# Trigeminal somatosensory evoked potentials for intraoperative monitoring and prognostic prediction in microvascular decompression for trigeminal neuralgia: a prospective cohort study

## TL;DR

This study shows that monitoring TSEP waveforms during surgery can help predict outcomes for patients with trigeminal neuralgia undergoing microvascular decompression.

## Contribution

A new prognostic model using TSEP amplitude changes and clinical factors for predicting MVD outcomes in trigeminal neuralgia patients.

## Key findings

- TNW2 amplitude change rate is strongly correlated with postoperative pain and can predict surgical outcomes.
- Hypertension, PTN duration ≥2.5 years, and TNW2 amplitude change rate <60% are independent risk factors for poor prognosis.
- The nomogram model based on TSEP, hypertension, and PTN duration accurately predicts recurrence risk and surgical efficacy.

## Abstract

This study aims to explore the monitoring techniques of trigeminal somatosensory evoked potentials (TSEP) and investigate their clinical significance in microvascular decompression (MVD) for primary trigeminal neuralgia (PTN). By analyzing the relationship between changes in TSEP waveforms during surgery and postoperative outcomes of MVD, a prognostic prediction model based on electrophysiological and clinical features will be constructed to provide a basis for individualized assessment of surgical risks and efficacy.

This study included 74 patients diagnosed with PTN and used statistical methods to analyze and optimize the waveform characteristics of TSEP. The amplitude change rate of TSEP before and after MVD surgery was calculated, and combined with postoperative pain scores, Spearman correlation analysis and ROC curves were used to determine the optimal cut-off value for predicting prognosis. Finally, univariate and multivariate Cox regression analyses were conducted to identify independent risk factors affecting poor prognosis of MVD surgery in PTN patients, a nomogram model was established, and the model’s performance was validated through Kaplan–Meier survival analysis and ROC curves.

(1) In this study, there was no statistically significant difference in the amplitudes of V1w1 and V1w2 between the healthy and affected sides in TSEP (p > 0.05), while the amplitudes of TNW1, TNW2, TNW3, V2w1, V2w2, V2w3, V3w1, V3w2, and V3w3 showed significant statistical differences (p < 0.05); the latencies of all TSEP branches showed no significant statistical differences before and after MVD surgery (p > 0.05). (2) The TSEP amplitude change rates were calculated, and the amplitude change rate of TNW2 was strongly negatively correlated with postoperative pain, with TNW2 showing the strongest correlation [r = −0.563, p < 0.05], followed by TNW3. (3) ROC curve analysis of the relationship between TNW2, TNW3, and surgical prognosis indicated that both could predict surgical outcomes (p < 0.05): TNW2 [AUC = 0.792, Cut-off = 1.595, i.e., 59.5%]; TNW3 [AUC = 0.760, Cut-off = 1.535, i.e., 53.5%]. (4) Cox proportional hazards regression analysis identified independent risk factors affecting surgical prognosis. Multivariate analysis showed that TNW2 amplitude change rate [HR = 0.27, 95% CI: 0.11–0.67, p = 0.005], hypertension [HR = 0.54, 95% CI: 0.30–0.97, p = 0.039], and PTN disease course [HR = 0.47, 95% CI: 0.24–0.90, p = 0.023] were independent prognostic factors. The nomogram model had AUC values of 0.80, 0.83, and 0.93 at 14, 30, and 90 days, respectively, showing good discrimination. Kaplan–Meier analysis further confirmed the significant association of TNW2 amplitude change rate, hypertension, and PTN disease course with prognosis (Log-rank p < 0.001).

The TSEP technique used in this study is simple to operate (only requiring puncture around the muscle groups near the puncture point), provides stable waveform results, and is convenient for intraoperative interpretation (only needing to observe changes in waveform amplitude). In addition, intraoperative monitoring of TNW2 amplitude change rate (≥60% indicates good prognosis) can provide real-time guidance during decompression and predict efficacy. The combination of hypertension, PTN duration ≥2.5 years, and TNW2 amplitude change rate <60% are independent risk factors for poor prognosis after MVD; patients with PTN who have hypertension, longer PTN duration, or TNW2 amplitude change rate <60% during microvascular decompression experience slower postoperative pain relief. The nomogram model based on TSEP waveforms, hypertension, and PTN duration has high accuracy and can individually assess recurrence risk, providing a tool for clinically identifying high-risk patients.