The MRI Study Of Facial And Acoustic Nerve In Internal Acoustic Meatus

PartⅠThe study of the relationship between facial nerve and blood vessels in internal acoustic meatus with different MR sequencesObjective: To evaluate the advantages and disadvantages of different MR sequences to show the relationship between facial nerve and blood vessels in internal acoustic meatus, and to look for the best sequence of showing internal acoustic meatus.Method: 10 volenteers and 20 facial spasm patients were examined on the same axial position of the internal acoustic meatus with T2WI-3D-TSE, B-TFE and T1WI-3D-FFE. Slices, slice thickness and slice interval were the same with different sequences. Then the same slices from the three different sequences were compared with rank. The images were analysed by two MR experts. The discover degree of nerves and vessels, contrast, signal to noise ratio and spatial resolution were observed in the same slice of different 3 sequences, and were generally evaluated with grade. The slices were counted in the sequence which presented facial nerves of both sides and correlated vessels most, including left-right asymmetry. Grade 0 was no presence, Grade 1 was with presence but no enough diagnostic requirement, Grade 2 was with good presence and rough diagnostic requirement, and Grade 3 was with excellent presence.Results: Facial nerve was well displayed with T2WI-3D-TSE and B-TFE. There was no significant difference between them (P>0.05). However, T1WI-3D-FFE was inferior to T2WI-3D-TSE and B-TFE, with significant difference between them(P<0.05). In showing blood vessels, T2WI-3D-TSE was superior to B-TFE and T1WI-3D-FFE(P<0.05).Conclusion: T2WI-3D-TSE sequence is the best sequence in showing facial nerve and blood vessels in internal acoustic meatus. B-TFE sequence can be used when only to show facial nerve. T1WI-3D-FFE sequence has the value of diagnosing the abnormality of the great vessels and of deciding the origin of the vessels.PartⅡApplication value of inner ear of MRI in infant sensorineural hearing lossAIM: To investigate the value of inner ear of MRI in infant sensorineural hearing loss.METHOD: 38 cases suspected inner ear disease were examined by Philips Gyroscan Intera 1.5 T MR system. Routine sequences included conventional brain scan and T2WI-3D-TSE axial scan and B-TFE oblique-sagittal scan of inner ear. Labyrinth diseases were reconstructed by MIP method.RESULT: 16 cases showed normal structure of cochlear nerve and labyrinth. Three ears of two cases presented Michel deformity; 12 ears of six cases presented Mondini deformity; 24 ears of 12 cases showed Vestibular Aqueduct Enlarge; some of them companied with absence of cochlear nerve. 4 ears of two cases showed cochlear nerve fine and stenosis of inner ear canal.CONCLUSION: MR imaging of inner ear has a great clinical value in diagnosing infant sensorineural hearing loss and in distinguishing the developmental condition of their labyrinthus oticus and neural development. MRI scan is the necessary examination before the artificial cochlea replacement.PartⅢThe value of the NVC of facial nerve with MRI on the diagnosis of hemifacial spasmObjective:To investigate the relation between NVC of facial nerve out of brain stem and clinical symptom. Methods:With MR T2WI-3D-TSE technique, facial nerves out of brain stem of 60 patients with hemifacial spasm and 60 volunteers were examined by axis position, oblique sagittal position and oblique coronal position. The relations between facial nerves and peripheral vessels were analysed aggregately, and 4-grade score was used, absence of contact (1 score), suspect of contact (2 scores), identification of contact (3 scores), compression (4 scores). The diameters of responsible vessel at contact point and the shortest distance of responsible vessel and the point of facial nerve from brain stem were measured. Then statistical analysis was carried out about the numbers of injured and uninjured sides.Results:The accurate degree of diagnosing with three positions was better than with any one position(87.50%), and diagnosing with three positions had fairly better sensibility ( 96.67% ) and specificity(84.44%). The positive ratio of 60 sides in injured sides was 96.67%, and the positive ratio of 180 sides in uninjured sides was 15.56%. The axis position had the best sensibility, and the oblique sagittal position had the best specificity. The diameters of responsible vessel in 58 sides of injured group were ranged 0.3-1.5mm, with the average value of 0.68±0.30mm. The diameters of responsible vessel in 28 sides of uninjured group were ranged 0.2-0.9mm, with the average value of 0.47±0.18mm. The average diameters of responsible vessels at injured sides were longer than those at uninjured sides and the differences had statistical significance (P<0.05). The shortest distance of responsible vessel and the point of facial nerve from brain stem in 58 sides of injured group were ranged 0.0-13.1mm, with the average value of 5.91±3.12mm. The distance in 28 sides of uninjured group were ranged 0.3-22.2mm, with the average value of 8.68±4.20mm. The shortest distances between the contact point of NVC and the point of facial nerve from brain stem in both groups had no significant differences, and there were no statistical significances in both groups (P>0.05).Conclusion: The use of the aggregate analysis of three sections could improve MR diagnosis and get better sensibility and specificity. The longer of the diameter of responsible vessels, the more symptoms. There was no direct relation between clinical symptom and the distance of contact point and facial nerve out of brain stem, and clinical symptoms may occur at any section of facial nerve out of brain stem.