Nerve Block Guided by Anatomic Landmarks Only Reduces Pain in Botulinum Toxin Type A Treatment for Glabellar and Forehead Wrinkles.

BACKGROUND: Botulinum toxin type A is widely used to treat glabellar and forehead wrinkles, but the pain caused by multiple injections often deters patients from receiving long-term treatment. Despite several methods used to alleviate this pain, consistency and effectiveness remain a challenge. Therefore, this study aimed to evaluate the effectiveness and safety of nerve block guided by anatomic landmarks only in reducing pain associated with botulinum toxin type A injections. PATIENTS AND METHODS: Between 2018 and 2022, the study enrolled 90 patients divided into 3 groups: the nerve block group (n = 30), the lidocaine cream group (n = 30), and the control group (n = 30). In the nerve block group, a landmarks-based technique was used to perform the nerve block. The study collected general information and comorbidities, and recorded pain at each point and time spent on preparation and treatment for each patient's forehead and glabellar area on each side. Patient-reported outcomes and complications were followed up at 2, 4, and 12 weeks after the injections. RESULTS: The nerve block group had significantly lower total pain scores in all regions compared to the lidocaine cream and control groups (P < 0.01). There were no significant differences in patient-reported outcomes between the groups at any follow-up point. Additionally, the complication rates related to injection were low and comparable among the 3 groups. CONCLUSIONS: Nerve block guided by anatomic landmarks only is a safe, effective, and consistent approach to reduce pain during botulinum toxin type A treatment for glabellar and forehead lines. This technique may offer advantages over other methods used to alleviate the pain associated with these injections.

Anatomic Variations of the Lateral Branch of the Supraorbital Nerve Observed in Endoscopic Forehead Surgery.

Surgeons dissect carefully in the medial third of the supraorbital rim to preserve the supraorbital nerve (SON) during surgical forehead rejuvenation. However, the anatomic variations of SON exit from the frontal bone have been researched in cadaver or imaging studies. In this study, we report a variation in the lateral branch of SON observed in an endoscopic view during forehead lifts. A retrospective review of 462 patients who underwent endoscopy-assisted forehead lifts between January 2013 and April 2020 was performed. Data, including the location, number, and form of the exit point and thickness of SON and its lateral branch variant, were recorded and reviewed intraoperatively, utilizing high-definition endoscopic assistance. Thirty-nine patients and 51 sides were included, and all patients were female, with a mean age of 44.53 (18-75) years. This nerve exited a foramen in the frontal bone ~8.82 ± 2.79 mm lateral to SON and ~1.89 ± 1.34 mm from the supraorbital margin vertically. Observed thickness variations of the lateral branch of SON included 20 small, 25 medium, and 6 large nerves. This study revealed various positional and morphologic variations of the lateral branch of SON in an endoscopic view. Thus, surgeons can be alerted of the anatomic variations of SON and establish careful dissection during procedures. In addition, the findings of this study will be useful in planning nerve blocks, filler injections, and migraine treatments in the supraorbital region.

Forehead Movement Discrepancies After Botulinum Toxin Injections: A Review of Etiology, Correction, and Prevention.

BACKGROUND: Forehead rhytides are a popular target for botulinum toxin injections, but neuromodulation of the frontalis can be fraught with complications because of its anatomic complexity and integral role in brow position and expressivity. OBJECTIVE: This article explores common forehead movement discrepancies that can occur after neuromodulation of the frontalis, as well as how to correct and prevent them. METHODS: A review of the literature was conducted and combined with clinical experience to examine underlying forehead anatomy, etiology and correction of forehead movement discrepancies, and important factors to consider before injecting the frontalis with botulinum toxin. RESULTS AND CONCLUSION: Variable anatomy from person to person necessitates an individualized treatment approach to achieve the best cosmetic results and prevent the occurrence of forehead movement discrepancies.

Computed Tomography-Guided Radiofrequency Ablation of the Cervical Dorsal Root Ganglia in 27 Patients with Cervical and Occipital Postherpetic Neuralgia.

