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

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.

Figure 1.. 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

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

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.