Clinical Study
Long-term prognostic factors for microvascular decompression for trigeminal neuralgia

https://doi.org/10.1016/j.jocn.2012.03.037Get rights and content

Abstract

The purpose of this retrospective study was to identify preoperative imaging characteristics and surgical findings that predict pain relief after microvascular decompression (MVD) for trigeminal neuralgia (TN). This study included 141 patients with follow-up ranging from 6 months to 10 years (mean follow-up = 26.3 months). Preoperative images were assessed in 90 patients who were evaluated with constructive interference in steady-state (CISS) MRI in the last 6 years. These findings were compared with the severity of neurovascular conflict (NVC) found at operation to identify imaging findings useful for prognosis. Using Kaplan–Meier analysis, we found that the success rate of MVD was 91.1 ± 2.5% at 1 year and was 76.3 ± 7.5% after 5 years. A higher degree of NVC at operation (p = 0.000), no vein compression (p = 0.049) and single vessel compression (p = 0.000) were good prognostic factors for pain relief. Two meaningful positive MRI findings, specifically, the “cerebrospinal fluid rim sign” and the “deviation sign” were statistically significantly associated with the severity of NVC at operation and MVD success (p = 0.000). In this study, 34 patients (24.1%) complained of facial numbness postoperatively, and the oral herpes simplex virus was reactivated in 19 patients (13.4%). The involvement of a single arterial offender in NVC is the most important prognostic factor for MVD in TN, and the positive MRI findings described in this report may be helpful in selecting patients for MVD.

Introduction

Trigeminal neuralgia (TN) is a facial pain syndrome characterized by paroxysmal, shock-like pain attacks that are distributed along the trigeminal nerve. Various surgical treatments have been used to treat TN. Among these treatments, microvascular decompression (MVD) has been the most attractive treatment strategy because it provides the highest rates of long-term patient satisfaction and the lowest rates of pain recurrence.1 However, not all patients with TN are cured by MVD. Although reports of initial pain relief after MVD range from 86–98.2%, the recurrence rates range from 15.1–30%.[2], [3], [4] Furthermore, open surgery has a higher mortality rate compared with other techniques used to treat TN including percutaneous techniques or stereotactic radiosurgery.[2], [3]

Most cases of TN are caused by a neurovascular conflict (NVC) at the root entry zone of the trigeminal nerve, and in several analyses, patients with more severe vascular compression of the trigeminal root have reported greater relief of their symptoms after microvascular decompression.[5], [6], [7], [8] Therefore, prediction of NVC severity using preoperative imaging may be useful for predicting long-term success and could help guide patient selection for MVD treatment.

This retrospective study was performed to determine the imaging predictors of pain relief after MVD. In addition, the preoperative patient factors and surgical findings were analyzed. The preoperative imaging studies were compared with the surgical findings to identify imaging findings predictive of success.

Section snippets

Methods

In this study, 153 consecutive patients were treated with MVD for typical TN by a single surgeon (K. Park) at the Samsung Medical Center in Seoul, Korea between January 1998 and March 2010 and were evaluated. Within this group, 12 patients were excluded due to a lack of recorded postoperative results. Therefore, only 141 patients were included in this study.

The prognostic factors were assessed by a review of the medical records and were classified into two categories, specifically, the

Overall outcome after microvascular decompression

The follow-up evaluation period ranged from 6 months to 10 years with a mean of 26.3 months. The Kaplan–Meier curves for success (excellent outcome) and acceptable success (excellent or good outcome) are shown in Fig. 1a, b. An immediate, complete postoperative relief from pain was achieved in 120 patients (85.1%), with immediate good relief being attained in 16 patients (11.3%) and poor relief in five patients (3.6%). Using the Kaplan–Meier analysis, the estimated probability of being pain-free

Discussion

Since Gardner proposed the theory of NVC, a growing body of evidence indicates that compression of the trigeminal nerve root at or near the dorsal root entry zone by a vessel is the major cause of TN.[2], [7], [12], [13], [14], [15] Although autopsy studies have revealed some degree of contact between the trigeminal nerve and a blood vessel in 14–60% of asymptomatic individuals, it is uncommon for arterial contact to produce a distortion or grooving of the nerve.[16], [17], [18], [19]

Conclusion

The presence of a definitive NVC with a single arterial offender at surgery is the most important prognostic factor in MVD for TN, and the preoperative MRI findings of deviation and a CSF rim sign are correlated with a more severe NVC. Due to the limitations of this retrospective study, a thorough prospective study is required to clarify the significance of these positive MRI findings.

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