Magnetic resonance neurography of the pelvis and lumbosacral plexus

3D MR neurography with gadolinium contrast to improve the visualization of pelvic nerves and the branches

Objective

To evaluate the effectiveness of 3D NerveVIEW sequence with gadolinium contrast on the visualization of pelvic nerves and their branches compared to that without contrast.

Methods

Participants were scanned twice using 3D NerveVIEW sequence with and without gadolinium contrast to acquire pelvic nerve images. The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and contrast ratio of the nerves were calculated and compared to determine the quality of images. To subjectively assess, using a 3-point scale, branch nerves critical to therapeutic decision-making, including the pelvic splanchnic nerve and pelvic plexus, the superior gluteal nerve, and the pudendal nerve.

Results

In the 32 eligible participants after using contrast, the CNRs of the images of nerve-to-bone and nerve-to-vessel significantly increased (p < 0.05). The CR of the images with contrast of all nerve-to-surrounding tissues (i.e., bone, muscle, blood vessels, and fat) were also found significantly higher (p < 0.05). The assessment of observers also shows higher scores for images with contrast compared to images without contrast.

Conclusion

The 3D NerveVIEW sequence combined with gadolinium contrast improved vascular suppression, increased the contrast between pelvic nerves and surrounding tissue, and enhanced the visualization of nerves and their branches. This study may be helpful for the technically challenging preoperative planning of pelvic diseases surgery.

Magnetic Resonance Neurography of the Lumbosacral Plexus

Pain and weakness in the low back, pelvis, and lower extremities are diagnostically challenging, and imaging can be an important step in the workup and management of these patients. Technical advances in magnetic resonance neurography (MRN) have significantly improved its utility for imaging the lumbosacral plexus (LSP). In this article, the authors review LSP anatomy and selected pathology examples. In addition, the authors will discuss technical considerations for MRN with specific points for the branch nerves off the plexus.

Improved 3D DESS MR neurography of the lumbosacral plexus with deep learning and geometric image combination reconstruction

OBJECTIVE

To evaluate the impact of deep learning (DL) reconstruction in enhancing image quality and nerve conspicuity in LSP MRN using DESS sequences. Additionally, a geometric image combination (GIC) method to improve DESS signals' combination was proposed.

MATERIALS AND METHODS

Adult patients undergoing 3.0 Tesla LSP MRN with DESS were prospectively enrolled. The 3D DESS echoes were separately reconstructed with and without DL and DL-GIC combined reconstructions. In a subset of patients, 3D T2-weighted short tau inversion recovery (STIR-T2w) sequences were also acquired. Three radiologists rated 4 image stacks ('DESS S2', 'DESS S2 DL', 'DESS GIC DL' and 'STIR-T2w DL') for bulk motion, vascular suppression, nerve fascicular architecture, and overall nerve conspicuity. Relative SNR, nerve-to-muscle, -fat, and -vessel contrast ratios were measured. Statistical analysis included ANOVA and Wilcoxon signed-rank tests. p < 0.05 was considered statistically significant.

RESULTS

Forty patients (22 females; mean age = 48.6 ± 18.5 years) were enrolled. Quantitatively, 'DESS GIC DL' demonstrated superior relative SNR (p < 0.001), while 'DESS S2 DL' exhibited superior nerve-to-background contrast ratio (p value range: 0.002 to < 0.001). Qualitatively, DESS provided superior vascular suppression and depiction of sciatic nerve fascicular architecture but more bulk motion as compared to 'STIR-T2w DL'. 'DESS GIC DL' demonstrated better nerve visualization for several smaller, distal nerve segments than 'DESS S2 DL' and 'STIR-T2w DL'.

CONCLUSION

Application of a DL reconstruction with geometric image combination in DESS MRN improves nerve conspicuity of the LSP, especially for its smaller branch nerves.

