Contrast-Enhanced CISS Imaging for Evaluation of Neurovascular Compression in Trigeminal Neuralgia: Improved Correlation with Symptoms and Prediction of Surgical Outcomes

Correlation of Prepontine Cisternal Space Thickness with the Severity of Neurovascular Conflict and its Role in Predicting Outcome of Medical Management in Cases of Trigeminal Neuralgia

Background

Trigeminal neuralgia (TN) is a debilitating disorder that presents with sudden onset of severe, unilateral, paroxysmal, and lancinating pain usually lasting for few seconds to few minutes.

Aims and Objectives

The main aim of our study was to correlate the prepontine cisternal space thickness, with a severity of neurovascular compression (NVC) and percentage reduction of pain (patient outcome).

Materials and Methods

Ours is an observational prospective study of 40 patients presenting with TN for magnetic resonance imaging in our department. Patients were followed up on medical treatment and their pain severity evaluated on their follow-up visit. Patients were divided into two groups based on prepontine cisternal space (Group A: ≤4 mm, Group B: >4 mm) and into three groups based on the percentage reduction of pain, Group 1 (0-35%), Group 2 (36-70%), and Group 3 consisted of patients with pain reduction of more than 70%. Ipsilateral prepontine cisternal space thickness was correlated with grade of NVC and percentage reduction of pain.

Results

Mean percentage of pain reduction in group A and group B was 34.12 and 60.68%, respectively. Approximately 23.80% of grade1 NVC were seen in group A and 76.20% in group B, while 80% of grade 3 NVC were seen in group A and only 20% were seen in group B.

Conclusion

There was poor response to medical treatment, in patients with narrowed prepontine cisternal space thickness with an inverse relationship between the grade of NVC and cisternal space thickness.

Probabilistic tractography of the extracranial branches of the trigeminal nerve using diffusion tensor imaging

PURPOSE

The peripheral course of the trigeminal nerves is complex and spans multiple bony foramen and tissue compartments throughout the face. Diffusion tensor imaging of these nerves is difficult due to the complex tissue interfaces and relatively low MR signal. The purpose of this work is to develop a method for reliable diffusion tensor imaging-based fiber tracking of the peripheral branches of the trigeminal nerve.

METHODS

We prospectively acquired imaging data from six healthy adult participants with a 3.0-Tesla system, including T2-weighted short tau inversion recovery with variable flip angle (T2-STIR-SPACE) and readout segmented echo planar diffusion weighted imaging sequences. Probabilistic tractography of the ophthalmic, infraorbital, lingual, and inferior alveolar nerves was performed manually and assessed by two observers who determined whether the fiber tracts reached defined anatomical landmarks using the T2-STIR-SPACE volume.

RESULTS

All nerves in all subjects were tracked beyond the trigeminal ganglion. Tracts in the inferior alveolar and ophthalmic nerve exhibited the strongest signal and most consistently reached the most distal landmark (58% and 67%, respectively). All tracts of the inferior alveolar and ophthalmic nerve extended beyond their respective third benchmarks. Tracts of the infraorbital nerve and lingual nerve were comparably lower-signal and did not consistently reach the furthest benchmarks (9% and 17%, respectively).

CONCLUSION

This work demonstrates a method for consistently identifying and tracking the major nerve branches of the trigeminal nerve with diffusion tensor imaging.

Current Neurosurgery

Neurosurgery is based on neuroscience, physiology and medical physics. Therefore, neurosurgery has also developed along with discoveries and innovations in these fields. The present article outlines the areas of neurosurgery and their development until 2022. Technology for the preservation of the central nervous system and cranial nerve function has made remarkable progress through the integration of diagnostic imaging and functional evaluation capabilities. Endovascular treatment strategies of cerebrovascular disorders have also progressed. The procedures have not only shifted from craniotomy to endovascular catheterization, but the devices used in these procedures have also changed. In addition to these traditional disease treatment strategies/techniques, neurosurgical techniques have recently been used in surgical procedures to improve quality of life. Epilepsy, is one of the diseases that does not significantly have a direct impact on life outcomes. However, epilepsy patients find it difficult to reintegrate into society. In epilepsy, seizure management is important, and some subgroups of patients can be better treated using surgical intervention than by using pharmacotherapy. In addition, the treatment of dementia due to idiopathic normal pressure hydrocephalus can be improved by surgical management of the cerebrospinal fluid. Neurosurgical intervention can help diseased patients reintegrate into society, which is difficult without treatment. Even in these disease groups, surgical intervention may have irreversible consequences. Therefore, its implications should be decided based on universal scientific evidence.

