Impact of high resolution 3 tesla MR neurography (MRN) on diagnostic thinking and therapeutic patient management

3D SHINKEI MR neurography in evaluation of traumatic brachial plexus

3D SHINKEI neurography is a new sequence for imaging the peripheral nerves. The study aims at assessing traumatic brachial plexus injury using this sequence. Fifty-eight patients with suspected trauma induced brachial plexus injury underwent MR neurography (MRN) imaging in 3D SHINKEI sequence at 3 T. Surgery and intraoperative somatosensory evoked potentials or clinical follow-up results were used as the reference standard. MRN, surgery and electromyography (EMG) findings were recorded at four levels of the brachial plexus-roots, trunks, cords and branches. Fifty-eight patients had pre- or postganglionic injury. The C5-C6 nerve postganglionic segment was the most common (average 42%) among the postganglionic injuries detected by 3D SHINKEI MRN. The diagnostic accuracy (83.75%) and the specificity (90.30%) of MRN higher than that of EMG (p < 0.001). There was no significant difference in the diagnostic sensitivity of MRN compared with EMG (p > 0.05). Eighteen patients with brachial plexus injury underwent surgical exploration after MRN examination and the correlation between MRN and surgery was 66.7%. Due to the high diagnostic accuracy and specificity, 3D SHINKEI MRN can comprehensively display the traumatic brachial plexus injury. This sequence has great potential in the accurate diagnosis of traumatic brachial plexus injury.

Diagnostic performance of deep learning-based reconstruction algorithm in 3D MR neurography

OBJECTIVE

The study aims to evaluate the diagnostic performance of deep learning-based reconstruction method (DLRecon) in 3D MR neurography for assessment of the brachial and lumbosacral plexus.

MATERIALS AND METHODS

Thirty-five exams (18 brachial and 17 lumbosacral plexus) of 34 patients undergoing routine clinical MR neurography at 1.5 T were retrospectively included (mean age: 49 ± 12 years, 15 female). Coronal 3D T2-weighted short tau inversion recovery fast spin echo with variable flip angle sequences covering plexial nerves on both sides were obtained as part of the standard protocol. In addition to standard-of-care (SOC) reconstruction, k-space was reconstructed with a 3D DLRecon algorithm. Two blinded readers evaluated images for image quality and diagnostic confidence in assessing nerves, muscles, and pathology using a 4-point scale. Additionally, signal-to-noise ratio (SNR) and contrast-to-noise ratios (CNR) between nerve, muscle, and fat were measured. For comparison of visual scoring result non-parametric paired sample Wilcoxon signed-rank testing and for quantitative analysis paired sample Student's t-testing was performed.

RESULTS

DLRecon scored significantly higher than SOC in all categories of image quality (p < 0.05) and diagnostic confidence (p < 0.05), including conspicuity of nerve branches and pathology. With regard to artifacts there was no significant difference between the reconstruction methods. Quantitatively, DLRecon achieved significantly higher CNR and SNR than SOC (p < 0.05).

CONCLUSION

DLRecon enhanced overall image quality, leading to improved conspicuity of nerve branches and pathology, and allowing for increased diagnostic confidence in evaluation of the brachial and lumbosacral plexus.

An Updated Review of Magnetic Resonance Neurography for Plexus Imaging

Magnetic resonance neurography (MRN) is increasingly used to visualize peripheral nerves in vivo. However, the implementation and interpretation of MRN in the brachial and lumbosacral plexi are challenging because of the anatomical complexity and technical limitations. The purpose of this article was to review the clinical context of MRN, describe advanced magnetic resonance (MR) techniques for plexus imaging, and list the general categories of utility of MRN with pertinent imaging examples. The selection and optimization of MR sequences are centered on the homogeneous suppression of fat and blood vessels while enhancing the visibility of the plexus and its branches. Standard 2D fast spin-echo sequences are essential to assess morphology and signal intensity of nerves. Moreover, nerve-selective 3D isotropic images allow improved visualization of nerves and multiplanar reconstruction along their course. Diffusion-weighted and diffusion-tensor images offer microscopic and functional insights into peripheral nerves. The interpretation of MRN in the brachial and lumbosacral plexi should be based on a thorough understanding of their anatomy and pathophysiology. Anatomical landmarks assist in identifying brachial and lumbosacral plexus components of interest. Thus, understanding the varying patterns of nerve abnormalities facilitates the interpretation of aberrant findings.

Magnetic Resonance Neurography of the Foot and Ankle

Peripheral neuropathies of the foot and ankle can be challenging to diagnose clinically due to concomitant traumatic and nontraumatic or degenerative orthopedic conditions. Although clinical history, physical examination, and electrodiagnostic testing comprised of nerve conduction velocities and electromyography are used primarily for the identification and classification of peripheral nerve disorders, MR neurography (MRN) can be used to visualize the peripheral nerves as well as the skeletal muscles of the foot and ankle for primary neurogenic pathology and skeletal muscle denervation effect. Proper knowledge of the anatomy and pathophysiology of peripheral nerves is important for an MRN interpretation.

The emerging role of MRI neurography in the diagnosis of chronic inguinal pain

INTRODUCTION

Chronic pain is a frequent and notable complication after inguinal hernia repair, it has been extensively studied, but its management and diagnosis are still difficult. The cause of chronic pain following inguinal hernia surgery is usually multifactorial. This case series highlights the utility of MRI neurography (MRN) in evaluating the damage to inguinal nerves after a hernia repair, with surgical confirmation of the preoperative imaging findings.

MATERIALS AND METHODS

A retrospective review was performed on patients who underwent inguinal mesh removal and triple denervation of the groin. Inclusion criteria included MRI neurography. All patients underwent surgical exploration of the inguinal canal for partial or complete mesh removal and triple denervation of the groin by the same senior surgeon.

RESULTS

A total of nine patients who underwent triple denervation were included in this case series. MRN was then performed on 100% of patients. The postoperative mean VAS score adjusted for all patients was 1.6 (SD p), resulting in a 7.5 score difference compared to the preoperative VAS score (p). Since chronic groin pain can be a severely debilitating condition, diagnosis, and treatment become imperative.

CONCLUSION

MRN can detect direct and indirect signs of neuropathy even in the absence of a detectable compressive cause aids in management and diagnosis by finding the precise site of injury, and grading nerve injury to aid pre-operative assessment for the nerve surgeon. Thus, it is a valuable diagnostic tool to help with the diagnosis of nerve injuries in the setting of post-inguinal hernia groin pain.

Neuropathy Score Reporting and Data System (NS-RADS): A Practical Review of MRI-Based Peripheral Neuropathy Assessment

The Neuropathy Score Reporting and Data System (NS-RADS) is a newly developed MR imaging-based classification that standardizes reporting and multidisciplinary communication for MR imaging diagnosis and follow-up of peripheral neuropathies. NS-RADS classification has shown to be accurate and reliable across different centers, readers' experience levels, and degrees of peripheral neuropathies, which include nerve injury, entrapment, neoplasm, diffuse neuropathy, post-interventional status, and temporal changes in muscle denervation. This article brings a practical review of NS-RADS classification, representative MR cases, and a step-by-step tutorial on how to approach this staging system. Readers can gain knowledge and apply it in their practice, aiming to standardize the communications between specialties and improve patient management.

