A single-blinded pilot study assessing neurovascular contact by using high-resolution MR imaging in patients with trigeminal neuralgia

A Systematic Review of the Role of Magnetic Resonance Imaging in the Diagnosis and Detection of Neurovascular Conflict in Patients With Trigeminal Neuralgia

Trigeminal neuralgia (TN) is a debilitating disorder causing severe, episodic, unilateral stabbing facial pain disturbing enough to disrupt the activities of daily life. Classic TN is caused due to compression injury of the trigeminal nerve at the cistern segment caused by either an artery or a vein, referred to as neurovascular contact or conflict (NVC). Magnetic resonance imaging (MRI) has been the standard tool for the diagnosis of NVC. This study aimed to determine the incidence of NVC in TN, as identified by MRI, assess the various MRI grading patterns among patients with TN, and identify the vessels primarily involved in NVC. A systematic search of studies that used MRI for the diagnosis of TN in reference to NVC was conducted on DOAJ and PubMed/PubMed Central. Data were extracted and entered into a Microsoft Excel spreadsheet. The outcomes measured were the incidence of NVC as shown in MRI, vessels involved in NVC, and MRI grading patterns. We identified and selected 20 studies that fulfilled inclusion/exclusion criteria. In total, 1,436 patients were enrolled in all included studies. The type of MRI used was 1.5 T or 3 T MRI. The mean age of the patients varied from 49 to 63 years, with an equivalent male-to-female ratio. NVC was seen in 1,276 cases out of 1,436 cases (88.85%) of TN on the ipsilateral side, as shown by MRI. The vessels involved were arteries in 80-90% of the cases, followed by veins. Among the arteries, the superior cerebellar artery was the most common artery (80-90% of cases). The grades of NVC as assessed by MRI included grades I, II, and III with varied proportions in different studies. NVC is a common problem in TN, wherein there is compression at the nerve root entry zone, and it shows a strong predilection for the elderly population. MRI seems to be a novel imaging diagnostic investigation to identify NVC associated with TN. Moreover, NVC grading must be done with MRI so that it may help the surgeon in stratifying the patient's treatment.

Brain imaging signatures of neuropathic facial pain derived by artificial intelligence

Advances in neuroimaging have permitted the non-invasive examination of the human brain in pain. However, a persisting challenge is in the objective differentiation of neuropathic facial pain subtypes, as diagnosis is based on patients' symptom descriptions. We use artificial intelligence (AI) models with neuroimaging data to distinguish subtypes of neuropathic facial pain and differentiate them from healthy controls. We conducted a retrospective analysis of diffusion tensor and T1-weighted imaging data using random forest and logistic regression AI models on 371 adults with trigeminal pain (265 classical trigeminal neuralgia (CTN), 106 trigeminal neuropathic pain (TNP)) and 108 healthy controls (HC). These models distinguished CTN from HC with up to 95% accuracy, and TNP from HC with up to 91% accuracy. Both classifiers identified gray and white matter-based predictive metrics (gray matter thickness, surface area, and volume; white matter diffusivity metrics) that significantly differed across groups. Classification of TNP and CTN did not show significant accuracy (51%) but highlighted two structures that differed between pain groups-the insula and orbitofrontal cortex. Our work demonstrates that AI models with brain imaging data alone can differentiate neuropathic facial pain subtypes from healthy data and identify regional structural indicates of pain.

Chinese expert consensus on minimally invasive interventional treatment of trigeminal neuralgia

BACKGROUND AND PURPOSE

Trigeminal neuralgia is a common condition that is associated with severe pain, which seriously affects the quality of life of patients. When the efficacy of drugs is not satisfactory or adverse drug reactions cannot be tolerated, minimally invasive interventional therapy has become an important treatment because of its simple operation, low risk, high repeatability and low cost. In recent years, minimally invasive interventional treatments, such as radiofrequency thermocoagulation (RF) of the trigeminal nerve and percutaneous microcompression (PMC), have been widely used in the clinic to relieve severe pain in many patients, however, some related problems remain to be addressed. The Pain Association of the Chinese Medical Association organizes and compiles the consensus of Chinese experts to standardize the development of minimally invasive interventional treatment of trigeminal neuralgia to provide a basis for its clinical promotion and application.

MATERIALS AND METHODS

The Pain Association of the Chinese Medical Association organizes the Chinese experts to compile a consensus. With reference to the evidence-based medicine (OCEBM) system and the actual situation of the profession, the Consensus Development Committee adopts the nominal group method to adjust the recommended level.