MRI Features of Pelvic Nerve Involvement in Endometriosis

Endometriosis is a common condition that mostly affects people assigned as female at birth. The most common clinical symptom of endometriosis is pain. Although the mechanism for this pain is poorly understood, in some cases, the nerves are directly involved in endometriosis. Endometriosis is a multifocal disease, and the pelvis is the most common location involved. Nerves in the pelvis can become entrapped and involved in endometriosis. Pelvic nerves are visible at pelvic MRI, especially when imaging planes and sequences are tailored for neural evaluation. In particular, high-spatial-resolution anatomic imaging including three-dimensional isotropic imaging and contrast-enhanced three-dimensional short inversion time inversion-recovery (STIR) fast spin-echo sequences are useful for nerve imaging. The most commonly involved nerves are the sciatic, obturator, femoral, pudendal, and inferior hypogastric nerves and the inferior hypogastric and lumbosacral plexuses. Although it is thought to be rare, the true incidence of nerve involvement in endometriosis is not known. Symptoms of neural involvement include pain, weakness, numbness, incontinence, and paraplegia and may be constant or cyclic (catamenial). Early diagnosis of neural involvement in endometriosis is important to prevent irreversible nerve damage and chronic sensorimotor neuropathy. Evidence of irreversible damage can also be seen at MRI, and radiologists should evaluate pelvic nerves that are commonly involved in endometriosis in their search pattern and report template to ensure that this information is incorporated into treatment planning.

Prominent caudal shift of the lumbar plexus roots in spines with 18 thoracolumbar vertebrae

PURPOSE

It remains unclear whether concomitant changes in the thoracolumbar (TL) vertebrae and lumbar plexus roots seen in experimental embryology are present in humans with different vertebral formulas, particularly in humans with 18 TL vertebrae. We thus investigated the human lumbar plexus root changes occurring in spines with an additional TL vertebra (18TL).

METHODS

The lumbosacral plexus was macroscopically dissected in TL anomaly cases found in 161 computed tomography examinations. TL anomalies were distinguished as simple abnormalities in total TL count and abnormal TL trade-offs, i.e., exchanges between the last thoracic and first lumbar vertebrae, and were analyzed separately.

RESULTS

One additional TL vertebra (7C_18TL_5S) was observed in 4/159 cases (2.5%), excluding cases with cervical and sacral abnormalities. Different from the unclear shifts of nerve roots in cases with 16TL and 17TL trade-offs, the 18TL trade-off tended to involve a caudal shift at the cranial limit, without event change at the caudal limit. In addition, only one nerve segment shift was reconfirmed with a change in two vertebral segments from 16 to 18 TL vertebrae.

CONCLUSIONS

We revealed that concomitant changes in the lumbar plexus roots and vertebrae in humans with 18TL vertebrae may become more pronounced than those in humans with 16 or 17TL vertebrae, by approaching the typical mammalian TL formula (19TL). This study showed that the TL formula can be used to estimate changes in the lumbar plexus roots, which may assist in the planning of nerve-sparing spinal and pelvic surgery.

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.

Perineural Invasion and Spread in Common Abdominopelvic Diseases: Imaging Diagnosis and Clinical Significance

Malignancies and other diseases may spread by multiple pathways, including direct extension, hematogenous spread, or via lymphatic vessels. A less-well-understood route is the peripheral nervous system, which is known as perineural spread (PNS). In addition to accounting for pain and other neurologic symptoms, PNS affects both disease prognosis and management. Although PNS is commonly discussed in relation to head and neck tumors, there is emerging data regarding PNS in abdominopelvic malignancies and other conditions such as endometriosis. Due to improved contrast and spatial resolution, perineural invasion, a finding heretofore diagnosed only at pathologic examination, can be detected at CT, MRI, and PET/CT. PNS most commonly manifests as abnormal soft-tissue attenuation extending along neural structures, and diagnosis of it is aided by optimizing imaging parameters, understanding pertinent anatomy, and becoming familiar with the typical neural pathways of spread that largely depend on the disease type and location. In the abdomen, the celiac plexus is a central structure that innervates the major abdominal organs and is the principal route of PNS in patients with pancreatic and biliary carcinomas. In the pelvis, the lumbosacral plexus and inferior hypogastric plexus are the central structures and principal routes of PNS in patients with pelvic malignancies. Although the imaging findings of PNS may be subtle, a radiologic diagnosis can have a substantial effect on patient care. Knowledge of anatomy and known routes of PNS and optimizing imaging parameters is of utmost importance in providing key information for prognosis and treatment planning. © RSNA, 2023 Supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article. Quiz questions for this article are available through the Online Learning Center.

