Demonstration of neurovascular compression in trigeminal neuralgia with magnetic resonance imaging. Comparison with surgical findings in 52 consecutive operative cases

The Superior Cerebellar Artery: Variability and Clinical Significance

The superior cerebellar artery (SCA) arises from the distal part of the basilar artery and passes by the oculomotor, trochlear, and trigeminal nerves. SCA is known to play a crucial role in the development of trigeminal neuralgia. However, due to its anatomical variability, it may also trigger other neurovascular compression (NVC), including hemifacial spasm, oculomotor nerve palsy, and ocular neuromyotonia. Additionally, it may be associated with ischemic syndromes and aneurysm development, highlighting its clinical significance. The most common anatomical variations of the SCA include duplication, a single vessel origin from the posterior cerebral artery (PCA), and a common trunk with PCA. Rarely observed variants include bifurcation and origin from the internal carotid artery. Certain anatomical variants such as early bifurcation and caudal course of duplicated SCA trunk may increase the risk of NVC. In this narrative review, we aimed to examine the impact of the anatomical variations of SCA on the NVCs based on papers published in Pubmed, Scopus, and Web of Science databases with a snowballing approach. Our review emphasizes the importance of a thorough understanding of the anatomical variability of SCA to optimize the management of patients with NVCs associated with this artery.

Identification of the NRF2 transcriptional network as a therapeutic target for trigeminal neuropathic pain

Trigeminal neuralgia, historically dubbed the "suicide disease," is an exceedingly painful neurologic condition characterized by sudden episodes of intense facial pain. Unfortunately, the only U.S. Food and Drug Administration (FDA)-approved medication for trigeminal neuralgia carries substantial side effects, with many patients requiring surgery. Here, we identify the NRF2 transcriptional network as a potential therapeutic target. We report that cerebrospinal fluid from patients with trigeminal neuralgia accumulates reactive oxygen species, several of which directly activate the pain-transducing channel TRPA1. Similar to our patient cohort, a mouse model of trigeminal neuropathic pain also exhibits notable oxidative stress. We discover that stimulating the NRF2 antioxidant transcriptional network is as analgesic as inhibiting TRPA1, in part by reversing the underlying oxidative stress. Using a transcriptome-guided drug discovery strategy, we identify two NRF2 network modulators as potential treatments. One of these candidates, exemestane, is already FDA-approved and may thus be a promising alternative treatment for trigeminal neuropathic pain.

The role of the P2X4 receptor in trigeminal neuralgia, a common neurological disorder

Neurological disorders, which include various types of diseases with complex pathological mechanisms, are more common in the elderly and have shown increased prevalence, morbidity and mortality worldwide. Unfortunately, current therapies for these diseases are usually suboptimal or have undesirable side effects. This necessitates the development of new potential targets for disease-modifying therapies. P2X4R, a type of purinergic receptor, has multiple roles in neurological disorders. In this review, we briefly introduce a neurological disorder, trigeminal neuralgia and its' symptoms, etiology and pathology. Moreover, we focused on the role of P2X4R in neurological disorders and their related pathophysiologic mechanisms. Further studies of P2X4R are required to determine potential therapeutic effects for these pathophysiologies.

Microvascular compression of the vestibulocochlear nerve

PURPOSE

Vascular compression of cranial nerves has been widely accepted as a cause for trigeminal neuralgia and hemifacial spasm. In contrast, vascular compression of the vestibulocochlear nerve remains controversial.

METHOD

A comprehensive literature review including 175 articles between 1960 and 2020 was performed in an attempt to summarise the published hypotheses of the pathophysiological mechanisms of vascular compression of the vestibulocochlear nerve and their management strategies.

RESULTS

Vascular loops in the cerebellopontine angle (CPA) and internal auditory meatus (IAM) are very common and should be regarded primarily as a normal variant. Advances in anatomical understanding with the development of models for the tonotopy of the vestibulocochlear nerve help explain the complexity of symptoms created by possible neurovascular interaction.

CONCLUSION

Widely accepted, validated and sensitive diagnostic criteria and outcome measures need to be established in order to evaluate the role of surgery in vestibulocochlear nerve vascular compression.

P2X receptors and trigeminal neuralgia

There is currently no effective cure for trigeminal neuralgia (TN) - a relatively common disease that causes long-term pain in patients. Previous research has shown that ionotropic ATP signaling through excitatory and calcium-permeable P2X receptor channels plays a critical role in pathological pain generation and maintenance. In this paper, we review several hypotheses on the pathogenic mechanisms underlying TN. We further discuss pathways or agents that can target P2X expression in TN, thereby affecting pain induction and maintenance.

Sensitivity of magnetic resonance tomographic angiography for detecting the degree of neurovascular compression in trigeminal neuralgia

PURPOSE

Neurovascular compression (NVC) is hypothesized to be the main pathogenic factor of trigeminal neuralgia (TN). Microvascular decompression (MVD) has become a popular surgery for TN, and the success rate depends on the degree of NVC. As the routine examination before MVD, magnetic resonance tomographic angiography (MRTA) shows high sensitivity for detecting NVC. However, there are no reports on the sensitivity of MRTA for assessing the degree of NVC.

METHODS

This study aimed to evaluate the sensitivity of MRTA for determining the degree of NVC by comparing preoperative MRTA and intraoperative endoscopy findings. A total of 480 patients who suffered from TN and underwent MVD were included. Their preoperative MRTA and intraoperative endoscopy findings were reviewed. The kappa test was used to identify similarities between the MRTA and endoscopy findings.

RESULTS

The degree of NVC on preoperative MRTA was similar to that on endoscopy (kappa = 0.770). The number of offending vessels according to preoperative MRTA was coincident with that according to endoscopy (kappa = 0.722).

