Outcomes of trigeminal nerve microsurgical internal neurolysis for trigeminal neuralgia without neurovascular conflict: a systematic review and meta-analysis.

Trigeminal neuralgia (TN) without neurovascular conflict poses a therapeutic challenge. Microsurgical internal neurolysis (IN), also known as nerve combing, has emerged as a viable surgical option when microvascular decompression (MVD) is not indicated. This systematic review and meta-analysis, conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, included eight case series with a total of 193 patients. Pain relief outcomes were assessed using the University of California at San Francisco (UCSF) criteria and the Barrow Neurological Institute (BNI) pain intensity score. Excellent pain relief (UCSF criteria) was achieved in 76.3% (67.4-85.2%) of patients, while 9.9% (3.6-16.2%) had a good outcome, and 5.9% (1-10.9%) experienced poor outcomes. Based on the BNI scale, successful pain relief (BNI I-II) was observed in 82.2% (72.2-92.2%) of patients. Hypoesthesia occurred in 49.2% (17.5-81.0%) of cases, while pain recurrence was reported in 10.2% (4.8-15.7%). Our findings, demonstrating high rates of pain relief, suggest that IN can be viable therapeutic alternative for patients with TN in the absence of neurovascular conflict. However, the risk of hypoesthesia highlights not only the importance of careful patient selection but also the significance of the microsurgical technique -specifically, the extent of disruption and whether the cut is longitudinal or transversal-both of which likely account for the wide variability reported, ranging from 17.5% to 81%. According to the GRADE framework, the overall certainty of the evidence was rated as very low, primarily due to the inclusion of non-randomized studies, predominantly high risk of bias, and considerable variability in results across studies. Further comparative studies are necessary to refine surgical indications and optimize outcomes for this patient population.