{'fraction_non_alphanumeric': 0.03262846157842781, 'fraction_numerical': 0.02675741674027121, 'mean_word_length': 5.587268993839836, 'pattern_counts': {'":': 0, '<': 3, '<?xml version=': 0, '>': 2, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Decompression Surgery for Frontal Migraine Headache

Introduction: Migraine headache (MH) is one of the most common diseases worldwide and pharmaceutical treatment is considered the gold standard. Nevertheless, one-third of patients suffering from migraine headaches are unresponsive to medical management and meet the criteria for “refractory migraines” classification. Surgical treatment of MH might represent a supplementary alternative for this category of patients when pharmaceutical treatment does not allow for satisfactory results. The goal of this article is to provide a comprehensive review of the literature regarding surgical treatment for site I migraine management. Methods: A literature search using PubMed, Medline, Cochrane and Google Scholar database according to Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines was conducted using the following MeSH terms: “frontal neuralgia,” “frontal trigger site treatment,” “frontal migraine surgery” and “frontal headache surgery” (period: 2000 -2020; last search on 12 March 2020). Results: Eighteen studies published between 2000 and 2019, with a total of 628 patients, were considered eligible. Between 68% and 93% of patients obtained satisfactory postoperative results. Complete migraine elimination rate ranged from 28.3% to 59%, and significant improvement (>50% reduction) rates varied from 26.5% to 60%. Conclusions: Our systematic review of the literature suggests that frontal trigger site nerve decompression could possibly be an effective strategy to treat migraine refractory patients, providing significant improvement of symptoms in a considerable percentage of patients.


INTRODUCTION
Trigger site I migraine is most common 20 and originates from the irritation of the supraorbital (SON) and supratrochlear nerves (STN), as well as the terminal branches of the frontal nerve. Different anatomical studies have been conducted to better understand supraorbital and supratrochlear nerve anatomy and to identify their possible irritation points. [21][22][23][24] The supratrochlear nerve exits the orbit medially, runs along its medial roof, and penetrates into the corrugator at about 1.8 cm from the midline, exiting the muscle approximately 2 cm from the midline. 24,25 In most cases, the nerve splits into 2 branches in the retroorbicularis oculi fat pad before penetrating the muscle. 25 The supraorbital nerve exits the orbit via a supraorbital notch or via a foramen, splitting in a superficial and in a deep branch. [21][22][23] Four different patterns of branching were identified based on their interaction with the corrugator muscle. 24 However, different studies show that the mean distance of supraorbital nerve entrance into the brow and the midline is about 2.7 cm. 21,22,25 The irritation mechanism depends on the compression of the nerve structures by either their arteries, the glabellar muscles group (procerus, depressor, and corrugator supercilii), the supraorbital foramen, or by a fascial band present at the supraorbital notch.
Clinically, patients affected by trigger site I MH usually report pain starting above the eyebrows and show deep frown lines and corrugator muscles hypertrophy or eyelid ptosis. 26 Often, clinical history and clinical examination (tenderness of the trigger point at manual compression) are sufficient to clearly identify the MH trigger site. 19 Complementary signs can be an audible vessel signal using a handheld Doppler on the trigger point, botulinum toxin-A injection 27 (useful only in case of "non-vascular" etiology), or local anesthetic injection if the patient examination is contextual to a pain episode. 26 Currently, frontal trigger site deactivation is performed through a transpalpebral or an endoscopic approach, under local anesthesia, sedo-analgesia, or general anesthesia, including different surgical procedures. The goal of this article is to provide a comprehensive review of the literature about surgical treatment for site I migraine management.

METHODS
A literature search using PubMed, Medline, Cochrane, and Google Scholar database according to Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines was conducted to perform a review of the different surgical techniques and to evaluate the outcomes of surgical deactivation of frontal trigger site migraines. The following MeSH terms were used: "frontal neuralgia," "frontal trigger site treatment," "frontal migraine surgery," and "frontal headache surgery" (period: 2000-2020; last search conducted on March 12, 2020). Two independent reviewers performed two-stage screening and data extraction. Abstracts were screened to identify eligible papers. Reference lists of relevant articles were searched for additional studies. The search strategy is shown in the form of a flow chart (Fig. 1).