CONCLUSION

MRTA had high sensitivity for detecting not only the presence of NVC but also the degree of NVC.

Computational Fluid Dynamics Analysis of the Offending Artery at Sites of Neurovascular Compression in Trigeminal Neuralgia Using Preoperative MRI Data

This study aimed to analyze the hemodynamic features of the offending artery at sites of neurovascular compression (NVC) using computational fluid dynamics (CFD). A total of 23 patients who underwent microvascular decompression (MVD) for primary trigeminal neuralgia (TN) between January 2015 and December 2016 were enrolled in this study. The compressing vessel at the NVC site was identified microsurgically in all cases, and patients were divided into two groups based on the intraoperative findings: (1) the arterial NVC group and (2) the non-arterial NVC control group. A 3D surface model of the structures surrounding the NVC was created using preoperative magnetic resonance imaging (MRI), and CFD analysis was performed for the target artery. In addition to standard parameters, such as the wall shear stress (WSS), flow velocity, and pressure, we calculated the WSS ratio (WSSR) by dividing the WSS at the NVC by the mean WSS of the target. Arterial compression was observed intraoperatively in 13 patients. The mean WSSR of the arterial NVC group was significantly higher than that of the control group (2.36 ± 1.00 vs. 1.18 ± 0.73, P <0.05). There were no significant intergroup differences in the other calculated parameters. High WSSR, which indicates elevated WSS at the sites of NVC, was identified as a unique parameter of arterial compression that may contribute to TN. CFD could be a useful clinical tool in determining the target of MVD under preoperative conditions.

Guidelines for radiographic imaging of cranial neuropathies

Disruption of the complex pathways of the 12 cranial nerves can occur at any site along their course, and many, varied pathologic processes may initially manifest as dysfunction and neuropathy. Radiographic imaging (computed topography or magnetic resonance imaging) is frequently used to evaluate cranial neuropathies; however, indications for imaging and imaging method of choice vary considerably between the cranial nerves. The purpose of this review is to provide an analysis of the diagnostic yield and the most clinically appropriate means to evaluate cranial neuropathies using radiographic imaging. Using the PubMed MEDLINE NCBI database, a total of 49,079 articles' results were retrieved on September 20, 2014. Scholarly articles that discuss the etiology, incidence, and use of imaging in the context of evaluation and diagnostic yield of the 12 cranial nerves were evaluated for the purposes of this review. We combined primary research, guidelines, and best practice recommendations to create a practical framework for the radiographic evaluation of cranial neuropathies.

Reliability of MRI for predicting characteristics of neurovascular conflicts in trigeminal neuralgia: implications for surgical decision making

OBJECTIVE

The choice of microvascular decompression (MVD), among the several other surgical options, for treating refractory classical trigeminal neuralgia (TN) relies mostly on preoperative imaging, but the degree of reliability of MRI remains a matter of debate. The authors approached the question of predictability of neurovascular conflict (NVC) in a series of 100 protocolized MRI studies from patients with TN who underwent MVD, by reexamination of MR images, blinded to the clinical data and surgical findings, including the side of the neuralgia.

METHODS

Patients included in the study were those who underwent MVD after surgical indication had been determined based on a protocolized imagery workup (3D high-resolution T2-weighted cisternography centered on the trigeminal nerve, 3D time-of-flight angiography, and 3D gadolinium-enhanced T1-weighted imaging) performed at our institution. All MR images were blindly reexamined, and neurovascular relationships were described on both sides, noting the existence of compression, vessels involved, situation along the root, and degree of compression. The results of MRI evaluation were then compared with actual surgical findings. The extent of agreement and quality of the prediction were expressed with Cohen's kappa coefficient (κ) and receiver operating characteristic (ROC) statistics.

RESULTS

A conflict had actually been found during surgery in 94 of 100 patients. The sensitivity of MRI to detect a conflict was 97% and the specificity was 50%. Vessel type was identified with high reliability (κ = 0.80), while the grade of the conflict and its situation along the root showed poor to average reliability (κ = 0.38 and κ = 0.40, respectively). The area under the ROC curve for predicting the presence of a conflict according to the grades of conflict seen on MRI was 0.93, which is considered very good. The positive predictive value was differentiated according to the grade of conflict, with a very high value for high grades of vascular conflict.

CONCLUSIONS

This study shows an overall good reliability of MRI to predict the existence of an NVC. The prediction value is excellent for high grades of compression. Some apparent low-grade compressions on MRI may be revealed as false positives in surgical exploration. This raises the question of what other imaging methods might be used to determine not only the existence of a conflict but also its degree of compression. The degree of compression is of paramount importance to predict the probability of long-term pain relief, and therefore in the decision to propose MVD as the first choice of surgical treatment.

Prognostic Impact and Post-operative Evaluation of Volumetric Measurement of the Cerebellopontine Cistern in Trigeminal Neuralgia Using 3 Tesla Magnetic Resonance Imaging

The aim of this study was to evaluate the importance of pre- and post-operative volumetric measurement of the cerebellopontine angle (CPA) using 3 Tesla (3T) magnetic resonance imaging (MRI). Between April 2012 and December 2015, a total of 87 consecutive patients underwent microvascular decompression (MVD) for trigeminal neuralgia (TN), of whom 51 with primary TN caused by arterial compression were enrolled in this study. Bilateral CPA cistern volume was evaluated using 3T MRI before and after surgery; the Cistern Deviation Index was used to represent the degree of deviation of the CPA cistern. The relationships between CPA cistern volume and the etiology of TN were assessed, and post-operative changes in anatomical parameters were examined to determine differences between recurrent and non-recurrent patients with TN. The mean volume of the CPA cistern on the affected side was significantly smaller than the unaffected side (P < 0.001). Five of 51 (10%) patients experienced TN recurrence. The recurrent cases demonstrated significantly lower pre-operative Cistern Deviation Index scores than non-recurrent cases (P = 0.035). On the unaffected side-but not the affected side-post-operative volume reduction was significantly greater in the recurrence group than in the non-recurrence group (P = 0.004). The pre-operative Cistern Deviation Index was a useful parameter to predict the recurrence of TN. In recurrent patients, post-operative inflammatory reaction may extend to not only the operated side but also the healthy side and reduce the volume of the CPA cistern.

