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Figure 1.
Facial Nerve Mapping Examples in 3 Patients in the FNM Group
Facial Nerve Mapping Examples in 3 Patients in the FNM Group

Shown are preoperative photographs, the facial grid schematic, preoperative facial nerve mapping, and a postoperative photograph for each patient. A, A small venous malformation on the midface occupying one grid space is shown. Note that only distal facial nerve branches involve the lesion, which enabled direct lesion excision immediately after glue embolization. B, An infantile hemangioma on the midface, incompletely responsive to propranolol hydrochloride, occupying 3 grid spaces is shown. Note that the distal facial nerve branches surround the lesion, enabling near-complete direct excision with peripheral nerve identification and preservation. C, A lymphatic malformation (stage 4) occupying 6 grid spaces and involving all branches of the facial nerve is shown. Note that the main trunk of the facial nerve is significantly inferior to normal facial nerve anatomic landmarks. FNM indicates facial nerve mapping.

Figure 2.
Distribution of Lesion-Occupied Grid Spaces in the NIM and FNM Groups by Surgical Approach
Distribution of Lesion-Occupied Grid Spaces in the NIM and FNM Groups by Surgical Approach

The most frequent diagnoses are color coded. There were more instances of retrograde and direct excision in the FNM group compared with the NIM group. The distribution of lesions was more distal on the facial nerve branches for those treated with direct excision (transoral or transcutaneous). CN indicates cranial nerve; FNM, facial nerve mapping; and NIM, nerve integrity monitoring.

Figure 3.
Time to Completion of Surgery in the NIM and FNM Groups
Time to Completion of Surgery in the NIM and FNM Groups

Shown are results of the multivariable analysis adjusting for age, sex, diagnosis, anomaly volume, number of facial nerve branches involved, and depth relative to cranial nerve VII. The proportion of patients whose surgery has ended vs operative time is shown for both groups. For the “No. at risk” at the bottom, the number of patients whose surgery is ongoing is shown, as well as (in parentheses) the number of patients whose surgery is completed. FNM indicates facial nerve mapping; NIM, nerve integrity monitoring.

Table 1.  
Preoperative Characteristics, Operative Details, and Outcome Data in the NIM and FNM Groups
Preoperative Characteristics, Operative Details, and Outcome Data in the NIM and FNM Groups
Table 2.  
Logistic Regression of the Association Between FNM and Various Outcomes
Logistic Regression of the Association Between FNM and Various Outcomes
1.
Lee  GS, Perkins  JA, Oliaei  S, Manning  SC.  Facial nerve anatomy, dissection and preservation in lymphatic malformation management.  Int J Pediatr Otorhinolaryngol. 2008;72(6):759-766.PubMedGoogle ScholarCrossref
2.
Slaughter  KA, Chen  T, Williams  E  III.  Vascular lesions.  Facial Plast Surg Clin North Am. 2016;24(4):559-571.PubMedGoogle ScholarCrossref
3.
Hu  X, Chen  D, Jiang  C,  et al.  Retrospective analysis of facial paralysis caused by ethanol sclerotherapy for facial venous malformation.  Head Neck. 2011;33(11):1616-1621.PubMedGoogle ScholarCrossref
4.
Nyberg  EM, Chaudry  MI, Turk  AS, Turner  RD.  Transient cranial neuropathies as sequelae of Onyx embolization of arteriovenous shunt lesions near the skull base: possible axonotmetic traction injuries.  J Neurointerv Surg. 2013;5(4):e21.PubMedGoogle ScholarCrossref
5.
de Serres  LM, Sie  KC, Richardson  MA.  Lymphatic malformations of the head and neck: a proposal for staging.  Arch Otolaryngol Head Neck Surg. 1995;121(5):577-582.PubMedGoogle ScholarCrossref
6.
Adams  MT, Saltzman  B, Perkins  JA.  Head and neck lymphatic malformation treatment: a systematic review.  Otolaryngol Head Neck Surg. 2012;147(4):627-639.PubMedGoogle ScholarCrossref
7.
Lowry  TR, Gal  TJ, Brennan  JA.  Patterns of use of facial nerve monitoring during parotid gland surgery.  Otolaryngol Head Neck Surg. 2005;133(3):313-318.PubMedGoogle ScholarCrossref
8.
Sood  AJ, Houlton  JJ, Nguyen  SA, Gillespie  MB.  Facial nerve monitoring during parotidectomy: a systematic review and meta-analysis.  Otolaryngol Head Neck Surg. 2015;152(4):631-637.PubMedGoogle ScholarCrossref
9.
Amano  M, Kohno  M, Nagata  O, Taniguchi  M, Sora  S, Sato  H.  Intraoperative continuous monitoring of evoked facial nerve electromyograms in acoustic neuroma surgery.  Acta Neurochir (Wien). 2011;153(5):1059-1067.PubMedGoogle ScholarCrossref
10.
Chiara  J, Kinney  G, Slimp  J, Lee  GS, Oliaei  S, Perkins  JA.  Facial nerve mapping and monitoring in lymphatic malformation surgery.  Int J Pediatr Otorhinolaryngol. 2009;73(10):1348-1352.PubMedGoogle ScholarCrossref
11.
Ulkatan  S, Waner  M, Arranz-Arranz  B,  et al.  New methodology for facial nerve monitoring in extracranial surgeries of vascular malformations.  Clin Neurophysiol. 2014;125(4):849-855.PubMedGoogle ScholarCrossref
Original Investigation
May 2018