MRI Advancements in Musculoskeletal Clinical and Research Practice

Over the past decades, MRI has become increasingly important for diagnosing and longitudinally monitoring musculoskeletal disorders, with ongoing hardware and software improvements aiming to optimize image quality and speed. However, surging demand for musculoskeletal MRI and increased interest to provide more personalized care will necessitate a stronger emphasis on efficiency and specificity. Ongoing hardware developments include more powerful gradients, improvements in wide-bore magnet designs to maintain field homogeneity, and high-channel phased-array coils. There is also interest in low-field-strength magnets with inherently lower magnetic footprints and operational costs to accommodate global demand in middle- and low-income countries. Previous approaches to decrease acquisition times by means of conventional acceleration techniques (eg, parallel imaging or compressed sensing) are now largely overshadowed by deep learning reconstruction algorithms. It is expected that greater emphasis will be placed on improving synthetic MRI and MR fingerprinting approaches to shorten overall acquisition times while also addressing the demand of personalized care by simultaneously capturing microstructural information to provide greater detail of disease severity. Authors also anticipate increased research emphasis on metal artifact reduction techniques, bone imaging, and MR neurography to meet clinical needs.

Feasibility of in vivo multi-parametric quantitative magnetic resonance imaging of the healthy sciatic nerve with a unified signal readout protocol

Magnetic resonance neurography (MRN) has been used successfully over the years to investigate the peripheral nervous system (PNS) because it allows early detection and precise localisation of neural tissue damage. However, studies demonstrating the feasibility of combining MRN with multi-parametric quantitative magnetic resonance imaging (qMRI) methods, which provide more specific information related to nerve tissue composition and microstructural organisation, can be invaluable. The translation of emerging qMRI methods previously validated in the central nervous system to the PNS offers real potential to characterise in patients in vivo the underlying pathophysiological mechanisms involved in a plethora of conditions of the PNS. The aim of this study was to assess the feasibility of combining MRN with qMRI to measure diffusion, magnetisation transfer and relaxation properties of the healthy sciatic nerve in vivo using a unified signal readout protocol. The reproducibility of the multi-parametric qMRI protocol as well as normative qMRI measures in the healthy sciatic nerve are reported. The findings presented herein pave the way to the practical implementation of joint MRN-qMRI in future studies of pathological conditions affecting the PNS.

Role of MR Neurography for Evaluation of the Lumbosacral Plexus: A Scoping Review

Purpose

MR neurography (MRN) is an imaging technique optimized to visualize the peripheral nerves. This review aimed to discover an optimized protocol for MRN of the lumbosacral plexus (LSP) and identify evidence for the clinical benefit of lumbosacral plexopathies.

Materials and Methods

We performed a systematic search of the two medical databases until September 2021. 'Magnetic resonance imaging', 'lumbosacral plexus', 'neurologic disease', or equivalent terms were used to search the literature. We extracted information on indications, MRN protocols for LSP, and clinical efficacy from 55 studies among those searched.

Results

MRN of the LSP is useful for displaying the distribution of peripheral nerve disease, guiding perineural injections, and assessing extraspinal causes of sciatica. Three-dimensional short-tau inversion recovery turbo spin-echo combined with vascular suppression is the mainstay of MRN.

Conclusion

Future work on the MRN of LSP should be directed to technical maturation and clinical validation of efficacy.

Prospective pre-operative 3-T MR neurography peripheral nerve mapping of upper extremity amputations implanted with FAST-LIFE electrode interfaces of robotic hands: technical report

BACKGROUND AND PURPOSE

Fascicular targeting of longitudinal intrafascicular electrode (FAST-LIFE) interface enables hand dexterity with exogenous electrical microstimulation for sensory restoration, custom neural recording hardware, and deep learning-based artificial intelligence for motor intent decoding. The purpose of this technical report from a prospective pilot study was to illustrate magnetic resonance neurography (MRN) mapping of hand and nerve anatomy in amputees and incremental value of MRN over electrophysiology findings in pre-surgical planning of FAST-LIFE interface (robotic hand) patients.

MATERIALS AND METHODS

After obtaining informed consent, patients with upper extremity amputations underwent pre-operative 3-T MRN, X-rays, and electrophysiology. MRN findings were correlated with electrophysiology reports. Descriptive statistics were performed.

RESULTS

Five patients of ages 21-59 years exhibited 3/5 partial hand amputations, and 2/5 transradial amputations on X-rays. The median and ulnar nerve end bulb neuromas measured 10.1 ± 3.04 mm (range: 5.5-14 mm, median: 10.5 mm) and 10.9 ± 7.64 mm (2-22 mm, 9.75 mm), respectively. The ADC of median and ulnar nerves were increased at 1.64 ± 0.1 × 10^-3 mm²/s (range: 1.5-1.8, median: 1.64 × 10^-3 mm²/s) and 1.70 ± 0.17 × 10^-3 mm²/s (1.49-1.98 × 10^-3 mm²/s, 1.65 × 10^-3 mm²/s), respectively. Other identified lesions were neuromas of superficial branch of the radial nerve and anterior interosseous nerve. On electrophysiology, 2/5 reports were unremarkable, 2/5 showed mixed motor-sensory neuropathies of median and ulnar nerves along with radial sensory neuropathy, and 1/5 showed sensory neuropathy of lateral cutaneous nerve of the forearm. All patients regained naturalistic sensations and motor control of digits.

CONCLUSION

3-T MRN allows excellent demonstration of forearm and hand nerve anatomy, altered diffusion characteristics, and their neuromas despite unremarkable electrophysiology for pre-surgical planning of the FAST-LIFE (robotic hand) interfaces.

Neuropathy Score Reporting and Data System (NS-RADS): MRI Reporting Guideline of Peripheral Neuropathy Explained and Reviewed

A standardized guideline and scoring system should be used for the MR imaging diagnosis of peripheral neuropathy. The MR imaging-based Neuropathy Score Reporting and Data System (NS-RADS) is a newly devised classification system (in press in AJR) that can be used to communicate both type and severity of peripheral neuropathy in the light of clinical history and examination findings. The spectrum of neuropathic conditions and peripheral nerve disorders covered in this system includes nerve injury, entrapment, neoplasm, diffuse neuropathy, and post-interventional states. This classification system also describes the temporal MR imaging appearances of regional muscle denervation changes. This review article is based on the multicenter validation study pre-published in American journal of Roentgenology and discusses technical considerations of optimal MR imaging for peripheral nerve evaluation and discusses the NS-RADS classification and its severity scales with illustration of conditions that fall under each classification. The readers can gain knowledge of the NS-RADS classification system and learn to apply it in their practices for improved inter-disciplinary communications and timely patient management.

Diagnostic values of 2 different techniques for controversial lumbar disc herniation by conventional imaging examination: 3D-DESS vs. CT plain scan

Background: The aim of this study was to explore the significance of three-dimensional double-echo steady-state (3D-DESS) sequence and multidetector computed tomography (CT) plain scan in the diagnosis of lumbar disc herniation (LDH) remaining controversial in conventional magnetic resonance imaging (MRI), and to compare the efficiency between 3D-DESS and CT in diagnosing controversial patients by conventional MRI.

Methods: A total of 61 patients with controversial LDH diagnosed by conventional MRI were collected. Before operation, the disease of these patients was further confirmed by 3D-DESS sequences and continuous CT plain scan from L3 to S1. Finally, for patients whose postoperative curative effect was marked and symptoms were obviously alleviated, the sensitivity, specificity and accuracy.

Results: Among, 59 patients with remarkably relieved symptoms after operation were included, and 2 patients with varying degrees of non-remission of pain and partial dysfunction after operation were excluded. The sensitivity, specificity and accuracy of 3D-DESS were 94.6, 100 and 94.9%, respectively, and those of CT were 75.0, 33.3 and 72.9%, respectively.

Conclusion: 3D-DESS is a very useful diagnostic method for patients with some special types of LDH that remain controversial in conventional imaging diagnostic methods. Through 3D-DESS, the morphology of lumbosacral nerve roots can be directly observed, which is conducive to the improvement of the sensitivity, specificity and accuracy, thus further reducing the misdiagnosis rate. Moreover, 3D-DESS plays a guiding role in the formulation of operative methods.

