Introduction

Trigeminal neuralgia (TN) complicating the clinical course of multiple sclerosis (MS) patients has been treated with various procedures. While in the literature there are many papers on the efficacy of different techniques for the treatment of TN in MS patients [4, 12, 16, 20], the results for percutaneous balloon compression (PBC) have been reported only marginally in a small amount of patients [1, 3, 5]. Moreover, to the best of our knowledge, there are no reports analysing the potential prognostic factors of PBC in this particular population. The aim of this study was to investigate the role of PBC in the treatment of TN in MS patients and to analyse different clinical and technique-related factors in determining the prognosis.

Methods and materials

We retrospectively analysed 21 MS patients (10 male and 11 female) harbouring TN and submitted to PBC, from January 2000 to February 2011. The mean age was 52.23 ± 11.26 years with a follow-up of 51.57 ± 20.89 months. SM and TN duration before the procedure was 13.81 ± 8.41 years and 5.61 ± 4.51 years, respectively. The pain was atypical in two patients. Five cases had a pre-operative hypoesthesia and eight cases had undergone previous operations (Table 1). Patients reported their pain as the worst possible pain. The operation was performed under general anaesthesia and fluoroscope image intensifier using a 14-gauge needle and a 4-French Fogarty balloon catheter filled with 0.75 ml contrast medium, with a compression time ranging from 2 to 12 min (Table 1),as previously reported [7, 8]. We used, as outcome indicators, acute pain relief (APR: pain-free at hospital discharge) and pain-free survival (PFS). At follow-up, the outcome was assessed using the Barrow Neurological Institute (BNI) pain scale [14].

Table 1 Clinical findings of MS patients affected by TN and submitted to PBC
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Furthermore, we investigated the role of sex, number of affected trigeminal divisions, pre-operative deficit, previous operations, compression time (≤5 min vs >5 min), balloon shape at operation (pear-like vs elliptical-like) as potential prognostic factors. A comparison of categorical variables was performed by chi-squared statistic. Kaplan-Meier curves were plotted and differences in pain-free survival between groups of patients were compared using the log-rank test. Those p values less than 0.05 were considered as statistically significant.

Results

Seventeen out of 21 patients (80.95%) reported an APR. No major complication was observed after the procedure. Only two patients (cases 4 and 8) complained of the onset of mild hypoesthesia (Table 1). None of the evaluated factors was associated to an higher probability of APR. Twelve patients (57.14%) experienced a recurrence of pain with a mean pain-free survival of 15.0 ± 17.24 months. All of them required one (cases 2, 3, 5, 8, 9, 10, 15, 17, 20, 21) or more (cases 9, 10, 17) PBC (see Table 2). In two cases with a recurrence in the third branch (cases 4, 13) percutaneous radiofrequency rhizothomy was performed [7, 18].

Table 2 Follow-up of patients
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All patients who did not recur after the first PBC (42.8%) showed an excellent outcome (BNI I-II) at latest follow-up. Globally, considering also the patients submitted to more procedures, an excellent outcome (BNI I-II) was obtained in 16 patients out of 21 (76.1%) and a good outcome (BNI III) in the remaining ones. No patients had an uncontrolled pain (Table 2).

Among potentially prognostic factors, the presence of a single affected trigeminal division (p = 0.042), the absence of previous operations (p = 0.048), compression time ≤5 min (p = 0.0067) and pear-like shape of the balloon at the operation (p < 0.05) were associated to higher pain-free survival (Fig. 1).

Fig. 1
figure 1

Kaplan-Meier curves of MS patients submitted to PBC and stratified by (a) number of affected trigeminal divisions, (b) history of previous operations, (c) compression time and (d) balloon shape at operation. Single affected trigeminal division (p = 0.042), absence of previous operations (p = 0.048), time of compression ≤5 min (p = 0.0067) and pear-like shape of the balloon at the operation (p < 0.05) were associated with higher pain-free survival

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Discussion

The prevalence of TN in MS patients is high, ranging from 1% [15] to 6.3% [13]. While the results and the factors associated with the prognosis for PBC have been extensively investigated in the general population (see two recent reviews comparing different surgical modalities [6, 19]), the results of PBC and the role of different factors involved in the prognosis of MS patients have been poorly addressed so far [1, 3, 5].

In our series, we obtained 100% of excellent (BNI I-II)-good (BNI III) responses with a single or repeated procedures. Only two patients out of 21 (9.5%) required other techniques than PBC to control their pain (cases 4, 13).

Considering the literature reporting on MS patients submitted to different procedures, (Supplementary Table S1), we found that, globally, the APR rate after different procedures in MS patients was high, ranging from 84.8% of gamma knife surgery to 95.4% of percutaneous radiofrequency rhizothomy. PBC and microvascular decompression (MVD) showed an APR rate of 89.6% and 90.8%, respectively. We found that percutaneous radiofrequency rhizothomy showed a better pain-free rate at follow-up (73.5%). Considering the recurrence rate (RR), this procedure showed an high RR (43.1%) as well as PBC (59.2%), as demonstrated by our results and previously reported results [1, 5]. However, taking into account the complication rate (CR), PBC was associated to lower CR (4.7%). Moreover, according to our experience (no effects or very mild side effects, not requiring any treatment) and other reported experience [10], PBC was well accepted and could be easily repeated, when needed.

The analysis of possible prognostic factors documented a statistically better prognosis in patient whose pain involved a single trigeminal division. The different pathogenesis of typical TN and MS-related TN might explain the difference between our data and those reported by Kouzounias et al. [5], who did not find any difference, considering the number of affected divisions, in patients with typical TN.

The history of previous operations has been reported to negatively influence the prognosis [14, 15], although this has not been confirmed by other authors [9, 17]. In our series, we found a worse prognosis in patients who had undergone previous operations, even if we observed a mean pain-free survival higher compared with that reported for typical TN (15.07 months in our MS population and 7.3 months in general population [10]).

The compression time is the only technically operator-modifiable parameter. It was evidenced that a longer time of compression did not improve the prognosis of patients and was associated with an increased complication rate [2, 11]. These findings are confirmed by our results. In our study population, a compression time ≤5 min was associated with a better pain-free survival, as we previously demonstrated also for the general population [7].

A recent report [5] demonstrated that the pear-like balloon shape was an important prognostic factor with a better impact on the outcome. This was true also in our MS patient series. The pear-like shape likely reflects an engagement of the balloon with the porus trigeminus and this could produce a better compression of the retro-gasserian root [5].

In summary, considering that PBC, MVD and percutaneous radiofrequency rhizothomy have the best APR rate, but PBC shows the lowest complication rate, can be easily repeated and is well accepted by patients, we consider PBC as first choice in MS patients with drug-resistant TN. Some factors, such as single affected trigeminal division, absence of previous operations, compression time ≤5 min and pear-like shape of the balloon at the operation, seem to be associated with a better prognosis in these patients.