BACKGROUND Postherpetic neuralgia (PHN) is a common complication of herpes zoster virus infection that is associated with intense pain. The present study aimed to investigate the use of computed tomography (CT)-guided radiofrequency ablation (RFA) of the cervical dorsal root ganglia (DRG) for treatment of cervical and occipital PHN in 27 patients at a single center. MATERIAL AND METHODS Twenty-seven patients with PHN in the cervical and/or occipital region were enrolled. After imaging the area of PHN in the patients, axial scanning was performed on the upper cervical segment in the spinal scanning mode. The puncture path was defined and then RFA therapy (90°C for 180 s) was performed by targeting the corresponding intervertebral foramen. Patients were followed 2 days later and at 1, 3, 6, and 12 months after surgery. Observation at each follow-up visit included rating of pain on a visual analog scale (VAS) and assessment of complications and adverse events. RESULTS VAS scores significantly decreased in patients with PHN after RFA compared with their scores before RFA (P<0.05). Skin sensation decreased in the area that was originally painful and allodynia significantly diminished. CONCLUSIONS The findings from this small study from a single center showed that CT-guided percutaneous RFA of cervical DRG safely and effectively reduced cervical and occipital PHN in the short term.

Aesthetic ONE21 Technique for Injecting IncobotulinumtoxinA into the Forehead: Initial Experience With 86 Patients.

BACKGROUND: Treatment of upper facial lines is a common aesthetic practice; however, there is limited information on systematic tailored approaches for the treatment of forehead wrinkles using botulinum toxin A. OBJECTIVE: To describe the safety and efficacy of the ONE21 technique using incobotulinumtoxinA (INCO) for the treatment of forehead wrinkles. METHODS: Single-center, retrospective study with 86 females presenting a baseline Merz Aesthetic Scale (MAS) score ≥2 for dynamic forehead lines who had been treated with INCO using the ONE21 technique. Assessment was performed by two independent blinded raters using MAS for forehead lines (dynamic and at rest), and eyebrow positioning, based on standardized pictures taken before (baseline) and 4 (±2) weeks after treatment injection. The primary outcome was the percentage of subjects with a MAS improvement ≥2 points for dynamic forehead lines at week 4 (±2). Secondary outcomes were MAS scores for resting forehead lines and for eyebrow positioning. RESULTS: The mean age was 46.2 years, and mean total dose of INCO, 20.3 U. Most (97.7%) subjects had a MAS improvement of ≥2 points for dynamic forehead lines at week 4 (±2); 100% improved ≥1 point. MAS scores for resting and dynamic lines, and eyebrow positioning were significantly improved (P<0.001). Eyebrow positioning MAS improved ≥1 point in 56.9% of subjects, and 39.5% maintained the original shape. CONCLUSION: INCO injection using the ONE21 technique is effective and safe in treating forehead wrinkles, providing a natural result, with a customized treatment and a predictable eyebrow shape. J Drugs Dermatol. 2021;20(1):31-37. doi:10.36849/JDD.5617.

Painful stimulation of a sensitized site in the forearm inhibits ipsilateral trigeminal nociceptive blink reflexes.

Exposure to moderate levels of ultraviolet B radiation (UVB) is painless but nevertheless induces an inflammatory response that sensitizes primary afferent nociceptors. Subsequently, heating the UVB-treated site can sensitize spinal nociceptors. We used a repeated-measures design to determine whether heating the UVB-treated site also triggers ipsilateral inhibitory controls. Specifically, a 2-cm diameter site on the forearm of 20 participants was exposed to UVB at twice the minimum erythema dose. 48 h later mechanical and thermal sensitivity had increased at the UVB-treated site, indicating primary hyperalgesia. In addition, sensitivity to blunt pressure had increased in the ipsilateral forehead, implying activation of an ipsilateral supra-spinal pro-nociceptive mechanism. Despite this, the area under the curve of the ipsilateral nociceptive blink reflex decreased when the UVB-treated site was heated to induce moderate pain. Together, these findings suggest that the UVB treatment sensitized primary nociceptive afferents and generated an ipsilateral supra-spinal pro-nociceptive mechanism. In addition, sensitization to heat induced by the UVB treatment strengthened an ipsilateral anti-nociceptive process elicited by heat-pain. Infrequent but enduring discharge of sensitized primary nociceptive afferents, driven by inflammation after UVB exposure, might initiate a lateralized supra-spinal pro-nociceptive influence that heightens awareness of impending harm on the sensitized side of the body. In addition, a lateralized anti-nociceptive response triggered by an intense barrage of nociceptive signals may help to differentiate stronger from weaker sources of pain.

Painful Neuroma Treatment of the Supraorbital Nerve and Forehead Neurotization Using Human Cadaveric Nerve Allograft.