The current role and future directions of imaging in failed back surgery syndrome patients: an educational review

BACKGROUND

Failed back surgery syndrome (FBSS) is an umbrella term referring to painful sensations experienced by patients after spinal surgery, mostly of neuropathic nature. Adequate treatment of FBSS is challenging, as its etiology is believed to be multifactorial and still not fully clarified. Accurate identification of the source of pain is difficult but pivotal to establish the most appropriate treatment strategy. Although the clinical utility of imaging in FBSS patients is still contentious, objective parameters are highly warranted to map different phenotypes of FBSS and tailor each subsequent therapy.

MAIN BODY

Since technological developments have weakened the applicability of prior research, this educational review outlined the recent evidence (i.e., from January 2005 onwards) after a systematic literature search. The state of the art on multiple imaging modalities in FBSS patients was reviewed. Future directions related to functional MRI and the development of imaging biomarkers have also been discussed.

CONCLUSION

Besides the fact that more imaging studies correlated with symptomatology in the postoperative setting are warranted, the current educational review outlined that contrast-enhanced MRI and MR neurography have been suggested as valuable imaging protocols to assess alterations in the spine of FBSS patients. The use of imaging biomarkers to study correlations between imaging features and symptomatology might hold future potential; however, more research is required before any promising hypotheses can be drawn.

Characteristics of Patients With Complex Limb Pain Evaluated Through an Interdisciplinary Approach Utilizing Magnetic Resonance Neurography

Patients with persistent complex limb pain represent a substantial diagnostic challenge. Physical exam, and tests such as nerve conduction, are often normal even though the patient suffers from severe pain. In 2015, we initiated a team-based approach to evaluate such patients. The approach included physicians from several specialties (Anesthesiology/Pain Medicine, Radiology, Plastic Surgery, Neurosurgery) combined with the use of advanced imaging with Magnetic Resonance Neurography (MRN). This preliminary case series discusses MRN findings identified in patients with previously difficult-to-diagnose peripheral limb pain and describes how this combination of approaches influenced our diagnosis and treatment plans. We extracted demographics, patient characteristics, presenting features, diagnostic tests performed, treatments provided, referral diagnosis and the diagnosis after interdisciplinary team evaluation from patient charts. We evaluated MRN and electrodiagnostic studies (EDX) ability to identify injured nerves. We compared abnormal findings from these diagnostics to patient reported outcome after ultrasound-guided nerve block. A total of 58 patients, 17 males and 41 females, were identified. The majority of patients presented with lower extremity pain (75%) and had prior surgery (43%). The most commonly identified abnormality on MRN was nerve signal alteration on fluid sensitive sequences, followed by caliber change and impingement. Comparing the outcome of diagnostic nerve blocks with abnormal nerve findings on MRN or EDX, we found that MRN had a sensitivity of 67% and specificity of 100% while for EDX it was 45 and 0%, respectively. After interdisciplinary discussion and imaging review, a more specific diagnosis was produced in 78% of evaluated cases opening up additional treatment pathways such as nerve-targeted surgery, which was performed in 36% cases. This descriptive case series demonstrates that a majority of patients evaluated by our team for complex limb pain were women with lower extremity pain resulting from surgery. In addition, an interdisciplinary team evaluation and the use of the moderately sensitive but highly specific MRN imaging modality resulted in a change in diagnosis for a majority of patients with complex limb pain. Future studies investigating patient outcomes after diagnosis change are currently underway based on the findings of this preliminary study.

Neuropathy Score Reporting and Data System: A Reporting Guideline for MRI of Peripheral Neuropathy With a Multicenter Validation Study

Background: A standardized guideline and scoring system would improve evaluation and reporting of peripheral neuropathies on MRI. Objective: The objective of this study was to create and validate a neuropathy classification and grading system, which we named the Neuropathy Score Reporting and Data System (NS-RADS). Methods: This retrospective study included 100 patients with nerve imaging studies and known clinical diagnoses. Experts crafted NS-RADS using mutually agreed-upon qualitative criteria for the classification and grading of peripheral neuropathies. Different classes were created to account for the spectrum of underlying pathologies: unremarkable (U), injury (I), neoplasia (N), entrapment (E), diffuse neuropathy (D), not otherwise specified (NOS), and postintervention state (PI). Subclasses were established to describe the severity or extent of the lesions. Validation testing was performed by 11 readers from multiple institutions with experience levels ranging from 3 to 18 years after residency. After initial reader training, cases were presented to readers, who were blinded to final clinical diagnoses. Interobserver agreement was assessed using correlation coefficients and the Conger kappa, and accuracy testing was performed. Results: Final clinical diagnoses included normal (n = 5), nerve injury (n = 25), entrapment (n = 15), neoplasia (n = 33), diffuse neuropathy (n = 18), and persistent neuropathy after intervention (n = 4). The miscategorization rate for NS-RADS classes was 1.8%. Final diagnoses were correctly identified by readers in 71-88% of cases. Excellent interreader agreement was found on the NS-RADS pathology categorization (κ = 0.96; 95% CI, 0.93-0.98) as well as muscle pathology categorization (κ = 0.76; 95% CI, 0.68-0.82]. The accuracy for determining milder versus more severe categories per radiologist ranged from 88% to 97% for nerve lesions and from 86% to 94% for muscle abnormalities. Conclusion: The proposed NS-RADS classification is accurate and reliable across different reader experience levels and a spectrum of peripheral neuropathy conditions. Clinical Impact: NS-RADS can be used as a standardized guideline for reporting peripheral neuropathies and improved multidisciplinary communications.

Magnetic resonance neurography: is it so complicated that it needs a touch of genius?

KEY POINTS

• Neuropathy imaging is not that complicated or illusive that it needs a touch of genius.• By gaining MR imaging expertise of peripheral nerve lesions and using knowledge of common clinical patterns and diseases, general radiology practitioners can prudently participate in the multidisciplinary care for appropriate and timely management of peripheral neuropathy patients.

Intravenous contrast does not improve detection of nerve lesions or active muscle denervation changes in MR neurography of the common peroneal nerve

OBJECTIVE

To evaluate the effect of intravenous (IV) contrast on sensitivity, specificity, and accuracy of magnetic resonance (MR) neurography of the knee with attention to the common peroneal nerve (CPN) in identifying nerve lesions and active muscle denervation changes.

MATERIALS AND METHODS

A retrospective search for contrast-enhanced MR neurography cases evaluating the CPN at the knee was performed. Patients with electrodiagnostic testing (EDX) within 3 months of imaging were included and those with relevant prior surgery were excluded. Two radiologists independently reviewed non-contrast sequences and then 4 weeks later evaluated non-contrast and contrast sequences. McNemar's tests were performed to detect a difference between non-contrast only and combined non-contrast and contrast sequences in identifying nerve lesions and active muscle denervation changes using EDX as the reference standard.

RESULTS

Forty-four exams in 42 patients (2 bilateral) were included. Twenty-eight cases had common peroneal neuropathy and 29, 21, and 9 cases had active denervation changes in the anterior, lateral, and posterior compartment/proximal muscles respectively on EDX. Sensitivity, specificity, and accuracy of non-contrast versus combined non-contrast and contrast sequences for common peroneal neuropathy were 50.0%, 56.2%, and 52.3% versus 50.0%, 56.2%, and 52.3% for reader 1 and 57.1%, 50.0%, and 54.5% versus 64.3%, 56.2%, and 61.4% for reader 2. Sensitivity, specificity, and accuracy of non-contrast and combined non-contrast and contrast sequences in identifying active denervation changes for anterior, lateral, and posterior compartment muscles were not significantly different. McNemar's tests were all negative.