Microvascular Decompression for Glossopharyngeal Neuralgia: Clinical Analyses of 30 Cases

Objective

We present our experience of microvascular decompression (MVD) for glossopharyngeal neuralgia (GPN) and evaluate the postoperative outcomes in accordance with four different operative techniques during MVD.

Methods

In total, 30 patients with intractable primary typical GPN who underwent MVD without rhizotomy and were followed for more than 2 years were included in the analysis. Each MVD was performed using one of four different surgical techniques: interposition of Teflon pieces, transposition of offending vessels using Teflon pieces, transposition of offending vessels using a fibrin-glue-coated Teflon sling, and removal of offending veins.

Results

The posterior inferior cerebellar artery was responsible for neurovascular compression in 27 of 30 (90%) patients, either by itself or in combination with other vessels. The location of compression on the glossopharyngeal nerve varied; the root entry zone (REZ) only (63.3%) was most common, followed by both the REZ and distal portion (26.7%) and the distal portion alone (10.0%). In terms of detailed surgical techniques during MVD, the offending vessels were transposed in 24 (80%) patients, either using additional insulation, offered by Teflon pieces (15 patients), or using a fibrin glue-coated Teflon sling (9 patients). Simple insertion of Teflon pieces and removal of a small vein were also performed in five and one patient, respectively. During the 2 years following MVD, 29 of 30 (96.7%) patients were asymptomatic or experienced only occasional pain that did not require medication. Temporary hemodynamic instability occurred in two patients during MVD, and seven patients experienced transient postoperative complications. Neither persistent morbidity nor mortality was reported.

Conclusion

This study demonstrates that MVD without rhizotomy is a safe and effective treatment option for GPN.

Structural Magnetic Resonance Imaging Can Identify Trigeminal System Abnormalities in Classical Trigeminal Neuralgia

Classical trigeminal neuralgia (TN) is a chronic pain disorder that has been described as one of the most severe pains one can suffer. The most prevalent theory of TN etiology is that the trigeminal nerve is compressed at the root entry zone (REZ) by blood vessels. However, there is significant evidence showing a lack of neurovascular compression (NVC) for many cases of classical TN. Furthermore, a considerable number of patients who are asymptomatic have MR evidence of NVC. Since there is no validated animal model that reproduces the clinical features of TN, our understanding of TN pathology mainly comes from biopsy studies that have limitations. Sophisticated structural MRI techniques including diffusion tensor imaging provide new opportunities to assess the trigeminal nerves and CNS to provide insight into TN etiology and pathogenesis. Specifically, studies have used high-resolution structural MRI methods to visualize patterns of trigeminal nerve-vessel relationships and to detect subtle pathological features at the trigeminal REZ. Structural MRI has also identified CNS abnormalities in cortical and subcortical gray matter and white matter and demonstrated that effective neurosurgical treatment for TN is associated with a reversal of specific nerve and brain abnormalities. In conclusion, this review highlights the advanced structural neuroimaging methods that are valuable tools to assess the trigeminal system in TN and may inform our current understanding of TN pathology. These methods may in the future have clinical utility for the development of neuroimaging-based biomarkers of TN.

Cochleovestibular Nerve Compression Syndrome Caused by Intrameatal Anterior Inferior Cerebellar Artery Loop: Synthesis of Best Evidence for Clinical Decisions

INTRODUCTION

Intrameatal cochleovestibular neurovascular conflict is a rare condition with specific clinical and therapeutic implications. Although surgery is commonly indicated in other neurovascular conflicts, for this subset of patients there is little evidence to guide treatment decisions. Moving from a case description, we performed a review of the literature on this topic to systematically present the best available evidence to guide clinical decisions.

METHODS

We performed a literature review on reported cases of surgically treated intrameatal anterior inferior cerebellar artery (AICA)-cochleovestibular nerve neurovascular conflict, analyzing preoperative clinical data, surgical techniques, and outcomes. We analyzed the levels of evidence using the King's College guidelines.

DISCUSSION

We found 35 studies of neurovascular compression of the cochleovestibular nerve by AICA for 536 patients operated on to resolve their neurovascular conflict. Only 4 of these studies describe intrameatal AICA neurovascular conflicts, for 9 cases, including our own. Tinnitus was the most frequent symptom (9/9), followed by vertigo (2/9). Our case was the only one showing unilateral hearing loss. Surgery consisted of microsurgical mobilization of the AICA loop performed through a retrosigmoid craniotomy. Tinnitus and vertigo resolved after surgery in all cases, whereas hearing loss did not improve after surgery.

CONCLUSIONS

Surgical treatment offers the best results for tinnitus and vertigo, but it seems to have no effect on hearing loss, not even at long-term follow-up. Microvascular decompression should be proposed to intrameatal symptomatic patients before the onset of hearing loss.

