Morphological analysis in patients with sciatica: a magnetic resonance imaging study using three-dimensional high-resolution diffusion-weighted magnetic resonance neurography techniques

Imaging Biomarkers of Peripheral Nerves: Focus on Magnetic Resonance Neurography and Ultrasonography

Peripheral neuropathy is a prevalent and debilitating condition affecting millions of individuals globally. Magnetic resonance neurography (MRN) and ultrasonography (US) are noninvasive methods offering comprehensive visualization of peripheral nerves, using anatomical and functional imaging biomarkers to ensure accurate evaluation. For optimized MRN, superior and high-resolution two-dimensional and three-dimensional imaging protocols are essential. The anatomical MRN and US imaging markers include quantitative measures of nerve and fascicular size and signal, and qualitative markers of course and morphology. Among them, quantitative markers of T2-signal intensity ratio are sensitive to nerve edema-like signal changes, and the T1-mapping technique reveals nerve and muscle tissue fatty and fibrous compositional alterations.The functional markers are derived from physiologic properties of nerves, such as diffusion characteristics or blood flow. They include apparent diffusion coefficient from diffusion-weighted imaging and fractional anisotropy and tractography from diffusion tensor imaging to delve into peripheral nerve microstructure and integrity. Peripheral nerve perfusion using dynamic contrast-enhanced magnetic resonance imaging estimates perfusion parameters, offering insights into nerve health and neuropathies involving edema, inflammation, demyelination, and microvascular alterations in conditions like type 2 diabetes, linking nerve conduction pathophysiology to vascular permeability alterations.Imaging biomarkers thus play a pivotal role in the diagnosis, prognosis, and monitoring of nerve pathologies, thereby ensuring comprehensive assessment and elevating patient care. These biomarkers provide valuable insights into nerve structure, function, and pathophysiology, contributing to the accurate diagnosis and management planning for peripheral neuropathy.

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.

ACR Appropriateness Criteria® Plexopathy: 2021 Update

Plexopathy may be caused by diverse pathologies, including trauma, nerve entrapment, neoplasm, inflammation, infection, autoimmune disease, hereditary disease, and idiopathic etiologies. For patients presenting with brachial or lumbosacral plexopathy, dedicated plexus MRI is the most appropriate initial imaging modality for all clinical scenarios and can identify processes both intrinsic and extrinsic to the nerves. Other imaging tests may be appropriate for initial imaging depending on the clinical scenario. This document addresses initial imaging strategies for brachial and lumbosacral plexopathy in the following clinical situations: nontraumatic plexopathy with no known malignancy, traumatic plexopathy (not perinatal), and plexopathy occurring in the context of a known malignancy or posttreatment syndrome. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Comparison of electrodiagnosis, neurosonography and MR neurography in localization of ulnar neuropathy at the elbow

INTRODUCTION

In patients with ulnar neuropathy at the elbow (UNE) the precise determination of the site of lesion is important for subsequent differential diagnostic considerations and therapeutic management. Due to a paucity of comparable data, to better define the role of different diagnostic tests, we performed the first prospective study comparing the diagnostic accuracy of short segment nerve stimulation, nerve ultrasonography, MR neurography (MRN), and diffusion tensor imaging (DTI) in patients with UNE.

METHODS

UNE was clinically diagnosed in 17 patients with 18 affected elbows. For all 18 affected elbows in patients and 20 elbows in 10 healthy volunteers, measurements of all different diagnostic tests were performed at six anatomical positions across the elbow with measuring points from distal (D4) to proximal (P6) in relation to the medial epicondyle (P0). Additional qualitative assessment regarding structural changes of surrounding nerve anatomy was conducted.

RESULTS

The difference between affected arms of patients and healthy control arms were most frequently the largest at measure intervals D2 to P0 and P0 to P2 for electrophysiological testing, or measure points P0 and P2 for all other devices, respectively. At both levels P0 and at P2, T2 contrast-to-noise ratio (CNR) of MRN and mean diffusivity (MD) of DTI-based MRN showed best accuracies.

DISCUSSION

This study revealed differences in diagnostic performance of tests concerning a specific location of UNE, with better results for T2 contrast to noise ratio (CNR) in MRN and mean diffusivity of DTI-based MRN. Additional testing with MRN and nerve ultrasonography is recommended to uncover anatomical changes.

Identifying lumbosacral plexus nerve root abnormalities in patients with sciatica using 3T readout-segmented echo-planar diffusion weighted MR neurography

Objectives

To investigate the accuracy of Diffusion Weighted Imaging (DWI) using the Readout Segmentation of Long Variable Echo-trains (RESOLVE) sequence in detecting lumbosacral nerve abnormalities.