Inclusion and Exclusion Criteria
Studies were selected based on the following inclusion criteria: (i) studies selectively investigating surgical treatment of frontal headache; (ii) studies that include more than 10 patients; (iii) full text available in English. Studies were excluded due to any one of the following criteria: (i) review articles; (ii) case report; (iii) articles reporting only radiologic anatomic data; (iv) studies that included fewer than 10 patients; (v) studies investigating simultaneous decompression of multiple sites surgical site I decompression (vi) contextual to other sites decompression; (vii) non-referenced articles; and (viii) expert opinion (Level V).

Data Collection
Extracted data included: number of patients, sex, mean age, surgical strategy (incision type, myotomy versus muscle, foraminotomy, fasciotomy, and vessel obliteration), mean follow-up time, method of outcome measurements used, outcomes after surgical treatment (including resolution of migraine headache and postoperative complication).

Statistical Analysis
Statistical analyses were performed using SPSS statistical software (version 24.0; IBM Corporation, Somers, N.Y.).

RESULTS
After duplicate exclusion, 1266 articles were identified. Two different reviewers analyzed all the records by titles and abstracts. Forty full-text articles were examined for eligibility. Eighteen studies published between 2000 and 2019 were considered eligible and included in this systematic review based on appropriateness, relevance, and actuality 7, 28-44 (Fig. 1).
From the 16 selected studies, 6 were retrospective studies, 7,32-34,37,39 11 were prospective studies, [28][29][30][31]35,36,38,[40][41][42] of which 1 was a blinded randomized cohort study, 41 1 was a double-blind, sham surgery, controlled clinical trial, 30 and 1 was a cross sectional study. 40 A total of 628 patients were included in the review, and the sample size of each study ranged from 10 to 132 patients. Ten of 16 studies reported patient gender showing female prevalence ranged from 68.14% to 100%. Twelve of 16 studies reported the age of patients (as mean or as range). Moreover, two additional studies investigating supraorbital region anatomy were included 43,44 : one study 43 described the supraorbital  [28][29][30]39,40,43,44 : 6 studies reported an endoscopic approach 31,[35][36][37][38]42 and 5 studies reported both. 27,[31][32][33][34]41 Studies further mentioned that among endoscopic techniques from 1 single incision (1.5 cm) to 5 incisions, all were positioned behind the hairline. Moreover, the tip to place three surgical sutures bilaterally in the superciliary region to lift the frontal skin allowing for better visualization of the SON, STN, and the surrounding muscles [36][37][38] was given. Among transpalpebral approaches, 5 studies referenced the transposition of fat from the medial compartment of the upper eyelid to fill any defect left by the excised muscles. [31][32][33][34]40 One paper 34 consisted of a comparative study between the two approaches and reported significantly higher success and elimination rates in the endoscopic decompression group than in the transpalpebral decompression group (89% versus 79%, P < 0.05 and 67% versus 52%, P < 0.03, respectively). In any case, the surgical approach corrugator and depressor supercilii resections or myotomies and careful preservation of SON and STN were described in all the procedures. Procerus muscle weakening was reported in 10 articles. 29,30,[32][33][34][35][36][37][38]40 Three articles expressly mentioned vessels coagulation or arterectomy. 