Surgery is the main treatment modality for parotid tumors. However, resection of parotid tumors can be challenging owing to the complex anatomy of the intraparotid facial nerve (IFN). Any incorrect procedure could lead to facial paralysis, which could greatly affect the facial expressions and functions of the patients, disrupting their social interactions and deteriorating their quality of life. A 27.2% incidence of temporary facial paralysis and 4.1% incidence of permanent facial paralysis have been reported after parotid tumor resection (Zhang et al., 2013; Schapher et al., 2021). Therefore, a thorough preoperative assessment of the anatomy of the IFN is crucial before parotid tumor resection.

Surgeons typically use preoperative imaging data to obtain information about the tumor location. The approximate location of the IFN is determined by the hypothetical connection of some specific anatomical landmarks on the image, such as the retromandibular vein, U-line, and facial nerve line (the connection between the lateral surface of the posterior belly of the digastric and the lateral surface of mandibular ramus) (de Ru et al., 2002; Divi et al., 2005; Lim et al., 2008; Fujii et al., 2019). These methods enable quick localization of tumors in the parotid gland. However, as the IFN cannot be directly visualized, these methods indirectly judge the anatomical relationship between the tumors and the IFN, and are therefore, unable to create a detailed anatomical map of the tumor and the key structures in the parotid gland, which could lead to the spatial relationship between the tumor and the IFN being misdiagnosed (Fujii et al., 2019; Kim et al., 2021).

Direct imaging and visualization of the IFN can help improve the diagnostic accuracy of the positional relationship between the tumor and the IFN. High-field magnetic resonance imaging (MRI) has shown its potential in the direct imaging of IFN, and some specific sequences were reported to be able to directly display the IFN with high signal intensity (Li et al., 2012; Chu et al., 2013; Guenette et al., 2019; El Kininy et al., 2020; Lee et al., 2021). Three-dimensional double-echo steady-state with water excitation (3D-DESS-WE) was one of the MRI sequences that showed promising diagnostic accuracy in the direct visualization of the IFN and localization of parotid tumors (Qin et al., 2011; Fujii et al., 2019; Jung et al., 2020; Kim et al., 2021). With the enhancement of visualization of IFN, the treatment process of parotid tumor resection was predicted to be improved by applying image-guided surgical techniques such as mixed reality and surgical navigation.

Through this research, we aimed to introduce a novel method of parotid tumor resection assisted by preoperative and intraoperative direct visualization of IFN, and to preliminarily explore the application effect of direct visualization of IFN in parotid tumor resection.