MR Imaging Analysis Of Vascular Compressive Trigeminal Neuralgia

PURPOSE:1.To compare the effect of 3D-TOF(Three-dimensional Time Of Flight)sequence and 3D-CISS(Three-dimensional constructive interference in steady-state)sequence in demonstrating the cisternal segments of bilateral trigeminal nerves, adjacent vessels and their positional relationship in healthy volunteers and further to find a better and more reasonable modality for the morphological evaluation of NVC in the cisternal segment of cranial nerve. 2. Have the cisternal segments of the symptomatic trigeminal nerves and the asymptomatic trigeminal nerves using 3D-TOF and the 3D-CISS two kind of sequences to carry on the analysis, compared with whether there is symptomatic sides and asymptomatic sides trigeminal nerve vessel situation. 3.To evaluate the usefulness of MR tomographic angiography (MRTA) in diagnosing the neurovascular contact/compression (NVC) at the root exit zone (REZ) of trigeminal nerve of Trigeminal neuralgia(TN) patients according to the operative results of TN and further to investigate the relationship between various MR diagnosing indicators and find the most valuable indicators to improve the diagnosing accuracy.METHOD AND MATERIALS: (1)Routine transverse MR scanning was performed on the cisternal Segments of bilateral trigeminal nerves of 30 healthy volunteers using both 3D-TOF sequence and 3D-CISS sequence. The oblique images respectively perpendicular to and parallel to the cranial nerves were obtained on workstation by multiplanar reconstruction( MPR).The effect of visualization of the cisternal segments of all bilateral trigeminal nerves and their branches depicted by 3D-TOF sequence and 3D-CISS sequence respectively were evaluated and compared. The visualization of the vessels adjacent to the cisternal segments of bilateral trigeminal nerves , the signal intensity of these vessels and the neurovascular positional relationship were also observed and assessed. The maximum and minimum spans of the section of the cisternal segments of bilateral trigeminal nerves were measured on 3D-CISS images. (2) 141 patients with unilateral trigeminal neuralgia underwent MR examination of trigeminal nerve. Totally there were 141 symptomatic nerves and 141 asymptomatic nerves. 3D -TOF sequence was used for the MRTA scan. However,if the imaging sequence 3D -TOF cisternal trigeminal nerve segment showed no responsibility to clear or sweep increases to scan 3D-CISS sequence. Two experienced radiologists who were blinded to the clinical findings analysed the root entry zone (REZ) of both side trigeminal nerves in all images. Judgment was made on if there were some vessels close to the trigeminal nerve and on the relationship between the vessel and the nerve, and the direction of the vessel toward the nerve were also record at the same time. The maximum and minimum spans of the section of the cisternal segments of bilateral trigeminal nerves were measured. SPSS 10 software was used to compare the 141 asymptomatic trigeminal nerves to the 141 symptomatic trigeminal nerves. The relationship between the offending vessel and the trigeminal nerve was categorized as no offending vessel, suspected, compression, and compression of the nerve. The direction of the offending vessel was recorded according to the angle between the vessel and the nerve, such as no offending vessel, the angle less than 45 degrees, and the angle larger than 45 degrees. (3) 56 patients had operations due to unilateral trigeminal neuralgia. Among these patients, 50 were primary trigeminal neuralgia. All the 50 patients had MRTA exam before the operation. The methodology on how to do the MRTA exam and how to analyse the images was same to part two. SPSS10 software was used to evaluate the sensitivity, specificity and the accuracy of MRTA by comparing the manifestation of the images and the operation result.RESULTS: (1)The visualization of the cisternal segments of all bilateral trigeminal nerves and their branches and the vessels adjacent to the cisternal segments of bilateral trigeminal nerves were better by 3D-CISS sequence than 3D-TOF sequence( P<0.01).The positive rates of NVC detected in the cisternal segments of trigeminal nerves by both sequences with high 43%.All the maximum and minimum spans of the section of the cisternal segments of bilateral trigeminal nerves could be measured accurately on 3D-CISS images because of its high spacial resolution. (2) In the blinded study, 170 trigeminal nerves of all 282 nerves can be detected offending vessels on MRTA images. Statistical analysis indicated that the direction of the vessel toward the nerve in the symptomatic group had significant difference from that in the asymptomatic group. The rate of the vessel-nerve contact in the symptomatic group was much higher than that in the asymptomatic group. It implies that vessel compression is an important cause of primary trigeminal neuralgia. Nevertheless, the analysis further revealed that offending vessel could be detected in 14.9% of the asymptomatic sides' images, whereas offending vessel cannot be seen in 5.7% symptomatic sides. These data indicates that vessel compression is not the only cause of primary trigeminal neuralgia. Measuring asymptomatic and asymptomatic lateral side of the trigeminal nerve cisternal segments of the largest and the smallest was indicated by asymptomatic and asymptomatic lateral side of the trigeminal nerve section cisternal segments of the trail there is a difference (P<0.05).prompted because of the long-term symptoms can lead to trigeminal neuralgia nerve tissue loss or atrophy. According to the analysis of all planes of the MRTA images in both asymptomatic and symptomatic groups, significant differences between the two groups can be observed. Therefore, MRTA is a pertinent examination for the patients with trigeminal neuralgia, and it is propitious to detect the offending vessel. (3) 6 of all 56 patients who had the operations for trigeminal neuralgia were secondary trigeminal neuralgia. According to the statistical analysis of MVD result of primary trigeminal neuralgia, vascular loops commonly around the trigeminal nerve include branches of the superior cerebellar artery (SCA), anterior inferior cerebellar artery (AICA), simply veins and multiple vessels. Only for 3D-TOF sequence cannot show slow blood flow structures especially in some small veins,combined with 3D-CISS necessary to exclude small artery and vein .Comparing MRTA result with the MVD result, it showed the suspected results of the imaging-reading were categorized in the compression group is conducive to improve diagnostic the sensitivity, specificityand the accuracy .CONCLUSIONS: MRTA is a reliable imaging technique for diagnosing NVC in TN patients. Multiplanar reconstruction MRTA may improve the sensitivity, specificity and accuracy in detecting NVC by MRI. The trigeminal nerve and adjacent vessels are visualized more clearly on 3D-CISS images because of its higher spacial resolution than 3D-TOF images. Hence combination is conducive to improve the detection rate of vascular responsibility.