Neuroma pain can be severe, persistent, and treatment-resistant. Forehead and scalp anesthesia is troublesome for patients. Following an iatrogenic ablative injury to the right supraorbital nerve, with subsequent painful neuroma formation, a human cadaveric nerve allograft (AxoGen, Alachua, FL) was used to restore sensation of the right forehead and treat pain. At 1-year follow-up, the patient was pain-free, and protective sensation to the right forehead was recovered with comparable static and dynamic 2-point discrimination between the injured (20 mm, 12 mm respectively) and the normal side (15 mm, 10 mm respectively). This is the first reported case of using a cadaver nerve allograft for successful direct neurotization of the skin and restoration of sensation in the upper part of the face, and for treating painful neuromas. Moreover, a brief review of the available techniques for treating neuromas of the supraorbital and supratrochlear nerves is provided.

Three-Dimensional Topography of the Supratrochlear Nerve With Reference to the Lacrimal Caruncle, and Its Danger Zone in Asians.

BACKGROUND: The supratrochlear nerve (STN) is relatively superficial and therefore vulnerable to iatrogenic injury. OBJECTIVE: To elucidate the course of STN with reference to the lacrimal caruncle, with the aim of preventing nerve injury during surgery in the forehead region. MATERIALS AND METHODS: Thirty-four hemifaces from 18 Korean cadavers were dissected. The vertical line through the apex of lacrimal caruncle and the horizontal line through the supraorbital margin were used as horizontal and vertical reference lines, respectively. The course of STN in the frontal view and the point at which it pierced the overlaying musculature were examined. RESULTS: After exiting the corrugator muscle cushion, the STN enters the subcutaneous plane by piercing the frontalis muscle. These piercing points occurred at mean horizontal and vertical distances relative to the medial branch of the STN of 9.2 and 9.6 mm, respectively; the corresponding distances for the lateral branch of the STN were 1.1 and 15.3 mm, respectively. CONCLUSION: When performing surgery in the medial forehead region, the surgeon must ensure that the dissection plane of forehead tissue is more superficial: superiorly within 1.5 cm from the supraorbital margin and medially within 1.0 cm from the vertical line through the apex of lacrimal caruncle.

Superficial temporal artery perforator flap: Anatomic study of number and reliability of distal branches of the superficial temporal artery and clinical applications in three cases.

BACKGROUND: Limited information is available about the anatomical feasibility and clinical applications of flaps based on distal divisions of the superficial temporal artery (STA). The aim of this study was to investigate the anatomy of the STA, focusing on the number and reliability of distal branches and to show representative cases for the use of such flaps for zygomatic, parieto-frontal and occipital reconstructions. METHODS: Fifty volunteers were examined bilaterally by Doppler to investigate the presence and variability of the distal divisions of STA branches. Dissection was performed on 14 temporal regions of 7 fresh cadavers. Three cases of reconstruction following skin cancer in the zygomatic (7 × 5 cm defect), parieto-frontal (4 × 4 cm defect) and occipital areas (4 × 2 cm defect) are presented. All the flaps were pedicled and based on a single vessel. RESULTS: In all the 50 volunteers, the parietal branch split into 2 ± 0 branches (anterior and posterior), bilaterally, while an average of 2.84 ± 0.46 and 2.82 ± 0.48 branches originated from the frontal vessel on the right and left side, respectively. 2 ± 0 parietal and 3 ± 0 frontal (superior, central, and inferior) cutaneous perforator branches were identified in all cadaveric specimens. Flaps (4 × 10 cm, 5 × 7 cm, and 2 × 5 cm, respectively, width × length) healed uneventfully providing stable coverage. CONCLUSIONS: STA distal perforator branches proved to be anatomically constant in both the cadaveric and clinical settings. Although a larger series of cases is needed, island flaps based on such vessels may represent a versatile surgical option, allowing a wide range of reconstructions in the different facial subunits.

Whole-body mapping of spatial acuity for pain and touch.

