mastication. This phenomenon results from the aberrant regeneration of postganglionic parasympathetic neurons originating from the auriculotemporal nerve and the subsequent acetylcholine secretion induced by masticatory stimuli. Although rare, this syndrome can have multiple underlying causes and is frequently observed, occurring in up to 65% of cases following lateral parotid resections. Additionally, it can less commonly manifest after neck dissection, facelift procedures, or be associated with diabetes mellitus.

Method

This article outlines a comprehensive diagnostic algorithm for Frey's syndrome, which includes the utilization of the Minor-Starch-Iodine Test. This test is a key component in diagnosing the syndrome and is discussed in detail, providing insights into its procedure and interpretation. Additionally, the gold standard of treatment for established Frey's syndrome, botulinum toxin A, is thoroughly described, including its mechanism of action, administration, and potential side effects.

Discussion

Finally, the article underscores the need for further research to enhance our understanding of Frey's syndrome, leading to better diagnostic methods and more tailored treatment options for patients.

Factors influencing Frey syndrome after parotidectomy with acellular dermal matrix

BACKGROUND

Frey syndrome, also known as ototemporal nerve syndrome or gustatory sweating syndrome, is one of the most common complications of parotid gland surgery. This condition is characterized by abnormal sensations in the facial skin accompanied by episodes of flushing and sweating triggered by cognitive processes, visual stimuli, or eating.

AIM

To investigate the preventive effect of acellular dermal matrix (ADM) on Frey syndrome after parotid tumor resection and analyzed the effects of Frey syndrome across various surgical methods and other factors involved in parotid tumor resection.

METHODS

Retrospective data from 82 patients were analyzed to assess the correlation between sex, age, resection sample size, operation time, operation mode, ADM usage, and occurrence of postoperative Frey syndrome.

RESULTS

Among the 82 patients, the incidence of Frey syndrome was 56.1%. There were no significant differences in sex, age, or operation time between the two groups (P > 0.05). However, there was a significant difference between ADM implantation and occurrence of Frey syndrome (P < 0.05). ADM application could reduce the variation in the incidence of Frey syndrome across different operation modes.

CONCLUSION

ADM can effectively prevent Frey syndrome and delay its onset.

An Extremely Delayed Onset of Frey Syndrome: A Case Report and Literature Review

We report the case of an 80-year-old man with Frey syndrome that developed 30 years postoperatively, which is an exceptionally long period before its occurrence. Sweating and flushing occurred on only the side of his face where the surgery was performed, and he had no other causative abnormalities. Following treatment with botulinum toxin, the patient's symptoms resolved. Extremely early- and late-onset cases do not fit the conventional paradigm of this pathology. Various surgical methods to prevent this syndrome have been explored, but complete prevention has not yet been achieved. These findings suggest that the underlying pathophysiology of Frey's syndrome may be more complex than previously recognized.

Frey syndrome after conservative parotidectomy: Importance of closing the remnant parotid parenchyma

BACKGROUND

Frey syndrome (FS) is a typical late complication following parotidectomy. Parotid surgery without proper coverage or reconstruction of exposed parotid parenchyma may contribute to the development of FS. Therefore, this study compared the closure versus the non-closure of exposed parotid parenchyma in the occurrence of FS.

METHODS

This study included 195 patients with parotid lesions who underwent partial or superficial parotidectomy plus closure or non-closure of exposed parotid parenchyma, both with the application of fibrin glue. Two surgical methods of closure and non-closure were allocated to patients without randomization and blinding processes. The primary outcome was FS, and the second outcome was other complication rates.

RESULTS

The closure and non-closure of exposed parotid parenchyma were performed in 102 and 93 patients, respectively. Early postoperative complications occurred with temporary events: transient facial weakness, 32 (16.4%); hematoma, 13 (6.7%); and wound infection, 2 (1.0%), without statistical difference between the two groups (P > 0.1). However, sialocele occurred in the non-closure group (n = 19) more than in the closure group (n = 7) (P = 0.005). In the first postoperative year, decreased sensation and local pain were found in 16 patients (8.2%) and 9 patients (4.6%), respectively, with no statistical difference between the two groups (P > 0.1). FS was found more in the non-closure group (n = 19, 20.4%) than in the closure group (n = 4, 3.9%) (P < 0.001).

CONCLUSION

The closure of exposed parotid parenchyma and covering fascia is preferred over the non-closure to prevent FS.

