The role of neurovascular conflict in patients with multiple sclerosis and trigeminal neuralgia

Dear Editor,

We read with great interest the article of Noory et. al. (1) about the role of neurovascular conflict (NVC) in patients with trigeminal neuralgia (TN) and multiple sclerosis (MS). They included 54 patients for a MRI analysis and found no significant difference between symptomatic and asymptomatic TN side concerning the prevalence of a NVC, while a brainstem demyelinating plaque (BDP) was more frequent on the symptomatic TN side compared to the asymptomatic one. Thus the authors assumed that NVC does not play a role in the pathogenesis of MS-related TN and concluded that microvascular decompression (MVD) should be excluded as a treatment option for these cases. We think that this conclusion is not justified by these data based on a small cohort of patients. In their series the authors found a BDP in the affected TN side in 31/54 (58%) of MS patients (1). In these cases it seems reasonable that the pathogenesis of TN could be related to the presence of the BDP. The question is the following: what is the pathogenesis of TN in MS patients without evidence of a BDP? Recently a systematic review analysed the results of MVD in patients with MS-related TN (2). In that systematic review an acute pain relief in 71.42% of cases was found. A pain recurrence was reported in 26% of patients with a mean pain-free interval of 24.07 ± 44.98 months. Moreover, the lack of a BDP positively affected the possibility to be a responder after MVD (2). This evidence seems to confirm a role of NVC also in patients with MS-related TN. Moreover, the finding that no significant differences in NVC were observed between symptomatic and asymptomatic TN side (66% vs 68%, respectively) (1) should not be considered as a proof of the lack of significance of NCV in the MS-related TN pathogenesis. In fact, it is important to underline that the NVC should not be considered a disease ‘per se’. The diagnosis of TN is based on clinical criteria and the NVC assumes a role only in the correct clinical context. Moreover, it is well known that NVC can play a role as cause of TN even in cases with no morphological changes of trigeminal nerve making misleading the provided data of 14% of prevalence of NVC with morphological changes in the symptomatic TN side versus 9% on the asymptomatic side (1) as an additional proof of the lack of significance of NVC. Thus, we think that MVD should be considered as a valid surgical option in MS-related TN also taking into account recent evidence suggesting a lower efficacy of percutaneous techniques in MS patients with no BDP (3). In our opinion it is important to keep in mind that TN is difficult to treat in patients with MS. The surgical treatment should be tailored to each individual patient. To the best of current knowledge no treatment should be excluded ‘a priori’ in this cohort of patients.