Multi-echo in steady-state acquisition improves MRI image quality and lumbosacral radiculopathy diagnosis efficacy compared with T2 fast spin-echo sequence

PURPOSE

This study compares the performance of a 4-min multi-echo in steady-state acquisition (MENSA) with a 6-min fast spin echo with variable flip angle (CUBE) protocol for the assessment of lumbosacral plexus nerve root lesions.

METHODS

Seventy-two subjects underwent MENSA and CUBE sequences on a 3.0-T MRI scanner. Two musculoskeletal radiologists independently assessed the images for quality and diagnostic capability. A qualitative assessment scoring system for image quality and quantitative nerve signal-to-noise ratio (SNR) and iliac vein and muscle contrast-to-noise ratios (CNR) was applied. Using surgical reports as the reference, sensitivity, specificity, accuracy, and area under the receiver operating characteristic curves (AUC) were evaluated. Intraclass correlation coefficients (ICC) and weighted kappa were used to calculate reliability.

RESULTS

MENSA image quality rating (3.679 ± 0.47) was higher than for CUBE images (3.038 ± 0.68), and MENSA showed higher mean nerve root SNR (36.935 ± 8.33 vs. 27.777 ± 7.41), iliac vein CNR (24.678 ± 6.63 vs. 5.210 ± 3.93), and muscle CNR (19.414 ± 6.07 vs. 13.531 ± 0.65) than CUBE (P < 0.05). Weighted kappa and ICC values indicated good reliability. Sensitivity, specificity, and accuracy of diagnosis based on MENSA images were 96.23%, 89.47%, and 94.44%, respectively, and AUC was 0.929, compared with 92.45%, 84.21%, 90.28%, and 0.883 for CUBE images. The two correlated ROC curves were not significantly different. Weighted kappa values for intraobserver (0.758) and interobserver (0.768-0.818) reliability were substantial to perfect.

CONCLUSION

A time-efficient 4-min MENSA protocol exhibits superior image quality and high vascular contrast with the potential to produce high-resolution lumbosacral nerve root images.

MR Neurography of Lumbosacral Plexus: Incremental Value Over XR, CT, and MRI of L Spine With Improved Outcomes in Patients With Radiculopathy and Failed Back Surgery Syndrome

BACKGROUND

Lower back pain is often evaluated using magnetic resonance imaging (MRI) and conventional imaging, which provide incomplete information about the etiology of pain and lead to less than optimal management.

HYPOTHESIS

MR neurography (MRN) of the lumbosacral (LS) plexus renders a more accurate diagnosis, alters the management strategy, and clinical outcomes of radiculopathy or failed back surgery Syndrome (FBSS) patients when compared to the conventional imaging modalities.

STUDY TYPE

Retrospective, cross-sectional.

POPULATION

A total of 356 patients (mean age 65.8 ± 12.3; 48.9% female) from single university hospital over 6 years with MRN of LS plexus were included from a cohort of 14,775 total patients with lumbar spine MR imaging.

ASSESSMENT

Conventional imaging obtained before and after MRN of LS plexus was reevaluated and categorized into three levels based on extent of imaging findings' correlation to presenting clinical symptoms (contributory levels). Clinical notes were reviewed for changes in ordering provider's recommended management and subsequent patients' symptom level pre-MRN to post-MRN.

FIELD STRENGTH/SEQUENCE

A 5 T and 3.0 T. T1-weighted (T1W), T2-weighted (T2W), short T1 inversion recovery (STIR), T1 turbo spin echo (T1 TSE), T2 spectral attenuated inversion recovery (T2 SPAIR).

STATISTICAL TESTS

Chi-squared test. Statistical significance was set at P < 0.05.