CONCLUSION

IV contrast does not improve the ability of MR neurography to detect CPN lesions or active muscle denervation changes.

Assessing Lumbar Plexus and Sciatic Nerve Damage in Relapsing-Remitting Multiple Sclerosis Using Magnetisation Transfer Ratio

Background: Multiple sclerosis (MS) has traditionally been regarded as a disease confined to the central nervous system (CNS). However, neuropathological, electrophysiological, and imaging studies have demonstrated that the peripheral nervous system (PNS) is also involved, with demyelination and, to a lesser extent, axonal degeneration representing the main pathophysiological mechanisms. Aim: The purpose of this study was to assess PNS damage at the lumbar plexus and sciatic nerve anatomical locations in people with relapsing-remitting MS (RRMS) and healthy controls (HCs) in vivo using magnetisation transfer ratio (MTR), which is a known imaging biomarker sensitive to alterations in myelin content in neural tissue, and not previously explored in the context of PNS damage in MS. Method: Eleven HCs (7 female, mean age 33.6 years, range 24-50) and 15 people with RRMS (12 female, mean age 38.5 years, range 30-56) were recruited for this study and underwent magnetic resonance imaging (MRI) investigations together with clinical assessments using the expanded disability status scale (EDSS). Magnetic resonance neurography (MRN) was first used for visualisation and identification of the lumbar plexus and the sciatic nerve and MTR imaging was subsequently performed using identical scan geometry to MRN, enabling straightforward co-registration of all data to obtain global and regional mean MTR measurements. Linear regression models were used to identify differences in MTR values between HCs and people with RRMS and to identify an association between MTR measures and EDSS. Results: MTR values in the sciatic nerve of people with RRMS were found to be significantly lower compared to HCs, but no significant MTR changes were identified in the lumbar plexus of people with RRMS. The median EDSS in people with RRMS was 2.0 (range, 0-3). No relationship between the MTR measures in the PNS and EDSS were identified at any of the anatomical locations studied in this cohort of people with RRMS. Conclusion: The results from this study demonstrate the presence of PNS damage in people with RRMS and support the notion that these changes, suggestive of demyelination, maybe occurring independently at different anatomical locations within the PNS. Further investigations to confirm these findings and to clarify the pathophysiological basis of these alterations are warranted.

MR Neurography of Peripheral Nerve Injury in the Presence of Orthopedic Hardware: Technical Considerations

As the frequency of orthopedic procedures performed each year in the United States continues to increase, evaluation of peripheral nerve injury (PNI) in the presence of pre-existing metallic hardware is in higher demand. Advances in metal artifact reduction techniques have substantially improved the capability to reduce the susceptibility effect at MRI, but few reports have documented the use of MR neurography in the evaluation of peripheral nerves in the presence of orthopedic hardware. This report delineates the challenges of MR neurography around metal given the high spatial resolution often required to adequately depict small peripheral nerves. It offers practical tips, including strategies for prescan assessment and protocol optimization, including use of more conventional two-dimensional proton density and T2-weighted fat-suppressed sequences and specialized three-dimensional techniques, such as reversed free-induction steady-state precession and multispectral imaging, which enable vascular suppression and metal artifact reduction, respectively. Finally, this article emphasizes the importance of real-time monitoring by radiologists to optimize the diagnostic yield of MR neurography in the presence of orthopedic hardware. © RSNA, 2021.

Magnetic resonance neurography in the management of trigeminal neuralgia: a cohort study of 55 patients

OBJECTIVE

To explore the usefulness of magnetic resonance neurography (MRN) in the diagnosis and management of trigeminal neuralgia (TN).

STUDY DESIGN

In total, 55 patients clinically diagnosed with TN were imaged with 3.0-T magnetic resonance imaging. Images were reconstructed to show the full course of the trigeminal nerve. Clinical findings included mean duration of symptoms (41.99 months) and mean visual analog scale pain intensity (5.98). Final diagnoses were microvascular compression (19), inflammation (21), microvascular compression with inflammation (5), normal (5), tumor (1), peripheral nerve injury (2), and multiple sclerosis (2).

RESULTS

MRN had substantial impact on diagnosis and treatment in 56.4% of cases. A total of 33 patients underwent intervention for pain. MRN had substantial impact on 54.5% of the treated patients. The correlation between MRN results and intervention response was excellent in 19 patients (57.6%) and moderate in 14 (42.4%). Pain was reduced after surgery or interventional procedure in most cases (75.8%).

CONCLUSIONS

MRN is suitable for the diagnosis of clinical TN with beneficial impact on diagnosis and clinical management and moderate-to-excellent correlation with intervention response. Diagnosis of TN should focus not only on microvascular compression but also on the conditions of the peripheral branches of the trigeminal nerve.

Magnetic Resonance Neurography for Evaluation of Peripheral Nerves

Peripheral nerve injuries (PNIs) continue to present both diagnostic and treatment challenges. While nerve transections are typically a straightforward diagnosis, other types of PNIs, such as chronic or traumatic nerve compression, may be more difficult to evaluate due to their varied presentation and limitations of current diagnostic tools. As a result, diagnosis may be delayed, and these patients may go on to develop progressive symptoms, impeding normal activity. In the past, PNIs were diagnosed by history and clinical examination alone or techniques that raised concerns regarding accuracy, invasiveness, or operator dependency. Magnetic resonance neurography (MRN) has been increasingly utilized in clinical settings due to its ability to visualize complex nerve structures along their entire pathway and distinguish nerves from surrounding vasculature and tissue in a noninvasive manner. In this review, we discuss the clinical applications of MRN in the diagnosis, as well as pre- and postsurgical assessments of patients with peripheral neuropathies.

Musculoskeletal trauma imaging in the era of novel molecular methods and artificial intelligence

Over the past decade rapid advancements in molecular imaging (MI) and artificial intelligence (AI) have revolutionized traditional musculoskeletal radiology. Molecular imaging refers to the ability of various methods to in vivo characterize and quantify biological processes, at a molecular level. The extracted information provides the tools to understand the pathophysiology of diseases and thus to early detect, to accurately evaluate the extend and to apply and evaluate targeted treatments. At present, molecular imaging mainly involves CT, MRI, radionuclide, US, and optical imaging and has been reported in many clinical and preclinical studies. Although originally MI techniques targeted at central nervous system disorders, later on their value on musculoskeletal disorders was also studied in depth. Meaningful exploitation of the large volume of imaging data generated by molecular and conventional imaging techniques, requires state-of-the-art computational methods that enable rapid handling of large volumes of information. AI allows end-to-end training of computer algorithms to perform tasks encountered in everyday clinical practice including diagnosis, disease severity classification and image optimization. Notably, the development of deep learning algorithms has offered novel methods that enable intelligent processing of large imaging datasets in an attempt to automate decision-making in a wide variety of settings related to musculoskeletal trauma. Current applications of AI include the diagnosis of bone and soft tissue injuries, monitoring of the healing process and prediction of injuries in the professional sports setting. This review presents the current applications of novel MI techniques and methods and the emerging role of AI regarding the diagnosis and evaluation of musculoskeletal trauma.

Post-Contrast 3D Inversion Recovery Magnetic Resonance Neurography for Evaluation of Branch Nerves of the Brachial Plexus

PURPOSE

To compare 3.0 Tesla brachial plexus three-dimensional (3D) T2-weighted short tau inversion recovery fast spin echo (STIR-FSE) MRI sequences before (pre-contrast STIR) and after (post-contrast STIR) administration of gadolinium intravenous contrast.

