MR3D-CISS And MR DTI In Patient With Trigeminal Neuralgia Due To Neurovascular Compression

Purpose1. To assess the value of high-resolution three-dimensional constructive interference in steady state (3D-CISS) in the visualization of neurovascular compression (NVC) in patients with trigeminal neuralgia (TN) and to evaluate the relationship between clinical symptoms related to trigeminal branches and those related to the site of trigeminal nerve compression.2. To detect diffusion abnormalities in the trigeminal nerves of patients with TN caused by NVC and to evaluate the pathologic sign of NVC by using a high-resolution diffusion tensor imaging (DTI).Materials and MethodsPART Ⅰ The evaluation of trigeminal neurovascular relationship in patient with trigeminal neuralgia by using3D-CISS1. SubjectsThe subjects were37patients with TN (16women and21men; age range,26～81years; mean age,55.3years) who visited our hospital from January2011to october2012.All of the patients have unilateral, medically intractable TN with median duration of5.5years (range,2～17years). These patients underwent3D-CISS examinations were to be treated with microvascular decompression (MVD) of the trigeminal nerve.2. MR scanning and Image analysis All3D CISS images and other related MR images were independently analyzed by an experienced neuroradiologist, who was blinded to the clinical details. The relationship of the trigeminal nerve and adjacent blood vessel was evaluated.(a) Assessing the severity of vascular contact with the trigeminal nerve by analyzing the3D-CISS. The assessment of the severity of the NVC was based on the morphologic contact between the outer walls of the offending vessel and the trigeminal nerve.The degree of vascular contact with the trigeminal nerve was classified into the following categories:type Ⅰ (compression type, distortion or deviation of the nerve resulted from vascular compression), type Ⅱ (simple contact type, nerve and blood vessel only existed contact) and type Ⅲ (noncontact and noncompression type).(b) Identifying the position of the blood vessel compressing the nerve on the3D-CISS image. The position of the compressing vessels relative to the trigeminal nerve was classified into one of the following sites:cranial, caudal, superior or inferior.3. MVD analysisThe degree of NVC and the position of responsible vessel relative to the trigeminal nerve were recorded by the surgeon.4. Statistical analysisStatistical analysis was performed by using the commercial software SPSS for windows release16(SPSS Inc., Chicago, IL, USA). P values of less than0.05were considered statistically significant.PART Ⅱ The evaluation of trigeminal neurovascular abnormalities in patient with trigeminal neuralgia by using DTI1. Subjects1.1TN group:the subjects were15TN patients(9women and6men; age range,35-67years; mean age,51.3years), who were proven by surgery that the symptoms side exist NVC and were not detected with NVC sign on the other side by3D-CISS image.1.2Normal group I:15healthy age/gender-matched controls who were detected with NVC sign on one side by3D-CISS image.1.3Normal group II:15healthy age/gender-matched controls who were not detected with NVC sign by3D-CISS image.2. MR scanningAll imaging were get from a Siemens Verio3T MRI scanner. The3D-CISS and DTI sequences were used and the scanning area were focus on the trigeminal nerve. All3D-CISS and DTI imaging were independently analyzed by one experienced neuroradiologists,.3. Image and dates analysis3.1.The bilateral differences between the FA and ADC values for the trigeminal nerves in every group were analysis by using the absolute value respectively, which was the mean value of the continuous three levels value measured on coronary imaging (the range is just0-6mm from the brainstem)3.2. The differences of FA and ADC values among the three groups were analysis by using the standard values which were compared rations(CRs):the CRs of value for the affected side and value for the unaffected side)in the TN group,(the CRs of value for the NVC side and value for the normal side) in the group Ⅰ and (the CRs of value for the right side and value for the left side) in group Ⅱ.3.3. Analyse the relationship between the change in FA and ADC using the differences between the two sides compared with the unaffected side in patient with TN.4. Statistical analysis4.1The differences between the absolute values of the FA and ADC values of the patients and corresponding values for the healthy controls were examined using the Mann-Whitney T test.4.2The differences between the CRs of the FA or ADC values among the three groups were examined using one-way ANOVA.4.3The relationship between the change in FA and ADC in patient with TN were examined using Spearman’s correlation analysis.P values of less than0.05were considered statistically significant. Result1.3D-CISS image and MVD result analysis1.1In37patients with TN,3D-CISS identified surgically verified neurovascular contact in35of36symptomatic nerves. Based on surgical findings, the sensitivity of MR imaging was97.2%and the specificity100%.1.2Twelve (85.7%) of fourteen patients with symptoms related to the maxillary division had their NVC at the medial site of the REZ. Thirteen (81.3%) of sixteen patients with symptoms related to the mandibular division had their NVC at the lateral site of the REZ. A statistically significant difference was observed between the NVC site and the clinically manifested symptoms in the branches of the trigeminal nerve (P <0.001).1.3Agreement between the position (cranial, caudal, superior or inferior) of the compressing vessel relative to the trigeminal nerve defined by MR imaging and findings at surgery was good (K=0.81;95%confidence interval,0.56-1.00).2. DTI image analysis2.1The mean absolute FA value in the symptomatic trigeminal never (0.29±0.07) was significantly lower(P<0.05) than the mean FA value in the contralateral TN trigeminal never (0.37±0.06). The mean ADC value in the symptomatic1trigeminal never(2.75±0.58)was significantly higher(P<0.05) than the mean ADC value in the contralateral trigeminal never (2.25±0.31)2.2There were no significant differences between the absolute FA and ADC values for the NVC side and non-NVC sides in the healthy people who were detected with NVC sign as well as those who were not detected with NVC sign..2.3The mean CRs of the FA values in the patient group(0.80±0.25) was lower than the normal control groups (group Ⅰ,1.03±0.23; group Ⅱ,0.98±0.13) with significantly differences respectively (p<0.5). The mean CRs of ADC values for the trigeminal nerves of the patients(1.26±0.36) was significantly higher than the normal groups(group Ⅰ,0.98±0.21)(p<0.5),(groupⅡ,1.03±0.21)(p<0.5) respectively. There was no difference for mean CRs of the FA values and ADC values between group I and group Ⅱ.2.4The spearman showed a strong negative correlation between loss of FA and increase in ADC(r=-0.725, p<0.01).Conclusion1.3D-CISS is useful in the detection of NVC in patients with trigeminal neuralgia. Anatomic relationships defined by this method can be useful in predicting surgical findings.2. DTI enables the identification and quantification of anisotropic changes between normal nerve tissue and TN-affected trigeminal nerves.3.The bilateral differences between the FA and ADC values for the trigeminal nerves in healthy group with NVC is no statistical differences reflect that compression had not caused pathological changes in the trigeminal nerve. TN may happen only when the NVC reach to a certain degree.4. DTI is an effective and non-invasive in vivo study method to TN due to NVC, helps to clarify the pathogenesis of trigeminal nerve.