Preoperative Facial Nerve Mapping to Plan and Guide Pediatric Facial Vascular Anomaly Resection

Author Affiliations
  • 1Division of Pediatric Otolaryngology, Seattle Children’s Hospital, Seattle, Washington
  • 2Department of Otolaryngology–Head and Neck Surgery, University of Washington, Seattle
  • 3Neuromonitoring Program, Department of Rehabilitation Medicine, University of Washington, Seattle
JAMA Otolaryngol Head Neck Surg. 2018;144(5):418-426. doi:10.1001/jamaoto.2018.0054
Key Points

Question  Does preoperative facial nerve mapping affect intraoperative facial nerve injury risk and expand safe surgical approach options compared with standard nerve integrity monitoring?

Findings  In this historically controlled study of 92 cervical facial vascular anomalies, the preoperative facial nerve mapping group had significantly fewer long-term facial nerve injuries (1 in 61 patients) compared with the control group (6 in 31 patients), more direct surgical approaches were used, and operative times were reduced in the facial nerve mapping group.

Meaning  Preoperative facial nerve mapping is recommended in the surgical treatment of cervicofacial vascular anomalies.

Abstract

Importance  Facial vascular anomalies are surgical challenges due to their vascularity and facial nerve distortion. To assist facial vascular anomaly surgical treatment, presurgical percutaneous facial nerve stimulation and recording of compound motor action potentials can be used to map the facial nerve branches. During surgery, the nerve map and continuous intraoperative motor end plate potential monitoring can be used to reduce nerve injury.

Objective  To investigate if preoperative facial nerve mapping (FNM) is associated with intraoperative facial nerve injury risk and safe surgical approach options compared with standard nerve integrity monitoring (NIM).

Design, Setting, and Participants  This investigation was a historically controlled study at a tertiary vascular anomaly center in Seattle, Washington. Participants were 92 pediatric patients with facial vascular anomalies undergoing definitive anomaly surgery (from January 1, 1999, through January 1, 2015), with 2 years’ follow-up. In retrospective review, a consecutive FNM patient cohort after 2005 (FNM group) was compared with a consecutive historical cohort (1999-2005) (NIM group).

Main Outcomes and Measures  Postoperative facial nerve function and selected surgical approach. For NIM and FNM comparisons, statistical analysis calculated odds ratios of nerve injury and operative approach, and time-to-event methods analyzed operative time.