METHOD

Eighteen patients were included. Each patient was imaged before and after intravenous contrast administration during the same session. 3D STIR-FSE sequences were obtained at 3.0 Tesla using two 16-channel flexible coils positioned over the lower neck and chest wall region. Three musculoskeletal radiologists qualitatively assessed degree of vascular signal suppression, visualization of the axillary, musculocutaneous, and suprascapular nerves, diagnostic confidence in nerve evaluation, and lesion conspicuity. Marginal ordinal logistic regression models were used to compare subjective ratings between sequences. Pre- and post-STIR lesion conspicuity was compared using Wilcoxon signed-rank test. Inter- and intra-observer agreements were assessed using Gwet's agreement coefficient.

RESULTS

Vascular signal suppression significantly improved following contrast administration (odds ratio, OR = 209.9, 95% confidence interval, CI: 21.0-2094.6, p < .001). The post-contrast STIR technique significantly improved nerve visualization (OR = 8.4, 95% CI: 3.6-19.9, p < .001) and diagnostic confidence in evaluation (OR = 13.2, 95% CI: 4.8-36.0, p < .001) across all nerve segments. Post-contrast STIR improved lesion conspicuity by 1 point, but statistical significance was not reached (Reader 1: p = 0.5, Reader 2: p = 0.063). Post-contrast STIR imaging demonstrated substantial to near-perfect inter- and intra-rater agreement coefficients for both nerve visualization (inter-rater: 0.74-1.0, intra-rater: 0.94-1.0) and diagnostic confidence (inter-rater: 0.79-1.0, intra-rater: 0.94-1.0). Quantitatively, post-contrast STIR demonstrated a 24% increase in mean C6 nerve-to-muscle signal intensity ratio (p = 0.017).

CONCLUSIONS

Post-contrast STIR improved nerve-to-muscle contrast ratio, allowing for enhanced visualization and diagnostic confidence in evaluation of branch nerves of the brachial plexus.

Magnetisation transfer ratio combined with magnetic resonance neurography is feasible in the proximal lumbar plexus using healthy volunteers at 3T

Magnetic resonance neurography (MRN) has been used extensively to study pathological conditions affecting the peripheral nervous system (PNS). However, tissue damage is assessed qualitatively with little information regarding the underlying pathophysiological processes involved. Magnetisation transfer ratio (MTR) is a quantitative magnetic resonance imaging method which is sensitive to tissue macromolecular content and may therefore have an important role in the study of pathologies affecting the PNS. This study explored the feasibility of obtaining reliable MTR measurements in the proximal lumbar plexus of healthy volunteers using MRN to identify and segment each lumbar segment (L2-L5) and regions (preganglionic, ganglionic and postganglionic). Reproducibility of the MTR measurements and of the segmentation method were assessed from repeated measurements (scan-rescan), and from the reanalysis of images (intra- and inter-rater assessment), by calculating the coefficient of variation (COV). In all segments combined (L2-L5), mean (± SD) MTR was 30.5 (± 2.4). Scan-rescan, intra- and inter-rater COV values were 3.2%, 4.4% and 5.3%, respectively. One-way analysis of variance revealed a statistically significant difference in MTR between the preganglionic and postganglionic regions in all lumbar segments. This pilot study in healthy volunteers demonstrates the feasibility of obtaining reliable MTR measurements in the proximal lumbar plexus, opening up the possibility of studying a broad spectrum of neurological conditions in vivo.

Enhanced MR neurography of the lumbosacral plexus with robust vascular suppression and improved delineation of its small branches

PURPOSE

To evaluate whether gadolinium enhanced 3D SPACE STIR sequence technique increases the visualization of the lumbosacral plexus (LSP) and its small branches.

METHODS

A retrospective study was performed on 24 patients who had underwent 3D SPACE STIR sequences scan with and without the administration of gadolinium contrast. In this study, we focused on the healthy sides of the LSP and its branches in each patient. The contrast ratio (CR), contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) were objectively calculated by two experienced radiologists. The subjective visualization scores of the branches that were vitally important to therapeutic decision-making including femoral nerves, obturator nerves, lumbosacral trunks, superior gluteal and extra-pelvic sciatic nerves, were assessed using post-processing images.

RESULTS

Of the 24 subjects, all LSP nerve roots, femoral nerves, lumbosacral trunks and sciatic nerves were illustrated on both contrast-enhanced and non-contrast images. The enhanced images were found to have higher nerve to vein CNRs compared to non-contrast images. Compared to non-contrast images, the CRs of nerves versus surrounding fat tissues, bones, veins and muscles were improved in contrast-enhanced images, while the SNRs were better but not significantly so. Targeted maximum intensity projection (MIP) nerves including femoral, obturator, superior gluteal and extra-pelvic sciatic nerves obtained significantly higher subjective scores when gadolinium was administered.

CONCLUSIONS

The gadolinium enhanced 3D SPACE STIR sequence provided superior vascular suppression, resulting in increased conspicuity of LSP and its small branches. Altogether, this shows great potential for therapeutic decision-making in traumatic LSP lesions cases.

Degenerative lumbar scoliosis: added value of coronal images to routine lumbar MRI for nerve root compromise

OBJECTIVES

Radiating pain in degenerative scoliosis is primary indication for surgery. However, axial and sagittal MR images are limited for identifying nerve root compromise. Therefore, we aimed to assess the value of coronal images for evaluating nerve root compromise in degenerative scoliosis.

METHODS

Forty-six patients (mean 70 years; range 41-91 years; 8 men) with degenerative scoliosis were enrolled. Coronal images were added to routine MRI. Two radiologists independently reviewed 350 nerve roots in two MRI sets: sagittal images alone (set 1) and coronal and sagittal images combined (set 2). The following features were evaluated: interpedicular height, lateral osteophyte, asymmetric bulging disc, lateral listhesis, anterolisthesis, axial rotation angle, facet arthrosis, ligamentum flavum thickening, and pseudoarticulation. Symptomatic levels were determined by transforaminal selective nerve root block.

RESULTS

There were 80 symptomatic and 270 asymptomatic nerve roots. The sensitivity (86%) and accuracy (93%) of set 2 were significantly higher than set 1 (53% and 87%) for radiculopathy, while specificity was similar between two sets (set 1, 97%; set 2, 95%). The AUC was significantly different between two sets (set 1, 0.853; set 2, 0.942). The negative interpedicular height difference, longer lateral osteophyte, asymmetric bulging disc, lateral listhesis, negative axial rotation angle difference, and pseudoarticulation were associated with change of grades between set 1 and set 2.

CONCLUSION

Coronal images are helpful for diagnosing nerve root compromise in patients with degenerative scoliosis.

KEY POINTS

• Sagittal and axial images have low sensitivity for detection of extraforaminal nerve root compromise in degenerative scoliosis. • Addition of coronal images may improve the sensitivity in nerve root compromise. • The structural changes that may contribute to nerve root compromise can also be easily assessed with coronal images.

Recent Advances in Pediatric Brain, Spine, and Neuromuscular Magnetic Resonance Imaging Techniques

Magnetic resonance imaging (MRI) is a powerful radiologic tool with the ability to generate a variety of proton-based signal contrast from tissues. Owing to this immense flexibility in signal generation, new MRI techniques are constantly being developed, tested, and optimized for clinical utility. In addition, the safe and nonionizing nature of MRI makes it a suitable modality for imaging in children. In this review article, we summarize a few of the most popular advances in MRI techniques in recent years. In particular, we highlight how these new developments have affected brain, spine, and neuromuscular imaging and focus on their applications in pediatric patients. In the first part of the review, we discuss new approaches such as multiphase and multidelay arterial spin labeling for quantitative perfusion and angiography of the brain, amide proton transfer MRI of the brain, MRI of brachial plexus and lumbar plexus nerves (i.e., neurography), and T2 mapping and fat characterization in neuromuscular diseases. In the second part of the review, we focus on describing new data acquisition strategies in accelerated MRI aimed collectively at reducing the scan time, including simultaneous multislice imaging, compressed sensing, synthetic MRI, and magnetic resonance fingerprinting. In discussing the aforementioned, the review also summarizes the advantages and disadvantages of each method and their current state of commercial availability from MRI vendors.

