Facial nerve mapping and monitoring in lymphatic malformation surgery

International Journal of Pediatric Otorhinolaryngology 73 (2009) 1348–1352

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Facial nerve mapping and monitoring in lymphatic malformation surgery Jospeh Chiara c, Greg Kinney d, Jefferson Slimp d, Gi Soo Lee b, Sepehr Oliaei a, Jonathan A. Perkins a,b,* a

Division of Pediatric Otolaryngology, Seattle Children’s Hospital, Seattle, WA, United States Department of Otolaryngology – Head and Neck Surgery, University of Washington, Seattle, WA, United States c Division of Otolaryngology – Head and Neck Surgery, Madigan Army Medical Center, Tacoma, WA, United States d Department of Rehabilitation Medicine, University of Washington, Seattle, WA, United States b

A R T I C L E I N F O

A B S T R A C T

Article history: Received 31 January 2009 Received in revised form 5 May 2009 Accepted 12 June 2009 Available online 9 July 2009

Objective: Establish the efficacy of preoperative facial nerve mapping and continuous intraoperative EMG monitoring in protecting the facial nerve during resection of cervicofacial lymphatic malformations. Methods: Retrospective study in which patients were clinically followed for at least 6 months postoperatively, and long-term outcome was evaluated. Patient demographics, lesion characteristics (i.e., size, stage, location) were recorded. Operative notes revealed surgical techniques, findings, and complications. Preoperative, short-/long-term postoperative facial nerve function was standardized using the House-Brackmann Classification. Mapping was done prior to incision by percutaneously stimulating the facial nerve and its branches and recording the motor responses. Intraoperative monitoring and mapping were accomplished using a four-channel, free-running EMG. Neurophysiologists continuously monitored EMG responses and blindly analyzed intraoperative findings and final EMG interpretations for abnormalities. Results: Seven patients collectively underwent 8 lymphatic malformation surgeries. Median age was 30 months (2–105 months). Lymphatic malformation diagnosis was recorded in 6/8 surgeries. Facial nerve function was House-Brackmann grade I in 8/8 cases preoperatively. Facial nerve was abnormally elongated in 1/8 cases. EMG monitoring recorded abnormal activity in 4/8 cases—two suggesting facial nerve irritation, and two with possible facial nerve damage. Transient or long-term facial nerve paresis occurred in 1/8 cases (House-Brackmann grade II). Conclusions: Preoperative facial nerve mapping combined with continuous intraoperative EMG and mapping is a successful method of identifying the facial nerve course and protecting it from injury during resection of cervicofacial lymphatic malformations involving the facial nerve. ß 2009 Elsevier Ireland Ltd. All rights reserved.

Keywords: Facial nerve Lymphangioma Monitoring Mapping

1. Introduction Cervicofacial lymphatic malformations (LMs) of the face and parotid region are frequently intimately associated with the facial nerve (FN) [1]. The infiltrative nature of these lesions and their intimate involvement with and distortion of surrounding normal tissues, including the parotid gland and FN itself, alter typical anatomic associations and increase the likelihood of FN damage during surgery [1–3]. As shown in this study, the FN has a variable relationship with the LM and can be completely surrounded or even elongated by it. Compounding this problem, the propensity of these malformations to recur often warrants repeated surgeries

* Corresponding author at: Seattle Children’s Hospital, Division of Otolaryngology – Head and Neck Surgery, 4800 Sand Point Way N.E./W-7729, Seattle, WA 98105-0371, United States. Tel.: +1 206 987 3468; fax: +1 206 987 3925. E-mail address: [email protected] (J.A. Perkins). 0165-5876/$ – see front matter ß 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijporl.2009.06.008

that require FN identification amidst fibrosis and adhesions [4]. FN paralysis commonly occurs in surgeries to remove cervicofacial LM. It has been reported in as many as one-third to three-fourths of patients undergoing surgery for cervicofacial LM associated with the FN [5]. The high rates of FN paralysis in cervicofacial LM underscore the need for improved techniques in identifying the FN and its course as well as in performing close monitoring of FN throughout the surgical procedure. Any surgery in the parotid region requires meticulous dissection to avoid injury to the FN. Rates of short-term, postparotidectomy facial paresis range from 27 to 65%, with rates of permanent paralysis being 4–7% [6–9]. Intraoperative facial nerve monitoring during parotid surgery allows for early identification of the FN, mapping of its course through the facial region, warning of unexpected stimulation during dissection, and determination of FN prognosis at conclusion of surgery. A majority of otolaryngologists in the U.S. use some form of intraoperative nerve monitoring during parotid gland surgery [10]. Current methods of intraopera-