Methods

Following institutional ethics committee approval, patients with sciatica-type lower limb radicular symptoms (n = 110) were recruited and prospectively scanned using 3T MRI. Additional participants (n = 17) who underwent neurophysiological testing (EMG/NCV), were also prospectively studied. In addition to routine lumbar spine MRI, a DWI-RESOLVE sequence of the lumbosacral plexus was performed. Two radiologists, blinded to the side of patient symptoms, independently evaluated the MR images. The size and signal intensity changes of the nerves were evaluated using ordinal 4-point Likert-scales. Signal-to-noise ratio (SNR), apparent diffusion coefficient (ADC) and size were measured for affected and normal nerves. Inter-observer agreement was determined with kappa statistics; κ.

Results

In patients who did not undergo EMG/NCV testing (n = 110), the DWI-RESOLVE sequence detected lumbosacral nerve abnormalities that correlated with symptoms in 36.3% (40/110). This is a similar percentage to patients who underwent EMG/NCV testing, which was positive and correlated with symptoms in 41.2% (7/17). Inter-observer agreement for evaluation of lumbosacral nerve abnormalities was excellent and ranged from 0.87 to 0.94. SNR and nerve size measurements demonstrated statistically significant differences for the L5 and S1 nerves (p value < 0.05) for patients who did not undergo EMG/NCV testing.

Conclusion

The DWI-RESOLVE sequence is a promising new method that may permit accurate detection and localization of lumbar nerve abnormalities in patients with sciatica.

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.

What abdominal radiologists should know about extragenital endometriosis-associated neuropathy

PURPOSE

The aim of this study is to provide an overview of endometriosis-associated neuropathy and to review main anatomical concepts of intrapelvic peripheral nerves.

METHODS

In this pictorial essay, we review the anatomy of pelvic nerves and imaging features of endometriosis-associated neuropathy. We also evaluate clinical findings, imaging features, and outcome of seven patients with endometriosis-associated neuropathy.

RESULTS

Nerve involvement by endometriosis is rare and may manifest with neurological symptoms, including pain, muscle weakness, bowel and bladder incontinence, and paraplegia. The neural involvement may be isolated or caused by a direct extension of a deep infiltrating endometriosis of the pelvic structure. Magnetic resonance imaging (MRI) is a reliable imaging modality for detecting neural involvement of endometriosis. On MRI, the main imaging features are retractile fibrous tissue and endometriomas. The signal intensity of the endometriotic tissue may vary depending on the age of the hemorrhage and the proportion of endometrial cells and stroma. Early diagnosis and treatment may avoid permanent neural damage.

CONCLUSION

Considering that patients with endometriosis usually undergo pelvic MRI, which is generally reported by a non-musculoskeletal-trained radiologist, abdominal radiologists need to be familiar with the pelvic nerve anatomy and the possible patterns of presentation of neural endometriosis. Early diagnosis may obviate permanent nerve damage and MRI is a reliable tool for the diagnosis.

The Variation of Cross-Sectional Area of the Sciatic Nerve in Flexion-Distraction Technique: A Cross-Sectional Study

OBJECTIVE

The purpose of this study was to compare the cross-sectional area of the sciatic nerve in different positions of spinal manipulation using flexion-distraction technique.

METHODS

Thirty healthy participants were assessed in 6 different flexion-distraction technique positions of varying lumbar, knee, and ankle positions. Participants stood in the following 3 positions with the lumbar in the neutral position: (A) with knee extended, (B) with knee flexed, and (C) with the knee extended and ankle dorsiflexion. Participants then stood in the following 3 positions with the lumbar flexed: (D) with the knee extended, (E) with the knee flexed, and (F) with knee extended and ankle dorsiflexion. The cross-sectional area (CSA) of the sciatic nerve was measured with ultrasound imaging in transverse sections in the posterior medial region of the left thigh. The CSA values measured at each position were compared.

RESULTS

We analyzed 180 ultrasound images. The cross-sectional area of the sciatic nerve (in mm²) in position B (mean; standard deviation) (59.71-17.41) presented a higher mean cross-sectional area value compared with position D (51.18-13.81; P =.005), position F (48.71-15.16; P = .004), and position C (48.37-16.35; P = .009).

CONCLUSION

The combination of knee extension and ankle dorsiflexion reduced the CSA of the sciatic nerve, and flexing the knee and keeping the ankle in the neutral position increased it.

Pragmatic neural tissue management improves short-term pain and disability in patients with sciatica: a single-arm clinical trial

Objectives: To evaluate the clinical effect of sciatic neural mobilization in combination with the treatment of surrounding structures for sciatica patients. Secondly, we were also interested in identifying possible baseline characteristics that may be associated with improvements in pain and disability for sciatica patients. Methods: Twenty-eight patients with a clinical diagnosis of sciatica were treated with neural mobilization, joint mobilization and soft tissue techniques. Pain intensity and lumbar disability were assessed at baseline and after treatment using a Numerical Rating Scale (0-10) and the Oswestry Disability Index (0-100), respectively. The pre- and post-intervention data were compared. The research protocol was registered under the number NCT03663842. Results: Participants attended an average of 16 (SD±5.6) treatment
sessions over an average of 12 weeks. Decrease in pain scores (before median = 8, after median = 2; p < 0.001) and improvement in lumbar disability scores (before median = 33.3%, after median = 15.6%; p < 0.001) were observed. A multiple linear regression analysis showed that duration of pain and age of the patient predicted the disability improvement: F (2, 24) = 4.084, p < 0.030, R² = 0.254. Discussion: Patients with sciatica may benefit from neural mobilization in combination with manual therapy for pain and lumbar disability. Longer pain duration and younger age had a negative influence on lumbar disability improvement.