Comparison of Clinical Symptoms and Magnetic Resonance Angiographic (MRA) Results in Patients with Trigeminal Neuralgia and Persistent Idiopathic Facial Pain. Medium-Term Outcome after Microvascular Decompression of Cases with Positive MRA Findings

To evaluate whether NC could be demonstrated preoperatively, high-resolution magnetic resonance angiography (MRA) was performed in 287 consecutive patients with TN and persistent idiopathic facial pain (PIFP) on a 0.5-T and a 1-T MR unit. Depending on the clinical symptoms, the TN cases were divided into typical TN and trigeminal neuralgia with non-neuralgic interparoxysmal pain (TNWIP) groups. Microvascular decompression (MVD) was performed in 103 of the MRA-positive cases. The patients were followed up postoperatively for from 1 to 10 years. The clinical symptoms were compared with the imaging results. The value of MRA was assessed on the basis of the clinical symptoms and surgical findings. The outcome of MVD was graded as excellent, good or poor. The clinical symptoms were compared with the type of vascular compression and the outcome of MVD. The MRA image was positive in 161 (56%) of the 287 cases. There were significant differences between the clinical groups: 66.5% of the typical TN group, 47.5% of the TNWIP group and 3.4% of the PIFP group were positive. The quality of the MR unit significantly determined the ratio of positive/negative MRA results. The surgical findings corresponded with the MRA images. Six patients from the MRA-negative group were operated on for selective rhizotomy and no NC was found. Venous compression of the trigeminal nerve was observed in a significantly higher proportion in the background of TNWIP than in that of typical TN on MRA imaging (24.1% and 0.8%, respectively) and also during MVD (31.2% and 1.2%, respectively). Four years following the MVD, 69% of the patients gave an excellent, 23% a good and 8% a poor result. The rate of some kind of recurrence of pain was 20% in the typical TN and 44% in TNWIP group. The rate of recurrence was 57% when pure venous compression was present. The only patient who was operated on from the PIFP group did not react to the MVD. The clinical symptoms and preoperative MRA performed by at least a 1-T MR unit furnish considerable information, which can play a role in the planning of the treatment of TN.

Venous compression as a cause of trigeminal neuralgia

AIM

The study objective was to verify venous compression as a cause of trigeminal neuralgia (TN) and to define the optimal surgical tactics for TN patients.

MATERIAL AND METHODS

Four hundred twenty one patients were operated on for TN at the Neurosurgical Department of the City Hospital №2 from 1998 to 2015. Veins in the trigeminal nerve root entry zone, as a significant compression factor, were identified in 40 patients (9.5%). Intraoperative data, questionnaires, and self-assessment inventories were analyzed. Treatment outcomes were assessed using the Barrow Neurological Institute (BNI) scale.

RESULTS

Patients with venous compression were divided into two groups. Eleven (27.5%) patients in the first group had isolated venous compression. The feature of microvascular decompression (MVD) in these patients was identification of all veins, vein mobilization, and, if possible, vein coagulation and resection. Resection of the vein along its course is a basic procedure to avoid recurrent neuralgia. The second group included 29 (72.5%) patients with a combination of venous and arterial compression. In these patients, a vein acted as an "assisting" compression factor: the vein changed the course of a compressing artery or nerve and exerted an additional compression effect on the nerve. The surgical tactics involved exploration of the trigeminal nerve root entry zone, arterial loop mobilization, and placement of a Teflon protector; venous vessels were coagulated and resected. The MVD efficacy was as follows: in group 1, 10 patients had a BNI score I-III, and 1 patient had a BNI score IV; in group II, 25 patients had a BNI score I-III, and 4 patients had a BNI score IV.

CONCLUSION

Venous compression can play both independent and assisting roles in the TN genesis. When exploring the trigeminal nerve, examination of the proximal trigeminal nerve is of particular importance, with paying attention to veins that may be a compression factor. In the case of isolated venous compression, the MVD surgical technique has some peculiarities, in particular coagulation and resection of veins compressing the trigeminal nerve root entry zone.

A Blinded, Case-Control Trial Assessing the Value of Steady State Free Precession Magnetic Resonance Imaging in the Diagnosis of Trigeminal Neuralgia

OBJECTIVE

High-resolution magnetic resonance imaging (MRI) may be a useful and readily available adjunct in identifying trigeminal neuralgia secondary to vascular contact (TNVC). This study evaluated the reliability and predictive ability of 1.5-tesla steady state free precession (SSFP) MRI sequences for the diagnosis of symptomatic vascular contact and response to operative intervention in patients with TNVC.

METHODS

We performed a blinded, case-matched control trial evaluating SSFP MRI sequences in consecutive patients with unilateral TNVC with operatively proven vascular contact of the trigeminal nerve compared with healthy control subjects matched on age, sex, and laterality of the pathologic neurovascular complex. Interrater reliability was compared between 2 blinded, expert reviewers. Predictive ability of MRI was assessed in regard to accuracy, discrimination, and clinical utility.

RESULTS

Inclusion criteria were met by 44 patients (22 consecutive patients with TNVC and 22 matched control subjects). Interrater reliability ranged from fair to excellent for vessel contact (κ = 0.40), location (κ = 0.81), type (κ = 0.72), and multiplicity (κ = 0.31). Vascular contact on MRI sequences did not differ significantly between cases and controls (75% vs. 82%, P = 0.30). MRI demonstrates accurate (Brier 0.15) and good discriminatory ability for clinical response after microvascular decompression (area under the receiver operating characteristic curve 0.81, 95% confidence interval = 0.6-1.0). Decision-curve analysis demonstrated that MRI could result in a net reduction of 5 cases likely to be unsuccessful per 100 patients treated.

CONCLUSIONS

These results suggest the utility of SSFP MRI lies not in the diagnosis of TNVC, but rather in stratifying the likelihood of response to microvascular decompression in patients with characteristic symptoms.

The effectiveness of percutaneous balloon compression in the treatment of trigeminal neuralgia in patients with multiple sclerosis

OBJECT

Trigeminal neuralgia (TN) is more common in multiple sclerosis (MS) patients than in the general population and among the former has an incidence of approximately 2%. The pathophysiology of TN in MS patients is believed to be caused by a demyelinating plaque at the root entry zone, and therefore procedures that cause direct nerve damage are thought to be the most effective surgical modality. The authors aimed to compare the efficacy of percutaneous balloon compression (PBC) in TN patients with and without MS.