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Fig. 1. Preoperative percutaneous facial nerve mapping and monitoring electrodes in place out of the surgical field.

tive FN monitoring include use of hand-held nerve stimulators [11], electromyography (EMG) [12] and mechanical surface pressure gauge sensors [13]. Continuous EMG monitoring has been shown to improve surgical outcome in complicated parotid surgeries and has recently been reported during sclerotherapy for parotid lesions [12,14]. In this technique, high frequency bursts of motor unit potentials triggered by injury to FN are used to alert the surgeon during the operation [15]. In this study, we present the results of our experience with preoperative FN mapping and continuous intraoperative EMG monitoring and mapping in a retrospective case series of patients undergoing surgery for cervicofacial LM at a tertiary care pediatric hospital. 2. Materials and methods Medical records of all LM patients who presented to Seattle Children’s Hospital from 2000 to 2005 were reviewed. Inclusion criteria included diagnosis of cervicofacial LM, surgical procedure with FN dissection and use of FN mapping with continuous EMG FN monitoring. In addition, one patient with diagnosis of facial hemangioma and another diagnosed with a facial parapharyngeal cyst were included, both of whom preoperatively included LM as potential diagnosis and underwent preoperative FN mapping and intraoperative facial nerve dissection with continuous EMG monitoring and mapping. Seven patients who met these criteria underwent a total of 8 FN dissections. Patient demographics and lesion characteristics, including size, stage, and location (determined by CT imaging), were recorded. Operative notes provided

information regarding surgical techniques, approach to FN, extent of FN dissection, anatomic relationship of the LM to the FN, intraoperative nerve monitoring, and intraoperative complications. LM staging was determined according to the criteria defined by de Serres et al. [16]. Stage I has unilateral infrahyoid disease; stage II, unilateral suprahyoid disease; stage III, unilateral infraand suprahyoid disease; stage IV, bilateral suprahyoid disease; stage V, bilateral infra- and suprahyoid disease. Intraoperative FN monitoring was accomplished using four channels of free-running and triggered EMG (Cascade Intraoperative Neuromonitoring Equipment, Cadwell Laboratories Inc.; Kennewick, WA). Monopolar paired needle electrodes were placed in each of the following ipsilateral areas and muscles: (1) lateral to palpebral commissure (obicularis oculi), (2) inferolateral to oral commissure (obicularis 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 FN. These electrodes recorded and monitored facial nerve EMG signals. Prior to making the incision, preoperative mapping of the FN was done by percutaneous stimulation of the FN and its branches and recording of compound motor action potentials (CMAPs) (Fig. 1). Using a blunt probe, electrical stimulation was delivered to points on the skin via a 0.2 ms duration pulse at a rate of 1–2 s 1 and an intensity sufficient to elicit motor responses (usually 10–15 mA). Points that elicited a motor response were marked with ink. In this manner, the course of the FN and its branches were mapped on the skin and could be visualized in relationship to the LM.

Fig. 2. Preoperative facial nerve map and correlation of this map with intraoperative facial nerve location. Note the proximal trunk of the facial nerve was difficult to map due to the large cyst overlying this region. At surgery this trunk was displaced inferiorly over the posterior belly of the digastric muscle.

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1350 Table 1 Preoperative evaluation. Patient number

Age (months)

LM size

LM stage

LM location

House-Brackmann preop

1 1 2 3 4 5 6 7

30 40 32 105 8 2 10 17

Large Large Large Small Large Large Large Small

IV IV III Parapharyngeal cyst V III III Hemangioma

Neck, floor of mouth, parotid, parapharyngeal and buccal region Inferior partoid, parapharyngeal space, floor of mouth Left face, neck, parotid Right face Right neck, anterior and posterior face Lateral neck, floor of mouth, parapharyngeal region Posterior triangle, larynx, carotid sheath, parapharyngeal space Left face