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.

ACR Appropriateness Criteria® Plexopathy

MRI without and with contrast is the most accurate imaging method to determine whether a process is intrinsic or extrinsic to a nerve of the brachial or lumbosacral plexus. However, there are no Current Procedural Terminology codes to correspond to imaging studies of the brachial or lumbar plexus discretely. This assessment uses "MRI of the brachial plexus" or "MRI of the lumbosacral plexus" as independent entities given that imaging acquisition for the respective plexus differs in sequences and planes compared with those of a routine neck, chest, spine, or pelvic MRI, yet acknowledges the potential variability of ordering practices across institutions. In patients unable to undergo MRI, CT offers the next highest level of anatomic evaluation. In oncologic patients, PET/CT imaging can identify the extent of tumor involvement and be beneficial to differentiate radiation plexitis from tumor recurrence but provides limited resolution of the plexus itself. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer-reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Recent advances in magnetic resonance neuroimaging of lumbar nerve to clinical applications: A review of clinical studies utilizing Diffusion Tensor Imaging and Diffusion-weighted magnetic resonance neurography

Much progress has been made in neuroimaging with Magnetic Resonance neurography and Diffusion Tensor Imaging (DTI) owing to higher magnetic fields and improvements in pulse sequence technology. Reports on lumbar nerve DTI have also increased considerably. Many studies have shown that the use of DTI in lumbar nerve lesions, such as lumbar foraminal stenosis and lumbar disc herniation, makes it possible to capture images of interruptions of tractography at stenotic sties, enabling the diagnosis of stenosis. DTI can also reveal significant decreases in fractional anisotropy (FA) with significant increases in apparent diffusion coefficient (ADC) values in compression lesions. FA values have higher accuracy than ADC values. Furthermore, strong correlations exist between FA values and indications of neurological severity, including the Japanese Orthopedic Association (JOA) score, the Oswestry Disability Index (ODI), and the Roland-Morris Disability Questionnaire (RDQ) in patients with lumbar disc herniation-induced radiculopathy. Most lumbar DTI has become 3T; 3T MRI has made it possible to take high-resolution DTI measurements in a short period of time. However, increased motion artifacts in the magnetic susceptibility effect lead to signal irregularities and image distortion. In the future, high-resolution DTI with reduced field-of-view may become useful in clinical applications, since visualization of nerve lesions and quantification of DTI parameters could allow more accurate diagnoses of lumbar nerve dysfunctions. Future translational studies will be necessary to successfully bring MR neuroimaging of lumbar nerve into clinical use.

MR Neurography of Greater Occipital Nerve Neuropathy: Initial Experience in Patients with Migraine

BACKGROUND AND PURPOSE

MR imaging of peripheral nerves (MR neurography) allows improved assessment of nerve anatomy and pathology. The objective of this study was to evaluate patients with unilateral occipital neuralgia using MR neurography and to assess the differences in greater occipital nerve signal and size between the symptomatic and asymptomatic sides.

MATERIALS AND METHODS

In this case-control evaluation using MR neurography, bilateral greater occipital nerve caliber, signal intensity, signal-to-noise ratios, and contrast-to-noise ratios were determined by 2 observers.

RESULTS

Among 18 subjects with unilateral occipital migraines, the average greater occipital nerve diameter for the symptomatic side was significantly greater at 1.77 ± 0.4 mm than for the asymptomatic side at 1.29 ± 0.25 mm (P = .001). The difference in nerve signal intensity between the symptomatic and asymptomatic sides was statistically significant at 269.06 ± 170.93 and 222.44 ± 170.46, respectively (P = .043). The signal-to-noise ratios on the symptomatic side were higher at 15.79 ± 4.59 compared with the asymptomatic nerve at 14.02 ± 5.23 (P = .009). Contrast-to-noise ratios were significantly higher on the symptomatic side than on the asymptomatic side at 2.57 ± 4.89 and -1.26 ± 5.02, respectively (P = .004). Intraobserver performance was good to excellent (intraclass coefficient correlation, 0.68-0.93), and interobserver performance was fair to excellent (intraclass coefficient correlation, 0.54-0.81).

CONCLUSIONS

MR neurography can be reliably used for the diagnosis of greater occipital nerve neuropathy in patients with unilateral occipital migraines with a good correlation of imaging findings to the clinical presentation.

Apparent diffusion coefficient maps in the assessment of surgical patients with lumbar spine degeneration

Purpose

To assess the utility of apparent diffusion coefficient (ADC) maps for the assessment of patients with advanced degenerative lumbar spine disease and describe characteristic features of ADC maps in various degenerative lumbar spinal conditions.