RESULTS

Precise imaging positioning and guidance are the keys to ensuring the efficacy and safety of the procedures. RF and PMC are the most widely performed and effective treatments among minimally invasive interventional treatments for trigeminal neuralgia.

CONCLUSIONS

The pain degree of trigeminal neuralgia is severe, and a variety of minimally invasive intervention methods can effectively improve symptoms. Radiofrequency and percutaneous microcompression may be the first choice for minimally invasive interventional therapy.

Preoperative Decision-Making in Microvascular Decompression for Trigeminal Neuralgia: A Survey of Practicing Neurosurgeons

OBJECTIVE

Microvascular decompression (MVD) for trigeminal neuralgia (TN) results in durable pain freedom in a large percentage of appropriately selected patients. The decision to perform MVD is based on a combination of clinical symptomatic presentation and imaging findings demonstrating neurovascular compression (NVC) with surgeons weighting these variables differently. This study sought to determine the relative importance of clinical symptomatic presentation and imaging findings of NVC in decision-making to pursue MVD for TN among North American board-certified neurosurgeons.

METHODS

An online survey detailing the decision-making process involved in the workup and treatment of TN with MVD was distributed to all American Association of Neurological Surgeons registered board-certified neurosurgeons in North America.

RESULTS

From 3010 functional email addresses, there were 309 responses to the survey (10% response rate). The majority of respondents (76%) reported only operating on patients with classic type 1 TN (T1TN) while only 32% chose to operate on patients with imaging findings of vascular compression in the absence of T1TN symptoms. In contrast to low-volume surgeons, high-volume surgeons weighed imaging evidence of vascular compression more heavily into the decision-making process to operate.

CONCLUSIONS

The majority of responding neurosurgeons weigh symptomatic presentation more heavily than imaging evidence of NVC when deciding on whom to perform MVD. High-volume surgeons tend to be more attentive to NVC in their decision-making to perform MVD when compared with low-volume surgeons.

The Use of MRI in Preoperative Decision-Making for Trigeminal Neuralgia: A Single-Center Study

OBJECTIVE

Few studies have examined associations between vascular compression and postoperative pain relief in patients undergoing microvascular decompression (MVD) for treatment of medically refractory type 1 trigeminal neuralgia (TN). The authors sought to examine for associations between vascular compression and postoperative pain relief to determine the utility of preoperative magnetic resonance imaging (MRI) in surgical decision-making for TN.

METHODS

The charts of 59 patients who underwent 60 MVDs for TN between 2007 and 2017 at a single academic institution were reviewed. Patient demographics, the presence of compressing vessel on preoperative MRI and intraoperatively, complications, follow-up time, performance of a partial sensory rhizotomy, and pain resolution at most recent follow-up were recorded. Sensitivity and specificity of MRI for detecting vascular compression were calculated and associations between preoperative and intraoperative evidence of vascular compression with postoperative pain relief were examined.

RESULTS

Sensitivity and specificity of preoperative MRI determined through blinded reads by the senior author were 65.3% (95% confidence interval, 13.5-32.0) and 90.9% (95% confidence interval, 86.1-100.0), respectively. Overall, 76.3% of patients were pain free at most recent follow-up. Preoperative MRI and intraoperative evidence of vascular compression were not associated with postoperative pain relief at most recent follow-up (P = 0.47 and 0.43, respectively).

CONCLUSIONS

The findings of lower sensitivity and poor interrater reliability of MRI, as well as a lack of association between compressive vessel and postoperative pain relief reported in this study, suggest the decision to pursue MVD for TN should be based more heavily on classic symptomatic presentation over preoperative evidence of vascular compression.

Correlations between the trigeminal nerve microstructural changes and the trigeminal-pontine angle features

BACKGROUND

Morphological and microstructural changes of the trigeminal nerve due to neurovascular compression (NVC) have been reported in primary trigeminal neuralgia (PTN) patients. This investigation was to examine the relationship between the trigeminal-pontine angle and nerve microstructural changes.

METHODS

Twenty-five patients underwent microvascular decompression (MVD) for trigeminal neuralgia, and 25 age- and sex-matched controls were studied. The two groups underwent high-resolution three-dimensional MRI and diffusion tensor imaging (DTI). Bilateral trigeminal-pontine angle, cross-sectional area of cerebellopontine angle (CPA) cistern, and the length of trigeminal nerve were evaluated. The mean values of fractional anisotropy and apparent diffusion coefficient at the site of NVC were also measured. Correlation analyses were performed for the trigeminal-pontine angle and the diffusion metrics (FA and ADC) in PTN patients.