METHODS

Retrospectively collected clinical data on 80 consecutive patients who underwent 144 procedures and who received PBC for TN treatment between January 2000 and January 2010 were analyzed. The cohort included 17 MS and 63 non-MS patients.

RESULTS

The mean age at first operation was significantly younger in the MS group compared with the non-MS group (59 years vs 72 years, respectively, p < 0.0001). After a mean follow-up of 43 months (MS group) and 25 months (non-MS group), the symptom recurrence rate following the first operation was higher in the MS group compared with that in the non-MS group (86% vs 47%, respectively, p < 0.01). During long-term follow-up, more than 70% of MS patients required multiple procedures compared with only 44% of non-MS patients. Excellent or satisfactory outcomes were not significantly different between the MS and non-MS cohorts, respectively, at 1 day postoperatively (82% vs 91%, p = 0.35), 3 months postoperatively (65% vs 81%, p = 0.16), and at last follow-up (65% vs 76%, p = 0.34). A similar incidence of postoperative complications was observed in the 2 groups.

CONCLUSIONS

PBC is effective in the treatment of trigeminal neuralgia in patients with MS, but, compared with that in non-MS patients, symptom recurrence is higher and requires multiple procedures.

Predicting the outcome of microvascular decompression for primary trigeminal neuralgia by the use of magnetic resonance tomographic angiography

BACKGROUND

Microvascular decompression (MVD) has been the available method to cure trigeminal neuralgia (TN), and several factors have been discussed as significant predictors of excellent outcome after MVD.

OBJECTIVE

This study aimed to find out the value of magnetic resonance tomographic angiography (MRTA) in predicting the outcome of MVD for TNs.

METHOD

A total of 157 cases of TNs who underwent MVD have taken MRTA preoperatively and postoperatively and then were followed up for 5 years. The possible prognostic factors were analyzed by χ(2) test and Kaplan-Meier survival analysis.

RESULT

Five years after MVD, 83.4% (131 cases) gave excellent, 10.2% (16 cases) gave good, and 6.4% (10 cases) gave poor results. A significant difference was found between the severity of postoperative neurovascular compression (χ(2) = 16.307, P < 0.01)/the relief rate of neurovascular compression (NVC) (χ(2) = 17.221, P < 0.01) and the outcome after MVD. However, no significant correlation was found between the severity of preoperative NVC and the outcome (χ(2) = 6.275, P = 0.329). The Kaplan-Meier survival curves showed that lower degree of postoperative NVC severity group and higher relief rate group had better pain relief after MVD.

CONCLUSIONS

Postoperative MRTA can help us predict the outcome of MVD; less severity of postoperative NVC and more relief of compression could be possible prognostic factors.

Differences in individual susceptibility affect the development of trigeminal neuralgia

Trigeminal neuralgia is a syndrome due to dysfunctional hyperactivity of the trigeminal nerve, and is characterized by a sudden, usually unilateral, recurrent lancinating pain arising from one or more divisions of the nerve. The most accepted pathogenetic mechanism for trigeminal neuralgia is compression of the nerve at its dorsal root entry zone or in its distal course. In this paper, we report four cases with trigeminal neuralgia due to an unknown mechanism after an intracranial intervention. The onset of trigeminal neuralgia after surgical interventions that are unrelated to the trigeminal nerve suggests that in patients with greater individual susceptibility, nerve contact with the vascular structure due to postoperative pressure and changes in cerebrospinal fluid flow may cause the onset of pain.

Atrophic changes in the trigeminal nerves of patients with trigeminal neuralgia due to neurovascular compression and their association with the severity of compression and clinical outcomes

Object

The aim of this study was to prospectively evaluate atrophic changes in trigeminal nerves (TGNs) using measurements of volume (V) and cross-sectional area (CSA) from high-resolution 3-T MR images obtained in patients with unilateral trigeminal neuralgia (TN), and to correlate these data with patient and neurovascular compression (NVC) characteristics and with clinical outcomes.

Methods

Anatomical TGN parameters (V and CSA) were obtained in 50 patients (30 women and 20 men; mean age 56.42 years, range 22–79 years) with classic TN before treatment with microvascular decompression (MVD). Parameters were compared between the symptomatic (ipsilateralTN) and asymptomatic (contralateralTN) sides of the face. Twenty normal control subjects were also included. Two independent observers blinded to the side of pain separately analyzed the images. Measurements of V (from the pons to the entrance of the nerve into Meckel's cave) and CSA (at 5 mm from the entry of the TGN into the pons) for each TGN were performed using imaging software and axial and coronal projections, respectively. These data were correlated with patient characteristics (age, duration of symptoms before MVD, side of pain, sex, and area of pain distribution), NVC characteristics (type of vessel involved in NVC, location of compression along the nerve, site of compression around the circumference of the root, and degree of compression), and clinical outcomes at the 2-year follow-up after surgery. Comparisons were made using Bonferroni's test. Interobserver variability was assessed using the Pearson correlation coefficient.

Results

The mean V of the TGN on the ipsilateralTN (60.35 ± 21.74 mm3) was significantly smaller (p < 0.05) than those for the contralateralTN and controls (78.62 ± 24.62 mm3 and 89.09 ± 14.72 mm3, respectively). The mean CSA of the TGN on the ipsilateralTN (4.17 ± 1.74 mm2) was significantly smaller than those for the contralateralTN and controls (5.41 ± 1.89 mm2 and 5.64 ± 0.85 mm2, respectively). The ipsilateralTN with NVC Grade III (marked indentation) had a significantly smaller mean V than the ipsilateralTN with NVC Grade I (mere contact), although it was not significantly smaller than that of the ipsilateralTN with NVC Grade II (displacement or distortion of root). The ipsilateralTN with NVC Grade III had a significantly smaller mean CSA than the ipsilateralTN with NVC Grades I and II (p < 0.05). The TGN on the ipsilateralTN in cured patients had a smaller mean CSA than that on the ipsilateralTN of patients with partial pain relief or treatment failure (p < 0.05). The same finding was almost found in relation to measurements of V, but the p value was slightly higher at 0.05.