Methods

T1-weighted, T2-weighted and diffusion weighted (DWI) MR images of 100 consecutive patients admitted to the spinal surgery service were assessed. ADC maps were generated from DWI images using Osyrix software. The ADC values and characteristic ADC maps were assessed in the regions of interest over the different pathological entities of the lumbar spine.

Results

The study included 452 lumbar vertebral segments available for analysis of ADCs. Characteristic ADC map features were identified for protrusion, extrusion and sequester types of lumbar disk herniations, spondylolisthesis, reactive Modic endplate changes, Pfirrmann grades of IVD degeneration, and compromised spinal nerves. Compromised nerve roots had significantly higher mean ADC values than adjacent (p < 0.001), contralateral (p < 0.001) or adjacent contralateral (p < 0.001) nerve roots. Compared to the normal bone marrow, Modic I changes showed higher ADC values (p = 0.01) and Modic 2 changes showed lower ADC values (p = 0.02) respectively. ADC values correlated with the Pfirrmann grading, however differed from herniated and non-herniated disks of the matched Pfirrmann 3 and 4 grades.

Conclusion

Quantitative and qualitative evaluation of ADC mapping may provide additional useful information regarding the fluid dynamics of the degenerated spine and may complement standard MRI imaging protocol for the comprehensive assessment of surgical patients with lumbar spine pathology. ADC maps were advantageous in differentiating reactive bone marrow changes, and more precise assessment of the disk degeneration state. ADC mapping of compressed nerve roots showed promise but requires further investigation on a larger cohort of patients.

Pudendal nerve and branch neuropathy: magnetic resonance neurography evaluation

Pudendal neuralgia is being increasingly recognized as a cause of chronic pelvic pain, which may be related to nerve injury or entrapment. Due to its complex anatomy and branching patterns, the pudendal nerve abnormalities are challenging to illustrate. High resolution 3 T magnetic resonance neurography is a promising technique for the evaluation of peripheral neuropathies. In this article, the authors discuss the normal pudendal nerve anatomy and its variations, technical considerations of pudendal nerve imaging, and highlight the normal and abnormal appearances of the pudendal nerve and its branches with illustrative case examples.

Comparison with Magnetic Resonance Three-Dimensional Sequence for Lumbar Nerve Root with Intervertebral Foramen

Study Design

Prospective study based on magnetic resonance (MR) imaging of the lumbar spinal root of the intervertebral foramen.

Purpose

This study was to compare MR three-dimensional (3D) sequences for the evaluation of the lumbar spinal root of the intervertebral foramen.

Overview of Literature

The diagnosis of spinal disorders by MR imaging is commonly performed using two-dimensional T1- and T2-weighted images, whereas 3D MR images can be used for acquiring further detailed data using thin slices with multi-planar reconstruction.

Methods

On twenty healthy volunteers, we investigated the contrast-to-noise ratio (CNR) of the lumbar spinal root of the intervertebral foramen with a 3D balanced sequence. The sequences used were the fast imaging employing steady state acquisition and the coherent oscillatory state acquisition for the manipulation of image contrast (COSMIC). COSMIC can be used with or without fat suppression (FS). We compared these sequence to determine the optimized visualization sequence for the lumbar spinal root of the intervertebral foramen.

Results

For the CNR between the nerve root and the peripheral tissue, these were no significant differences between the sequences at the entry of foramen. There was a significant difference and the highest CNR was seen with COSMIC-FS for the intra- and extra-foramen.

Conclusions

In this study, the findings suggest that the COSMIC-FS sequences should be used for the internal or external foramen for spinal root disorders.

Changes in lumbosacral spinal nerve roots on diffusion tensor imaging in spinal stenosis

Lumbosacral degenerative disc disease is a common cause of lower back and leg pain. Conventional T1-weighted imaging (T1WI) and T2-weighted imaging (T2WI) scans are commonly used to image spinal cord degeneration. However, these modalities are unable to image the entire lumbosacral spinal nerve roots. Thus, in the present study, we assessed the potential of diffusion tensor imaging (DTI) for quantitative assessment of compressed lumbosacral spinal nerve roots. Subjects were 20 young healthy volunteers and 31 patients with lumbosacral stenosis. T2WI showed that the residual dural sac area was less than two-thirds that of the corresponding normal area in patients from L₃ to S₁ stenosis. On T1WI and T2WI, 74 lumbosacral spinal nerve roots from 31 patients showed compression changes. DTI showed thinning and distortion in 36 lumbosacral spinal nerve roots (49%) and abruption in 17 lumbosacral spinal nerve roots (23%). Moreover, fractional anisotropy values were reduced in the lumbosacral spinal nerve roots of patients with lumbosacral stenosis. These findings suggest that DTI can objectively and quantitatively evaluate the severity of lumbosacral spinal nerve root compression.

Accuracy of MRI in diagnosing peripheral nerve disease: a systematic review of the literature

OBJECTIVE

MRI is increasingly being used to evaluate extracranial peripheral nerve disease in clinical practice. The objective of this study was to systematically review the accuracy of MRI in distinguishing normal from abnormal extracranial peripheral nerves.