28,34,41 Three articles 32,34,41 expressly mentioned foraminotomy using a percutaneous 2 mm osteotome to perform a supraorbital foramen release, 32 and 2 articles expressly mentioned fasciotomy. 34,41 The anatomical cadaveric study included in the review 43 reported the presence of a supraorbital foramen or a supraorbital notch in 26.6% and 83.3% of the sample, respectively. Moreover, this study 43 documented the existence of a fascial band encasing the supraorbital neurovascular bundle in 86% of the supraorbital region that contained a notch. A recent study 44 describing the intraoperative anatomy of the supraorbital region on 118 sites reported a supraorbital nerve foramen and a supraorbital nerve notch prevalence pair to 41% and 49%, respectively. In addition, SON or STN compression appeared macroscopically evident in 95% of cases. Another interesting finding was the presence of nerve edema, nerve flattening, or nerve discoloration in 74% of patients. Table 2 shows the study characteristics and data collection regarding surgical strategies (surgical approach, incision type, glabellar muscle resection, formaninotomy, fasciotomy, or arterectomy).
With respect to outcome measurements, the most frequently used methods were migraine headache index (MHI) 32,33,38,41 and the headache questionnaire. [36][37][38][39]42 Follow-up period varied from 6 months to 126 months. The majority of the studies defined a successful migraine treatment as migraine attack elimination or at least a 50% reduction of its symptoms.
A double-blind controlled clinical trial 30 compared two groups of patients who had undergone actual surgery and sham surgery (placebo), expressing the result as an absolute score using the Migraine Disability Assessment, the Migraine-Specific Quality of Life, and the Medical Outcomes Study 36-Item Short Form Health Survey, where significantly better results were observed in the actual surgery group. Another comparative study 32 investigated the difference between performing only glabellar myectomy and performing glabellar myectomy combined with supraorbital foraminotomy. This study used MH severity, frequency, and duration, as well as the MHI and the forehead pain score and reported significantly better results in the group of patients who had undergone a glabellar myectomy combined with supraorbital foraminotomy compared with the group who had only undergone a myectomy (postoperative migraine frequency: 7.8 per month versus 4.1 per month; postoperative migraine severity: 5.6 versus 4.4; MHI: 26.5 versus 11.12; persistent forehead pain: 48.8% versus 25.6%). Punjabi et al 40 analyzed the appearance of secondary trigger sites after decompression primary surgery showing that the most frequent unmasked secondary trigger after site I surgery is in site III (20.83%). Another article 41 suggested that patients who had undergone arterectomy obtained better outcomes in terms of MHI (51.71 versus 5.55), MFD (18 versus 24), and frequency (12 versus 6.11) compared with patients who had not undergone arterectomy. Moreover, 31% of patients who had not undergone arterectomy needed a second surgery consisting of a revision arterectomy and after the procedure showed a statistically equivalent improvement in MFD (20.75 versus 24, P = 0.178) compared with the patients who had undergone arterectomy as primary surgery. Finally, the most recent study included in the review 37 showed a decrease in VAS headache intensity from 8.10 before surgery to 1.09 after surgery (P < 0.001).