RESULTS

The mean trigeminal-pontine angle and FA value on the affected side was significantly smaller than the unaffected side and the control group (p < 0.001), while the mean ADC value was significantly increased (p < 0.01). When taking the conflicting vessel types into consideration, the angle affected by the superior cerebellar artery (SCA) was statistically sharper than when affected by other vessels (p < 0.01). However, there were no significant changes in the area of the CPA cistern or the length of the trigeminal nerve between the groups. Correlation analyses showed that the trigeminal-pontine angle was positively correlated with FA and negatively correlated with ADC.

CONCLUSIONS

A sharp trigeminal-pontine angle may increase the chance of NVC and exacerbate nerve degeneration, which may be one of the supplementary factors that contribute to the pathogenesis of trigeminal neuralgia.

Imaging and Surgical Findings in Patients with Hemi-Laryngopharyngeal Spasm and the Potential Role of MRI in the Diagnostic Work-Up

BACKGROUND AND PURPOSE

Hemi-laryngopharyngeal spasm is a recently discovered condition characterized by episodic coughing and unilateral throat contractions that may lead to severe stridor. These symptoms are caused by a vascular compression of the ipsilateral vagus nerve, typically the PICA. Microvascular decompression of the vagus nerve has been demonstrated to be a potential cure for this neurovascular compression syndrome. The main aim of this study was to clarify the role of MR imaging in the diagnostic work-up of this rare condition.

MATERIALS AND METHODS

We describe the imaging and surgical findings of 3 patients from our prospective case series of patients with hemi-laryngopharyngeal spasm from 2015 to 2017. Second, the imaging data of 100 patients (control cohort) with symptoms unrelated to hemi-laryngopharyngeal spasm were reviewed to investigate the rate and degree of neurovascular conflict of the vagus nerve.

RESULTS

All patients with hemi-laryngopharyngeal spasm reported to date have had vascular compression of the vagus nerve due to the PICA. In the control cohort, there was a good interrater agreement in scoring the "contact" and "compression" of the vagus nerve (κ = 0.73. P = < .001). The frequency of contact or compression of the vagus nerve was approximately 50%. The PICA was the most frequent vessel involved in 74%.

CONCLUSIONS

The presence of unilateral neurovascular contact or compression of the vagus nerve does not confirm the diagnosis of hemi-laryngopharyngeal spasm. The MR imaging finding of ipsilateral vascular compression of the vagus nerve is a necessary but not sufficient finding for the diagnosis of hemi-laryngopharyngeal spasm.

Long-term pain outcomes for recurrent idiopathic trigeminal neuralgia after stereotactic radiosurgery: a prospective comparison of first-time microvascular decompression and repeat stereotactic radiosurgery

OBJECTIVE

Microvascular decompression (MVD) and stereotactic radiosurgery (SRS) are common surgical treatments for trigeminal neuralgia (TN). Many patients who receive SRS have pain recurrence; the ideal second intervention is unknown. The authors directly compared pain outcomes after MVD and repeat SRS in a population of patients in whom SRS failed as their first-line procedure for TN, and they identified predictors of pain control.

METHODS

The authors reviewed a prospectively collected database of patients undergoing surgery for TN between 1997 and 2014 at the University of California, San Francisco (UCSF). Standardized data collection focused on preoperative clinical characteristics, surgical characteristics, and postoperative outcomes. Patients with typical type 1, idiopathic TN with ≥ 1 year of follow-up were included.

RESULTS

In total, 168 patients underwent SRS as their first procedure. Of these patients, 90 had residual or recurrent pain. Thirty of these patients underwent a second procedure at UCSF and had ≥ 1 year of follow-up; 15 underwent first-time MVD and 15 underwent repeat SRS. Patients undergoing MVD were younger than those receiving repeat SRS and were more likely to receive ≥ 80 Gy during the initial SRS. The average follow-up was 44.9 ± 33.6 months for MVD and 48.3 ± 45.3 months for SRS. All patients achieved complete pain freedom without medication at some point during their follow-up. At last follow-up, 80% of MVD-treated patients and 33.3% of SRS-treated patients had a favorable outcome, defined as Barrow Neurological Institute Pain Intensity scores of I-IIIa (p < 0.05). Percentages of patients with favorable outcome at 1 and 5 years were 86% and 75% for the MVD cohort and 73% and 27% for the SRS cohort, respectively (p < 0.05). Multivariate Cox proportional hazards analysis demonstrated that performing MVD was statistically significantly associated with favorable outcome (HR 0.12, 95% CI 0.02-0.60, p < 0.01). There were no statistically significant predictors of favorable outcome in the MVD cohort; however, the presence of sensory changes after repeat SRS was associated with pain relief (p < 0.01).