CONCLUSION

There is significant heterogeneity between studies investigating the accuracy of MRI. Studies have shown that nerve T2-weighted or STIR hyperintensity, nerve enlargement, and nerve flattening are associated with peripheral nerve disease.

How to image patients with spine pain

Different radiological methods play an important role in the work-up of patients complaining of spine pain. Depending on the symptoms and the suspected underlying etiology different methods are selected. In the following presentation we briefly present the different radiological and magnetic resonance tomography methods that are at hand, give some guidance in which method to use, and present the typical imaging findings in some of the most common conditions that presents with spine pain.

Meralgia paresthetica: 3-Tesla magnetic resonance neurography

OBJECTIVE

To assess the diagnostic accuracy and observer performance of 3-Tesla magnetic resonance neurography (MRN) in the evaluation of meralgia paresthetica (MP).

MATERIALS AND METHODS

Two independent readers were blinded to the clinical diagnosis and evaluated the MRN studies of the pelvis of 11 patients with MP and 28 control participants. In each study, the lateral femoral cutaneous nerves were assessed for signal alteration and/or neuroma formation, indicating lateral femoral cutaneous neuropathy, at various levels along their course. Intra- and inter-observer reliability was evaluated.

RESULTS

Both readers exhibited substantial intraobserver agreement in detecting signal alterations and neuroma formation of the lateral femoral cutaneous nerve (LFCN). The readers demonstrated moderate interobserver agreement in detecting signal alteration of the LFCN and poor interobserver agreement in diagnosing neuroma formation. Sensitivity, specificity, positive predictive value, and negative predictive value of LFCN neuropathy diagnosis were ≥ 71 % and ≥ 94 % for both readers respectively. The diagnostic test accuracy was ≥ 90 % for both readers.

CONCLUSION

3-Tesla MRN provides reliable and accurate diagnostic evaluation of meralgia paresthetica.

Diffusion tensor imaging and T2 relaxometry of bilateral lumbar nerve roots: feasibility of in-plane imaging

Lower back pain is a common problem frequently encountered without specific biomarkers that correlate well with an individual patient's pain generators. MRI quantification of diffusion and T2 relaxation properties may provide novel insight into the mechanical and inflammatory changes that occur in the lumbosacral nerve roots in patients with lower back pain. Accurate imaging of the spinal nerve roots is difficult because of their small caliber and oblique course in all three planes. Two-dimensional in-plane imaging of the lumbosacral nerve roots requires oblique coronal imaging with large field of view (FOV) in both dimensions, resulting in severe geometric distortions using single-shot echo planar imaging (EPI) techniques. The present work describes initial success using a reduced-FOV single-shot spin-echo EPI acquisition to obtain in-plane diffusion tensor imaging (DTI) and T2 mapping of the bilateral lumbar nerve roots at the L4 level of healthy subjects, minimizing partial volume effects, breathing artifacts and geometric distortions. A significant variation in DTI and T2 mapping metrics is also reported along the course of the normal nerve root. The fractional anisotropy is statistically significantly lower in the dorsal root ganglia (0.287 ± 0.068) than in more distal regions in the spinal nerve (0.402 ± 0.040) (p < 10(-5) ). The T2 relaxation value is statistically significantly higher in the dorsal root ganglia (78.0 ± 11.9 ms) than in more distal regions in the spinal nerve (59.5 ± 7.4 ms) (p < 10(-5) ). The quantification of nerve root DTI and T2 properties using the proposed methodology may identify the specific site of any degenerative and inflammatory changes along the nerve roots of patients with lower back pain.

Peripheral MR neurography: approach to interpretation

The magnetic resonance neurography (MRN) examination is rapidly becoming a part of the diagnostic algorithm of patients with peripheral neuropathy; however, because of the technical demands and the lack of required reading skills, the examination is relatively underutilized and is currently limited to a few tertiary care centers. The radiologists with interest in peripheral nerve imaging should be able to perform and interpret this examination to exploit its potential for widespread use. This article outlines the systematic, stepwise approach to its interpretation and a brief discussion of the imaging pitfalls.

Magnetic resonance neurography: diffusion tensor imaging and future directions

Magnetic resonance (MR) neurography has progressed in the past 2 decades because of rapid technological developments in both hardware and software. In addition to improvements in high-resolution anatomic pulse sequences, functional techniques are becoming feasible. This article presents the current state-of-the-art three-dimensional anatomic techniques, discusses the advantages of functional techniques being exploited, and portrays novel contrast types and molecular techniques that are under development and promise a bright future for this rapidly evolving technique.

MR Neurography: Advances

High resolution and high field magnetic resonance neurography (MR neurography, MRN) is shown to have excellent anatomic capability. There have been considerable advances in the technology in the last few years leading to various feasibility studies using different structural and functional imaging approaches in both clinical and research settings. This paper is intended to be a useful seminar for readers who want to gain knowledge of the advancements in the MRN pulse sequences currently used in clinical practice as well as learn about the other techniques on the horizon aimed at better depiction of nerve anatomy, pathology, and potential noninvasive evaluation of nerve degeneration or regeneration.

