Accelerated recovery from facial paralysis using individual‐target transcranial magnetic stimulation after masseteric–facial nerve end‐to‐end anastomosis: A case report

Abstract

Dear Editor, The resection of intracranial tumors, such as acoustic neuroma, often causes facial paralysis.1 Injury to the facial nerve is the immediate cause of this paralysis. Nerve anastomosis, including hypoglossal–facial2 and masseteric–facial nerve anastomosis (MFA),3 is an effective method to remodel the injured nerve and establish a nerve regeneration pathway.4, 5 However, regaining normal facial function and good symmetry takes more than 12 months.6 Repetitive transcranial magnetic stimulation (rTMS) applies a continuously adjustable magnetic field to the central nervous system (CNS), achieving cumulative curative results. However, whether rTMS can be used to promote recovery from facial paralysis is known. Here, we report accelerated facial recovery with a novel form of rTMS, individual-target TMS (IT-TMS). The patient's recovery period was reduced to approximately 6 months with a corresponding improvement in House–Brackmann (HB) scale results. The patient was a 33-year-old woman who had surgery for the removal of a left acoustic neuroma on June 15, 2021. Then she gradually developed facial paralysis on the left side, evaluated as grade VI using the HB scale. The paralysis was initially complicated by loss of control of the left facial muscles, deviation of the mouth to the right side, facial asymmetry, and incomplete eyelid closure. Symptoms progressed to left facial dystonia and stiffness, loss of control of the angulus oris on the lesioned side, an expanded area of unclosed eyelid, and self-reported insomnia. Four months later, the patient underwent MFA (Figure 1A,B) on October 16, 2021. During the following 1 month prior to IT-TMS treatment, the patient received daily traditional Chinese medicine treatment. She was also prescribed nerve growth factor and vitamin B12. However, her facial function did not improve and the facial grade VI persisted. The patient denied a history of facial trauma or other tumor surgery, and she had had a normal facial function before the removal of the acoustic neuroma. The possibility of epilepsy, magnetic resonance imaging (MRI) contraindications, and other diseases were excluded (Table S1). The patient provided written informed consent. This study was approved by the Ethics Committee of Xijing Hospital and conducted under the Declaration of Helsinki. IT-TMS (Figure 1C) was initiated at the Department of Neurosurgery, Xijing Hospital, on November 15, 2021. IT-TMS was performed under established safety guidelines and protocols,7 using a stimulator with a figure-8 coil and a neuronavigational system, the Black Dolphin Navigation Robot (S-50, Solide Company, Xi'an, China), with a coupled three-dimensional individualized facial tracer and infrared cameras that guided the precise and repetitive targeting over the same site across different sessions. The specific anatomical sites are in the precentral gyrus that are corresponding to masseteric muscles (Figure 1D). Briefly, the predefined targets, based on individual MRI brain images collected prior to treatment, were integrated into the operation system, in which a three-dimensional restoration of brain images and targets was visualized (Figure 1C). This process allowed the visual operation for target selection and monitoring. The patient received 10 Hz stimulation at 120% of the resting motor threshold delivering 18 trains with an inter-train interval of 8 s (1800 pulses per session, 2 sessions/3600 pulses per day, 5 days/10 sessions per week, 1 week interval after 1 week stimulation). The intersession interval was 50 min, and the treatment lasted 6 months. The schematic signal transduction evoked by IT-TMS is shown in Figure 1E. The patient was instructed by a professional physiotherapist to perform 30 min of facial exercises daily (as shown in Video S1 and S2) immediately after IT-TMS. She was also encouraged to do the daily exercises during the weekly interval as well. The clinical information is summarized in Table S1. The HB results