OBJECTIVE: Tactile spatial acuity is routinely tested in neurology to assess the state of the dorsal column system. In contrast, spatial acuity for pain is not assessed, having never been systematically characterized. More than a century after the initial description of tactile acuity across the body, we provide the first systematic whole-body mapping of spatial acuity for pain. METHODS: We evaluated the 2-point discrimination thresholds for both nociceptive-selective and tactile stimuli across several skin regions. Thresholds were estimated using pairs of simultaneous stimuli, and also using successive stimuli. RESULTS AND INTERPRETATION: These two approaches produced convergent results. The fingertip was the area of highest spatial acuity, for both pain and touch. On the glabrous skin of the hand, the gradient of spatial acuity for pain followed that observed for touch. On the hairy skin of the upper limb, spatial acuity for pain and touch followed opposite proximal-distal gradients, consistent with the known innervation density of this body territory. Finally, by testing spatial acuity for pain in a rare participant completely lacking Aß fibers, we demonstrate that spatial acuity for pain does not rely on a functioning system of tactile primary afferents. This study represents the first systematic characterization of spatial acuity for pain across multiple regions of the body surface.

Anatomy of facial and trigeminal nerve branches associated with the corrugator supercilii muscle: microdissection and modified Sihler staining.

BACKGROUND: Deactivation of the corrugator supercilii for the treatment of unintentional glabellar lines requires high selectivity to avoid sensory complications. OBJECTIVE: The aim of this study was to delineate the topographic anatomy of facial and trigeminal nerves in relation to the corrugator supercilii to improve the selectivity and safety of deactivation of the corrugator supercilii muscle. MATERIALS AND METHODS: The number, courses, and attachments of the facial nerve to the corrugator supercilii muscle were investigated by dissection of 27 cadaveric hemifaces. Twelve cadaveric hemiforehead flaps were stained using a modified Sihler method to trace the supraorbital and supratrochlear branches. RESULTS: On average, 1.8 branches of the facial nerve at the zygomatic arch were associated with the corrugator supercilii muscle through 1 (29.3%) or 2 terminal rami (70.7%). The trigeminal nerve gave off 7.7 supraorbital and 5.1 supratrochlear branches emerging from orbit. The majority of the supraorbital branches became intramuscular branches (60.4%), whereas the majority of the supratrochlear branches became superficial branches (67.8%). CONCLUSION: Resection of the muscle may damage the intramuscular trigeminal branches, leading to sensory changes. The course of the facial nerve branches to the corrugator supercilii muscle was much more predictable at their distal part than the proximal part.

Development of an experimental model to study trigeminal nerve-mediated vasodilation on the human forehead.

BACKGROUND: During migraine, trigeminal sensory nerve terminals release calcitonin gene-related peptide (CGRP), inducing nociception and vasodilation. Applied on the skin, capsaicin activates the transient receptor potential vanilloid type 1 (TRPV1) channel and releases CGRP from sensory nerve terminals, thus increasing dermal blood flow (DBF). Using capsaicin application and electrical stimulation of the forehead skin, a trigeminal nerve-innervated dermatome, we aimed to develop a model to measure trigeminal nerve-mediated vasodilation in humans. METHODS: Using laser Doppler imaging, forehead DBF responses to application of capsaicin (0.06 mg/ml and 6.0 mg/ml) and saline, with and without iontophoresis, were studied in healthy subjects. The within-subject coefficient of variation (WCV) of repeated DBF measurements was calculated to assess reproducibility. RESULTS: Maximal DBF responses to 6.0 mg/ml capsaicin with and without iontophoresis did not differ (Emax 459 ± 32 and 424 ± 32 arbitrary units (a.u.), WCV 6 ± 4%). In contrast, DBF responses to 0.06 mg/ml capsaicin were significantly larger with than without iontophoresis (Emax 307 ± 60 versus 187 ± 21 a.u., WCV 21 ± 13%). Saline with iontophoresis significantly increased DBF (Emax: 245 ± 26 a.u, WCV 11 ± 8%), while saline application without iontophoresis did not affect DBF. CONCLUSION: Topical application of capsaicin and electrical stimulation induce reproducible forehead DBF increases and therefore are suitable to study trigeminal nerve-mediated vasodilation in humans.

Cutaneous depth of the supraorbital nerve: a cadaveric anatomic study with clinical applications to dermatology.