Comparison of wideband steady-state free precession and T₂-weighted fast spin echo in spine disorder assessment at 1.5 and 3 T

Wideband steady-state free precession (WB-SSFP) is a modification of balanced steady-state free precession utilizing alternating repetition times to reduce susceptibility-induced balanced steady-state free precession limitations, allowing its use for high-resolution myelographic-contrast spinal imaging. Intertissue contrast and spatial resolution of complete-spine-coverage 3D WB-SSFP were compared with those of 2D T₂-weighted fast spin echo, currently the standard for spine T₂-imaging. Six normal subjects were imaged at 1.5 and 3 T. The signal-to-noise ratio efficiency (SNR per unit-time and unit-volume) of several tissues was measured, along with four intertissue contrast-to-noise ratios; nerve-ganglia:fat, intradural-nerves:cerebrospinal fluid, nerve-ganglia:muscle, and muscle:fat. Patients with degenerative and traumatic spine disorders were imaged at both MRI fields to demonstrate WB-SSFP clinical advantages and disadvantages. At 3 T, WB-SSFP provided spinal contrast-to-noise ratios 3.7-5.2 times that of fast spin echo. At 1.5 T, WB-SSFP contrast-to-noise ratio was 3-3.5 times that of fast spin echo, excluding a 1.7 ratio for intradural-nerves:cerebrospinal fluid. WB-SSFP signal-to-noise ratio efficiency was also higher. Three-dimensional WB-SSFP disadvantages relative to 2D fast spin echo are reduced edema hyperintensity, reduced muscle signal, and higher motion sensitivity. WB-SSFP's high resolution and contrast-to-noise ratio improved visualization of intradural nerve bundles, foraminal nerve roots, and extradural nerve bundles, improving detection of nerve compression in radiculopathy and spinal-stenosis. WB-SSFP's high resolution permitted reformatting into orthogonal planes, providing distinct advantages in gauging fine spine pathology.

Three-dimensional magnetic resonance rendering imaging of lumbosacral radiculography in the diagnosis of symptomatic extraforaminal disc herniation with or without foraminal extension

STUDY DESIGN

Retrospective analysis of lumbosacral radiculography using 3-dimensional (3D) magnetic resonance (MR) rendering in patients with extraforaminal disc herniation.

OBJECTIVE

To investigate the significance of lumbosacral radiculography as depicted by 3D MR rendering in the diagnosis of symptomatic extraforaminal disc herniation with or without foraminal extension.

SUMMARY OF BACKGROUND DATA

Given that accurate evaluation of the extraforaminal zones on routine axial and sagittal images is difficult, extraforaminal disc herniations tend to be sometimes overlooked. In addition, oblique coronal images along intervertebral foramina and MR myelography may not clearly demonstrate a detailed full view of nerve root changes. Furthermore, the detection of the morphologic changes of the nerve root is very important for the diagnosis of symptomatic extraforaminal disc herniation. Thus, a useful method for evaluating the nerve root in order to diagnose symptomatic extraforaminal disc herniation is required.

METHODS

Twenty-four patients with extraforaminal and combined (extraforaminal with foraminal) lumbar disc herniations were included in this study. Conventional spin-echo sequence and 3D coronal fast-field echo sequences with selective water excitation by using the principles of the selective excitation technique (Proset imaging) were acquired. Indentation and swelling of the nerve roots and dorsal root ganglion (DRG) in the symptomatic sides and levels were evaluated on the basis of 3D MR rendering images of the lumbar spine. The tilting angle of the nerve root in the symptomatic side was compared with those in the asymptomatic contralateral side again on the basis of the 3D MR rendering images.

RESULTS

Dorsal root ganglion indentation without swelling of the nerve roots was found in 7 patients whereas that with swelling of the nerve roots was observed in 6 patients. Swelling of the entire segment of the nerve from nerve root to spinal nerve (n = 9) or only the spinal nerve (n = 2) was observed in 11 patients. Compared with the contralateral nerve root, 7 patients exhibited a tilting angle abnormality of the ipsilateral nerve root.

CONCLUSION

Based on lumbosacral radiculography through 3D MR rendering, important findings related to the diagnosis of symptomatic extraforaminal disc herniation include swelling of DRG and/or nerve roots and DRG indentation. Ultimately, 3D MR lumbosacral radiculography is a very useful method in the diagnosis of the symptomatic extraforaminal disc herniation.

Peripheral nerve surgery: the role of high-resolution MR neurography

High-resolution MRN is becoming increasingly available due to recent technical advancements, including higher magnetic field strengths (eg, 3T), 3D image acquisition, evolution of novel fat-suppression methods, and improved coil design. This review describes the MRN techniques for obtaining high-quality images of the peripheral nerves and their small branches and imaging findings in normal as well as injured nerves with relevant intraoperative correlations. Various microsurgical techniques in peripheral nerves, such as neurolysis, nerve repairs by using nerve grafts, and conduits are discussed, and MRN findings of surgically treated nerves are demonstrated.