Three-Dimensional Constructive Interference in Steady State (3D CISS) Imaging and Clinical Applications in Brain Pathology

Three-dimensional constructive interference in steady state (3D CISS) is a steady-state gradient-echo sequence in magnetic resonance imaging (MRI) that has been used in an increasing number of applications in the study of brain disease in recent years. Owing to the very high spatial resolution, the strong hyperintensity of the cerebrospinal fluid signal and the high contrast-to-noise ratio, 3D CISS can be employed in a wide range of scenarios, ranging from the traditional study of cranial nerves, the ventricular system, the subarachnoid cisterns and related pathology to more recently discussed applications, such as the fundamental role it can assume in the setting of acute ischemic stroke, vascular malformations, infections and several brain tumors. In this review, after briefly summarizing its fundamental physical principles, we examine in detail the various applications of 3D CISS in brain imaging, providing numerous representative cases, so as to help radiologists improve its use in imaging protocols in daily clinical practice.

ACR Appropriateness Criteria® Cranial Neuropathy: 2022 Update

Cranial neuropathy can result from pathology affecting the nerve fibers at any point and requires imaging of the entire course of the nerve from its nucleus to the end organ in order to identify a cause. MRI with and without intravenous contrast is often the modality of choice with CT playing a complementary role. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer-reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer-reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

The practical limits of high-quality magnetic resonance imaging for the diagnosis and classification of trigeminal neuralgia

BACKGROUND

Neurovascular compression (NVC) has been the primary hypothesis for the underlying mechanism of classical trigeminal neuralgia (TN). However, a substantial body of literature has emerged highlighting notable exceptions to this hypothesis. The purpose of this study is to assess the reliability and diagnostic accuracy of high resolution, high contrast MRI-determined neurovascular contact for TN.

METHODS

We performed a retrospective, randomized, and blinded parallel characterization of neurovascular interaction and diagnosis in a population of TN patients and controls using four expert reviewers. Performance statistics were calculated, as well as assessments for generalizability using shuffled bootstraps.

RESULTS

Fair to moderate agreement (ICC: 0.32-0.68) about diagnosis between reviewers was observed using MRIs from 47 TN patients and 47 controls. On average reviewers performed no better than chance when diagnosing participants, with an accuracy of 0.57 (95% CI 0.40, 0.59) per patient.

CONCLUSION

While MRI is useful in determining structural causes in secondary TN, expert reviewers do no better to only slightly better than chance with distinguishing TN with MRI, despite moderate agreement. Further, the causal role of NVC for TN is not clear, limiting the applicability of MRI to diagnose or prognosticate treatment of TN.

Correlation of Trigeminopontine Angle with Severity of Trigeminal Neuralgia due to Neurovascular Conflict over Medial Aspect of Nerve: Can We Prognosticate the Reduction in Pain in Patients on Medical Management?

Background  Neurovascular conflicts (NVCs) are one of the major causative factors in patients presenting with trigeminal neuralgia (TN). We found a wide range of variation in degrees of acute angle formed between medial border of trigeminal nerve and anterior border of pons in patients with TN, i.e., medial trigeminopontine angle (mTPA), and tried to find its correlation with pain severity due to NVC over the medial aspect of nerve (mNVC).

Aims and Objectives  To correlate mTPA measurement with severity of TN due to mNVC. To calculate the reduction in pain in patients kept on medical management and its correlation with mTPA.