Conclusions

Results showed that TGN atrophy in patients with TN can be demonstrated by high-resolution imaging. These data suggest that atrophic changes in TGNs, which significantly correlated with the severity of compression and clinical outcomes, may help to predict long-term prognosis after vascular decompression.

Aetiology and pathogenesis of trigeminal neuralgia: a comprehensive review

Objectives

The aim of present paper was to discuss issues related to trigeminal neuralgia with strong emphasis on the aetiology and pathogenesis of this problem.

Material and Methods

An electronic search of 5 databases (1965 - Oct 2012) and a hand search of peer-reviewed journals for relevant articles were performed. In addition, experience acquired from treating 3263 patients in the Department of Maxillofacial Surgery, Lithuanian University of Health Sciences, were also summarized.

Results

Generally, aetiological factors can be classified into 3 most popular theories that were based on: 1) Related to other disease, 2) Direct injury to the trigeminal nerve, and 3) Propagates the polyetiologic origin of the disease. In addition, two pathogenesis mechanisms of trigeminal neuralgia were proposed. First: the peripheral pathogenetic mechanism that is often induced by progressive dystrophy around the peripheral branches of the trigeminal nerve. Second, central pathogenetic mechanism which often triggered by peripheral pathogen that causes long-lasting afferent impulsation and the formation of a stable pathologic paroxysmal type irritation focus on the central nerve system (CNS).

Conclusions

Patients with susceptive trigeminal neuralgia should be examined carefully by specialists who have expertise in assessing and diagnosing of possible pathological processes and be able to eliminate the contributing factors so the trigeminal neuralgia can be properly managed.

Long-term follow-up of microvascular decompression for trigeminal neuralgia

We conducted a study to evaluate the follow-up characteristics of patients with trigeminal neuralgia (TN) and to evaluate the factors affecting long-term outcome of microvascular decompression (MVD) in TN. Between 1983 and 2003, 156 patients with TN treated with MVD by 4 neurosurgeons at University Medical Centre Groningen/the Netherlands were evaluated. Baseline data from operative outcome were evaluated using univariate and multivariate analysis. The group consisted of 156 patients with TN: 90 females and 66 males with a median follow-up period of 9.7 years. The average age of initial symptoms was 51 years. The average duration of symptoms was 58 months. Postoperative 22 patients had a facial hyperpathia or hyperesthesia. Postoperatively, 137 patients had immediate relief. Postoperatively 1 year, 140 patients still had a good outcome of the operation. Twenty-seven patients with good immediate postoperative results had recurrent pain. From the group of patients with typical TN, 82% had good long-term results after operation. Patients with typical TN and immediate postoperative remission, in univariate analysis, had significantly more often an excellent/good postoperative outcome. Immediate postoperative remission is an independent predictive factor for a good long-term outcome. The long-term results of MVD in majority of patients were good with no mortalities and no major morbidities. Patients with typical TN had better long-term outcomes and less recurrence.

What is the best treatment of drug-resistant trigeminal neuralgia in patients affected by multiple sclerosis? A literature analysis of surgical procedures

OBJECTIVE

Drug-resistant trigeminal neuralgia (TN) can complicate the clinical course of patients affected by multiple sclerosis (MS). Various surgical procedures have been reported for the treatment of this condition, but there is no agreement on the best management of these patients. To our knowledge, there is no critical literature analysis focusing on this particular topic. The aim of this study was to evaluate the clinical outcome of different surgical procedures utilized for drug-resistant TN in MS patients.

METHODS

We reviewed the literature about the studies reporting on surgical treatment of drug-resistant TN in MS patients. Case reports and case series less than 4 patients were excluded from the analysis. Nineteen studies were selected for the statistical analysis. To reduce the variability of the data, the selected studies were evaluated for the following outcome parameters: acute pain relief rate (APR), rate of recurrence (RR), pain free at follow-up rate (PF at FU) and complication rate (CR). For the statistical analysis, chi-square statistic, using the Fisher's exact test was utilized.

RESULTS

There was no procedure statistically superior in terms of APR rate in MS patients following the surgical treatment of TN. The highest RR was observed for percutaneous balloon compression (PBC) (60.2±14.4%). This result was statistically significant when compared to gamma knife surgery (GKS) (p=0.0129) and microvascular decompression (MVD) (p=0.0281). MVD together with percutaneous radiofrequency rhizothomy (PRR) was associated with a statistically better PF at FU rate (56.5±16.8% and 73.5±14.2%, respectively). However PBC and MVD showed statistical significant minor CR compared to other techniques (no complications and 18.7±17.4%, respectively).

CONCLUSION

Our study shows no differences in the short term results among different procedures for TN in MS patients. Each technique demonstrate advantages and limits in terms of long term pain, recurrence rate and complication rate. Each patient should be accurately informed on pros and cons of each procedure in order to be involved in the most appropriate choice.

A rodent model of trigeminal neuralgia

Trigeminal Neuralgia (Tic Douloureux) is a neuropathic pain syndrome caused by compression of the trigeminal nerve root and is characterized by severe paroxysms of pain in the face commonly triggered by light mechanical stimulation to the peri-oral area. Trigeminal neuralgia is very difficult to treat in part due to the lack of an suitable animal model for testing novel therapeutic approaches. This chapter describes a model of trigeminal neuralgia in which crystals of a superabsorbent polymer are placed next to the trigeminal nerve root of rats, producing ongoing mechanical compression of the nerve root. The chapter then describes means of behaviorally assessing the robust mechanical hypersensitivity consequent to the compression that can be used to determine the efficacy of potential therapies for this devastating condition.