T2 mapping of lumbosacral nerves in patients suffering from unilateral radicular pain due to degenerative disc disease

OBJECTIVE

Lumbosacral radicular syndrome (LRS) is a very common condition, often requiring diagnostic imaging with the aim of elucidating a structural cause when symptoms are longer lasting. However, findings on conventional anatomical MRI do not necessarily correlate with clinical symptoms, and it is primarily performed for the qualitative evaluation of surrounding compressive structures, such as herniated discs, instead of to evaluate the nerves directly. The present study investigated the performance of quantitative imaging by using magnetic resonance neurography (MRN) in patients with LRS.

METHODS

Eighteen patients (55.6% males, mean age 64.4 ± 10.2 years), with strict unilateral LRS matching at least one dermatome and suspected disc herniation, underwent high-resolution 3-T MRN using T2 mapping. On T2 maps, the presumably affected and contralateral unaffected nerves were identified; subsequent regions of interest (ROIs) were placed at preganglionic, ganglionic, and postganglionic sites; and T2 values were extracted. Patients then underwent an epidural steroid injection (ESI) with local anesthetic agents at the site of suspected nerve affection. T2 values of the affected nerves were compared against the contralateral nerves. Furthermore, receiver operating characteristics were calculated based on the measured T2 values and the responsiveness to ESI.

RESULTS

The mean T2 value was 77.3 ± 1.9 msec for affected nerves and 74.8 ± 1.4 msec for contralateral nerves (p < 0.0001). In relation to ESI performed at the site of suspected nerve affection, MRN with T2 mapping had a sensitivity/specificity of 76.9%/60.0% and a positive/negative predictive value of 83.3%/50.0%. Signal alterations in affected nerves according to qualitative visual inspection were present in only 22.2% of patients.

CONCLUSIONS

As one of the first of its kind, this study revealed elevated T2 values in patients suffering from LRS. T2 values of lumbosacral nerves might be used as more objective parameters to directly detect nerve affection in such patients.

Diffusion Tensor Imaging of the Brachial Plexus: A Comparison between Readout-segmented and Conventional Single-shot Echo-planar Imaging

Purpose:

Diffusion tensor imaging (DTI) adds functional information to morphological magnetic resonance neurography (MRN) in the assessment of the brachial nerve plexus. To determine the most appropriate pulse sequence in scan times suited for diagnostic imaging in clinical routine, we compared image quality between simultaneous multi-slice readout-segmented (rs-DTI) and conventional single-shot (ss-DTI) echo-planar imaging techniques.

Methods:

Institutional Review Board (IRB) approved study including 10 healthy volunteers. The supraclavicular brachial plexus, covering the nerve roots and trunks from C5 to C7, was imaged on both sides with rs-DTI and ss-DTI. Both sequences were acquired in scan times <7 min with b-values of 900 s/mm² and with isotropic spatial resolution.

Results:

In rs-DTI image, the overall quality was significantly better and distortion artifacts were significantly lower (P = 0.001–0.002 and P = 0.001–0.002, respectively) for both readers. In ss-DTI, a trend toward lower degree of ghosting and motion artifacts was elicited (reader 1, P = 0.121; reader 2, P = 0.264). No significant differences between the two DTI techniques were found for signal-to-noise ratios (SNR), contrast-to-noise ratios (CNR) and fractional anisotropy (FA) (P ≥ 0.475, P ≥ 0.624, and P ≥ 0.169, respectively). Interreader agreement for all examined parameters and all sequences ranged from intraclass correlation coefficient (ICC) 0.064 to 0.905 and Kappa 0.40 to 0.851.

Conclusion:

Incomparable acquisition times rs-DTI showed higher image quality and less distortion artifacts than ss-DTI. The trend toward a higher degree of ghosting and motion artifacts in rs-DTI did not deteriorate image quality to a significant degree. Thus, rs-DTI should be considered for functional MRN of the brachial plexus.

MR Neurography of the Lumbosacral Plexus for Lower Extremity Radiculopathy: Frequency of Findings, Characteristics of Abnormal Intraneural Signal, and Correlation with Electromyography

BACKGROUND AND PURPOSE

MR neurography enables high resolution imaging of peripheral nerves. Our aim was to evaluate the utility of MR neurography in lumbosacral radiculopathy and correlate abnormal intraneural signal with history, physical examination, and abnormal electrodiagnostic study findings.

MATERIALS AND METHODS

Retrospective review of lumbosacral MR neurography examinations performed from December 2014 through January 2017 on a 3T scanner was undertaken. MR neurography examinations were independently reviewed in a blinded fashion by 2 radiologists, and the intraneural signal was graded on a 0-2 scale relative to adjacent vasculature. Abnormal nerve signal was correlated with subjective and objective findings from clinical notes in the electronic medical record and compared with results of electrodiagnostic studies (nerve conduction study/electromyography).

RESULTS

Three hundred three lumbosacral MR neurography examinations were performed during the study period, 64 of which met the inclusion criteria, including symptoms of radiculopathy on electromyography performed within 3 months of MR neurography. Twenty-nine (45%) MR neurography examinations had abnormal intraneural signal. There was no statistically significant correlation between subjective clinical findings and intraneural signal abnormality on MR neurography. There was a statistically significant correlation between abnormal intraneural T2 signal and findings of active radiculopathy on electromyography (P < .001).

CONCLUSIONS

Lumbosacral MR neurography appears to demonstrate abnormal intraneural signal in a substantial portion of patients with clinical symptoms of lower extremity radiculopathy and correlates with findings of active radiculopathy on electromyography. This finding further bolsters the growing body of evidence on the utility of MR neurography and suggests that abnormal intraneural signal may provide a useful adjunct to electrodiagnostic testing. Further research is required to evaluate the prognostic value of MR neurography, which may help guide therapeutic decision-making.

MR imaging features of presumed retroclavicular and periscapular intermuscular vascular plexi - An observational, anatomic study

OBJECTIVE

To describe MR imaging features of presumed vascular plexi in the periscapular (PSC) and retroclavicular (RC) locations.

MATERIALS/METHODS

443 consecutive MR studies performed as "brachial plexus" protocol (axialT1-W and sagittal STIR) were reviewed for presence, size and characteristics of PSC and RC plexi.

RESULTS

Presumed PSC and RC vascular plexi were present in 10%. Both plexi more commonly occurred on the left side. Percutaneous biopsy (n = 1) yielded no vascular neoplasm.

CONCLUSION

RC and PSC vascular plexi are commonly encountered on routine brachial plexus MR imaging and may represent variant vascular networks, as they are frequently found on the contralateral asymptomatic side.

Magnetic Resonance Neurography of the Lumbosacral Plexus in Failed Back Surgery Syndrome

STUDY DESIGN

Retrospective clinical case series.

OBJECTIVE

To study the role of magnetic resonance neurography (MRN) of the lumbosacral plexus in management of patients with failed back surgery syndrome (FBSS).

SUMMARY OF BACKGROUND DATA

FBSS is one of the major problems in health care, affecting up to 40% of patients after spine surgery. To date, no imaging modality has been used to effectively classify nerve compression, because nerve injuries are challenging to detect on conventional lumbar spine magnetic resonance imaging (MRI). To our knowledge, no previous studies have addressed the use of MRN in FBSS or compared it to lumbar spine MRI.