Results  The NIM group had 31 patients (median age, 3.3 years [interquartile range, 2.2-11.4 years]; 20 [65%] male), and the FNM group had 61 patients (median age, 4.4 years [interquartile range, 1.5-11.0 years]; 26 [43%] male). In both groups, lymphatic malformation resection was most common (19 of 31 [61%] in the NIM group and 32 of 61 [52%] in the FNM group), and the median anomaly volumes were similar (52.4 mL; interquartile range, 12.8-183.3 mL in the NIM group and 65.4 mL; interquartile range, 18.8-180.2 mL in the FNM group). Weakness in the facial nerve branches at 2 years after surgery was more common in the NIM group (6 of 31 [19%]) compared with the FNM group (1 of 61 [2%]) (percentage difference, 17%; 95% CI, 3%-32%). Anterograde facial nerve dissection was used more in the NIM group (27 of 31 [87%]) compared with the FNM group (28 of 61 [46%]) (percentage difference, 41%; 95% CI, 24%-58%). Treatment with retrograde dissection without identification of the main trunk of the facial nerve was performed in 21 of 61 (34%) in the FNM group compared with 0 of 31 (0%) in the NIM group. Operative time was significantly shorter in the FNM group, and patients in the FNM group were more likely to complete surgery sooner (adjusted hazard ratio, 5.36; 95% CI, 2.00-14.36).

Conclusions and Relevance  Facial nerve mapping before facial vascular anomaly surgery was associated with less intraoperative facial nerve injury and shorter operative time. Mapping enabled direct identification of individual intralesional and perilesional nerve branches, reducing the need for traditional anterograde facial nerve dissection, and allowed for safe removal of some lesions after partial nerve dissection through transoral or direct excision.

Introduction

Surgical treatment of cervicofacial vascular anomalies is challenging due to malformation location, vascularity, and risk to surrounding structures, particularly the often elongated, displaced branches of the facial nerve. Compared with parotidectomy, the incidence of facial nerve injury for treatment of vascular malformations is higher, reported at 9% compared with 5%.1,2 Other treatment modalities, including sclerotherapy, are not without risk to the branches of the facial nerve, and injury rates can be higher than with surgical excision, especially in the region of the zygomatic branch.3,4 Although it is understood that the risk of posttreatment facial nerve dysfunction is high after vascular anomaly treatment, particularly lymphatic malformations, facial nerve functional outcomes have not been consistently reported, and now the importance of including these outcomes in treatment reports is recognized.5,6

Most pediatric facial mass excision procedures are performed with intraoperative nerve integrity facial nerve monitoring (ie, standard nerve integrity monitoring [NIM]), which typically refers to a device that continuously performs electromyography at 2 or 4 locations.7 The device is used routinely in otologic and parotid surgery and is typically set up and used by the surgeon or operating room staff. It enables stimulation of the nerve and provides audible feedback. A recent systematic review and meta-analysis8 of parotidectomy surgery showed no significant long-term nerve outcome improvement using the device. It is known that facial nerve anatomy can be significantly altered in association with facial vascular anomalies, creating increased risk of nerve injury and lifelong morbidity when facial vascular lesions are treated with invasive therapy.1,2

To reduce the risk of facial nerve injury and dysfunction, a more sophisticated form of nerve monitoring and mapping has been described, in which the main trunk and all facial nerve branches are percutaneously defined by a neurophysiologist and continuously monitored during surgery.9,10 In this scenario, motor nerve identification and functional status are determined by the neurophysiologist in direct communication with the operating surgeon, allowing the surgeon to completely focus on efficient lesion removal, while relying on the neurophysiologist’s interpretation of nerve activity. A 2014 uncontrolled case series (>200 cases) of facial nerve mapping (FNM) and facial vascular anomaly surgery found a low incidence of facial nerve injury using the preoperative nerve mapping technique.11

Beginning in 2005, surgeons (S.C.M., J.A.P., and a nonauthor) and neurophysiologists (R.N.H., J.S., G.A.K., and V.M.) at Seattle Children’s Hospital adopted the technique of FNM with continuous monitoring of the facial nerve branches in the treatment of all cervicofacial vascular malformations. As such, 2 distinct groups of patients were defined in retrospective review, one that underwent surgery with NIM facial nerve monitoring from 1999 to 2005, and another that underwent surgery using FNM with a neurophysiologist after 2005. Through comparison of the NIM and FNM groups, the objectives of this study were to test the hypotheses that FNM (1) decreases intraoperative facial nerve injury risk and (2) increases safe surgical approach options for parotid and facial vascular anomaly treatment.