CONCLUSIONS

Patients who received MVD after failed SRS had a longer duration of favorable outcome compared to those who received repeat SRS; however, both modalities are safe and effective. The presence of post-SRS sensory changes was predictive of a favorable pain outcome in the SRS cohort.

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.

Preoperative evaluation of neurovascular relationship in trigeminal neuralgia by three-dimensional fast low angle shot (3D-FLASH) and three-dimensional constructive interference in steady-state (3D-CISS) MRI sequence

OBJECTIVE

The purpose of the study was to evaluate the value of high-resolution three-dimensional fast low angle shot (3D-FLASH) and three-dimensional constructive interference in steady-state (3D-CISS) MRI sequence solely or the combination of both in the visualization of neurovascular relationship in patients with trigeminal neuralgia (TN).

METHODS

65 patients with unilateral TN underwent 3D-FLASH and 3D-CISS imaging were retrospectively studied. Neurovascular relationship at the intracisternal segment of trigeminal nerve was reviewed by two experienced neuroradiologist, who was blinded to the clinical details. The imaging results were compared with the operative findings in all patients.

RESULTS

The accuracy and positive rates of the 3D-FLASH + CISS imaging (98.46, 92.31%) in judging the symptomatic side according to the presence of vascular contacts were higher than those of 3D-CISS (90.77%, 84.62) or 3D-FLASH (89.23, 83.08%) sequence. In addition, the statistical analysis showed the sensitivity and accuracy of 3D-FLASH + CISS imaging was higher than that of 3D-FLASH (p < 0.05). The 3D-FLASH + CISS imaging was more accurate in determining the type of offending vessel than 3D-CISS or 3D-FLASH imaging.

CONCLUSION

The retrospective study demonstrates that the combination of 3D-FLASH with 3D-CISS sequence well delineates the relationship between intracisternal segment of trigeminal nerve and adjacent vessels in terms of increased positive rates and accuracy. Advances in knowledge: The study firstly dealt with the combination of 3D-CISS and 3D-FLASH imaging in TN.

Presurgical visualization of the neurovascular relationship in trigeminal neuralgia with 3D modeling using free Slicer software

OBJECTIVE

To explore whether segmentation and 3D modeling are more accurate in the preoperative detection of the neurovascular relationship (NVR) in patients with trigeminal neuralgia (TN) compared to MRI fast imaging employing steady-state acquisition (FIESTA).

METHOD

Segmentation and 3D modeling using 3D Slicer were conducted for 40 patients undergoing MRI FIESTA and microsurgical vascular decompression (MVD). The NVR, as well as the offending vessel determined by MRI FIESTA and 3D Slicer, was reviewed and compared with intraoperative manifestations using SPSS.

RESULTS

The k agreement between the MRI FIESTA and operation in determining the NVR was 0.232 and that between the 3D modeling and operation was 0.6333. There was no significant difference between these two procedures (χ² = 8.09, P = 0.088). The k agreement between the MRI FIESTA and operation in determining the offending vessel was 0.373, and that between the 3D modeling and operation was 0.922. There were significant differences between two of them (χ² = 82.01, P = 0.000). The sensitivity and specificity for MRI FIESTA in determining the NVR were 87.2 % and 100 %, respectively, and for 3D modeling were both 100 %.

CONCLUSION

The segmentation and 3D modeling were more accurate than MRI FIESTA in preoperative verification of the NVR and offending vessel. This was consistent with surgical manifestations and was more helpful for the preoperative decision and surgical plan.

Large-diameter compression arteries as a possible facilitating factor for trigeminal neuralgia: analysis of axial and radial diffusivity

Background

Neurovascular compression (NVC) of the trigeminal nerve is associated with trigeminal neuralgia (TN). Some arteries that compress the trigeminal nerve are large, while others are small. This study evaluated the influence of diameter of compression arteries (DCA) on NVC with and without TN using axial diffusivity (AD) and radial diffusivity (RD) of magnetic resonance (MR) imaging.