METHODS

From 203 consecutive 3 T MRN studies of lumbosacral plexus in 1 year, 12% (25/203) presented as FBSS. Demographic data, number of previous lumbar MRIs and their findings, MRN findings, interval between MRI and MRN, pre-and post-MRN diagnosis, pain levels, and treatments were recorded. Changes in diagnosis, treatment, and outcomes after MRN were determined.

RESULTS

The final sample of 25 patients had a mean age 62 ± 15 and male to female ratio 1:1.08. Approximately 88% (22/25) had previous lumbar MRI, of which 27% had 3 or more. Most common imaging findings were neuroforaminal stenosis 22.6% (7/31) on MRI and neuropathy 22.9% (19/83) on MRN. Mean interval between MRI and MRN was 13.9 ± 28.3 months. Lumbar MRIs were inconclusive in 36% (8/22). MRN detected 63% (52/83) more findings and changed the diagnosis and treatment in 12% and 48% of FBSS cases, respectively. Favorable outcomes were recorded in 40% to 67% of patients following MRN-guided treatments.

CONCLUSION

FBSS is a complex problem and MRN of lumbosacral plexus impacts its management by better directing source of symptoms.

LEVEL OF EVIDENCE

4.

Magnetic Resonance Neurography in Chronic Lumbosacral and Pelvic Pain: Diagnostic and Management Impact-Institutional Audit

BACKGROUND/OBJECTIVE

Low back and pelvic pain are among the most prevalent conditions worldwide, with major social and economic costs. The aim of this study was to evaluate the role of magnetic resonance neurography (MRN) of lumbosacral plexus in the management and outcomes of these patients with chronic pain.

METHODS

Consecutive patients with chronic lumbosacral and pelvic pain referred for MRN over a year were included. Preimaging and postimaging clinical diagnosis and treatment, pain levels, and location were recorded. Pain-free survival was compared between treatments using a Cox proportional hazards model.

RESULTS

A total of 202 patients with mean age 53.7 ± 14.8 years and a male/female ratio of 1:1.53 were included. Of these patients, 115 presented with radiculopathy (57%), 56 with pelvic pain (28%), and 31 with groin pain (15%). Mean initial pain level was 6.9 ± 1.9. Mean symptom duration was 4.21 ± 5.86 years. Of these patients, 143 (71%) had a change in management because of MRN. After MRN, reduction in pain levels was observed in 21 of 32 patients receiving conservative treatment (66%), 42 of 67 receiving injections (63%), and 27 of 33 receiving surgery (82%). Follow-ups were available in 131 patients. Median pain-free survival was 12 months. Patients treated with surgery had significantly lower pain recurrence than patients receiving other treatments in the same time frame (hazard ratio, 3.6; 95% confidence interval, 1.4-9.2; P = 0.0061).

CONCLUSIONS

MRN use in chronic lumbosacral and pelvic pain led to a meaningful change in diagnosis and treatment. After MRN, conservative treatment and injections provided pain relief; however, patients benefited more from surgery than from any other treatment.

Magnetic resonance neurography: current perspectives and literature review

Magnetic resonance neurography (also called MRN or MR neurography) refers to MR imaging dedicated to the peripheral nerves. It is a technique that enhances selective multiplanar visualisation of the peripheral nerve and pathology by encompassing a combination of two-dimensional, three-dimensional and diffusion imaging pulse sequences. Referring physicians who seek imaging techniques that can depict and diagnose peripheral nerve pathologies superior to conventional MR imaging are driving the demand for MRN. This article reviews the pathophysiology of peripheral nerves in common practice scenarios, technical considerations of MRN, current indications of MRN, normal and abnormal neuromuscular appearances, and imaging pitfalls. Finally, the emerging utility of diffusion-weighted and diffusion tensor imaging is discussed and future directions are highlighted.

KEY POINTS

• Lesion relationship to neural architecture is more conspicuous on MRN than MRI. • 3D multiplanar imaging technique is essential for pre-surgical planning. • Nerve injuries can be classified on MRN using Sunderland's classification. • DTI provides quantitative information and insight into intraneural integrity and pathophysiology.

High-resolution metal artifact reduction MR imaging of the lumbosacral plexus in patients with metallic implants

OBJECTIVE

To assess the quality and accuracy of metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) for the diagnosis of lumbosacral neuropathies in patients with metallic implants in the pelvis.

MATERIALS AND METHODS

Twenty-two subjects with lumbosacral neuropathy following pelvic instrumentation underwent 1.5-T MARS MRI including optimized axial intermediate-weighted and STIR turbo spin echo sequences extending from L5 to the ischial tuberosity. Two readers graded the visibility of the lumbosacral trunk, sciatic, femoral, lateral femoral cutaneous, and obturator nerves and the nerve signal intensity of nerve, architecture, caliber, course, continuity, and skeletal muscle denervation. Clinical examination and electrodiagnostic studies were used as the standard of reference. Descriptive, agreement, and diagnostic performance statistics were applied.

RESULTS

Lumbosacral plexus visibility on MARS MRI was good (4) or very good (3) in 92% of cases with 81% exact agreement and a Kendall's W coefficient of 0.811. The obturator nerve at the obturator foramen and the sciatic nerve posterior to the acetabulum had the lowest visibility, with good or very good ratings in only 61% and 77% of cases respectively. The reader agreement for nerve abnormalities on MARS MRI was excellent, ranging from 95.5 to 100%. MARS MRI achieved a sensitivity of 86%, specificity of 67%, positive predictive value of 95%, and negative predictive value of 40%, and accuracy of 83% for the detection of neuropathy.

CONCLUSION

MARS MRI yields high image quality and diagnostic accuracy for the assessment of lumbosacral neuropathies in patients with metallic implants of the pelvis and hips.

Advanced MRI Techniques for the Ankle

OBJECTIVE

The purposes of this article are to present a state-of-the-art routine protocol for MRI of the ankle, to provide problem-solving tools based on specific clinical indications, and to introduce principles for the implementation of ultrashort echo time MRI of the ankle, including morphologic and quantitative assessment.

CONCLUSION

Ankle injury is common among both athletes and the general population, and MRI is the established noninvasive means of evaluation. The design of an ankle protocol depends on various factors. Higher magnetic field improves signal-to-noise ratio but increases metal artifact. Specialized imaging planes are useful but prolong acquisition times. MR neurography is useful, but metal reduction techniques are needed whenever a metal prosthesis is present. An ultrashort echo time sequence is a valuable tool for both structural and quantitative evaluation.

Impact of MR Neurography in Patients with Chronic Cauda Equina Syndrome Presenting as Chronic Pelvic Pain and Dysfunction

BACKGROUND AND PURPOSE

Chronic cauda equina syndrome, defined as persistent damage of the cauda equina nerve roots within the spinal canal can be a challenging diagnosis with varied presentations. MR neurography imaging is more commonly being used to evaluate the lumbosacral spine of patients suspected of having subacute or chronic cauda equina syndrome. Our aim was to evaluate the impact of lumbosacral plexus MR neurography in the diagnostic thinking and therapeutic management of patients presenting with chronic pelvic pain and dysfunction and suspected chronic cauda equina syndrome.

MATERIALS AND METHODS

Consecutive MR neurography lumbosacral plexus examinations at our institution were reviewed retrospectively. Relevant data collected included the following: patient demographics, clinical history, pertinent physical examination findings, preimaging diagnostic impression, prior MR imaging lumbar spine findings, MR neurography findings, postimaging diagnosis, and postimaging treatment plan. The impact of imaging on the preimaging clinical diagnosis and therapeutic management was evaluated.