Methods

This investigation was a historically controlled trial at a tertiary vascular anomaly center (Seattle Children’s Hospital) in Seattle, Washington. A consecutive FNM patient cohort after 2005 (FNM group) was compared with a consecutive historical cohort (1999-2005) (NIM group). After Seattle Children’s Hospital institutional review board approved the retrospective study and waived informed patient consent, Current Procedural Terminology codes for consecutive cervicofacial resections with neurovascular dissection were queried for by 3 surgeons (S.C.M., J.A.P., and a nonauthor) treating vascular anomalies from January 1, 1999, through January 1, 2015. The query was cross-referenced with neuromonitoring clinical and vascular anomaly quality improvement databases. Inclusion criteria were vascular anomaly surgical resection with at least one facial nerve branch involved and 2 years’ follow-up. Patients were excluded if the facial nerve was not involved or in case of inadequate follow-up or documentation. The medical records were reviewed, and data were collected for demographics, surgical approach, lesion location, lesion size, involved facial nerve branches, operative time, nerve mapping time, pathology, facial nerve examination before and after surgery at 30 days and 2 years, and nerve monitoring data. The size of the lesion was quantified by computed tomography or magnetic resonance imaging by recording the dimensions and then calculating the volume of ellipsoid with those axes dimensions. In addition to the volume, the specific location on the face was recorded because that may be an independent factor for facial nerve outcome. For example, a lesion with a large volume may involve a single facial nerve branch, or it could involve all 5 branches. This location was quantified within a schematic grid dividing the face into 9 regions. If the lesion was present within a grid space, then it was scored a 1 in a binary fashion, with a maximum score of 9 (Figure 1 and eFigure 1 in the Supplement). Surgical approaches were divided into the following 3 facial nerve dissection categories: (1) anterograde dissection with identification of the main trunk; (2) direct excision with dissection limited to affected distal branches, including transcutaneous or transoral; and (3) retrograde dissection without prior identification of the main trunk. Retrograde dissection was most commonly found in coordination with a neck dissection that involved one or more branches of the facial nerve. In these cases, retrograde dissection followed distal nerve branches, making identification of the main trunk unnecessary.

The surgical approach was chosen by the surgeon. In the NIM group, conventional facial nerve monitoring was used with the Nerve Integrity Monitor (Medtronic), which was set up by the operating room staff or operating surgeon.

FNM Technique

In the FNM group, intraoperative FNM and monitoring were accomplished with triggered and free-running electromyogram (EMG) (Cascade Intraoperative Neuromonitoring Equipment; Cadwell Industries, Inc). Monopolar paired needle electrodes were placed in each of the following ipsilateral areas and muscles: (1) lateral to palpebral commissure (orbicularis oculi), (2) inferolateral to oral commissure (orbicularis oris, risorius, and depressor anguli oris), (3) superolateral upper lip (levator labii superioris and zygomatic minor), and (4) depressor labii (inferior to lower lip). This allowed for adequate monitoring of the ipsilateral temporal, zygomatic, buccal, and marginal mandibular branches of the facial nerve. Electrodes were also placed in the frontalis muscle if required by the location of the lesion.

Before making the incision, preoperative mapping of the facial nerve was done by percutaneous stimulation of the facial nerve and its branches and recording of compound motor action potentials (CMAPs) (eFigure 2 in Supplement). Using a ball-tipped probe, electrical stimulation (0.2-millisecond pulse duration; rate, 1-2 Hz) was delivered to points on the skin with an intensity sufficient to elicit motor responses. To avoid current spread to nearby facial nerve branches, stimulation intensity did not exceed that which gave consistent CMAPs (usually 6-15 mA). Higher intensities were needed for branches underneath large lesions. Points that elicited a motor response were indicated with a marking pen. In this manner, the course of the facial nerve and its branches was mapped on the skin and could be compared with the location of the lesion.