The Minor's test in Frey syndrome treated with botulinum toxin: Methodology and efficacy

In this paper, we aimed at methodologically presenting a video-case of Frey Syndrome occurred after parotidectomy, assessed by means of Minor's Test and treated with intradermic botulinum toxin A (BoNT-A) injection. Although largely described in the literature, a detailed explanation of both the procedures has not been previously elucidated. In a more original approach, we also highlighted the role of the Minor's test in identifying the most affected skin areas and new insight on the patient-tailored approach provided by multiple injections of botulinum toxin. Six months after the procedure, the patient's symptoms were resolved, and no evident signs of Frey syndrome were detectable through the Minor's test.

The incidence of Frey syndrome and treatment with botulinum toxin in the Central Denmark Region

Objectives

Frey syndrome (FS) is a common complication to large salivary glands surgery. This study primarily aims to describe the incidence of FS among parotid surgery patients in the Central Denmark Region. The secondary aim is to describe predisposing characteristics to syndrome development and the effect of treatment with botulinum toxin (Botox) injection.

Methods

This is a retrospective qualitative study spanning the years 2015-2020. Data on patients diagnosed with FS after parotid surgery with symptoms severe enough to require Botox was extracted from electronic patient records. Incidence of FS development was calculated using data from all parotid gland surgeries in the same period and region.

Results

The incidence of treatment-requiring FS was 2.6% (20/775), with an annual incidence ranging from 0.8% (1/125) in 2017 to 4.5% (5/112) in 2016. Difference in FS development for men and women was not statistically significant (p = .07), although it was significantly more common after total parotidectomy compared to superficial resection (p = .003), and after malignant compared to benign diagnosis (p = .01). Complications in the postoperative period arose for 30% of FS patients. Repeated treatment with Botox was necessary after 6-12 months and at a median interval of 11 months. Forty-five percent of patients received only one injection. The average dose per injection was 48.3 IU.

Conclusion

This study revealed a rather low incidence of FS in the Central Denmark Region compared to current international literature. Total parotidectomy and malignant diagnosis predisposed to syndrome development. Botox injection had a wide-ranging effective duration but typically lasted for around 1 year.

Level of evidence

Level IV.

Auriculotemporal Frey syndrome not associated with surgery or diabetes: systematic review

Patients who undergo salivary gland, neck, or facelift surgery or suffer from diabetes mellitus often develop Frey syndrome (also known as auriculotemporal syndrome or gustatory sweating). Frey syndrome has been occasionally reported to occur in subjects without history of surgery or diabetes but this variant of Frey syndrome has not been systematically investigated. We searched for original articles of Frey syndrome unrelated to surgery or diabetes without date and language restriction. Article selection and data extraction were performed in duplicate. Our systematic review included 76 reports describing 121 individual cases (67 males and 54 females) of Frey syndrome not associated with surgery or diabetes. The age at onset of symptoms was ≤ 18 years in 113 (93%) cases. The time to diagnosis was 12 months or more in 55 (45%) cases. On the other hand, an allergy evaluation was performed in half of the cases. A possible cause for Frey syndrome was detected in 85 (70%) cases, most frequently history of forceps birth (N = 63; 52%). The majority of the remaining 22 cases occurred after a blunt face trauma, following an auriculotemporal nerve neuritis or in association with a neurocutaneous syndrome. The cause underlying Frey syndrome was unknown in 36 cases.   Conclusion: Frey syndrome not associated with surgery or diabetes almost exclusively affects subjects in pediatric age and is uncommon and underrecognized. Most cases occur after forceps birth. There is a need to expand awareness of this pseudo-allergic reaction among pediatricians and allergists. What is Known: • Pre-auricular reddening, sweating, and warmth in response to mastication or a salivary stimulus characterize Frey syndrome. • It usually occurs after salivary gland surgery and in diabetes. What is New: • In children, Frey syndrome is rare, and most cases occur after a forceps-assisted birth. • In childhood, this condition is often erroneously attributed to food allergy.

