Article
Diffusion MRI indicating structural nerve recovery after microvascular decompression in trigeminal neuralgia
Erholung der Faserintegrität nach mikrochirurgischer Dekompression bei Trigeminusneuralgie
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Published: | May 25, 2022 |
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Objective: Previous studies using MRI techniques such as diffusion tensor imaging (DTI) as a diagnostic tool for trigeminal neuralgia found a significantly lower fractional anisotropy (FA) in the root-entry-zone of the affected nerve. We hypothesized that postoperative DTI might show an increase in fibre directionality, corresponding to structural recovery of the trigeminal nerve, going along with clinical improvement.
Methods: 62 patients (26 male, 36 female, median age 64 years) who underwent microvascular decompression were assessed using a standardized questionnaire including a numeric rating scale and a brief pain inventory-facial and an MRI (3D-T1, -T2, DTI) at three points in time each: MRI/questionnaire 1 day preoperatively, MRI 48 hours postoperatively / questionnaire 7 days postoperatively, and MRI/questionnaire 3 months postoperatively. All patients were operated using an autologous cushion (muscle patch), allowing for widely artefact-free postoperative diffusion MRI. Data processing was performed using FSL. Bilateral FA-values were measured in the root-entry-zone and the cisternal segment of the brainstem. Regions of interest (ROIs) were drawn in three-dimensional space using the software iPlan, and a standardized ROI volume of 0.02 cm2.
Results: Pain relief was achieved in 93.61% of the patients whereas 6.39% were defined as partial or non-responders. Overall, a significant decrease in pain levels was found at both 7 days (by 90.3 ± 17.9%; p<0.001) and 3 months postoperatively (by 83.0 ± 34.1%; p<0.001). FA-values of the ipsilateral trigeminal nerve (root-entry-zone) showed a significant increase after 3 months (p<0.05), as opposed to no significant change of the FA on the contralateral side.
Conclusion: Pain relief achieved by microvascular decompression of the trigeminal nerve (using interposition of muscle tissue) is reflected by a significant improvement of ipsilateral fibre integrity. This suggests that the clinical success of surgery translates to a structural recovery of the affected trigeminal nerve in the root entry zone.