I I I I I I I I

During LM surgery, an experienced neurophysiologist continuously monitored (a) the free-running EMG output for motor unit action potentials and (b) the triggered CMAPs to intrafield stimulation. A baseline recording was obtained before beginning the operation. Any discharge was displayed on the viewing screen, and the operating surgeon was notified regarding its degree and location. Neurotonic discharges, including high-frequency or sustained discharges, were specifically monitored and recorded. The continuous EMG was supplemented with intrafield electrical stimulation with a monopolar hand-held electrode (Xomed flush tip probe, Medtronic, Jackonsville, FA) applied directly to the nerve with a 0.05 ms duration pulse at intensities from 0.5 to 1.0 mA pulses to evoke a CMAP. Localization of the FN branches, by intrafield stimulation and recording of CMAPs, was used to aid dissection. Secondly, decrement in a CMAP of greater than 50% was used as a warning of potential FN compromise. Intraoperative findings and final interpretations of the EMGs were blindly analyzed by a senior neurophysiologist to detect any abnormalities. Standard technique for localization of the FN was undertaken using a combination of the two-tunnel technique and retrograde FN dissection, while using the FN map to accelerate nerve identification (Fig. 2). For the two-tunnel technique, a superior tunnel separated the parotid tissue from the tragus. The tragal pointer and tympanomastoid suture were identified. An inferior tunnel separated the tail of the parotid from the sternocleidomastoid muscle. This allowed for identification of the posterior belly of the digastric muscle and the main trunk of the FN. For retrograde dissection, the distal FN branches were directly identified through use of the cutaneous nerve map, blunt dissection and nerve stimulation. The cutaneous nerve map is used by redraping the skin flap over the operative site intraoperatively. The nerve map marks remain consistent during the procedure. Once all peripheral facial nerve branches have been identified with the map, intrafield stimulation and direct visualization FN dissection are completed as necessary. Preoperative, short- and long-term postoperative FN functions were standardized using the House-Brackmann Classification (HBC), as documented in clinic notes [17]. Patients were observed in clinic for a period of at least 6 months following surgery, and their long-term outcomes were thus evaluated.

This study was approved by the Seattle Children’s Hospital Institutional Review Board. 3. Results Seven patients underwent a total of 8 LM surgeries, all of which were monitored using the technique described above (Table 1). The median age of patients at time of surgery was 30 months (range of 2–105 months). Preoperative diagnosis of LM was recorded in 6/8 surgeries. LM stage varied from III to V. FN function was HB grade I in all patients preoperatively. The average time to map the FN, main trunk and distal branches prior to surgery ranged from 25 to 30 min. During the operation, the FN was noted to be abnormally elongated in 1/8 cases. In all cases, the nerve was surrounded by the LM or was located deep to the lesion. We were unable to time the speed of FN identification during surgery, due to variation in LM location and extent. All operations involved total parotidectomy and complete FN dissection involving the lower facial nerve division or both upper and lower divisions (Table 2). Using the percutaneous nerve mapping, rapid identification of the FN was possible at the main trunk or individual distal branches. The percutaneous mapping was consistently within 5 mm of each of these branches, which, along with continuous intraoperative EMG monitoring of peripheral FN branches, greatly refined our ability to identify FN branches in either proximal or distal locations (Figs. 2 and 3). Nerve dissection was facilitated by identification of both proximal and distal nerves by intrafield stimulation technique, in the midst of distorted, inflamed malformation tissue. This type of nerve localization enabled more complete extirpation of malformation tissue when it extended medially into the parapharyngeal region, anteriorly into the midface and oral commisure region or when the malformation tissue was indistinguishable for neural tissue. Electromyographic monitoring recorded abnormal activity in 4/ 8 cases, suggesting FN irritation (neurotonic discharges) in 2 of these cases and possible FN damage in the other 2 cases (reduced CMAPs). When nerve irritation occurred, nerve monitoring enabled the dissection to be completed while leaving a half-to-one millimeter thick soft tissue covering around the distal FN branches,

Table 2 Intraoperative and postoperative evaluation. Patient number

Extent of FN dissection

Intraoperative EMG changes

Type of dissection

Relationship of LM to FN

House-Brackmann postop/long-term

1

Total upper and lower

Blunt, sharp, BPE

Surrounding

I/I

1 2 3

Total lower Total upper and lower Total upper and lower

Blunt, sharp, BPE Blunt, sharp, BPE Sharp, BPE

Surrounding Surrounding Deep

I/I I/I II/II

4 5 6 7

Total Total Total Total

Possibe mandibular and buccal damage (lost signal) None None Reduced response in levator nasi, orbicularis oris, and depressor labii Facial nerve irritation None FN and spinal accessory irritation None

Blunt, sharp, BPE BPE, UPE Sharp Unknown

Deep Deep Deep Surrounding

I/I I/I I/I I/I

lower lower Lower upper and lower

BPE = bipolar electrocautery, UPE = unipolar electrocautery.