[Complications in the surgery of the parotid salivary glands. Causes, mechanisms of development, methods of prevention]

Operations for neoplasms of the parotid salivary gland require from the surgeon a deep knowledge of the anatomical and topographic features of this area and technical skill, which puts it in a number of «jewelry» operations that require patience and concentration. The review is devoted to the topic of specific postoperative complications after parotidectomy or subtotal resection of the gland. These include relapses of tumors, paralysis or paresis of facial muscles, Frey syndrome, salivary fistulas or sialocele, violation of skin sensitivity, soft tissue deformity. The review presents the frequency and causes of complications, mechanisms of their development, methods of prevention and elimination.

Soft Tissue Reconstruction of Parotidectomy Defect

This article provides a review of soft tissue reconstructive options for the parotidectomy defect, including skin incision, primary closure, acellular dermis, autologous fat transfer, local and regional flaps, and free tissue transfer. The authors discuss considerations for volume enhancement, skin coverage, prevention of Frey syndrome, tumor surveillance, and potential complications.

Fat transfer after parotidectomy: fat resorption rates, aesthetic and functional outcomes of en-bloc fat graft versus lipofilling technique

PURPOSE

Reconstruction of parotidectomy involves the correction of facial contour abnormalities and prevention from Frey Syndrome. Reconstruction of parotidectomy field with autologous fat has not been popular among head and neck surgeons due to unclear predictability of fat resorption rates. The aim of this paper is to compare the fat resorption rates between different fat transfer techniques using radiologic measurements and reviewing the aesthetic and functional outcomes.

METHODS

We retrospectively reviewed medical records of patients, who underwent parotidectomy in Hacettepe University Hospital between 2015 and 2018. The aesthetic and functional outcomes of en-bloc fat graft and lipofilling techniques were compared among themselves, as well as with patients who had no reconstruction, using objective parameters. Fat resorption rates were compared using calculation of fat volumes obtained by MRI scans, 1 year after surgery.

RESULTS

Among 77 patients, 26 underwent reconstruction with en-bloc fat graft (P-EBFG); 21 patients reconstruction with lipofilling technique (P-LFT), whereas 30 patients had no reconstruction of parotidectomy field (P-NR). In three groups, there was no statistically significant difference in mean resected parotid tissue volumes (mean 18 ± 10.8 cm³, p = 0.754). We found a significant difference in decreased presence of Frey Syndrome and increased satisfation rates of cosmetic appearance in P-EBFG and P-LFT, in comparison to P-NR (p < 0.001). There was no significant difference in fat resorption rates between P-EBFG (50.75 + 21.20%) and P-LFT (48.59 + 17.93%) (p = 0.771).

CONCLUSION

Both en-bloc fat graft and lipofilling techniques have been found to be safe and to have similar fat resorption rates for reconstruction after parotidectomy.

What is the best method for prevention of postparotidectomy Frey syndrome? Network meta-analysis

BACKGROUND

Prevention of Frey syndrome (FS) after parotidectomy using an interposition barrier has long been gaining a wide popularity; however, there is no clear evidence regarding which preventive technique is more effective. The aim of this network meta-analysis (NMA) is to answer the question: What is the best method for prevention of FS after parotidectomy?

METHODS

A comprehensive search of the PubMed, Embase, SCOPUS, and Cochrane library was conducted to identify the eligible studies. The outcome was the incidence of subjective Frey syndrome (SFS) and objective Frey syndrome (OFS). The Bayesian NMA accompanied with a random effects model and 95% credible intervals (CrIs) were calculated using GeMTC R package.

RESULTS

Thirty-four studies (n = 2987 patients) with five interventions, namely Alloderm (ADM), temporoparietal fascia (TPF), sternocleidomastoid muscle (SCM), superficial musculoaponeurotic system (SMAS), and free fat graft (FFG), were compared together and with no interposition barrier (NB). The results of NMA showed a statistically significant reduction in both SFS and OFS when ADM, TPF, SMAS, FFG, and SCM were compared with NB. No statistical differences were observed when comparing ADM, SCM, SMAS, FFG, and TPF. TPF ranked the best of all treatments (59.4%) and was associated with the least incidence of SFS; whereas ADM ranked the best of all treatments (61.1%) and was associated with the least incidence of OFS.

CONCLUSIONS

All interventions (TPF flap, ADM, FFG, SMAS, and SCM) were associated with a significant reduction in the incidence of FS when compared with NB. TPF and ADM showed the best outcome with the least incidence of SFS and OFS, respectively.

