Outcome comparison between interposition and "contactless" transposition microvascular decompression approaches for trigeminal neuralgia.

Objective: Microvascular decompression (MVD) is an effective method of treating trigeminal neuralgia (TN). The traditional approach is an interposition technique in which Teflon is placed between the nerve and offending vessel. However, recurrent TN pain has been attributed to the Teflon itself, its migration, inflammatory granuloma formation, or continued direct compression. Thus, transposition techniques in which the nerve is fully decompressed without any contact with the offending vessel or the Teflon have been described. In this study, the authors report their institutional experience with interposition and newer transposition techniques such as sling transposition.

Methods: A retrospective chart review was performed on patients who had undergone MVD from July 2015 to March 2024. Demographic, surgical, and clinical variables were collected, including modified Barrow Neurological Institute (BNI) pain intensity scale scores. Clinical outcomes were assessed using univariate and multivariate regression, and propensity score matching (PSM) was employed to minimize inherent heterogeneity in the surgical cohorts.

Results: Three hundred five patients underwent MVD for TN. Eighty-four patients underwent interposition; 139, transposition with Teflon (full decompression with no contact to the nerve); and 48, transposition using a pericranium sling to the tentorium. A subset of these patients underwent concurrent rhizotomy: 73% interposition cases, 15% Teflon transposition cases, 4% sling transposition cases. Rhizotomy alone was performed in 34 patients. Transposition primarily involved the superior cerebellar artery (90%) and was associated with severe compression and nerve indentation. There were no differences in BNI scores at the last follow-up or in complications among the treatment groups. The only significant predictor of pain freedom on multivariate analysis was MRI demonstrating clear compression (OR 2.49, 95% CI 1.147-5.404, p = 0.021). However, subgroup analyses of patients with at least 1 year of follow-up showed a trend for increased pain freedom (BNI scores I and IIIa) with the sling transposition technique at 1 year, which was statistically significant at the 2-year follow-up (1 year: sling 96.6%, Teflon 86.9%, interposition 81.1%, p = 0.053; 2 years: sling 100%, Teflon 87.5%, interposition 77.5%, p = 0.049). PSM cohort analysis showed that sling transposition patients had higher rates of pain-free outcomes (BNI scores I and IIIa) at the last follow-up than the Teflon transposition patients (93.1% vs 62.1%, respectively, p = 0.003).

Conclusions: Interposition and transposition techniques for MVD are both effective. The authors' midterm data suggest longer-term TN pain control with sling transposition. Further studies will need to confirm the durability of long-term pain freedom.