BACKGROUND: Common dermatologic procedures performed on the forehead may injure the supraorbital nerve (SON) leading to adverse outcomes. OBJECTIVE: To describe SON anatomic course and cutaneous depth. MATERIALS AND METHODS: Sixteen cadaver specimens were dissected. RESULTS: The supraorbital nerve originated 2.63 ± 0.27 (range, 2.1-3.5) cm from the midline and 0.25 ± 0.16 (range, 0-0.5) cm above the orbital rim. Supraorbital nerve emerged as 1 root dividing into superficial (SON-S) and deep (SON-D) branches. The supraorbital nerve deep branch remained deep to the aponeurosis of the corrugator supercilii and frontalis muscles and coursed laterally toward the scalp. Supraorbital nerve superficial branch emerged nearly perpendicular to the orbital rim and traveled under the corrugator supercilii with an average depth of 0.75 ± 0.16 (range, 0.5-1.1) cm. Supraorbital nerve superficial branches entered the subfrontalis plane at a mean distance of 1.29 ± 0.20 (range, 1.0-1.8) cm above the orbital rim with an average depth of 0.45 ± 0.13 (range, 0.3-0.8) cm. These branches entered the subcutaneous plane by piercing through the frontalis muscle at a mean distance of 2.60 ± 0.32 (range, 1.9-3.2) cm above the orbital rim with an average depth of 0.30 ± 0.10 (range, 0.2-0.6) cm. CONCLUSION: The supraorbital nerve depth and course are relevant when performing procedures on the forehead. A thorough understanding of the anatomy and depth of SON-S is critical to help minimize nerve damage and optimize patient counseling.

Selective neurolysis in post-paralytic facial nerve syndrome (PFS).

UNLABELLED: Post-paralytic facial nerve syndrome (PFS) summarizes specific symptoms that result from an incomplete or poor recovery of the facial nerve after peripheral facial palsy. Selective chemodenervation using botulinum toxin A (Btx A) and mime therapy represent the therapeutic standard for treating PFS. We report on a 35-year-old male who was suffering greatly from unilateral PFS-specific movement disorders, including periorbital contractions and oculofacial synkinesis that did not respond to Btx A administration. We present a surgical alternative to overcome periorbital movement disorders by selective neurolysis and review therapeutic options for this rare syndrome. In conclusion, selective neurolysis appears to be an efficient alternative treatment method of PFS in which the quality of life is severely impacted due to movement disorders and there was no therapeutic benefit from Btx A. LEVEL OF EVIDENCE V: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors http://www.springer.com/00266 .

Reconstruction of large supra-eyebrow and forehead defects using the hatchet flap principle and sparing sensory nerve branches.

BACKGROUND: To reconstruct a forehead defect, a plastic surgeon must be knowledgeable about the neural, vascular, and muscular anatomy. The position of fixed structures such as eyebrows and hairline should be respected. For the past 5 years, we have used double hatchet flaps for reconstruction of relatively large supra-eyebrow and forehead defects. Because this flap does not appear to be among the techniques used by young plastic surgeons, we thought that it would be valuable to report our experience. METHODS: Supra-eyebrow and forehead defects ranging from 2.5 × 2.5 cm to 3.5 × 3.5 cm were reconstructed using double hatchet flaps in 10 patients. Pearls and pitfalls of the technique are discussed along with the presentation of 3 cases. RESULTS: The reconstructions were uneventful and the flaps were highly viable in all patients. There was no significant distortion in the eyebrow or hairline due to reconstruction in any of the patients. All the flaps were sensate. A mild anesthesia in the distribution of supraorbital/trochlear nerve proximal to the flaps was noted only in 3 patients. This was associated with inevitable nerve damage during excision of malignant skin lesions and/or flap dissection. No recurrence was noted during the follow-up period which ranged from 6 to 36 months (mean, 13.5 months). Overall patient satisfaction score based on scar appearance and perceived degree of forehead anesthesia was 3 (neither satisfied nor dissatisfied) in 1 patient, was 4 (somewhat satisfied) in 4 patients, and was 5 (very satisfied) in 5 patients. CONCLUSION: Hatchet flaps have similar color and texture to that of the adjacent supra-eyebrow and forehead defects. The scarring is acceptable with reliable and reproducible results. Oftentimes, sensory nerve branches can be preserved with careful planning and tedious dissection. This type of reconstruction should be considered in the armamentarium of supra-eyebrow and forehead defects.

Percutaneous selective radiofrequency nerve ablation for glabellar frown lines.