Not only gustatory sweating and flushing: Signs and symptoms associated to the Frey syndrome and the role of botulinum toxin A therapy

BACKGROUND

The classic symptoms of Frey syndrome are gustatory sweating and flushing. Aims of the study were to describe prevalenceand severity of typical and atypical presentations of the disorder and to assess the effects of botulinum neurotoxin A (BoNT-A) therapy in patients with Frey syndrome after parotidectomy.

METHODS

In this prospective, observational study on 18 patients, we assessed symptom severity before therapy, after 15 days, 1, 3 and 6 months' follow-up with the sweating-flushing-itch-paresthesia-pain (SFIPP) Frey scale specifically designed by the authors themselves for this study.

RESULTS

Before BoNT-A injection, all patients (100%) complained gustatory sweating, 80% paresthesia, 77% gustatory flushing, 60% pain and 60% gustatory itch. The SFIPP-Frey overall score and the symptom-specific ones decreased significantly at each post-therapy control.

CONCLUSIONS

The prevalence of "unusual" manifestations is not negligible. BoNT-A improves symptoms severity. The SFIPP-Frey scale may be useful to assess symptoms and to monitor post-therapy outcomes.

Reconstruction using sternocleidomastoid muscle flap versus posterior belly of digastric muscle flap compared with no reconstruction following superficial parotidectomy

INTRODUCTION

The most common complications following superficial parotidectomy are formation of contour deformity and development of Frey's syndrome. Multiple modalities are being used to prevent these complications. We hereby intend to compare the reconstruction modalities (sternocleidomastoid (SCM) muscle flap, posterior belly of digastric (PBD) muscle flap) with) No reconstruction (NR) following superficial parotidectomy.

MATERIALS AND METHODS

A comparative study was designed which included 15 patients requiring parotidectomy. These patients were divided into three groups viz. SCM, PBD, and NR. The functional outcome (facial nerve involvement, Frey syndrome, ear lobule sensation, neck movements) and the esthetic results were evaluated subjectively and objectively. The outcomes were statistically evaluated using chi-square test and ANOVA test.

RESULTS

Facial nerve palsy occurred in 2 cases in each group, and all of them recovered completely within 6 months. The Minor starch iodine test was positive in 1 patient in the SCM group, in 2 patients in the PBD group, and in 4 patients in the NR group; only 1 patient of PBD group and 3 patients of NR group complained of gustatory sweating. Neck movements were unaffected in the PBD and NR groups; however, 1 patient complained of mild discomfort and pain during neck movements in the SCM group.

CONCLUSION

Primary closure showed the worst results regarding cosmetic deformity. Hence, it is recommended to mandatorily reconstruct the defect. However, the sternocleidomastoid muscle flap is a better cosmetic option compared with posterior belly of digastric muscle flap. In cases with larger defects, a combination of both the flaps can be used. SCM flap also lowers the incidence of Frey syndrome objectively and subjectively with no reported hazard of the spinal accessory nerve and mildly affected neck movements.

Use of Botulinum Toxin in Orofacial Clinical Practice

Introduction: Botulinum neurotoxin (BoNT) is a potent biological toxin and powerful therapeutic tool for a growing number of clinical orofacial applications. BoNT relaxes striated muscle by inhibiting acetylcholine’s release from presynaptic nerve terminals, blocking the neuromuscular junction. It also has an antinociceptive effect on sensory nerve endings, where BoNT and acetylcholine are transported axonally to the central nervous system. In dentistry, controlled clinical trials have demonstrated BoNT’s efficiency in pathologies such as bruxism, facial paralysis, temporomandibular joint (TMJ) disorders, neuropathic pain, sialorrhea, dystonia and more. Aim: This study’s aim was to conduct a systematic literature review to assess the most recent high-level clinical evidence for BoNT’s efficacy and for various protocols (the toxin used, dilution, dosage and infiltration sites) used in several orofacial pathologies. Materials and methods: We systematically searched the MedLine database for research papers published from 2014 to 2019 with randomly allocated studies on humans. The search included the following pathologies: bruxism, dislocation of the TMJ, orofacial dystonia, myofascial pain, salivary gland disease, orofacial spasm, facial paralysis, sialorrhea, Frey syndrome and trigeminal neuralgia. Results: We found 228 articles, of which only 20 met the inclusion criteria: bruxism (four articles), orofacial dystonia (two articles), myofascial pain (one article), salivary gland disease (one article), orofacial spasm (two articles), facial paralysis (three articles), sialorrhea (four articles) or trigeminal neuralgia (three articles). Discussion: The clinical trials assessed showed variations in the dosage, application sites and musculature treated. Thus, applying BoNT can reduce symptoms related to motor muscular activity in the studied pathologies efficiently enough to satisfy patients. We did not identify the onset of any important side effects in the literature reviewed. We conclude that treatment with BoNT seems a safe and effective treatment for the reviewed pathologies.