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Fig. 3. Preoperative facial nerve map and correlation of this map with intraoperative facial nerve location. Note the distal branches of the facial nerve are very close to superimposed map.

so that nerve trauma was minimized. Transient or long-term FN paresis occurred in only one case. This patient, diagnosed with a parapharyngeal cyst, continued to exhibit grade II facial weakness in subsequent clinic visits. EMG monitoring in this case had indicated ‘‘reduced response in levator nasi, orbicularis oris, and depressor labi muscles,’’ but electrical stimulation at conclusion of surgery did not suggest a ‘‘profound compromise of function,’’ since responses were still present. 4. Discussion Cervicofacial LMs are rare but are a cause of significant functional limitation interfering with glutition, respiration, head and neck positioning, bone development, vision and hearing. Additionally, they present a serious cosmetic issue, altering the aesthetic appearance of the face and neck. Multiple methods have been described for treating cervicofacial LM, but in many cases surgical excision is the most effective and best treatment option available to these patients [18–23]. It is difficult to firmly establish the rate of FN injury during surgery for removal of cervicofacial LM because the risk of injury varies with each LM and its respective association with the FN. However, amongst LMs closely associated with the FN, some incidences of FN injury have been reported as much higher than the rate for standard parotid surgery [4–9]. This is expected because the LM can involve local soft tissue altering typical anatomy, can completely surround the FN, and can elongate the FN, thus displacing branches of the facial nerve from their typical and expected locations [1]. The goal of this research was to review our practice of preoperative FN mapping with continuous intraoperative EMG monitoring and describe a successful technique for identifying the FN and protecting it from injury during surgery. In this retrospective case series, we demonstrated the utility of preoperative FN mapping and continuous intraoperative EMG monitoring in LM surgery involving the FN. In practice, preoperative percutaneous FN mapping made localization and identification of the facial nerve rapid and simple, once the skin flap was raised. Preoperative nerve mapping has the potential to increase total operative time, but the trade-offs of more rapid nerve identification, increased surgeon confidence in nerve dissection and probable decrease in surgical time are well worth the extra effort and cost. In our series, we did not have any incidents of profound facial nerve damage or paralysis, and we reported only one case of mild paresis in a non-LM patient. Preoperative FN mapping allows the surgeon to visualize the course of the FN and its branches in relation to the LM

prior to making the first incision, to plan the dissection accordingly, and to improve intraoperative localization. Continuous intraoperative EMG reinforces the preoperative mapping and allows the surgeon to continue to map the course of the nerve through or around the LM during surgery as well as be alerted when the dissection is placing undue stress on the FN or its distal branches. A small amount of tissue may be left on the distal FN branches to help preserve postoperative FN function while not increasing the risk of LM persistence. Overall, we observed an incidence of FN injury that was lower than the reported rate and quite low overall, consisting of a single (1/8) HB grade II paresis. 5. Conclusion We believe that preoperative FN mapping and continuous EMG monitoring reduce the incidence of FN injury and the overall morbidity associated with resection of cervicofacial LM involving the FN. Conflict of interest statement The following authors have no personal, organizational, or other relationships that would influence or bias the statements made in this manuscript: Joseph Chiara, MD; Greg Kinney, PhD; Jefferson Slimp, PhD; Gi Soo Lee, MD; Sepehr Oliaei, MD; Jonathan A. Perkins, DO. Acknowledgements Eden Palmer, figure preparation; Stacy Russ, manuscript preparation. Funding source: None. References [1] G.S. Lee, J.A. Perkins, S. Oliaei, S.C. Manning, Facial nerve anatomy, dissection and preservation in lymphatic malformation management, Int. J. Pediatr. Otorhinolaryngol. 72 (6) (2008 June) 759–766. [2] C.M. Giguere, N.M. Bauman, Y. Sato, D.K. Burke, J.H. Greinwald, S. Pransky, et al., Treatment of lymphangiomas with OK-432 (Picibanil) sclerotherapy: a prospective multi-institutional trial, Arch. Otolaryngol. Head Neck Surg. 128 (10) (2002 October) 1137–1144. [3] B.J. Hancock, D. St-Vil, F.I. Luks, M. Di Lorenzo, H. Blanchard, Complications of lymphangiomas in children, J. Pediatr. Surg. 27 (2) (1992 February) 220–224, discussion 4–6. [4] L.J. Fliegelman, D. Friedland, M. Brandwein, M. Rothschild, Lymphatic malformation: predictive factors for recurrence, Otolaryngol. Head Neck Surg. 123 (6) (2000 December) 706–710.

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