Study Of Contrast Enhanced Magnetic Resonance Neurography In Evaluating The Influence Of Maxillofacial Tumor On Peripheral Branches Of Cranial Nerves

【Part 1】The Value of Contrast Enhanced Magnetic Resonance Neurography（ceMRN）in Displaying Peripheral Branches of cranial nervesObjective:To explore the value of contrast enhanced magnetic resonance neurography（ceMRN）in displaying peripheral branches of cranial nerves.Methods:35 volunteers were enrolled prospectively from November 2016 to March2017,who underwent three-dimensional flip-angle evolution short-tau inversion（3D SPACE STIR）sequence on a Siemens 3.0T MRI scanner.Conventional magnetic resonance neurography（cMRN）and ceMRN images were processed with multi-plane reconstruction（MPR）in post-processing workstation.The signal to noise ratio（SNR）of inferior alveolar nerve,mandible bone marrow,medial pterygoid muscle,subcutaneous fat,submandibular gland and standard deviation of background noise（σ₀）were obtained.The contrast signal-to-noise ratio（CNR）and contrast ratio（CR）of inferior alveolar nerve relative to other tissues were calculated,and the parameters between cMRN and ceMRN group were compared.According to Gray’s Anatomy,three radiologists were used MPR and maximum intensity projection（MIP）on ceMRN images were used by three radiologists to evaluate the continuity of 10 major branches of the cranial nerves on ceMRN based on the 5-score（0-4）subjective score,including the supraorbital nerve,infraorbital nerve,auriculotemporal nerve,masseteric nerve,buccal nerve,lingual nerve,inferior alveolar nerve,facial nerve,glossopharyngeal-vagus-accessory nerve complex and hypoglossal nerve,and their interobserver variability was tested.Results:All 35 volunteers were examined by ceMRN,of which 16 volunteers were examined by cMRN.The SNR（nerve）,SNR（bone marrow）,SNR（muscle）,SNR（fat）,SNR（gland）of cMRN were significantly higher than those on ceMRN.The CNR_{（nerve-bone marrow）},CNR_{（nerve-muscle）},CNR_{（nerve-fat）}of cMRN were significantly higher than those on ceMRN.CR（nerve-bone marrow）,CR（nerve-muscle）,CR（nerve-gland）of ceMRN were significantly higher than those on cMRN（all P<0.05）.In ceMRN,the whole course of normal peripheral branches of the cranial nerves are continuously and clearly displayed,with good contrast with the surrounding tissue.Each pair of cranial nerve present symmetrically,the course is natural with homogeneous hyper-intensity.Visualization of the inferior alveolar nerve,hypoglossal nerve and lingual nerve was excellent,with scores of 3.95±0.22,3.77±0.42,3.63±0.49,respectively.Detection of the facial nerve,infraorbital nerve,masseteric nerve,and glossopharyngeal-vagus-accessory nerve complex was relatively good,with scores of 3.25±0.49,3.15±0.5,3.04±0.82,3.04±0.77,respectively.Depiction of the supraorbital nerve and auriculotemporal nerve was moderate,with scores of 2.87 and 2.79,respectively.Delineation of the buccal nerve was fair,with a score of 1.88.The interobserver consistency of all nerves across the 3 readers was excellent,with an averageκvalue>0.83.Conclusion:High CR images of peripheral nerve can be obtain using ceMRN,and it can be used as a promising MR method of peripheral branches for visualizing cranial nerves.【Part 2】Application of Contrast Enhanced Magnetic Resonance Neurography（ce MRN）in Evaluating the Influence of Maxillofacial Tumor on Peripheral Branches of Cranial NervesObjective: To explore the value of contrast enhanced magnetic resonance neurography（ce MRN）in evaluating the influence of maxillofacial tumor on peripheral branches of cranial nerves.Methods: From March 2017 to November 2018,44 patients with maxillofacial tumors confirmed by surgical and pathological biopsy were enrolled.All patients underwent maxillofacial ce MRN.The features of involved peripheral nerves were observed and summarized by MPR and MIP in ce MRN images of all patients.The relationship between maxillofacial tumors and adjacent peripheral nerves was classified as isolated,compressed,invaded,embodied or spread perineurally,the number of involved peripheral branches of cranial nerves in various relationships was recorded,and the relationship between benign and malignant tumors of the maxillofacial region and the peripheral branches of cranial nerves were summarized.Results: There were 32 cases of malignant tumor confirmed by operation and pathology,including lymphoma（4 cases）,nasopharyngeal carcinoma（16 cases）,gingival carcinoma（6 cases）,carcinoma of tongue（4 cases）,orbital melanoma（1 case）and infiltrating carcinoma of trigeminal nerve（1 case）.There were 12 benign tumors,including parotid basal cell adenoma（1 case）,parotid gland Warthin tumor（2 cases）,parotid pleomorphic adenoma（1 case）,maxillofacial hemangioma（5 cases）,trigeminal neurilemmoma（2 cases）and intraorbital optic nerve sheath meningioma（1 case）.Based on the influence of different tumors,the affected peripheral nerves show differences in course,shape,margin and signal intensity.According to the relationship between tumor and peripheral nerve,there were 17 cases of nerves isolated to tumor,a total of 63 abnormal nerves were identified,including 25 nerves were compressed,25 nerves were invaded,5 nerves were embodied,and 8 tumors spread perineurally.Malignant tumors often presented as compressed,invaded,embodied or spread perineurally.Benign tumors often show isolated or compressed to peripheral nerves.Conclusion: ce MRN can be utilized to display the relationship and between maxillofacial tumor and peripheral branches of the cranial nerves and to evaluate nerve involvement.