J Korean Neurosurg Soc.  2023 Mar;66(2):183-189. 10.3340/jkns.2022.0134.

Significance of Preoperative Nerve Reconstruction Using Diffusion Tensor Imaging Tractography for Facial Nerve Protection in Vestibular Schwannoma

• Zhang Y
• Ge H
• Xu M
• Mei W

• KMID: 2539879
• DOI: http://doi.org/10.3340/jkns.2022.0134

Abstract

Objective
: The facial nerve trace on the ipsilateral side of the vestibular schwannoma was reconstructed by diffusion tensor imaging tractography to identify the adjacent relationship between the facial nerve and the tumor, and to improve the level of intraoperative facial nerve protection.
Methods
: The clinical data of 30 cases of unilateral vestibular schwannoma who underwent tumor resection via retrosigmoid approach were collected between January 2019 and December 2020. All cases underwent magnetic resonance imaging examination before operation. Diffusion tensor imaging and anatomical images were used to reconstruct the facial nerve track of the affected side, so as to predict the course of the nerve and its adjacent relationship with the tumor, to compare the actual trace of the facial nerve during operation, verify the degree of coincidence, and evaluate the nerve function (House-Brackmann grade) after surgery.
Results
: The facial nerve of 27 out of 30 cases could be displayed by diffusion tensor imaging tractography, and the tracking rate was 90% (27/30). The intraoperative locations of facial nerve shown in 25 cases were consistent with the preoperative reconstruction results. The coincidence rate was 92.6% (25/27). The facial nerves were located on the anterior middle part of the tumor in 14 cases, anterior upper part in eight cases, anterior lower part in seven cases, and superior polar in one case. Intraoperative facial nerve anatomy was preserved in 30 cases. Among the 30 patients, total resection was performed in 28 cases and subtotal resection in two cases. The facial nerve function was evaluated 2 weeks after operation, and the results showed grade I in 12 cases, grade II in 16 cases and grade III in two cases.
Conclusion
: Preoperative diffusion tensor imaging tractography can clearly show the trajectory and adjacent position of the facial nerve on the side of vestibular schwannoma, which is beneficial to accurately identify and effectively protect the facial nerve during the operation, and is worthy of clinical application and promotion.

Keyword

Acoustic neuroma; Diffusion tensor imaging; Facial nerve; Fiber tracking

Figure

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  Fig. 1. In the case 22, the facial nerve (FN) was located on the anterior upper part of the vestibular schwannoma (VS). A : The three-dimensional reconstruction showing the spatial relationship between the FN (red) and the VS (green). The blue object represents the brain stem. B-D : Axial/coronal/sagittal view showing the FN on the anterior upper of the VS. E and F : Neurophysiological monitoring and intraoperative image confirming the FN and its relationship with VS. G and H : Axial/coronal/sagittal view showing the preoperative and postoperative magnetic resonance imaging images of the VS.

Reference

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