During the surgery, an experienced neurophysiologist (R.N.H., J.S., G.A.K., or V.M.) continuously monitored (1) the free-running EMG output for motor unit action potentials and (2) the triggered CMAPs to intrafield stimulation. Neurotonic discharges, including high-frequency or sustained discharges, were specifically monitored and recorded. The continuous EMG was supplemented with intrafield electrical stimulation (0.1-millisecond pulse duration, 0.1-1.0 mA, and repetition rate of 2 Hz) with a monopolar insulated 1.0-mm-diameter ball-tipped handheld probe (Xomed; Medtronic). For intrafield stimulation, the intensity was varied, and real-time feedback was obtained with direct communication between the surgeon and the neurophysiologist or technician. Localization of the facial nerve branches by intrafield stimulation and recording of CMAPs was used to aid dissection.8

Statistical Analysis

Baseline demographic and clinical characteristics of children in the NIM and FNM groups were summarized with appropriate statistics. Continuous variables were summarized by means (SDs) and compared using the 2-sample t test if normality assumptions were met; otherwise, medians (interquartile ranges [IQRs]) were used for a summary and the Wilcoxon-Mann-Whitney test for comparisons. Categorical variables were summarized by counts and proportions and compared between study groups with Pearson χ2 test or Fisher exact test as appropriate. Univariate and multivariable logistic regressions were used to evaluate the association of study group (FNM vs NIM) with binary outcome variables of new facial nerve injury at 30 days and 2 years after surgery and anterograde facial nerve dissection. Unadjusted and adjusted odds ratios from the models and corresponding 95% CIs are reported.

The duration of surgery was analyzed with time-to-event methods. At each observed operative time, the cumulative proportions of patients whose surgical procedures had ended were calculated as Kaplan-Meier failure probabilities and plotted. Failure in this case was end of surgery. The Kaplan-Meier curves of operative time were compared between patients in the NIM and FNM groups using the log-rank test. Univariate and multivariable Cox proportional hazards regression models were used to assess the independent association of FNM (vs NIM) and time to completion of surgery (operative time) adjusting for select baseline demographic and clinical variables. Unadjusted and adjusted hazard ratios (relative risks) from Cox proportional hazards regression models and corresponding 95% CIs are reported. All analyses were conducted using Stata (version 15.1; Stata Corp LP).

Results

One hundred six consecutive procedures were identified in the query; 14 were excluded because on review of the operative report the facial nerve was not involved in the lesion resection. Thirty-one procedures occurred before January 1, 2005, the date on which the surgeons adopted FNM and monitoring with the neurophysiologist. These 31 procedures were performed with NIM facial nerve monitoring. Sixty-one procedures were performed with FNM after January 1, 2005. All cases were performed by 1 of 3 surgeons (S.C.M., J.A.P., and a nonauthor) and had documented follow-up for a minimum of 24 months after surgery.