DISCUSSION
Since the unexpected finding of frontal headache amelioration consequent to glabellar muscle resection and periosteal release performed during brow-lift procedures, 27 the field of migraine surgery has rapidly progressed. Our study evidences the positive effects of frontal nerve decompression surgery and underlines how the migraine surgical field is still evolving. In our review, seven studies reported a transpalpebral approach, 6 studies reported an endoscopic approach, and 5 studies reported both. This proportion denotes that there is still no consensus as to what the best approach to treat frontal migraine is. The transpalpebral approach consents the direct visualization and the excision of the glabellar muscles, leaving the periosteal and the fascial structures undamaged. This can be considered as an extension of an upper eyelid blepharoplasty. The anatomical findings that emerged from the two studies included in the review 43,44 reported a relatively high prevalence of supraorbital foramen, supraorbital notch, and fascial band encasing the supraorbital neurovascular bundle, which may suggest that a transpalpebral approach allows for better visualization and treatment of nerve compression. Conversely, some authors argue that the endoscopic technique, at the same time allowing a complete periosteal release on the orbital ridge and a wide glabellar muscles dissection, should be considered as the best choice whenever anatomically possible. The endoscopic approach is not recommended for patients with a forehead length greater than 8 cm or patients presenting with a protruding forehead. 45 A retrospective study 34 included in our review reported significantly higher success rates in cases of endoscopic approach than in the transpalpebral option. As aforementioned, among the described endoscopic techniques, surgical access varies from 1 single incision of 1.5 cm to 5 incisions, all of which are positioned behind the hairline. The minimally invasive technique described by Raposio,[36][37][38][46][47][48] in addition to the single midline incision, requires the use of a modified endoscope and the placement of 3 surgical sutures bilaterally in the superciliary region to have a better visualization of the anatomical structures lifting the frontal skin.
Regardless of the approach, another noticeable difference among the studies is related to surgical procedures. All the authors agree that glabellar muscles group excision and SON and STN preservation are mandatory. The necessity to perform an arterectomy, a fasciotomy, and a foraminotomy is still a matter of debate. Gatherwright,41 in a prospective blinded randomized cohort study, demonstrated the role of arterectomy in frontal migraine surgery showing that patients who undergo arterectomy obtain better outcomes. Moreover, the study reported that in about 30% of cases, patients who had not undergone arterectomy needed a revision consisting of an arterectomy; after which, a statistically equivalent improvement was achieved when compared with patients who had undergone arterectomy as the primary surgery. Another retrospective comparative study 32 investigated the role of supraorbital foraminotomy proving a reduction of migraine frequency, migraine severity, MHI, and forehead pain in patients who had undergone foraminotomy. This clinical finding is supported by recent radiological and anatomical evidence 49 showing that SON and especially supraorbital foramen contribute significantly to MH symptoms. This radiological study suggests that an analysis    of all available face or perinasal sinus CT images could be helpful in preoperative planning, possibly including foraminotomy and fasciotomy. An important criticism in frontal migraine management is the lack of consensus among clinicians regarding the methods to measure surgical outcomes. In our review the most frequently used methods were MHI 7,28,34,36 and the headache questionnaire. [36][37][38]40,42 Quality of life documentation before and after a migraine surgery is exiguous, mirroring the literature regarding trigger site decompression surgery. In our opinion, to improve the migraine surgery effect reporting, future investigations should spotlight what is the most complete evaluation method to universalize outcome measurements.
Patient follow-up period varied from 6 to 126 months; results were considered as stable three months after surgery by most of the authors. Overall, 68.3%-93.3% of patients presented satisfactory results. Complete migraine elimination rate ranged from 28.3% to 59% and significant improvement (>50% of reduction) rate varied from Raposio   Undeniably, some authors are not convinced that decompression surgery represents an effective treatment for headaches 50,51 and the neural entrapment theory is still a matter of debate. Certainly, the lack of clarity regarding patient selection criteria, the scarcity of controlled studies, the lack of consistent outcome measures, and the relative brevity of follow-ups represent weak points that can lead to prejudiced results. However, recent studies have described intraoperative findings of SON and STN compression, nerve edema, flattening, or discoloration, thus demonstrating the concreteness and the anatomical-clinical correlation of the neural entrapment theory. In our opinion, standardization of patient selection and outcome measures after decompression surgery are the most critical points needed to convince neurologists of the effectiveness of this type of treatment in selected patients. In fact, the MHI represents a non-validated instrument that may increase the possibility of obtaining positive results. 49 A constructive and open discussion between surgeon and neurologist would surely improve the management of these patients and allow for the building of an integrated therapeutic algorithm to better evaluate the postoperative results.
Postoperative complications were relatively rare and a few were reported. The most common complication was a transient paresthesia, followed by pruritus, eyebrow asymmetry or uneven movement, frontal muscle paralysis, eyelid ptosis, and hematoma formation.

CONCLUSIONS
Our systematic review of the literature suggests that frontal trigger site nerve decompression may be an effective strategy to treat migraine refractory patients, allowing for the resolution or at least a significant improvement of symptoms in a considerable percentage of patients. However, the poor quality of the included studies, the scarcity of controlled trials, the lack of consistent outcome measures, and the multitude of varied surgical techniques do not permit the conclusion of efficacy with respect to frontal migraine surgical treatment. Certainly, higher level studies need to be conducted to confirm the effectiveness of this treatment. Moreover, why some patients are still unresponsive to surgical treatment is still a matter of discussion.
Nowadays, there is not a standard surgical technique. Prospective studies to compare excision or blunt dissection of the glabellar muscles, periosteum release, vessel coagulation and foraminotomy would be helpful to reach a better understanding as to what is the best surgical strategy to treat these patients.