Value of 3D MR lumbosacral radiculography in the diagnosis of symptomatic chemical radiculitis

BACKGROUND AND PURPOSE

Radiologic methods for the diagnosis of chemical radiculitis associated with anular tears in the lumbar spine have been rare. Provocative diskography is one of the methods for diagnosing diskogenic chemical radiculitis but is invasive. A reliable imaging method for replacing provocative diskography and diagnosing chemical radiculitis is required. Our aim was to investigate the value of 3D MR radiculography depicted by rendering imaging in the diagnosis of symptomatic chemical radiculopathy associated with anular tears.

MATERIALS AND METHODS

The study population consisted of 17 patients (age range, 32-88 years) with unilateral radiculopathy. Symptomatic chemical radiculopathy was confirmed with provocative CT diskography and/or provocative selective nerve root block for agreement of sides and levels. Through adhering to the principles of selective excitation (Proset imaging), we acquired 3D coronal FFE sequences with selective water excitation. Morphologic changes in the ipsilateral symptomatic nerve root caused by chemical radiculopathy were compared with those in the contralateral nerve root on 3D MR lumbosacral radiculography.

RESULTS

Pain reproduction at the contrast-leak level during diskography (n = 4) and selective nerve root injection (n = 13) showed concordant pain in all patients. All patients with symptomatic chemical radiculopathy showed nerve root swelling in both ipsilateral levels and sides on 3D MR radiculography. The most common nerve root affected by the chemical radiculopathy was the L5 nerve root (n = 13), while the most common segment exhibiting nerve root swelling was the exit nerve root (n = 16).

CONCLUSIONS

All patients with radicular leg pain caused by chemical radiculopathy showed nerve root swelling on 3D MR radiculography. We believe that in cases without mechanical nerve root compression caused by disk herniation or stenosis in the lumbar spine, nerve root swelling on 3D MR radiculography in patients with radiculopathy associated with an anular tear may be relevant in the diagnosis of symptomatic chemical radiculopathy.

Diffusion-weighted magnetic resonance imaging of the musculoskeletal system: an emerging technology with potential to impact clinical decision making

Diffusion-weighted imaging (DWI) is an application of magnetic resonance imaging that allows the measurement of water movement within and between tissues. Originally developed as a way of detecting early signs of stroke or brain disease, DWI is now being used to study physiologic events within the musculoskeletal system. The accurate measurement of water diffusion can provide important information regarding tissue responses associated with trauma and disease, as well as offer insight toward the mechanism by which physical therapy interventions affect tissues. The purpose of this paper is to discuss the rationale for DWI and its potential clinical and research applications for patients with musculoskeletal disorders. Specific examples of the use of DWI for patients with painful spinal disorders are used as illustrations.

3T MR neurography using three-dimensional diffusion-weighted PSIF: technical issues and advantages

Three-dimensional (3D) diffusion-weighted reversed fast imaging with steady state precession (3D DW-PSIF) MR sequence has the potential to create nerve-specific images. The authors describe the technical issues and their initial experience with this imaging technique employed for peripheral MR neurography.

High-resolution 3T MR neurography of suprascapular neuropathy

RATIONALE AND OBJECTIVES

The purpose of this study was to illustrate the imaging findings on high-resolution 3T magnetic resonance neurography (MRN) in patients with suprascapular nerve (SSN) neuropathy.

MATERIALS AND METHODS

From 3T MRN examinations performed for brachial plexus evaluation in 51 patients over a 3-year period, 15 patients with final diagnosis of suprascapular neuropathy were recruited. The diagnosis was confirmed by electrodiagnostic studies (EDS), clinical, and/or surgical follow-up examinations. Studies performed for the evaluation of tumor, neurofibromatosis, or known diffuse polyneuropathy were excluded.

RESULTS

Two cases were excluded due to suboptimal imaging related to motion degradation and poor signal-to-noise ratio. MRN depicted asymmetric enlargement and/or abnormal T2 hyperintensity of C5 nerve root (10/13 cases), C6 nerve root (10/13 cases), both C5 and C6 nerve roots (7/13 cases), upper trunk (11/13 cases) and SSN (11/13 cases), and other brachial plexus segments involvement (4/13 cases). MR findings of denervation changes in the ipsilateral supraspinatus and infraspinatus muscles were detected in 12/13 cases. In all seven cases where contrast-enhanced images were available, MRN demonstrated enhancement of the denervated muscles but did not provide any additional information regarding the nerve abnormality. None of the MRN studies revealed a mass lesion along the course of the SSN.

CONCLUSION

3T MRN is a valuable diagnostic tool in clinically suspected cases of suprascapular neuropathy, because it can directly demonstrate the nerve abnormality, as well as secondary muscle denervation changes. The reader should be aware that brachial plexopathy may coexist in patients with clinical diagnosis of SSN neuropathy.