Materials and Methods  This was a retrospective observational study conducted between May 2018 and October 2020. A total of 41 patients presenting with TN and showing corresponding NVC were included in the study. Out of the total cases with NVC, 30 cases showed NVC over the medial surface of the nerve. All the patients were evaluated on MAGNETOM Skyra 3T magnetic resonance imaging (MRI; Siemens). Using the two-line Cobb angle method, the trigeminopontine angle was calculated. Pretreatment pain intensity and posttreatment pain relief of each patients were assessed by using the numeric rating scale (NRS) with numbers from 0 to 10 (“no pain” to “worst pain imaginable”). Relevant clinical details regarding pre- and posttreatment pain score, after a standard treatment plan of 600 mg of oxcarbazepine for 2 weeks, were collected.

Results  Patients showing response of more than or equal to 50% (≥50%) are considered as “good response” and those with response of less than 50% (<50%) are considered as “poor response.” In our study with trigeminopontine angle threshold of 45 degrees, 7 out of 8 (87.5%) patients with >45° mTPA showed poor response and 15/22 (68.2%) patients with ≤45° showed good response to medical management for TN with statistical significance difference with a p -valve of 0.007.

Conclusion  We found a negative correlation between the mTPA and percentage pain relief in patients kept on medical management and realized that mTPA measurement could become an important tool for prognosticating pain relief for patients of TN on medical therapy; however, more evidence and multicentric studies are required for the same.

MRI features of responsible contacts in vascular compressive trigeminal neuralgia and prediction modeling

BACKGROUND

Multiple neurovascular contacts in patients with vascular compressive trigeminal neuralgia often challenge the diagnosis of responsible contacts.

PURPOSE

To analyze the magnetic resonance imaging (MRI) features of responsible contacts and establish a predictive model to accurately pinpoint the responsible contacts.

MATERIAL AND METHODS

Sixty-seven patients with unilateral trigeminal neuralgia were enrolled. A total of 153 definite contacts (45 responsible, 108 non-responsible) were analyzed for their MRI characteristics, including neurovascular compression (NVC) grading, distance from pons to contact (D_pons-contact), vascular origin of compressing vessels, diameter of vessel (D_vessel) and trigeminal nerve (D_{trigeminal nerve}) at contact. The MRI characteristics of the responsible and non-responsible contacts were compared, and their diagnostic efficiencies were further evaluated using a receiver operating characteristic (ROC) curve. The significant MRI features were incorporated into the logistics regression analysis to build a predictive model for responsible contacts.

RESULTS

Compared with non-responsible contacts, NVC grading and arterial compression ratio (84.44%) were significantly higher, D_pons-contact was significantly lower at responsible contacts (P < 0.001, 0.002, and 0.033, respectively). NVC grading had a highest diagnostic area under the ROC curve (AUC) of 0.742, with a sensitivity of 64.44% and specificity of 75.00%. The logistic regression model showed a higher diagnostic efficiency, with an AUC of 0.808, sensitivity of 88.89%, and specificity of 62.04%.

CONCLUSION

Contact degree and position are important MRI features in identifying the responsible contacts of the trigeminal neuralgia. The logistic predictive model based on D_pons-contact, NVC grading, and vascular origin can qualitatively improve the prediction of responsible contacts for radiologists.

Imaging of the Postoperative Skull Base and Cerebellopontine Angle

For pathologic conditions affecting the skull base and cerebellopontine angle, imaging techniques have advanced to assess for residual disease, disease progression, and postoperative complications. Knowledge regarding various surgical approaches of skull base tumor resection, expected postoperative appearance, and common postsurgical complications guides radiologic interpretation. Complexity of skull base anatomy, small size of the relevant structures, lack of familiarity with surgical techniques, and postsurgical changes confound radiologic evaluation. This article discusses the imaging techniques, surgical approaches, expected postoperative changes, and complications after surgery of the skull base, with emphasis on the cerebellopontine angle, anterior cranial fossa, and central skull base regions.