The NIM and FNM groups had similar median ages at 3.3 years (IQR, 2.2-11.4 years) and 4.4 years (IQR, 1.5-11.0 years), respectively (Table 1). Lymphatic malformation was the most common pathology, observed in 19 of 31 (61%) in the NIM group and 32 of 61 (52%) in the FNM group (percentage difference, 9%; 95% CI, −12% to 30%). Among those, there were stage 3 or 4 lymphatic malformations in 9 of 19 (47%) in the NIM group compared with 18 of 32 (56%) in the FNM group (percentage difference, −9%; 95% CI, −37% to 19%). More diversity of pathology was observed in the FNM group, with infantile hemangiomas in 11 of 61 (18%) and venous malformations in 13 of 61 (21%), compared with no infantile hemangioma and only 1 venous malformation in the NIM group. A significant majority in both groups had at least 4 cranial nerve (CN) VII branches involved (20 of 31 [65%] in the NIM group vs 34 of 61 [56%] in the FNM group; percentage difference, 9%; 95% CI, −12% to 30%). The median anomaly volume was 52.4 mL (IQR, 12.8-183.3 mL) in the NIM group and 65.4 mL (IQR, 18.8-180.2 mL) in the FNM group (median difference, −13 mL; 95% CI, −32 to 23 mL). The median numbers of facial grid spaces occupied were similar at 3 (IQR, 2-6) in the NIM group and 4 (IQR, 3-6) in the FNM group (median difference, −1; 95% CI, −2 to 0). The preoperative facial nerve examination was normal in all patients for the NIM group and in 60 of 61 patients for the FNM group, in which one patient had a preoperative marginal mandibular nerve weakness from a prior surgery seen at our initial consultation. The numbers of patients who had previously undergone an operation for treatment of the same lesion were 3 in the NIM group and 6 in the FNM group.

Examples of 3 patients in the FNM group are shown with preoperative photographs, facial grid schematic assignment, FNM, and postoperative photographs for pathologies of venous malformation, infantile hemangioma, and lymphatic malformation, respectively (Figure 1 and eFigure 1 in the Supplement). The location and distribution of lesions in the FNM and NIM groups are shown organized by surgical approach in Figure 2. Qualitatively, Figure 2 shows that pathology treated with retrograde dissection was most densely distributed near the lower branches of the facial nerve, and pathology treated with direct excision (transcutaneous or transoral) was most densely distributed near distal facial nerve branches, anteriorly on the midface in the FNM group. Most patients (87% [27 of 31]) in the NIM group were treated with an anterograde facial nerve dissection compared with 46% (28 of 61) in the FNM group (percentage difference, 41%; 95% CI, 24%-58%). Retrograde dissection approaches were used in 34% (21 of 61) in the FNM group compared with 0% (0 of 31) in the NIM group (percentage difference, −34%; 95% CI, −46% to −23%).

Operative times were shorter for the FNM group, even when including the median 25 minutes for FNM (Table 1). The median operative time in the FNM group (131 minutes; IQR, 97-220 minutes) was 79 minutes (95% CI, 20-138 minutes) less than that in the NIM group (210 minutes; IQR, 141-385 minutes); univariate and multivariable Cox proportional hazards regression models demonstrated that patients in the FNM group were significantly more likely to complete surgery sooner (adjusted hazard ratio, 5.36; 95% CI, 2.00-14.36) (Figure 3).

Facial nerve outcomes at 30 days showed that 35% (11 of 31) in the NIM group had an abnormal examination compared with 12% (7 of 61) in the FNM group (percentage difference, 24%; 95% CI, 5%-43%) (Table 1). In multivariable analysis adjusting for differences between the FNM and NIM groups other than percutaneous mapping, new facial nerve injury was less at 30 days (odds ratio, 0.24; 95% CI, 0.07-0.86) in the FNM group (Table 2).

At 24 months, abnormal facial nerve examinations were observed in 19% (6 of 31) in the NIM group compared with 2% (1 of 61) in the FNM group (percentage difference, 17%; 95% CI, 3%-32%). Multivariable analysis at 24 months resulted in instability due to the paucity of events.

