Facial nerve tractography: A new tool for the detection of perineural spread in parotid cancers
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To determine whether facial nerve MR tractography is useful in detecting PeriNeural Spread in parotid cancers.
Forty-five participants were enrolled. Thirty patients with surgically managed parotid tumors (15 malignant, 15 benign) were compared with 15 healthy volunteers. All of them had undergone 3T-MRI with diffusion acquisition and post-processing constrained spherical deconvolution-based tractography. Parameters of diffusion-weighted sequences were b-value 1,000 s/mm2, 32 directions. Two radiologists performed a blinded visual reading of tractographic maps and graded the facial nerve average pathlength and fractional anisotropy (FA). We also compared diagnostic accuracy of tractography with morphological MRI sequences to detect PeriNeural Spread. Non-parametric methods were used.
Average pathlength was significantly higher in cases with PeriNeural Spread (39.86 mm [Quartile1: 36.27; Quartile3: 51.19]) versus cases without (16.23 mm [12.90; 24.90]), p<0.001. The threshold above which there was a significant association with PeriNeural Spread was set at 27.36 mm (Se: 100%; Sp: 84%; AUC: 0.96, 95% CI 0.904–1). There were no significant differences in FA between groups. Tractography map visual analyses directly displayed PeriNeural Spread in distal neural ramifications with sensitivity of 75%, versus 50% using morphological sequences.
Tractography could be used to identify facial nerve PeriNeural Spread by parotid cancers.
• Tractography could detect facial nerve PeriNeural Spread in parotid cancers.
• The average pathlength parameter is increased in case of PeriNeural Spread.
• Tractography could map PeriNeural Spread more precisely than conventional imaging.
KeywordsFacial nerve PeriNeural Spread Parotid cancers Tractography Track-weighted imaging
Constrained spherical deconvolution
Peripheral facial palsy
The authors acknowledge the valuable assistance of Patrice Jousse for his work editing the MRI images and diagrams. We also thank Dr Louise Ball and Dr Jeanne Maurice for critically editing the manuscript.
The authors state that this work has not received any funding.
Compliance with ethical standards
The scientific guarantor of this publication is Prof. Alexandre Krainik.
Conflict of interest
The authors of this manuscript declare no relationships with any companies whose products or services may be related to the subject matter of the article.
Statistics and biometry
One of the authors (MM) has significant statistical expertise.
Written informed consent was obtained from all subjects (patients) in this study.
Institutional Review Board approval was obtained (IRB 5891 for patients/ IRB 6705 for healthy volunteers).
• diagnostic study
• performed at one institution
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