Imaging of Trigeminal Neuralgia and Other Facial Pain

We review and illustrate the radiology of facial pain, emphasizing trigeminal neuralgia, relevant anatomy, current classification, concepts about etiology, and the role of imaging and its influence on the choice of treatment. We discuss glossopharyngeal neuralgia, other neuropathic causes of facial pain, postinflammatory and neoplastic causes, and nociceptive (end-organ) causes of facial pain, as well as referred otalgia. Other conditions that may present with facial pain, including trigeminal autonomic cephalgias and giant cell arteritis, are reviewed briefly. We discuss the elements of a comprehensive MR imaging protocol to enable detection of these diverse causes of facial pain.

Radiologic and Neurosurgical Diagnosis of Arterial Neurovascular Conflict on Magnetic Resonance Imaging for Trigeminal Neuralgia in Routine Clinical Practice

OBJECTIVE

The most common cause of trigeminal neuralgia is neurovascular conflict, particularly arterial compression of the trigeminal nerve (ACTN). It is possible to show this condition preoperatively on fine-cut constructive interference in steady state magnetic resonance imaging (MRI), supplemented by time-of-flight magnetic resonance angiography. We have noticed significant variability in the interpretation of these studies between radiologists and the treating neurosurgeon. We have assessed the sensitivity and specificity of these 2 styles of interpretation compared with the intraoperative observations.

METHODS

We studied 68 patients who underwent de novo microvascular decompression from 2011 to 2018 under the care of a single neurosurgeon in Melbourne, Australia. Data was recorded prospectively in the radiology reports, operation reports, hospital admission records and neurosurgeon correspondence from the perioperative clinic reviews. In particular, the surgical interpretation of the MRI was clearly described prospectively and preoperatively in the correspondence. The presence or absence of ACTN was recorded prospectively in the operation report. These data were collated retrospectively by the first author.

RESULTS

Of patients, 83.8% (57/68) had clear ACTN confirmed at surgery. Radiologists detected this abnormality in 50.9% (29/57) of these patients, with a sensitivity of 50.9% and specificity of 81.8%. The operating neurosurgeon detected ACTN in 87.7% (50/57) of the positive cases with a sensitivity of 87.7% and a specificity of 72.7%. Statistical analysis showed a significant disagreement between both styles of interpretation, with a radiologic accuracy of 55.9% compared with 85.3% neurosurgically (P < 0.0001). Follow-up review of the patient's response to surgery further supported the neurosurgical diagnosis of ACTN.

CONCLUSIONS

There was a strong tendency for radiologists to underreport ACTN on the preoperative MRI compared with the intraoperative findings. In this series, the neurosurgeon was able to accurately detect ACTN in 88% of patients preoperatively. However, the diagnosis of absent ACTN was still associated with a false-negative rate of 46.7% when the neurosurgeon performed the interpretation. At the current standard of fine-cut constructive interference in steady state MRI in Melbourne, underdetection of ACTN remains common. Clinicians using this test need to be acutely aware of its limitations in deciding whether to proceed to microvascular decompression.

The elastoplastic numerical model and verification by macroindentation experiment of femoral head

For internal fixation of proximal femoral fractures, a screw is commonly placed into the femoral head; therefore, mechanical matching of the femoral head and screw is important. This article proposes an elastoplastic numerical model of the femoral head that takes nonlinear deformation and cancellous bone heterogeneity into account. Force-depth curves from finite element analysis based on the model were compared with those from macroindentation experiments. The maximum difference between the indentation depth shown by the finite element model and that found with macroindentation testing was 5.9%, which demonstrates that the model is valid.

Improving the accuracy of pre-operative evaluation of neurovascular conflict in trigeminal neuralgia using magnetic resonance subtraction

PURPOSE

To investigate the ability of magnetic resonance (MR) subtraction to evaluate neurovascular conflict (NVC) and to compare it with conventional MR protocols.

METHODS

This prospective study included 82 patients with trigeminal neuralgia who underwent microvascular decompression for NVC. All patients had a pre-operative examination using 3T MRI. The MRI protocols used comprised 3D balanced (B)-fast field echo (FFE), 3D steady-state magnetic resonance angiography (MRA), and 3D T1-FFE sequences. MR subtraction images were obtained by subtracting native images from B-FFE and steady-state MRA. NVC evaluation was performed using subtraction images (MR subtraction) and combination images (conventional MR protocols using B-FFE and T1-FFE in combination). Clinical assessment of the degree of compression, the type of compressing vessel, and the location of conflict were undertaken by two independent observers. The two methods were then compared using surgical criteria.