Blockade of microglial activation reduces mechanical allodynia in rats with compression of the trigeminal ganglion

The present study investigated the role of microglia and p38 MAPK in the development of mechanical allodynia in rats with compression of the trigeminal ganglion. Male Sprague-Dawley rats weighing 250-260 g were used. Under pentobarbital sodium anesthesia, the animals were mounted onto a stereotaxic frame and given injections of 4% agar solution (10 μL) to compress the trigeminal ganglion. The air-puff thresholds significantly decreased after compression of the trigeminal ganglion. On postoperative day 14, immunoreactivity to both OX-42 and p-p38 MAPK was up-regulated in the medullary dorsal horn as compared to the sham group. P-p38 MAPK was found to be co-localized with OX-42, but not with NeuN, a neuronal cell marker, or with GFAP, an astroglial cell marker. Intracisternal administration of 100 μg of minocycline significantly inhibited both mechanical allodynia and activation of microglia produced by compression of the trigeminal ganglion. Intracisternal administration of 0.1, 1, or 10 μg of SB203580, a p38 MAPK inhibitor, also significantly decreased mechanical allodynia and p38 MAPK activation in the trigeminal ganglion-compressed group. These results suggest that activation of p38 MAPK in the microglia is an important step in the development of mechanical allodynia in rats with compression of the trigeminal ganglion and that the targeted blockade of microglial p38 MAPK pathway is a potentially important new treatment strategy for trigeminal neuralgia-like nociception.

Preoperative MRI/MRA for microvascular decompression in trigeminal neuralgia: consecutive series of 67 patients

BACKGROUND

Microvascular decompression is an accepted treatment for primary trigeminal neuralgia. In recent years, efforts have been made to investigate the role of preoperative MRI/MRA in selecting patients with neurovascular compression.

METHODS

Ninety-two consecutive patients underwent a standard retrosigmoid craniotomy for microvascular decompression between 2005 and 2009, of whom 67 had a preoperative MRI and MRA according to the protocol of our department. Operative findings were accurately recorded and compared to MRI/MRA results. Follow-up was in the form of telephone interview.

RESULTS

Preoperative MRI sensitivity was 96%, while specificity was 75% (1 false positive among 4 patients with negative intra-operative findings). The predictive value of a positive MRI/MRA was 98%, while the predictive value of a negative MRI/MRA was 50%. Fifty-four patients were available for outcome assessment at a mean follow-up of 3.8 years (range 1-5). Seventy-two percent of patients were pain-free, 9.5% had mild residual pain, while 18.5% had a poor outcome (moderate to severe residual pain). The correlation between preoperative MRI/MRA and outcome was not statistically significant (P = 0.570).

CONCLUSIONS

Preoperative MRI has both good sensitivity and positive predictive value. Specificity and negative predicitve value were limited in this series. No correlation was found between preoperative imaging and outcome. Both radiological and clinical criteria are important for patient selection.

Outcome of medical and surgical management in intractable idiopathic trigeminal neuralgia

Background:

The neurovascular conflict in trigeminal neuralgia is an intractable condition; medical treatment is usually of long duration and can be annoying for both patients and clinicians.

Aim:

This prospective study was designed to assess the outcome of microvascular decompression (MVD) in patients with more than 3 years' history of intractable idiopathic trigeminal neuralgia (TN) and poor response to drugs.

Materials and Methods:

Twenty-one patients (8 females and 13 males) with intractable idiopathic TN (group 1) underwent MVD and were followed up for 2 years. Group 2 (n = 15), which included 6 females and 9 males, received pharmacotherapy. The outcome responses of pain relief were evaluated using a 10-cm visual analog scale (VAS) and the Barrow Neurological Institute (BNI) scoring system. The patients' morbidity was recorded as well.

Results:

All patients fulfilling the inclusion criteria were offered MVD surgery. Freedom from pain was achieved immediately after surgery in 95.2% (n = 20) of patients in group 1, and 90.5% (n = 19) had sustained relief over the follow-up period. There were no statistical significance recurrences or surgical complications in group 1 (P>0.5), while 53.3% (n = 8) of the subjects in group 2 showed poor response with pharmacotherapy over the same period of time and many patients experienced drug intolerance that had statistical significance (P<0.01).

Conclusion:

Early MVD in TN can help patients avoid the side effects of drugs and the adverse psychological effects of long-term pharmacotherapy and prolonged morbidity.

Unusual recurrence of trigeminal neuralgia after microvascular decompression by muscle interposal

BACKGROUND

Patients with trigeminal neuralgia (TN) and persistent or recurrent facial pain after microvascular decompression (MVD) typically undergo less invasive procedures in the hope of providing pain relief. However, re-operation should be considered in selected patients.

CASE REPORT

A 48-year-old woman presented with recurrent trigeminal neuralgia (TN) 3 years following microvascular decompression (MVD). The patient underwent brain magnetic resonance angiography (MRA), which did not reveal neurovascular compression; therefore surgical re-exploration was carried out. During the operation, the fifth cranial nerve was seen without impingement from any blood vessels; however, a very firm tissue was observed and identified as the muscle fragment from the previous MVD procedure. The fifth cranial nerve was carefully separated from the muscle. Thereafter, the right SCA was dissected out from the muscle and suspended by a periosteum tape sutured to the nearby dura.

CONCLUSIONS

Our findings, along with similar cases reported in the literature, support the development of new inert materials and alternative surgical strategies that can limit TN recurrence.

