Letter to the Editor In Reply to “Predicting Shape, Location, and Course of Facial Nerve in Relation to Large Vestibular Schwannoma on Diffusion Tensor Imaging with Intraoperative Correlation: Important Surgical Adjunct”
LETTER: the favorable comments raised in the W eletterreallyfromappreciate Dr. Guru Dutta Satyarthee regarding our recently
published study1 on the association between diffusion tensor imaging (DTI) analysis and the features of the facial nerve in large vestibular schwannomas. The viewpoints of Dr. Satyarthee, along with the findings in our study, suggest that the application of DTI-based fiber tracking may provide important adjunct information for the surgeon preoperatively, which would allow one to plan the tumor removal accordingly and improve the feasibility of anatomic and functional preservation of the facial nerve. As we have pointed out in our study, Dr. Satyarthee also spelled out that DTI-based fiber tracking for facial nerve in large vestibular schwannomas has important limitations and caveats that must be recognized. Typically, DTI-based methods have limited potential to distinguish the facial nerve, specifically within the vestibulecochlear nerve complex. Fortunately, recent studies of diffusion spectrum imaging (DSI) found that DSI was able to distinguish the facial nerve from the vestibule-cochlear nerve complex.2 Another concern is the fact that the manual tracking results are highly
WORLD NEUROSURGERY 105: 1003, SEPTEMBER 2017
dependent on operator presumption. To address this question, automatization of fiber tracking is therefore clearly warranted. Finally, DTI analysis can provide quantitative metrics including fractional anisotropy, axial diffusivity, radial diffusivity, and mean diffusivity to characterize tissue microstructure. In our study, we only investigated the association between fractional anisotropy values and morphologic changes of the facial nerve. Other DTI metrics can also potentially provide insight into factors underlying facial nerve microstructure and therefore warrant further investigation. Again, thanks to Dr. Satyarthee for his valuable comments and the opportunity he created for sharing our opinions in WORLD NEUROSURGERY. Yanyang Zhang and Xinguang Yu Department of Neurosurgery, PLA General Hospital, Beijing, China To whom correspondence should be addressed: Xinguang Yu, M.D., Ph.D. [E-mail: [email protected]] http://dx.doi.org/10.1016/j.wneu.2017.06.039.
REFERENCES 1. Zhang Y, Mao Z, Wei P, Jin Y, Ma L, Zhang J, et al. Preoperative prediction of location and shape of facial nerve in patients with large vestibular schwannomas using diffusion tensor imaging-based fiber tracking. World Neurosurg. 2017;99: 70-78. 2. Yoshino M, Abhinav K, Yeh FC, Panesar S, Fernandes D, Pathak S, et al. Visualization of cranial nerves using high-definition fiber tractography. Neurosurgery. 2016;79:146-165.
www.WORLDNEUROSURGERY.org
1003
LETTER: the favorable comments raised in the W eletterreallyfromappreciate Dr. Guru Dutta Satyarthee regarding our recently
published study1 on the association between diffusion tensor imaging (DTI) analysis and the features of the facial nerve in large vestibular schwannomas. The viewpoints of Dr. Satyarthee, along with the findings in our study, suggest that the application of DTI-based fiber tracking may provide important adjunct information for the surgeon preoperatively, which would allow one to plan the tumor removal accordingly and improve the feasibility of anatomic and functional preservation of the facial nerve. As we have pointed out in our study, Dr. Satyarthee also spelled out that DTI-based fiber tracking for facial nerve in large vestibular schwannomas has important limitations and caveats that must be recognized. Typically, DTI-based methods have limited potential to distinguish the facial nerve, specifically within the vestibulecochlear nerve complex. Fortunately, recent studies of diffusion spectrum imaging (DSI) found that DSI was able to distinguish the facial nerve from the vestibule-cochlear nerve complex.2 Another concern is the fact that the manual tracking results are highly
WORLD NEUROSURGERY 105: 1003, SEPTEMBER 2017
dependent on operator presumption. To address this question, automatization of fiber tracking is therefore clearly warranted. Finally, DTI analysis can provide quantitative metrics including fractional anisotropy, axial diffusivity, radial diffusivity, and mean diffusivity to characterize tissue microstructure. In our study, we only investigated the association between fractional anisotropy values and morphologic changes of the facial nerve. Other DTI metrics can also potentially provide insight into factors underlying facial nerve microstructure and therefore warrant further investigation. Again, thanks to Dr. Satyarthee for his valuable comments and the opportunity he created for sharing our opinions in WORLD NEUROSURGERY. Yanyang Zhang and Xinguang Yu Department of Neurosurgery, PLA General Hospital, Beijing, China To whom correspondence should be addressed: Xinguang Yu, M.D., Ph.D. [E-mail: [email protected]] http://dx.doi.org/10.1016/j.wneu.2017.06.039.
REFERENCES 1. Zhang Y, Mao Z, Wei P, Jin Y, Ma L, Zhang J, et al. Preoperative prediction of location and shape of facial nerve in patients with large vestibular schwannomas using diffusion tensor imaging-based fiber tracking. World Neurosurg. 2017;99: 70-78. 2. Yoshino M, Abhinav K, Yeh FC, Panesar S, Fernandes D, Pathak S, et al. Visualization of cranial nerves using high-definition fiber tractography. Neurosurgery. 2016;79:146-165.
www.WORLDNEUROSURGERY.org
1003