Discussion

Ninety-two consecutive patients undergoing vascular anomaly operations involving at least one branch of the facial nerve were analyzed, the first 31 of which were performed using conventional NIM facial nerve monitoring and the remaining 61 performed in coordination with a neurophysiologist using intraoperative nerve mapping and monitoring (FNM). These comparisons of FNM with a historical control allow estimates of its efficacy for improving outcomes that were not possible with previously published case series. The results demonstrated a significant risk reduction of short-term and long-term facial nerve injury using the FNM technique (percentage difference at 2 years, 17%; 95% CI, 3%-32%). In both univariate and multivariable logistic regression analyses, patients in the FNM group had significantly reduced odds of abnormal CN VII examination (House-Brackman score >1) at 30 days after surgery (adjusted odds ratio, 0.24; 95% CI, 0.07-0.86) than those in the NIM group. In the NIM group, 87% (27 of 31) were treated with an anterograde facial nerve dissection approach, in which the main trunk of the facial nerve was first identified and then carefully followed distally to isolate distal branches. This approach and the dissection require an extensive face-lift or modified Blair incision, which traumatizes the whole facial nerve. In the FNM group, this approach was used only 46% (in 28 of 61) of the time, which means that vascular lesion removal was possible with less nerve trauma and surgical dissection. With FNM, there were 21 instances of retrograde dissection compared with none in the NIM group. Knowledge of the precise distal facial nerve branch locations following FNM before making a surgical incision enables planning of a less invasive surgical procedure, often through a small incision. The ability to accurately interrogate and stimulate distal nerve branch candidates frequently made distal nerve identification easy and enabled the retrograde technique, even when a total facial nerve dissection was necessary. If distal facial nerve branches could not be easily identified, then traditional anterograde facial nerve dissection could be performed. However, more frequent determination of the facial nerve location with FNM enabled reduced incision length and decreased frequency of the main trunk identification and dissection.

Ulkatan et al11 reported on more than 200 cases using a similar technique of FNM, and they also found low risk of facial nerve injury (1.5%). Other researchers have published smaller series, with similar results.10 Articles cited in the Introduction herein have generally reported that the risk of facial nerve injury is 5% to 10% for treatment of vascular anomaly in the cervicofacial region.1-4 The reason for dramatically improved facial nerve outcomes is in part explained by the FNM but also because the FNM enables (1) improved planning for an approach that has potentially less collateral tissue damage and (2) focused concentration by the surgeon, with confidence in the intraoperative interrogations of the nerve, as reported by the neurophysiologist.

A major observation in the present study was the real-time feedback from the neurophysiologist that the surgeon received, without removing attention from the operative site. The neurophysiologist adjusted the amplitude of the current to the stimulation probe based on where the surgeon was operating relative to the nerve. For example, if the surgeon was in close proximity to a branch of the facial nerve, the amplitude was reduced to a low value (0.1 mA) to identify and test the integrity of the nerve. In contrast, if the surgeon was away from the expected location of the nerve but wanted to confirm that, a high-amplitude stimulation (1.0 mA) was a sensitive test to rule out the presence of a nerve branch in that location before dividing tissue. Perhaps most important was the real-time interpretation of the stimulated responses to determine if the waveforms were a true evoked response vs stimulus (artifact). This is in contrast to the Nerve Integrity Monitor (Medtronic) used in the NIM group, which provided audible feedback and limited real-time interpretation. There was an opportunity to examine the waveforms, but this diverted the surgeon’s attention away from the surgical field. Confidence in the nerve interrogation with FNM enabled enhanced efficiency of surgical tasks and more direct surgical approaches, especially for benign vascular lesions, which are at high risk of nerve injury due to perineural bleeding. This is reflected in the number of surgical procedures in the FNM group for nonlymphatic malformation lesions. It was also supported in the operative times, which were significantly shorter in the FNM group; patients in this group were more likely to have had their surgery completed (adjusted hazard ratio, 5.36; 95% CI, 2.00-14.36). The median preoperative nerve mapping time in the FNM group was 25 minutes (IQR, 16-34 minutes), similar to prior findings.11 Reduction of actual operative time is not to be underestimated because it is an important means of reducing surgeon stress, infection risk, soft-tissue trauma, and immediate postoperative morbidity. The cost of facial nerve monitoring is difficult to estimate because it varies widely at different institutions. We believe that this cost is justified given not only the expense of operating room time but also the potential for reduced recovery time. Most important is the reduced risk of facial nerve injury, which can lead to lifelong morbidity.