Methods

Fifty TN patients with unilateral NVC, 50 asymptomatic patients with unilateral NVC, and 50 healthy controls (HC) were divided into three groups (NVC with TN, NVC without TN, and HC). The three groups were imaged with a 3.0-T MR system using three-dimensional fast imaging employing steady-state acquisition (3D FIESTA) and diffusion tensor imaging (DTI). We compared the mean size of DCA between NVC with and without TN. The mean values of AD and RD at the site of NVC were compared between the three groups. Correlation analyses were performed between the DCA and the diffusion metrics (AD and RD) in NVC patients with and without TN.

Results

The mean DCA in NVC patients with TN (1.58 ± 0.34 mm) was larger than that without TN (0.89 ± 0.29 mm). Compared with NVC without TN and HC, the mean values of RD at the site of NVC with TN were significantly increased; however, no significant changes of AD were found between the groups. Correlation analysis showed that DCA positively correlated with RD in NVC patients with and without TN (r = 0.830, p = 0.000). No significant correlation was found between DCA and AD (r = 0.178, p = 0.077).

Conclusions

Larger-diameter compression arteries may increase the chances of TN, and may be a possible facilitating factor for TN.

Imaging of Neurovascular Compression Syndromes: Trigeminal Neuralgia, Hemifacial Spasm, Vestibular Paroxysmia, and Glossopharyngeal Neuralgia

Neurovascular compression syndromes are usually caused by arteries that directly contact the cisternal portion of a cranial nerve. Not all cases of neurovascular contact are clinically symptomatic. The transition zone between the central and peripheral myelin is the most vulnerable region for symptomatic neurovascular compression syndromes. Trigeminal neuralgia (cranial nerve V) has an incidence of 4-20/100,000, a transition zone of 4 mm, with symptomatic neurovascular compression typically proximal. Hemifacial spasm (cranial nerve VII) has an incidence of 1/100,000, a transition zone of 2.5 mm, with symptomatic neurovascular compression typically proximal. Vestibular paroxysmia (cranial nerve VIII) has an unknown incidence, a transition zone of 11 mm, with symptomatic neurovascular compression typically at the internal auditory canal. Glossopharyngeal neuralgia (cranial nerve IX) has an incidence of 0.5/100,000, a transition zone of 1.5 mm, with symptomatic neurovascular compression typically proximal. The transition zone overlaps the root entry zone close to the brain stem in cranial nerves V, VII, and IX, yet it is more distal and does not overlap the root entry zone in cranial nerve VIII. Although symptomatic neurovascular compression syndromes may also occur if the neurovascular contact is outside the transition zone, symptomatic neurovascular compression syndromes are more common if the neurovascular contact occurs at the transition zone or central myelin section, in particular when associated with nerve displacement and atrophy.

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.

Vascular compression of the trigeminal nerve in asymptomatic individuals: a voxel-wise analysis of axial and radial diffusivity

BACKGROUND

Neurovascular compression (NVC) of the trigeminal nerve is associated with trigeminal neuralgia (TN), but also occurs in many asymptomatic individuals. The purpose of this study was to investigate the possible microstructural tissue changes of trigeminal nerves (TGN) in asymptomatic individuals with NVC by using axial diffusivity (AD) and radial diffusivity (RD) of MR imaging and to discuss its underlying mechanisms.

METHODS

Twenty asymptomatic individuals with unilateral NVC and 18 healthy controls (HCs) were divided into three groups (compressed, uncompressed side in asymptomatic individuals and HCs). Three groups were imaged with a 3.0-T MR system using three-dimensional fast imaging employing steady-state acquisition (3D FIESTA) and diffusion tensor imaging (DTI). We placed a region of interest over the root entry zone of the TGN and measured fractional anisotropy (FA), AD and RD. The mean values of FA, AD and RD were compared among the three groups.

RESULTS

No significant changes in any of the diffusion metrics (FA, RD and AD) were found among the three groups (compressed, uncompressed side in asymptomatic individuals and HCs).

CONCLUSIONS

Our study demonstrated that neither demyelination nor axonal injury is found in asymptomatic individuals with NVC.

Microvascular decompression for neurovascular conflicts in the cerebello-pontine angle: which role for endoscopy?

BACKGROUND

Microvascular decompression (MVD) is the surgical intervention designed to resolve neurovascular conflicts (NCs) in the cerebellopontine angle (CPA). Today, endoscopy is commonly used in many neurosurgical procedures. This study aims to retrospectively assess the usefulness of endoscopy during MVD, focusing on microscopic endoscopic-assisted (MEA) MVD.