Simultaneous visualization of nerves and vessels of the lower extremities using magnetization-prepared susceptibility weighted magnetic resonance imaging at 3.0 T

BACKGROUND

Identifying the extent of involvement of the vessel and nerve, particularly in regard to preoperative evaluation and precise localization of the tumor and its relation to the structures of the extremities, has important applications for advancing the treatment of lower extremity diseases.

OBJECTIVE

To review the technical feasibility of simultaneous visualization of nerves and vessels of the lower extremities by using magnetization-prepared susceptibility-weighted magnetic resonance (MR) imaging (MP-SWI) at 3.0T.

METHODS

Ten healthy volunteers and 10 patients were studied. Optimized MP-SWI, MR neurography (MRN) based on 3D diffusion-weighted steady-state free precession imaging and contrast-enhanced MR angiography (CE-MRA) sequences were performed for each subject. The means of signal-to-noise ratio (SNR)n, SNRv, SNRm, contrast-to-noise ratio (CNR)n,m and CNRv,m were calculated and the certainty of identifying nerves and vessels was determined. CNRn,m between MP-SWI and MRN, and CNRv,m between MP-SWI and CE-MRA were compared.

RESULTS

MP-SWI provides slightly poorer CNRv,m than CE-MRA, whereas MP-SWI provides a better CNRn,m than MRN. In thin-slice-thickness maximum-intensity projection arbitrary planes, the sciatic nerve and its branches were clearly identified (score 1 or 2 of 2) in 17 subjects (85%); the femoral artery and the main branches were identified (score 1 or 2 of 2) in all 20 subjects (100%). The nerves are isointense to slightly hypointense to muscle, and the vessels show a more obvious hyperintense signal than muscle in MP-SWI.

CONCLUSION

The proposed MP-SWI demonstrates the feasibility of simultaneously visualizing nerves and vessels of the lower extremities without using an exogenous contrast agent. It may enable straightforward localization of a disease process to a specific nerve and vessel.

The endoscopic treatment of sciatic nerve entrapment/deep gluteal syndrome

PURPOSE

The purpose of this study was to investigate the historical, clinical, and radiographic presentation of deep gluteal syndrome (DGS) patients, describe the endoscopic anatomy associated with DGS, and assess the effectiveness of endoscopic surgical decompression for DGS.

METHODS

Sciatic nerve entrapment was diagnosed in 35 patients (28 women and 7 men). Portals for inspection of the posterior peritrochanteric space (subgluteal space) of the hip were used as well as an auxiliary posterolateral portal. Patients were treated with sciatic nerve decompression by resection of fibrovascular scar bands, piriformis tendon release, obturator internus, or quadratus femoris or by hamstring tendon scarring. Postoperative outcomes were evaluated with the modified Harris Hip Score (MHHS), verbal analog scale (VAS) pain score, and a questionnaire related specifically to sciatic hip pain.

RESULTS

The mean patient age was 47 years (range, 20 to 66 years). The mean duration of symptoms was 3.7 years (range, 1 to 23 years). The mean preoperative VAS score was 6.9 ± 2.0, and the mean preoperative MHHS was 54.4 ± 13.1 (range, 25.3 to 79.2). Of the patients, 21 reported preoperative use of narcotics for pain; 2 continued to take narcotics postoperatively (unrelated to initial complaint). The mean time of follow-up was 12 months (range, 6 to 24 months). The mean postoperative MHHS increased to 78.0 and VAS score decreased to 2.4. Eighty-three percent of patients had no postoperative sciatic sit pain (inability to sit for >30 minutes).

CONCLUSIONS

Endoscopic decompression of the sciatic nerve appears useful in improving function and diminishing hip pain in sciatic nerve entrapment/DGS.

High-resolution MR neurography of diffuse peripheral nerve lesions

High-resolution MR imaging of peripheral nerves is becoming more common and practical with the increasing availability of 3T magnets. There are multiple reports of MR imaging of peripheral nerves in compression and entrapment neuropathies. However, there is a relative paucity of literature on MRN appearance of diffuse peripheral nerve lesions. We attempted to highlight the salient imaging features of myriad diffuse peripheral nerve disorders and imaging techniques for MRN. Using clinical and pathologically proved relevant examples, we present the MRN appearance of various types of diffuse peripheral nerve lesions, such as traumatic, inflammatory, infectious, hereditary, radiation-induced, neoplastic, and tumor variants.

Steady-state diffusion-weighted imaging: theory, acquisition and analysis

Steady-state diffusion-weighted imaging (DWI) has long been recognized to offer potential benefits over conventional spin-echo methods. This family of pulse sequences is highly efficient and compatible with three-dimensional acquisitions, which could enable high-resolution, low-distortion images. However, the same properties that lead to its efficiency make steady-state imaging highly susceptible to motion and create a complicated signal with dependence on T(1), T(2) and flip angle. Recent developments in gradient hardware, motion-mitigation techniques and signal analysis offer potential solutions to these problems, reviving interest in steady-state DWI. This review offers a description of steady-state DWI signal formation and provides an overview of the current methods for steady-state DWI acquisition and analysis.