Preoperative identification of the facial nerve in patients with large cerebellopontine angle tumors using high-density diffusion tensor imaging

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Facial nerve paresis can be a devastating complication following resection of large (> 2.5 cm) cerebellopontine angle (CPA) tumors. The authors have developed and used a new high-density diffusion tensor imaging (HD-DT imaging) method, aimed at preoperatively identifying the location and course of the facial nerve in relation to large CPA tumors. Their study objective was to preoperatively identify the facial nerve in patients with large CPA tumors and compare their HD-DT imaging method with a traditional standard DT imaging method and correlate with intraoperative findings.


The authors prospectively studied 5 patients with large (> 2.5 cm) CPA tumors. All patients underwent preoperative traditional standard- and HD-DT imaging. Imaging results were correlated with intraoperative findings.


Utilizing their HD-DT imaging method, the authors positively identified the location and course of the facial nerve in all patients. In contrast, using a standard DT imaging method, the authors were unable to identify the facial nerve in 4 of the 5 patients.


The HD-DT imaging method that the authors describe and use has proven to be a powerful, accurate, and rapid method for preoperatively identifying the facial nerve in relation to large CPA tumors. Routine integration of HD-DT imaging in preoperative planning for CPA tumor resection could lead to improved facial nerve preservation.

Abbreviations used in this paperCPA = cerebellopontine angle; DT = diffusion tensor; FA = fractional anisotropy; HD-DT = high-density DT; IAC = internal auditory canal; ROI = region of interest.

Article Information

Address correspondence to: Justin S. Cetas, M.D., Ph.D., Department of Neurological Surgery, Mail Code L-472, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239. email:

Please include this information when citing this paper: published online January 27, 2012; DOI: 10.3171/2011.12.JNS111404.

© AANS, except where prohibited by US copyright law.



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    A–C: Case 1. Contrast enhanced T1-weighted MR image (A) showing a large irregular CPA mass causing severe compression of the brainstem and displacement of the normal CPA contents. An HD-DT image (B) with an FA value of 1.5 viewed from left posterior direction, showing anterosuperior displacement of the facial nerve fibers (yellow bands) as they course from the brainstem to the IAC. An HD-DT image (C) again shows a coherent bundle of nerve fibers displaced in an anterosuperior directions coursing toward the IAC. Intraoperatively, this bundle of nerve fibers (yellow bands) correlated exactly with the location of the facial nerve. D–F: Case 2. An MR cisternography image (D) showing the large left CPA tumor causing compression and deformation of the brainstem and expansion of the IAC. An anterior coronal HD-DT image (E) showing the facial nerve exiting the brainstem and coursing around the equator of the tumor as it courses toward the IAC. A posterolateral HD-DT image (F) of the facial nerve, being displaced anteriorly around the midline of the tumor as identified intraoperative by visual and stimulation. The red and aqua lines indicate the displaced facial nerve. G–I: Case 3. Axial T1-weighted contrast-enhanced mass compressing the brainstem and expanding the IAC (G). Posterolateral HDDT image (H) in the sagittal plane showing the course of the nerve displaced inferiorly under the tumor. Coronal HD-DT image (I) of the nerve displaced inferiorly. In this view the opposite (normal) VII/VIII complex is identified as control (green). The red and purple lines indicate the displaced facial nerve. J–L: Case 4. Preoperative contrast enhanced T1-weighted MR image (J) showing a large left-sided CPA mass causing significant brainstem compression and expansion of the IAC. Anterolateral (K) and anteroposterior (L) HD-DT image reconstructions of the facial nerve showing an anterosuperior displacement of the origin and the nerve coursing inferiorly toward the IAC. Of note, the tractography of the nerve was done in 2 separate tracts as it rounded the apex of the tumor. This correlated with intraoperative findings where the nerve was severely attenuated to a thin ribbon.



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