Association between intraoperative parameters and pain reduction after radiofrequency rhizotomy in patients with...

Percutaneous radiofrequency (RF) rhizotomy is one of the most effective minimally invasive treatments for trigeminal neuralgia (TN) that is unresponsive to medication. Although it is commonly used, the impact of intraoperative parameters, especially CSF outflow, prelesion impedance, and total thermal dose, on long-term pain control remains unclear. This study aimed to evaluate the relationship between these procedural factors and postoperative pain reduction.

A retrospective analysis of a prospectively maintained database was performed of patients who underwent percutaneous RF rhizotomy for TN at a single tertiary facility from February 2019 to December 2023. Recorded variables included demographic data, TN subtype, impedance of electrodes, temperature and duration of lesioning, CSF outflow, and sensory responses during lesioning. Thermal dose was measured by cumulative equivalent minutes at 43°C (CEM43) and temperature-by-time summation. Outcomes were assessed using the Barrow Neurological Institute (BNI) pain intensity scale immediately after treatment and during the final follow-up. Treatment success was defined as a BNI score of IIIa or lower. Logistic regression and correlation analyses were performed to identify predictors of treatment efficacy.

A total of 165 patients met the inclusion criteria, with a median follow-up duration of 19 months. CSF outflow occurred in 116 of 165 procedures (70.3%), showing a moderate positive correlation with both immediate (ρ = 0.418, p < 0.001) and long-term (ρ = 0.539, p < 0.001) reduction in pain. Univariate analysis indicated that CSF outflow was a significant predictor of treatment success (p < 0.001), while higher prelesion impedance, longer lesioning durations, and greater thermal dose were associated with lower odds of success. In multivariate models, CSF outflow and prelesion impedance were the most significant independent predictors of achieving a BNI score ≤ IIIa at the final follow-up. Temperature-by-time summation outperformed CEM43 in predicting outcomes, suggesting that prolonged lesioning reflects technical difficulty rather than therapeutic benefit.

CSF outflow and low prelesion impedance were the most reliable intraoperative markers of effective percutaneous RF for TN, likely indicating accurate electrode placement within the trigeminal cistern and optimal electrical coupling. Conversely, longer lesion durations and increased cumulative thermal exposure did not improve outcomes, highlighting that accurate positioning, rather than aggressive lesioning, is key to achieving long-lasting pain relief. These results support incorporating CSF outflow and impedance into routine decision-making for RF rhizotomy.