BACKGROUND: The dynamic muscles of the glabellar region can be overactive, giving patients a "scowling" look and making them appear angry, worried, or stressed. OBJECTIVE: The authors describe percutaneous selective nerve ablation, a minimally-invasive procedure for treatment of glabellar frown lines, and report results from a series of patients treated with the technique. METHODS: From November 2007 to December 2009, 27 patients (22 women and five men) underwent percutaneous selective nerve ablation to improve glabellar frown lines. Initially, the surface pathway of the nerve to the corrugator supercilii and procerus was checked with a peripheral nerve stimulator. For percutaneous localization, a 22-gauge monopolar electrode was introduced into the lateral brow and cheek skin without incision. Short electrical stimulation (0.3-0.5 mA) was delivered to identify the proper lesion sites. Synchronous contraction of corrugator supercilii was elicited and radiofrequency nerve ablation performed (85°C, 70 seconds). In all patients, the frontal branch of the facial nerve and angular nerve were treated bilaterally. The improvement was evaluated with the Wrinkle Assessment Scale. RESULTS: Mean patient age was 54.5 years, and mean follow-up time was 18 months (range, 12-26 months). One patient had superficial second-degree burns to the brow skin, which healed with conservative treatment. Two patients had temporary paresthesia that completely resolved in a few weeks without sequelae. The Wrinkle Assessment Scale indicated a statistically significant improvement in the glabellar frown lines (preoperative vs postoperative mean, 3.7 vs 1.8; P < .05). CONCLUSIONS: Although long-term studies are necessary to determine the ideal amount of energy delivery for maximum efficacy and time for treatment of glabellar frown lines, the study lends support for the safety and efficacy of percutaneous selective nerve ablation.

Perineural involvement of squamous cell carcinoma presenting with formication.

Perineural involvement of a cutaneous neoplasm marks an aggressive feature. Tumors with perineural involvement share an increased propensity for local invasion via perineural spread. Formication may be an indicator of perineural involvement by cutaneous neoplasms. We present a case of an 82-year-old man with perineural involvement of a squamous cell carcinoma (SCC) identified by clinical symptoms of formication. Successful resolution of these symptoms was achieved with radiation therapy.

Radiofrequency (GFX) ablation for the reduction of glabellar frowning.

A new minimally invasive procedure is described for the reduction of glabellar frowning. Glabellar furrow relaxation or GFX (TM) utilizes bipolar radiofrequency energy targeted at peripheral motor nerve fibers to the depressor muscles of the forehead. This procedure is a useful adjunct in forehead rejuvenation when performed concomitantly with blepharoplasty or forehead lifting in a surgical setting. With proper training the procedure can be performed under local anesthesia in the office setting to produce very natural results. The relevant anatomy and technique is described here in detail because this represents new knowledge in facial plastic surgery. A cohort of patients has been studied for over 12 months demonstrating the efficacy of the relaxation that can be achieved with the procedure. The GFX procedure offers the patients and surgeons an alternative treatment to botulinum toxin A when longer lasting relaxation of the forehead depressor muscles is desired.

Migraine Surgery at the Frontal Trigger Site: An Analysis of Intraoperative Anatomy.

BACKGROUND: The development of migraine headaches may involve the entrapment of peripheral craniofacial nerves at specific sites. Cadaveric studies in the general population have confirmed potential compression points of the supraorbital and supratrochlear nerves at the frontal trigger site. The authors' aim was to describe the intraoperative anatomy of the supraorbital and supratrochlear nerves at the level of the supraorbital bony rim in patients undergoing frontal migraine surgery and to investigate associated pain. METHODS: PATIENTS: scheduled for frontal-site surgery were enrolled prospectively. The senior author (W.G.A.) evaluated intraoperative anatomy and recorded variables using a detailed form and operative report. The resulting data were analyzed. RESULTS: One hundred eighteen sites among 61 patients were included. The supraorbital nerve traversed a notch in 49 percent, a foramen in 41 percent, a notch plus a foramen in 9.3 percent, and neither a notch nor a foramen in one site. The senior author noted macroscopic nerve compression at 74 percent of sites. Reasons included a tight foramen in 24 percent, a notch with a tight band in 34 percent, and supraorbital and supratrochlear nerves emerging by means of the same notch in 7.6 percent or by means of the same foramen in 4.2 percent. Preoperative pain at a site was significantly associated with nerve compression by a foramen. CONCLUSIONS: The intraoperative anatomy and cause of nerve compression at the frontal trigger site vary greatly among patients. The authors report a supraorbital nerve foramen prevalence of 50.3 percent, which is greater than in previous cadaver studies of the general population. Lastly, the presence of pain at a specific site is associated with macroscopic nerve compression.