Walid El Kininy1, Darren Roddy2, Shane Davy3, Elena Roman4, Veronica O'Keane5, Erik O'Hanlon6, Denis Barry7, Leo F A Stassen8. 1. Trinity College Dublin - M.D. post graduate doctorate and Specialist Registrar, Oral & Maxillofacial Surgery, Kent Surrey Sussex Deanery, UK. Electronic address: elkininw@tcd.ie. 2. Neuroscience Institute, Trinity College Dublin, Dublin, Ireland. 3. Department of Anatomy, Trinity College Dublin. 4. Medical student, Trinity College Dublin. 5. Professor of psychiatry, Trinity College Dublin. 6. Senior postdoctoral research fellow, Neuroscience, Trinity College Dublin. 7. Assistant professor and M.D. supervisor, Department of Anatomy, Trinity College Dublin. 8. Professor and chair of Oral/Maxillofacial Surgery and M.D. supervisor, Trinity College Dublin.
Abstract
OBJECTIVE: To evaluate the accuracy of magnetic resonance diffusion weighted imaging (DWI) featuring constrained spherical deconvolution-based tractography in tracking the extracranial course of the facial nerve to provide a reliable facial nerve map to facilitate well-tolerated and effective tumor resection. STUDY DESIGN: Magnetic resonance DWI was conducted on 2 parotid-healthy cadaveric patients with various protocols to identify the best representation of the extracranial facial nerve tract. This was subsequently correlated to dissection of the facial nerves to ascertain anatomic validation. These protocols were applied to 2 live, parotid-healthy patients to assess feasibility of in vivo facial nerve tract identification. RESULTS: Correlations between imaged tracts and the anatomic course of the extracranial facial nerve were identified to an accuracy of 1 mm. The main trunk and bifurcation tracts were identified on imaging. Fractional anisometry values in cadaveric and live patients were within the range expected for the facial nerve within the parotid gland. CONCLUSIONS: Our results indicated the potential for accurate 3-dimensional visualization of the extracranial course of the facial nerve, which could have diagnostic implications in differentiating benign from malignant tumors and, crucially, neural involvement. Preoperative planning applications of DWI could help in planning surgical approaches and providing focused counseling.
OBJECTIVE: To evaluate the accuracy of magnetic resonance diffusion weighted imaging (DWI) featuring constrained spherical deconvolution-based tractography in tracking the extracranial course of the facial nerve to provide a reliable facial nerve map to facilitate well-tolerated and effective tumor resection. STUDY DESIGN: Magnetic resonance DWI was conducted on 2 parotid-healthy cadavericpatients with various protocols to identify the best representation of the extracranial facial nerve tract. This was subsequently correlated to dissection of the facial nerves to ascertain anatomic validation. These protocols were applied to 2 live, parotid-healthy patients to assess feasibility of in vivo facial nerve tract identification. RESULTS: Correlations between imaged tracts and the anatomic course of the extracranial facial nerve were identified to an accuracy of 1 mm. The main trunk and bifurcation tracts were identified on imaging. Fractional anisometry values in cadaveric and live patients were within the range expected for the facial nerve within the parotid gland. CONCLUSIONS: Our results indicated the potential for accurate 3-dimensional visualization of the extracranial course of the facial nerve, which could have diagnostic implications in differentiating benign from malignant tumors and, crucially, neural involvement. Preoperative planning applications of DWI could help in planning surgical approaches and providing focused counseling.