Intra-auricular modification of facelift incision decreased the risk of Frey syndrome

Objective

Frey syndrome is a complication followed by parotidectomy which caused gustatory sweating and facial flush. There were several methods for the prevention of Frey syndrome, but most of them had no obvious effects. In this study, we compare the intra-auricular modification of facelift incision with the traditional lazy-S incision to see if it can decrease the risk of Frey syndrome.

Materials and Methods

This is a retrospective study. From 2003 to 2009, a total of 61 patients with benign parotid tumor who received parotidectomy at Hualien Tzu Chi Hospital and were followed at outpatient department for at least 5 years were enrolled. Patients were divided into two groups according to the type of incisions during operation: (1) Group M: intra-auricular modification of facelift incision or (2) Group S: traditional lazy-S incision. All patients received the partial thickness sternocleidomastoid muscle flap. Clinical data including age, gender, pathologic result, presentation of Frey syndrome, size of tumor, length of operation, blood loss from surgery, length of placement of drain, total amount of drainage, and length of stay were collected and analyzed.

Results

Sixty-one patients were enrolled. Eighteen patients were in Group M and forty-three were in Group S. There was no significant difference of age, gender, and size of tumor between the two groups. The pathologic results included parotitis, pleomorphic adenoma, Warthin's tumor, and others. No significant difference of pathologic results, blood loss from surgery, length of placement of drain, total amount of drainage, and length of stay between two groups was obtained. The length of operation was longer in Group M (P = 0.001) and the incidence of Frey syndrome was lower in Group M than Group S (P < 0.05).

Conclusions

The use of intra-auricular modification of facelift incision can decrease the incidence of Frey syndrome.

[Analysis of predictors for Frey syndrome after parotidectomy]

Objective:To analysis the data of the patients with parotid tumors, clarify the contributing factors of Frey syndrome, and to evaluate the role of soft tissues membrane SIS in prevention of Frey syndrome after parotidectomy. Method:The data of 95 patients who suffered from parotid tumors and underwent parotidectomy were included in this study. The relationship between the patients' age, sex, tumor location ,tumor size, disease pathology, type of resection, SIS application and the incidence of Frey syndrome were statistically analyzed . Result:The incidence of Frey syndrome after parotidectomy for 95 patients was 25.3%. Age, sex, tumor location and size, disease pathology, type of resection did not appear to be associated with development of Frey syndrome（P>0.05）. SIS application was the only statistically significant factor（P<0.01）, and SIS could prevent Frey syndrome after parotidectomy. Conclusion:Frey syndrome is one of the common complicationsafter parotidectomy. Implantation of SIS is an effective method for prevention of Frey syndrome after parotidectomy.

Use of botulinum toxin in Frey's syndrome

Frey's syndrome is the most common adverse event after parotidectomy, and usually, it appears after 6 months. In our case, symptoms appear 20 years from surgery, an uncommon condition. Intralesional botulinum toxin gives excellent results in therapy, regardless of the time elapsed between surgery and the first treatment.

Use of the SMAS flap for reconstruction of the parotid lodge

The purpose of our study was to evaluate the benefits of the SMAS flap in patients with benign tumours of the parotid gland treated by superficial parotidectomy. We carried out a retrospective chart review on 123 patients suffering from benign tumours of the parotid gland admitted to our Institution between March 1997 and March 2010. A superficial parotidectomy was performed in all the cases reported. Our sample was divided in two groups basing SMAS flap reconstruction done (Group 2) or not (Group 1) after superficial parotidectomy. Reconstruction using SMAS flap was accomplished in 64 patients. Chi-square test was used to assess statistical difference between the two groups. The level of statistical significance was P < 0.05. No significant differences concerning hematoma, wound infection and facial paralysis were observed between the first and second group (3.38 vs 1.56% [P > 0.05], 8.47% vs 4.68% [P > 0.05], 5.08% vs 0.00% [P > 0.05]). Transient facial nerve weakness, fistula, dip skin and Frey's syndrome were significantly more frequent without SMAS flap reconstruction (10.16% vs 3.125% [P < 0.05], 13.55% vs 3.125% [P < 0.05], 13.55% vs 3.125% [P < 0.05], 20.33% vs 0% [P < 0.05] respectively). The use of the SMAS flap is able to reduce the cosmetic and functional complications that occur after the removal of a benign tumour of the parotid through the superficial parotidectomy technique, above all, it reduces the occurrence of Frey's syndrome.