METHODS

Between January 2010 and December 2012, 141 patients underwent MVD procedures: 119 (84.5 %) were affected by idiopathic trigeminal neuralgia (TN), 20 (14 %) by hemifacial spasm (HFS), 1 by glossopharyngeal neuralgia (GN) and 1 by TN and GN simultaneously; 128 (91 %) MVD were first time procedures, while 13 (9 %) were recurrences (10 TN, 3 HFS). Visualization techniques used were: pure microscopic in 89 (63 %) cases, fully endoscopic in 12 (8.5 %) and MEA in 40 (28.5 %). The MEA technique was used when the conflict was not clearly identified under microscopic view or it was not certainly resolved.

RESULTS

Overall, a NC was found in 130 (92 %) cases, while 11 patients had no intraoperative evidence of NC. Considering specifically the 40 MEA cases, 12 (8.5 % overall) conflicts not clearly visible with the microscope were revealed and solved, a complete conflict resolution was confirmed in 13 (9 % overall) cases, while an incomplete conflict resolution was shown in four cases (3 % overall).

CONCLUSION

Pure microscopic MVD remains the technique of choice. The endoscope is a useful adjunctive imaging tool in confirming NCs identified by the microscope, revealing conflicts missed by the microscopic survey alone and verifying adequate nerve decompression.

Trigeminal neuralgia: Assessment of neurovascular decompression by 3D fast imaging employing steady-state acquisition and 3D time of flight multiple overlapping thin slab acquisition magnetic resonance imaging

Background:

Trigeminal neuralgia is most commonly caused by vascular compression at the trigeminal nerve (TN) root entry zone. Microvascular decompression (MVD) has been established as a useful treatment. Outcome depends on the correct identification of the compression site and its adequate decompression at surgery. Preoperative identification of neurovascular compression might predict which patients will benefit from MVD. Management of persistent or recurrent trigeminal neuralgia after an MVD is a baffling problem for neurosurgeons. An accurate neuroradiological evaluation of the TN padding following a failed MVD might help identify the underlying cause and plan further treatment.

Case description:

A 68-year-old female presented with a right-sided trigeminal neuralgia (V3) refractory to medical therapy. A high-resolution three-dimensional magnetic resonance imaging (3D MRI) study included fast imaging employing steady-state acquisition (FIESTA) and time of flight multiple overlapping thin slab acquisition (TOF MOTSA) sequences to evaluate the neurovascular anatomy in the cerebellopontine angle. An unambiguous compression of the right TN at the rostral-medial site by the superior cerebellar artery (SCA) was identified. The SCA loop compressing the TN was identical in location and configuration to that predicted in the preoperative study. After the MVD, the patient was relieved from her pain and a postoperative high-resolution 3D MRI study confirmed the appropriate placement of the Teflon implant between the TN and SCA.

Conclusion:

To our knowledge, this is the first report that characterizes the proper TN padding by high-resolution 3D MRI after trigeminal MVD. The present case also emphasizes the importance of performing a 3D MRI in patients with trigeminal neuralgia to anticipate the surgeon's view and predict the outcome after MVD.

Preoperative evaluation of neurovascular relationship by using contrast-enhanced and unenhanced 3D time-of-flight MR angiography in patients with trigeminal neuralgia

BACKGROUND

Microvascular decompression is an etiological strategy for the therapy of trigeminal neuralgia (TN). Preoperative identification of neurovascular compression, therefore, could have an impact on the determination of appropriate treatment for TN.

PURPOSE

To evaluate the value of contrast-enhanced and unenhanced three-dimensional (3D) time-of-flight (TOF) MR angiography in the visualization of neurovascular relationship in patients with TN.

MATERIAL AND METHODS

Thirty-seven patients with unilateral TN underwent unenhanced and contrast-enhanced 3D TOF MR angiography with a 3.0-T MR system. Images were reviewed by a radiologist blinded to clinical details. Vascular contact with the trigeminal nerve was identified, and the nature of the involved vessels (artery or vein) was determined. All patients underwent microvascular decompression.

RESULTS

In 37 patients with TN, contrast-enhanced 3D TOF MR angiography identified surgically verified neurovascular contact in 35 of 36 symptomatic nerves, and there was no false-positive. Based on surgical findings, the sensitivity of MR imaging was 97.2% and specificity 100%. The nature of the offending vessel was correctly identified in 94.4% of the patients by using the combination of contrast-enhanced and unenhanced MR angiography.

CONCLUSION

Contrast-enhanced 3D TOF MR angiography is useful in the detection of vascular contact with the trigeminal nerve in patients with TN, and this MR imaging in combination with unenhanced MR angiography could help in the identification of the nature of the responsible vessels.