RESULTS

MR subtraction exhibited greater accuracy than the conventional method in terms of the estimated severity of conflict (87.80% vs. 57.32%, p < 0.05), and demonstrated better consistency with surgical findings (k = 0.794 vs. k = 0.365, p < 0.05). For the type of compressing vessel and the location of conflict, both methods were highly accurate and agreed to a similar extent with surgical findings (p = 0.987, compressing vessel; p = 0.665, location of conflict).

CONCLUSION

MR subtraction proved reliable in NVC pre-operative evaluation, with increased accuracy when estimating severity. This result strongly supports the wider use of MR subtraction as the preferred choice in clinical application.

Treatment Outcomes in Trigeminal Neuralgia-A Systematic Review of Domains, Dimensions and Measures

BACKGROUND

Trigeminal neuralgia (TN) is a painful disorder characterized by sudden electric shock-like pain. It is a rare condition for which multiple treatments are available, including medical and surgical. The best treatment option is yet to be defined, and this is related to the lack of definition in the treatment outcomes and outcome measures. The aim of this systematic review was to summarize all the outcomes and outcomes measures that have been published to date and highlight variability in their use.

METHODS

We have conducted a literature search using a wide range of databases (1946-2019 for medical and 2008-2019 for surgical treatment), for all intervention studies in TN. Four hundred and sixty-seven studies were selected for data extraction on TN classification, data collection method, intervention, and treatment outcomes mapped to the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT guidelines).

RESULTS

Most studies collected data on pain (n = 459) and side effects (n = 386) domains; however, very few collected data on the impact of treatment on physical (n = 46) and emotional functioning (n = 17) and on patient satisfaction (n = 35). There was high variability on outcome measures used for pain relief (n = 10), pain intensity (n = 9), and frequency of pain episodes (n = 3).

CONCLUSIONS

A clear definition of what are the important outcomes for patients with TN is essential. The choice of standardized outcome measures allowing for consistent reporting in TN treatment will allow for comparison of studies and facilitate treatment choice for patients and clinicians thus, improving health outcomes and reducing health care cost.

Correlation between pain assessment scale and neurovascular compression distance to the root exit zone in trigeminal neuralgia analysis using 3D CISS MRI sequence

BACKGROUND Trigeminal neuralgia (TN) is primarily caused by neurovascular compression (NVC) at root exit zone (REZ) in cerebellopontine angle cistern. In some NVC cases, it was suspected that clinical symptoms may be correlated with the distance of trigeminal nerve root to vascular contact. Pain assessment scale (PAS) was the most common scale used to evaluate TN pain, therefore this study was conducted to analyze the correlation between PAS usingnumeric rating scale (NRS) and distance from the NVC to REZ location in patients with TN using 3D CISS MRI sequence. METHODS This cross-sectional study was conducted at the Department of Radiology, Faculty of Medicine, Universitas Indonesia, Cipto Mangunkusumo Hospital, Jakarta, using secondary data of 32 patients, collected from Picture Archiving and Communication System from January 2013 to January 2016. Statistical analysis was performed using SPSS, version 20.0. Spearman p-value of < 0.05 was considered significant. RESULTS A total of 32 patients met the inclusion criteria. The mean (SD) distances from the NVC to the REZ were 2.1 (2.1), 2.31 (2.25), and 3.22 (2.63) mm on the shortest, medial, and lateral sides, respectively. The correlation coefficients (r) between the PAS value and the NVC distance in relation to the trigeminal nerve REZ were −0.39 (p = 0.021), −0.57 (p < 0.01), and −0.57 (p = 0.294) on the shortest, lateral, and medial sides, respectively. CONCLUSIONS PAS using the NRS instrument exhibited an inverse correlation to NVC distance to the REZ of the trigeminal nerve. Shorter distance increased the PAS value.