Auriculotemporal Syndrome (Frey Syndrome)

Frey syndrome is a common sequela of parotidectomy, and although it is not frequently manifested clinically, it can cause significant morbidity for those affected. Frey syndrome results from synkinetic autonomic reinnervation by transected postganglionic parasympathetic nerve fiber within the parotid gland to the overlying sweat glands of the skin. Many surgical techniques have been proposed to prevent the development of Frey syndrome. For those who develop clinical symptoms of Frey syndrome, objective testing can be performed with a Minor starch-iodine test. Some of the current methods to prevent and treat symptomatic Frey syndrome are reviewed.

Effectiveness of platysma muscle flap in preventing Frey syndrome and depressive deformities after parotidectomy

BACKGROUND

Frey syndrome (FS) or depressive deformity (DD) occurring after parotidectomy significantly reduces a patient's quality of life. However, there seems to be no effective treatment strategy against these complications. In this study, we report our experience of using platysma muscle flap (PMF) to prevent the development of FS and DD after parotidectomy, and evaluate its effect subjectively and objectively.

METHODS

Superficial parotidectomy was performed for eight cases of parotid gland tumor, and a PMF was transferred to cover the site. The incidence of FS and DD were evaluated subjectively, using a questionnaire to the patients and board-certified reconstructive surgeons, and objectively, using Minor's starch-iodine test.

RESULTS

In seven patients, the defect could be completely covered with PMF, and none of them developed FS or obvious DD. However, in one patient, the defect could be only partially covered, and the patient developed complications in the exact site that the flap did not cover. Overall scores from the questionnaire were high in relation to both cosmetic and functional perspectives from most of the patients and all the surgeons. No patients had major postoperative complications requiring revision.

CONCLUSIONS

PMF can be useful to cover the defect and prevent complications after parotidectomy. PMF is relatively easy to perform with fewer complications; however, a complete coverage of the defect should be ensured to obtain optimal results.

The sternocleidomastoid muscle flap for the prevention of Frey syndrome and cosmetic deformity following parotidectomy: A systematic review and meta-analysis

Approximately 34-86% of neoplasms of the salivary glands are located in the parotid gland and parotidectomy is the first-line treatment for parotid gland tumors. Frey syndrome and cosmetic deformity are common complications experienced by patients following parotidectomy and the sternocleidomastoid muscle flap (SCMF) is used to prevent them. Numerous studies have been performed to examine the effectiveness of the SCMF for the prevention of cosmetic deformity and Frey syndrome, however, they provide contradictory results and possess small sample sizes with consequently low statistical power. In order to evaluate the effectiveness of the SCMF for the prevention of Frey syndrome and cosmetic deformity following parotidectomy, we performed a systematic review and meta-analysis based on published randomized controlled trials (RCTs), which were identified using PubMed and CNKI databases, and references of studies up to August 2012 were included. Using these criteria, we yielded 11 RCTs. Following an independent assessment of the methodological quality of these studies and the extraction of data, a systematic review and meta-analysis was conducted. The results of the meta-analysis demonstrated that there was a significant trend towards a lower risk of objective incidence [67%; risk ratio (RR), 0.33; 95% confidence interval (CI), 0.16-0.67; P<0.01] and subjective incidence (66%; RR, 0.34; 95% CI, 0.16-0.75; P= 0.01) of Frey syndrome in the SCMF group. The sensitivity analysis also indicated that this result was significant. Due to the considerable variation between the included studies, a meta-analysis was not applicable to assess cosmetic deformity. Two RCTs demonstrated that the difference between the SCMF and no SCMF group was not statistically significant, while the other seven RCTs detected a statistically significant difference between the two groups. Publication bias was detected. In conclusion, based on currently available evidence, the use of the SCMF is benefical for the prevention of Frey syndrome, however, whether it is also benefical for cosmetic deformity remains inconclusive.