| Background:Recently,Magnetic Resonance Diffusion Tensor Imaging(MR-DTI)has been more widely used to study the diffusivity of the trigeminal nerve(CNV)in patients with trigeminal neuralgia(TN).MR-DTI has been used in the study of microvascular decompression(MVD)and Gamma Knife Radiosurgery(GKRS)in TN patients to explore the pathophysiological mechanisms and evaluate the treatment effects.In the field of functional neurosurgery,Radiofrequency Thermocoagulation(RFT),a conventional treatment for trigeminal neuralgia,is a procedure in which the foramen ovale(FO)is the puncture target and the trigeminal ganglion(TG)is the treatment target.Since the TG treatment target is not visualized intraoperatively,it is interesting to observe whether MR-DTI can detect the location of the abnormal diffusion manifestation on TG in TN patients,as abnormal trigeminal ganglion(ab-TG),and then perform percutaneous stereotactic radiofrequency thermocoagulation(PSR)directly targeting the ab-TG to further improve the treatment outcome in TN patients.Currently,studies on the application of MR-DTI in PSR have not been reported in the literature.Objective:To observe the feasibility of the diffusivity metrics of MR-DTI in the application of PSR with TN patients and its clinical effect.Methods:To detect diffusivity metrics of each segment of CNV in 49 healthy controls(control group)and 34 TN patients(TN group),including fractional anisotropy(FA),radial diffusivity(RD),axial diffusivity(AD)and mean diffusivity(MD).MR-DTI images were scanned and acquired with a 3.0T Siemens MR scanner,and post-processed with the 3D Slicer V4.11 software package application(HTTP://www.slicer.org/).All CNVs were performed segmentation according to the fused images of the 3D reconstructed CNV tracts and color-FA maps of MR-DTI,and the values of diffusivity metrics on each CNV segment were extracted from the scalar maps of diffusivity metrics in DTI.The TN group was divided into the PSR subgroup and the MVD subgroup.For the 15patients who underwent PSR,ab-TGs were detected using FA as the detection metric,and the location,shape,and size of ab-TG were measured in the 3 views of DTI images.The patients in the PSR subgroup were classified into L-FA(low FA)type and N-FA(normal FA)type according to two different manifestations of the abnormal FA value on ab-TG.The stereotactic puncture arc angle of PSR was planned to use the characteristics of the treatment target(ab-TG),and individualized PSR treatment was accomplished guiding by combining MR-DTI and 3D-CT skull base reconstruction.The immediate(2-3 days),short-term(6 months),and long-term(1 year)effects of PSR in patients were evaluated by visual analog scale(VAS)scores and the changes of diffusivity metrics in each segment of the CNV.The longitudinal changes in diffusivity metrics of bilateral CNVs were compared with the treatment outcome of TN patients to evaluate the role of diffusivity metrics in the objective quantitative assessment of treatment efficacy and the prediction of the possibility of short-term recurrence after PSR.Results:In all 83 patients with TN,CNVs can be divided into 8 segments,of which,segments 2-3 are in the REZ or cisternal segment,and segments 4-7 are in TG.In the control group,FA values decreased gradually from the pontine segment to TG of CNV,while MD,AD,and RD values increased gradually.In the TN group,segments in which low FA(value<0.30)or a decreased range of FA(d FA)>17%compared to adjacent FA were defined as ab-TG.In the TN group,ab-TGs all were present in 25 patients with VAS scores of 8-10,while6 patients with VAS scores<8 not have ab-TG.The distributions of ab-TG and affected branches are regular.Patients with the most severely affected V1 or V2 branches had ab-TGs in segment 7(80%)and segment 6(50%),respectively.The area of ab-TGs(s)<3.4 mm~2,long diameter(L1)<2.3 mm,and short diameter(L2)<1.7 mm was defined as"small ab-TGs".The proportion of ab-TG located in the center and other locations of the TG were 13.3%and 86.7%.The 15 patients in the PSR subgroup included 10(10/15,66.7%)with low FA values(<0.30)in TG,as L-FA type,and 5(5/15,33.3%)with FA values>0.30 and d FA>17%in TG,as N-FA type.In patients of the PSR subgroup,the FA values on TG is significantly lower than control group(P<0.001),while MD and RD values on TG are significantly higher than controls(P<0.01);AD values have not significantly difference(P>0.05).The FA values of the affected TG were significantly lower than the contralateral TG(P<0.05).The single puncture success rate was 93.3%(14/15)in PSR guided by ab-TG.At 2-3 days postoperatively,VAS scores decreased by 60%-90%in all patients(100%,15/15).Changes in FA(100%,14/14)and MD(78.6%,11/14)occurred simultaneously with changes in VAS in all 14 patients with post-treatment MR-DTI.On postoperative MR-DTI,there was no significant difference in FA values between the affected and the contralateral TG(P>0.05);but FA values of ab-TG were significantly increased(P<0.001),MD and RD values significantly decreased(P<0.01),and AD values did not change significantly(P>0.05)compared to preoperative.90%(9/10)of patients with L-FA were treated effectively;40%of patients with N-FA were treated effectively.FA values of TG were significantly correlated with PSR treatment outcome and pain scores(P<0.05).The short and long-term postoperative efficacy rates of PSR were 73.3%and 66.7%in patients.MR-DTI in postoperative and follow-up indicated that effective PSR treatment was predicted when the following manifestations were present:normal FA on the contralateral CNV(100%),FA of the affected TG<0.30(90%),and normal FA on the affected REZ(86%).When patients had FA of the affected TG≥0.30(3/5,60%)and abnormal FA on the affected REZ(3/8,38%),and abnormal FA values on the contralateral CNV(4/11,36%),those patients usually had poor outcomes after PSR.Conclusion:Diffusivity metrics of MR-DTI can reflect the microstructure abnormalities of the CNV tract in patients with TN.ab-TG detected by longitudinal changes of diffusivity metrics FA of CNVs in MR-DTI of TN patients can be used as the therapeutic target,which is universally and individually applied in PSR.“Small ab-TG”is a novel difficulty factor of puncture in PSR.The clinical role of MR-DTI in PSR is to improve the success rate of single-puncture of TG treatment target,to quantify and objectively evaluate the postoperative treatment effect,to better master indications of RFT,and predicting the possibility of short-term postoperative recurrence.Particularly important,FA may be a potential metric for future molecular typing diagnosis of TN. |
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