The Most Useful MRI Sequence for Detecting Neurovascular Conflict and Discrepancies Between Clinical and Imaging Findings in a Series of 80 Dominican Patients with Refractory Trigeminal Neuralgia Treated with Stereotactic Radiosurgery Using the Gamma Knife.

• DOI: https://doi.org/10.22533/at.ed.0159652616041

• Palavras-chave: Refractory Trigeminal Neuralgia, MRI Sequences, Neurovascular Conflict, Atrophy, Dystrophy, Trigeminal Eutrophy, Discrepancies in Trigeminal Neuralgia.

• Keywords: Refractory Trigeminal Neuralgia, MRI Sequences, Neurovascular Conflict, Atrophy, Dystrophy, Trigeminal Eutrophy, Discrepancies in Trigeminal Neuralgia.

• Abstract:

  Objectives: To determine which MRI sequence is most useful for demonstrating neurovascular conflict and to assess the percentage of discrepancies between expected and actual findings in the most relevant  imaging and structural  features of 80 Dominican patients with refractory trigeminal neuralgia who were consecutively treated at the Dominican Gamma Knife Center over an 8-year period.  Materials and Methods: A retrospective study of 80 patients (47 women, 33 men) with refractory trigeminal neuralgia treated at the Dominican Gamma Knife Center between March 2011 and March 2019. All patients underwent a 1.5-Tesla MRI with 1–1.5-mm slices for three-dimensional reconstruction, including the following sequences: FIESTA, T1 without and with contrast, FLAIR, T2, and TOF. Some patients also underwent a contrast-enhanced thin-slice computed tomography (CT) scan. The images were examined by the Principal Investigator (PI) using the Elekta Gamma Plan 11 stereotactic image management platform at the Dominican Gamma Knife Center. As documented in a recent publication we authored1, we determined the trophic status of the trigeminal nerves studied (eutrophic, dystrophic, atrophic), the size of the trigeminal cistern (large, intermediate, small), the precise site of neurovascular conflict (proximal, intermediate, distal), and the caliber of the involved artery (small, medium, large). We sought to determine which of all the MRI sequences used provided the clearest and most detailed images of thes . We also investigated the occurrence of unexpected findings, such as trigeminal nerve involvement in large rather than small cisterns, symptomatic nerves with good trophic status, the onset of neuralgia in nerves without tangible neurovascular conflict, and symptomatic nerves despite distal neurovascular conflict caused by a small-caliber artery. The collected data were processed using measures of central tendency and Pearson’s correlation coefficient in Microsoft Excel 2016. Results:   The MRI sequence where neurovascular conflict was most frequently found was FIESTA: 93.55% on the right, 95.52% on the left. Contrast-enhanced T1 and T2 sequences showed it in approximately 70% of cases. Using Time of Flight (TOF), neurovascular conflict can be detected in up to 54.55% of cases. Using non-contrast T1 does not reach 50%. When Computed Axial Tomography with contrast is used, neurovascular conflict is shown in 7.69% on the right and 13.79% on the left. Analyzing the discrepancies from what was expected, we found that on the side of the pain, 62% of the cisterns were large rather than small, as would be expected. There was strong concordance in that the affected nerve was expected to show atrophy: this was present in 73% of cases. The discrepancy of a symptomatic trigeminal nerve without neurovascular conflict occurred in only 7% of cases, and that of a symptomatic nerve with distal neurovascular conflict caused by a small-caliber artery occurred in only 6% of patients.  Conclusion: In this consecutive series of 80 patients with refractory trigeminal neuralgia treated with radiosurgery using the Gamma Knife, the MRI sequence that most effectively revealed neurovascular conflict was FIESTA. The discrepancy between the expected and observed imaging findings in the affected trigeminal nerves studied was associated with a predominance of large cisterns (62%) and the presence of normal trophicity in 27% of the affected nerves.