Trigeminal Neuralgia Caused By Vertebrobasilar Compression: Neuroimaging Features And Treatment Methods

Part 1:Does the patient with trigeminal neuralgia caused by vertebrobasilar compression have a small cerebellopontine angle cistern?Background: Previous studies have indicated that the small cerebellopontine angle(CPA)cistern plays a role in the pathogenesis of trigeminal neuralgia(TN),but these studies are likely not involved in TN associated with vertebrobasilar artery compression(VBA-associated TN)because of its rarity.The present study evaluates whether there is a small CPA cistern on the affected side in VBA-associated TN patients.Methods: 44 patients with VBA-associated TN and 44 age-,sex-,pain laterality,and hypertension-matched TN patients without VBA compression(non-VBA-associated TN)were included in this study.All patients underwent high-resolution MRI.The cross-sectional area of CPA cistern was measured bilaterally on the axial MRI slice through the trigeminal REZ.The presence of vertebrobasilar dolichoectasia(VBD)and laterality of the vertebrobasilar junction(VBJ)were analyzed.Results: The mean cross-sectional area of the CPA cistern on the affected side was significantly smaller than the unaffected side in non-VBA-associated TN(213.6±55.9 vs.235.9±59.6 mm2,p < 0.001),while VBA-associated TN patients show a larger CPA cistern on the affected side than the affected side(317.6±60.4 vs.241.9±44.9 mm2,p <0.001).The prevalence of VBD was higher in patients with VBA-associated TN(90.9%vs.4.5%,p <0.001),and a significant positive correlation between the laterality of the VBJ and the symptomatic laterality was found for VBA-associated TN group(p < 0.001).Conclusion: Large CPA cistern is a neuroradiological feature of VBA-associated TN,and most of VBA-associated TN is accompanied by VBD.We hypothesize that the presence of VBD and the lateral shift of VBJ may expand the CPA cistern by squeezing the surrounding tissue on the symptomatic side and also increase the chance of VBA compression on the trigeminal nerve,resulting in the onset of VBA-associated TN.Part 2:Microvascular decompression for trigeminal neuralgia caused by vertebrobasilar dolichoectasia: interposition technique versus transposition techniqueBackground: Various techniques of microvascular decompression have been proposed for trigeminal neuralgia(TN)caused by vertebrobasilar dolichoectasia(VBD)with two main modalities: interposition and transposition.This retrospective study compares the outcomes of two techniques belonging to different modalities for VBD-associated TN.Methods: From January 2011 to April 2017,39 patients underwent MVD for VBD-associated TN.The transposition method chosen was the biomedical glue sling technique.Patients were divided into the interposition group(n = 16)and the transposition group(n = 23).The radiologic data,intraoperative findings,complications,and outcomes were analyzed.Hemodynamics of the typical anatomic variants of the vertebrobasilar arteries were analyzed utilizing computational fluid dynamics(CFD)software.Results: The 1-,3-,and 5-year pain-free(BNI I)maintenance rates were 100.0,91.1,and 91.1 %,respectively,in the transposition group and 87.5,74.5,and 58.7 % in the interposition group(p = 0.032).Postoperative complications were similar in both groups,but there was a trend for higher incidence of postoperative facial hypoesthesia using the interposition technique(p = 0.06).CFD models demonstrated that the differences in wall shear stress(WSS)between vascular walls of opposite sides were remarkable at the bend of the vertebrobasilar artery where neurovascular conflicts occurred.Conclusion: In cases of VBD-associated TN,the transposition technique using biomedical glue was superior to the traditional interposition technique in maintaining a pain-free status.We hypothesized that vertebrobasilar artery transposition and fixation in the transposition technique could effectively inhibit the vessel shift toward trigeminal nerve exerted by local WSS differences.Hence,its pain relief effects are better than the interposition technique.Part 3:Outcomes of two isocenter gamma knife surgery for trigeminal neuralgia secondary to vertebrobasilar dolichoectasiaObjective:To evaluate the effectiveness and safety of two isocenter gamma knife surgery(GKS)for trigeminal neuralgia associated with vertebrobasilar dolichoectasia(VBD-associated TN).Methods: From March 2012 to July 2018,28 patients with VBD-associated TN underwent a two isocenter GKS.A 4 mm isocenter was placed at the trigeminal nerve root entry zone(REZ)and another isocenter at the distal cisternal segment or Meckel’s cave segment.The median maximum dose was 88 Gy(range 80-90 Gy).The treatment outcomes were compared with 28 case-matched controls who underwent two isocenter GKS for TN not associated with VBD(non-VBD-associated TN).Results: After two isocenter GKS,24 patients(85.7%)achieved initial pain relief(BNI I-III).The median time until pain relief was 8 weeks(range 0 day-9 months).Four patients(16.7%)with initial pain relief experienced pain recurrence between 14 and 56 months(median 38 months).The pain relief rate was 85.7% at 1 year,78.2%at 3 years,and 67.2% at 5 years.50.0% of VBD-associated TN patients had varying degrees of post-GKS facial numbness,of which 3.6% were very bothersome.There were no significant differences in the initial pain relief rate,long-term pain relief rate,pain recurrence,and complications between VBD-associated TN and non-VBD-associated TN patients,but the median time until pain relief was longer in VBD-associated TN patients(8 vs.4 weeks,p = 0.03).Conclusion: The two isocenter GKS provides similar therapeutic effects between VBD-associated TN and non-VBD-associated TN patients,except that VBD-associated TN patients take longer to achieve initial pain relief.Part 4:Comparison of microvascular decompression and gamma knife for the treatment of trigeminal neuralgia caused by vertebrobasilar dolichoectasiaObjective: This study evaluated the outcomes of microvascular decompression(MVD)and gamma knife surgery(GKS)for trigeminal neuralgia associated with vertebrobasilar dolichoectasia(VBD-associated TN).Methods: A retrospective review of patients with VBD-associated TN treated with MVD or GKS at our institution was performed from March 2011 to March 2019.A total of 80 patients were included in this study,and they were divided into MVD group(n = 46)and GKS group(n = 34)according to the surgical methods.All patients in GKS group underwent two isocenter GKS.The demographic characteristics,outcomes,and complications of the two groups were analyzed and compared.Results: Patients who underwent MVD were younger than patients who underwent GKS(mean,61.1 vs.65.4 years;p = 0.03).Initial favorable pain outcomes(BNI I-II)rates were 97.8% for MVD and 79.4% for GKS(p = 0.009).The 1-,3-,5-,and 7-year favorable pain outcomes maintenance rates were 95.7,85.1,74.2,and 74.2%,respectively,in the MVD group and 76.5,66.2,56.6,and 47.2%,respectively,in the GKS group(p = 0.031).The postoperative complications(except facial numbness)in the MVD group were higher than those in the GKS group(p = 0.036),but the incidence of new or worsened facial numbness was higher in the GKS group(p < 0.001).Conclusions: For VBD-associated TN,MVD was superior to GKS in obtaining and maintaining favorable pain outcomes,but it was accompanied by more complications(except facial numbness).Overall,both MVD and GKS were effective treatments,which could be selected according to the individual condition and wishes of patients.