RESULTS

Of 185 studies of patients who presented with chronic pelvic pain and/or dysfunction, 23 with clinically suspected chronic cauda equina syndrome and imaging findings were included in the study (2 subjects were lost to follow-up). The mean ages were 53 ± 12 years and 53 ± 16 years for men and women, respectively. The common etiologies included arachnoiditis (n = 8), tethered cord (n = 2), and simple/Tarlov cysts (n = 3). Eighteen of 23 (78%) subjects had a change in diagnosis resulting from MR neurography findings, and 5/23 (22%) had no change. Seventeen of 21 (81%) subjects had a change in management, and 4/21 (19%) had no change.

CONCLUSIONS

MR neurography impacts the diagnosis and therapeutic management of patients with suspected chronic cauda equina syndrome.

MRI shows thickening and altered diffusion in the median and ulnar nerves in multifocal motor neuropathy

Objectives

To study disease mechanisms in multifocal motor neuropathy (MMN) with magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) of the median and ulnar nerves.

Methods

We enrolled ten MMN patients, ten patients with amyotrophic lateral sclerosis (ALS) and ten healthy controls (HCs). Patients underwent MRI (in a prone position) and nerve conduction studies. DTI and fat-suppressed T2-weighted scans of the forearms were performed on a 3.0T MRI scanner. Fibre tractography of the median and ulnar nerves was performed to extract diffusion parameters: fractional anisotropy (FA), mean (MD), axial (AD) and radial (RD) diffusivity. Cross-sectional areas (CSA) were measured on T2-weighted scans.

Results

Forty-five out of 60 arms were included in the analysis. AD was significantly lower in MMN patients (2.20 ± 0.12 × 10^-3 mm²/s) compared to ALS patients (2.31 ± 0.17 × 10^-3 mm²/s; p < 0.05) and HCs (2.31± 0.17 × 10^-3 mm²/s; p < 0.05). Segmental analysis showed significant restriction of AD, RD and MD (p < 0.005) in the proximal third of the nerves. CSA was significantly larger in MMN patients compared to ALS patients and HCs (p < 0.01).

Conclusions

Thickening of nerves is compatible with changes in the myelin sheath structure, whereas lowered AD values suggest axonal dysfunction. These findings suggest that myelin and axons are diffusely involved in MMN pathogenesis.

Key Points

• Diffusion magnetic resonance imaging provides quantitative information about multifocal motor neuropathy (MMN).

• Diffusion tensor imaging allows non-invasive evaluation of the forearm nerves in MMN.

• Nerve thickening and lowered diffusion parameters suggests myelin and axonal changes.

• This study can help to provide insight into pathological mechanisms of MMN.

Electronic supplementary material

The online version of this article (doi:10.1007/s00330-016-4575-0) contains supplementary material, which is available to authorized users.

Clinical impact of magnetic resonance neurography in patients with brachial plexus neuropathies

OBJECTIVE

To study the impact of brachial plexus MR neurography (MRN) in the diagnostic thinking and therapeutic management of patients with suspected plexopathy.

METHODS

MRN examinations of adult brachial plexuses over a period of 18 months were reviewed. Relevant data collection included-patient demographics, clinical history, pre-imaging diagnostic impression, pre-imaging treatment plan, post-imaging diagnosis, post-imaging treatment plan, surgical notes and electrodiagnostic (ED) results. Impact of imaging on the pre-imaging clinical diagnosis and therapeutic management were classified as no change, mild change or substantial change.

RESULTS

Final sample included 121 studies. The common aetiologies included inflammatory in 31 (25.6%) of 121 patients, trauma in 29 (23.9%) of 121 patients and neoplastic in 26 (21.5%) of 121 patients. ED tests were performed in 47 (38.8%) of 121 patients and these showed concordance with MRN findings in 31 (66.0%) of 47 patients. Following MRN, there was change in the pre-imaging clinical impression for 91 (75.2%) of 121 subjects, with a mild change in diagnosis in 57 (47.1%) of 121 patients and a substantial change in 34 (28.0%) of 121 patients. 19 (15.7%) of 121 patients proceeded to therapies that would not have been performed in the same manner without the information obtained from MRN.

CONCLUSION

MRN of the brachial plexus significantly impacts clinical decision-making and should be routinely performed in suspected brachial plexopathy. Advances in knowledge: MRN significantly impacts the diagnostic thinking and therapeutic management of patients with suspected brachial plexopathy. MRN not only provides concordant information to ED tests in majority of cases, but also supplements with additional diagnostic data in patients who are ED negative.

Nerve Fascicles and Epineurium Volume Segmentation of Peripheral Nerve Using Magnetic Resonance Micro-neurography

RATIONALE AND OBJECTIVES

The aims of this study were to propose a semiautomated technique to segment and measure the volume of different nerve components of the tibial nerve, such as the nerve fascicles and the epineurium, based on magnetic resonance microneurography and a segmentation tool derived from brain imaging; and to assess the reliability of this method by measuring interobserver and intraobserver agreement.

MATERIALS AND METHODS

The tibial nerve of 20 healthy volunteers (age range = 23-69; mean = 47; standard deviation = 15) was investigated at the ankle level. High-resolution images were obtained through tailored microneurographic sequences, covering 28 mm of nerve length. Two operators manually segmented the nerve using the in-phase image. This region of interest was used to mask the nerve in the water image, and two-class segmentation was performed to measure the fascicular volume, epineurial volume, nerve volume, and fascicular to nerve volume ratio (FNR). Interobserver and intraobserver agreements were calculated.

RESULTS

The nerve structure was clearly visualized with distinction of the fascicles and the epineurium. Segmentation provided absolute volumes for nerve volume, fascicular volume, and epineurial volume. The mean FNR resulted in 0.69 with a standard deviation of 0.04 and appeared to be not correlated with age and sex. Interobserver and intraobserver agreements were excellent with alpha values >0.9 for each parameter investigated, with measurements free of systematic errors at the Bland-Altman analysis.

CONCLUSIONS

We concluded that the method is reproducible and the parameter FNR is a novel feature that may help in the diagnosis of neuropathies detecting changes in volume of the fascicles or the epineurium.

Magnetic resonance neurography in the management of peripheral trigeminal neuropathy: experience in a tertiary care centre

OBJECTIVE

This tertiary care experience examines the utility of magnetic resonance neurography (MRN) in the management of peripheral trigeminal neuropathies.

MATERIALS AND METHODS

Seventeen patients with clinically suspected peripheral trigeminal neuropathies (inferior alveolar nerve and lingual nerve) were imaged uniformly with 1.5-T examinations. MRN results were correlated with clinical and surgical findings in operated patients and the impact on clinical management was assessed.

RESULTS

Clinical findings included pain (14/17), sensory changes (15/17), motor changes (2/17) and palpable masses (3/17). Inciting events included prior dental surgery (12/17), trauma (1/17) and idiopathic incidents (4/17). Non-affected side nerves and trigeminal nerves in the intracranial and skull base course were normal in all cases. Final diagnoses on affected sides were nerve inflammation (4/17), neuroma in continuity (2/17), LN transection (1/17), scar entrapment (3/17), infectious granuloma (1/17), low-grade injuries (3/17) and no abnormality (3/17). Associated submandibular gland and sublingual gland oedema-like changes were seen in 3/17 cases because of parasympathetic effects. Moderate-to-excellent MRN-surgical correlation was seen in operated (8/17) patients, and neuroma and nerve transection were prospectively identified in all cases.

CONCLUSION

MRN is useful for the diagnostic work-up of suspected peripheral trigeminal neuropathy patients with significant impact on clinical management and moderate-to-excellent correlation with intra-operative findings.

KEY POINTS

• MRN substantially impacts diagnostic thinking and management in peripheral trigeminal neuropathy. • MRN has moderate-to-excellent correlation with intra-operative findings. • MRN should be considered in pre-surgical planning of peripheral trigeminal neuropathy subjects.