Limitations

This study is limited by its retrospective and nonrandomized design. There was an increased risk of bias from the historically controlled research design, which was subject to potential confounding from surgeon learning curves and unidentified or unmatched confounders in the 2 groups. However, the analysis of consecutive patients by 3 surgeons strengthens the comparison between the NIM and FNM groups. In most patients, the pathology is not a life-threatening problem. Without the FNM technique, many of these operations may not have even been offered, which is supported by the increased number of venous malformations, arteriovenous malformations, and hemangiomas in the FNM group compared with the NIM group. Although creating challenges in comparing the 2 groups, this would be expected to bias against finding a significant risk reduction for facial nerve injury in the FNM group. The pathology was more diverse in the FNM group, particularly with 11 infantile hemangiomas included. If the 11 infantile hemangiomas in the FNM group are excluded, the percentage difference was −17% (95% CI, −32% to −3%), with abnormal facial nerve examinations in 2% (1 of 50) in the FNM group compared with 19% (6 of 31) in the NIM group at 2 years after surgery. Because outcomes were better in the FNM group in terms of facial nerve function, FNM provides a degree of safety, despite increased complexity of the surgery. This association was not due to partial treatment. Of note, the same FNM technique can be used for other CNs, including hypoglossal and spinal accessory nerves. The data presented herein support increased safety of facial nerves with the use of FNM, as well as more surgical approach options, with no increase in total operative time, even when including the time for nerve mapping.

Conclusions

In this study of 92 consecutive patients with vascular anomaly, FNM in coordination with a neurophysiologist was associated with lower short-term and long-term facial nerve injury rates and enabled more surgical approach options compared with conventional NIM facial nerve monitoring. At 2 years after surgery, the rate of facial nerve injury was 19% (6 of 31) in the NIM group compared with 2% (1 of 61) in the FNM group. The surgical approach options were significantly different between the 2 study groups, and the frequency of anterograde facial nerve dissection with identification of the main trunk was 87% (27 of 31) in the NIM group compared with 46% (28 of 61) in the FNM group. Operative time was significantly shorter in the FNM group. As such, FNM is a technique that is recommended for surgical excision of vascular anomalies in the cervicofacial region that may involve a branch of the facial nerve.

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Article Information

Accepted for Publication: January 24, 2018.

Corresponding Author: Randall A. Bly, MD, Division of Pediatric Otolaryngology, Seattle Children’s Hospital, 4800 Sand Point Way, Ste OA 9.220, Seattle, WA 98105 (randall.bly@seattlechildrens.org).

Published Online: March 29, 2018. doi:10.1001/jamaoto.2018.0054

Author Contributions: Drs Bly and Perkins had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Bly, Holdefer, Slimp, Kinney, Perkins.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Bly, Holdefer, Perkins.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Bly, Holdefer.

Administrative, technical, or material support: Bly, Slimp, Kinney, Manning, Perkins.

Study supervision: Perkins.

Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported.

Funding/Support: This research was supported by the Seattle Children’s Hospital Guild Funding Focus Award (to Dr Perkins) and by grants R01 NS092772 and NIHMS-ID 905693 from the National Institutes of Health.

Role of the Funder/Sponsor: The funding sources had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Meeting Presentation: This study was presented at the 2017 Annual Meeting of the American Society of Pediatric Otolaryngology; May 19, 2017; Austin, Texas.

Additional Contributions: Eden Palmer (Seattle Children’s Hospital) assisted in the creation of the figures. Carrie Capri (Seattle Children’s Hospital) aided in the preparation of the manuscript. Andrew Inglis, MD (Seattle Children’s Hospital), contributed to the data collection. Biostatistician Frankline Onchiri, PhD (Seattle Children’s Research Institute), helped with the statistical design and analysis. No compensation was received outside of usual salary. We thank the patients and families for granting permission to publish this information.

References
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Lee  GS, Perkins  JA, Oliaei  S, Manning  SC.  Facial nerve anatomy, dissection and preservation in lymphatic malformation management.  Int J Pediatr Otorhinolaryngol. 2008;72(6):759-766.PubMedGoogle ScholarCrossref
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Slaughter  KA, Chen  T, Williams  E  III.  Vascular lesions.  Facial Plast Surg Clin North Am. 2016;24(4):559-571.PubMedGoogle ScholarCrossref
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