Different pain, different brain: thalamic anatomy in neuropathic and non-neuropathic chronic pain syndromes

Trigeminal neuropathic pain (TNP) and temporomandibular disorders (TMD) are thought to have fundamentally different etiologies. It has been proposed that TNP arises through damage to, or pressure on, somatosensory afferents in the trigeminal nerve, whereas TMD results primarily from peripheral nociceptor activation. Because some reports suggest that neuropathic pain is associated with changes in brain anatomy, it is possible that TNP is maintained by changes in higher brain structures, whereas TMD is not. The aim of this investigation is to determine whether changes in regional brain anatomy and biochemistry occur in both conditions. Twenty-one TNP subjects, 20 TMD subjects, and 36 healthy controls were recruited. Voxel-based morphometry of T1-weighted anatomical images revealed no significant regional gray matter volume change in TMD patients. In contrast, gray matter volume of TNP patients was reduced in the primary somatosensory cortex, anterior insula, putamen, nucleus accumbens, and the thalamus, whereas gray matter volume was increased in the posterior insula. The thalamic volume decrease was only seen in the TNP patients classified as having trigeminal neuropathy but not those with trigeminal neuralgia. Furthermore, in trigeminal neuropathy patients, magnetic resonance spectroscopy revealed a significant reduction in the N-acetylaspartate/creatine ratio, a biochemical marker of neural viability, in the region of thalamic volume loss. The data suggest that the pathogenesis underlying neuropathic and non-neuropathic pain conditions are fundamentally different and that neuropathic pain conditions that result from peripheral injuries may be generated and/or maintained by structural changes in regions such as the thalamus.

Visualization of Vascular Compression of the Trigeminal Nerve With High-Resolution 3T MRI: A Prospective Study Comparing Preoperative Imaging Analysis to Surgical Findings in 40 Consecutive Patients Who Underwent Microvascular Decompression for Trigeminal Neuralgia

BACKGROUND:

High-resolution three-dimensional (3D) magnetic resonance imaging (MRI) has demonstrated its ability to predict fine trigeminal neurovascular anatomy.

OBJECTIVE:

To address the predictive value of 3-Tesla (3T) MRI in detecting and assessing features of neurovascular compression (NVC), particularly regarding the degree of compression exerted on the root, in patients who underwent microvascular decompression (MVD) for classic primary trigeminal neuralgia.

METHODS:

This prospective study includes 40 consecutive patients who underwent MVD for classic primary trigeminal neuralgia. All patients underwent a preoperative 3T MRI with 3D T2-weighted driven equilibrium (DRIVE), 3D time-of-flight (TOF) magnetic resonance angiography (MRA), and 3D T1-weighted gadolinium-enhanced sequences in combination. Evaluations were performed by 2 independent observers and compared with the operative findings.

RESULTS:

For prediction of NVC, image analysis corresponded with surgical findings in 39 cases. Of the 3 patients in whom image analysis did not show NVC, 2 did not have NVC at the time of intraoperative observation. MRI sensitivity was 97.4% (37/38), and specificity was 100% (2/2). The kappa coefficients (κ) for predicting the offending vessel, its location, and the site of compression were 0.882, 0.813, and 0.942, respectively. Image analysis correctly defined the severity of the compression in 31 of the 37 cases. The κ coefficients predicting the degree of compression were 0.813, 0.833, and 0.852, respectively, for Grades 1 (simple contact), 2 (distortion), and 3 (marked indentation).

CONCLUSION:

3T MRI using 3D T2-weighted DRIVE in combination with 3D TOF-MRA and 3D T1-weighted gadolinium-enhanced sequences proved to be reliable in detecting NVC and in predicting the degree of root compression, the outcome being correlated with the latter.

Microvascular decompression may be an effective treatment for nervus intermedius neuralgia

Objective:

To report microvascular decompression as a possible effective treatment for patients with nervus intermedius neuralgia, and to contribute to the literature regarding both this syndrome and this specific form of treatment.

Method:

Case report of a patient with intermedius neuralgia. The main complaint was severe otalgia in the area innervated by the nervus intermedius, possibly caused by neurovascular compression of the nervus intermedius by the anterior inferior cerebellar artery. Microvascular decompression was undertaken, with good results.

Results:

Post-operatively, the patient felt immediate and total relief of her otalgia, with normal facial nerve function and no otological morbidity. One year post-operatively, she was still free from otalgia.

Conclusion:

Patients with nervus intermedius neuralgia who do not respond to medical treatment may benefit from microvascular decompression.

The long-term outcome of microvascular decompression for trigeminal neuralgia

OBJECTIVE

Evaluation of the effectiveness of Microvascular Decompression (MVD) for Trigeminal Neuralgia (TGN), with emphasis on patient's perception of outcome, and satisfaction with the procedure.

MATERIALS AND METHODS

A cohort of 372 MVD operations carried out between 1982 and 2005 were reviewed, contact could be attempted with 319 patients. Questionnaires assessing the patient's perception of outcome returned by 266 patients (71%). statistical analysis of the data was carried out using a cox proportional-hazard regression analysis. Anticipated outcome measures: Time to pain recurrence; predictive value of imaging, operative findings and complications; patients' satisfaction, and outcome of revision MVD.

RESULTS

Complete pain relief (off medication) achieved in 71% of patients at 10 years. Overall 84% of responders to questionnaires expressed satisfaction with the operative outcome, the mean duration of TGN was 80 months and mean post-operative follow-up of 7 years. No mortality reported in this series.

CONCLUSION

This is a large review of MVD, which confirms the long-term effectiveness of the procedure, and uniquely reflects patient's perception of the operation. Predictors of favourable outcome were shorter preoperative duration of TGN, older age at time of MVD, typical features, and vascular compression; moreover, complications, and previous neurodestructive procedures did not show significant effect on long-term pain relief. Satisfaction with MVD was exclusively related to long-term pain relief without medications.