Introduction: Aim of the present study was to pre-operatively evaluate the microstructural changes and of the trigeminal nerves and the possible clinical implications in patients with typical trigeminal neuralgia (TN) due to neurovascular compression (NVC) by diffusion tensor imaging (DTI) and a 3D fast imaging employing steady state acquisition sequence (3D FIESTA).
Methods: 80 consecutive patients (43 females, 37 males; mean age: 58 ±11 years) with TN (Type 1) and clinical suspicion of NVC were included, who all underwent microsurgical decompression (MVD). A single shot DTI-EPI-sequence along 15 different diffusion directions (3.0 T MR scanner (Signa HDx, GE, USA)) was acquired along with a 0.6mm isotropic three-dimensional fast imaging employing steady state acquisition sequence (3D-FIESTA) for anatomic correlation. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were correlated with intra-operative and clinical findings.
Results: Identification of trigeminal nerves was significantly improved by co-registration with the 3D-FIESTA sequence. FA was significantly (p<0.01) lower on the affected side (mean 0.32+0.07, contralateral side mean 0.45+0.09). ADC was higher on the affected side, but not significantly (2.20+0.26 vs. 1.92+0.36). Image-analysis showed NVC-features that were congruent with surgical findings in 74/80 patients (92,5%). In 4/7 patients, who did not show NVC on MRI, also no NVC was found intra operatively, resulting in 3 false-negative cases – however, FA-values were significantly lower on the affected side in 3/3. All patients operated were free from TN directly post-op and on follow-up at 6 months.
Conclusions: Pre-operative DTI, co-registered with a high-resolution 3D-FIESTA, allows the identification and quantification of microstructural changes due to vascular compression of the affected nerve in patients with typical TN with high sensitivity and specificity. This could facilitate therapeutic decisions in patients with clinical evidence of TN and allow for estimation of the probability of success-rate of microvascular decompression - both on an objective anatomical and “functional” basis.
Patient Care: The DTI-sequences applied in our series allows for the identification and quantification of microstructural changes due to vascular compression of the affected nerve in patients with typical TN with high sensitivity and specificity. These new "functional imaging" data might support and optimize therapeutic decisions in patients with clinical evidence of TN and allow for estimation of the probability of success-rate of microvascular decompression.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Understand the concept of NVC, Microstructural changes and MVD in TN., 2) Discuss, in small groups, the possible implications that DTI-Imaging myth have in decision-making in TN-Patients and 3) Identify the most effective treatment for affected patiens.