RESULTS

A total of 356 total patients (174 females) with mean age ± SD was 65.8 ± 12.3 years, 4.2% of patients imaged with lumbar spine MRI. Definitely contributory studies among X-rays, computed tomography, MRI, and MRN were 3 of the 129 (2.3%), 3 of the 48 (6.2%), 35 of the 184 (19.0%), and 283 of the 356 (79.8%), respectively. Pre-MRN vs. post-MRN led to change in recommendation in 219 of the 356 (61.5%) patients and 71 of the 99 (71.7%) patients had improved symptoms.

CONCLUSION

MRN of the LS plexus can provide more corroborative image findings for symptom correlation compared to other imaging modalities for accurate diagnosis, effects patient management and leads to positive clinical outcomes in a small subset of patients with radiculopathy or FBSS.

EVIDENCE LEVEL

4 TECHNICAL EFFICACY: Stage 5.

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.

Nerve Entrapments in the Pelvis and Hip

Clinical symptoms of pelvic entrapment neuropathies are widely variable and frequently nonspecific, thus rendering it difficult to localize and diagnose. Magnetic resonance imaging (MRI), and in particular MR neurography, has become increasingly important in the work-up of entrapment neuropathies involving the pelvic and hip nerves of the lumbosacral plexus. The major sensory and motor peripheral nerves of the pelvis and hip include the sciatic nerve, superior and inferior gluteal nerves, femoral nerve, lateral femoral cutaneous nerve, obturator nerve, and pudendal nerve. Familiarity with the anatomy and imaging appearance of normal and pathologic nerves in combination with clinical presentation is crucial in the diagnosis of entrapment neuropathies.

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.

Magnetic resonance tractography of the lumbosacral plexus: Step-by-step

ABSTRACT

MR tractography of the lumbosacral plexus (LSP) is challenging due to the difficulty of acquiring high quality data and accurately estimating the neuronal tracts. We proposed an algorithm for an accurate visualization and assessment of the major LSP bundles using the segmentation of the cauda equina as seed points for the initial starting area for the fiber tracking algorithm.Twenty-six healthy volunteers underwent MRI examinations on a 3T MR scanner using the phased array coils with optimized measurement protocols for diffusion-weighted images and coronal T2 weighted 3D short-term inversion recovery sampling perfection with application optimized contrast using varying flip angle evaluation sequences used for LSP fiber reconstruction and MR neurography (MRN).The fiber bundles reconstruction was optimized in terms of eliminating the muscle fibers contamination using the segmentation of cauda equina, the effects of the normalized quantitative anisotropy (NQA) and angular threshold on reconstruction of the LSP. In this study, the NQA parameter has been used for fiber tracking instead of fractional anisotropy (FA) and the regions of interest positioning was precisely adjusted bilaterally and symmetrically in each individual subject.The diffusion data were processed in individual L3-S2 nerve fibers using the generalized Q-sampling imaging algorithm. Data (mean FA, mean diffusivity, axial diffusivity and radial diffusivity, and normalized quantitative anisotropy) were statistically analyzed using the linear mixed-effects model. The MR neurography was performed in MedINRIA and post-processed using the maximum intensity projection method to demonstrate LSP tracts in multiple planes.FA values significantly decreased towards the sacral region (P < .001); by contrast, mean diffusivity, axial diffusivity, radial diffusivity and NQA values significantly increased towards the sacral region (P < .001).Fiber tractography of the LSP was feasible in all examined subjects and closely corresponded with the nerves visible in the maximum intensity projection images of MR neurography. Usage of NQA instead of FA in the proposed algorithm enabled better separation of muscle and nerve fibers.The presented algorithm yields a high quality reconstruction of the LSP bundles that may be helpful both in research and clinical practice.

Piriformis syndrome: pain response outcomes following CT-guided injection and incremental value of botulinum toxin injection

PURPOSE

Piriformis syndrome is a common pain condition affecting the buttock and posterior hip with or without radiation to the leg, and management of the condition involves many treatments. In this study, we hypothesize that a CT-guided injection with botulinum toxin is more effective in providing pain relief than a CT-guided injection without Botox.

METHODS

Overall, 97 consecutive patients with piriformis syndrome presented for a CT-guided injection of the piriformis muscle and perineural injection of the sciatic nerve. After the injection, the patients received a visual analog scale pain log to record their pain level until the follow-up appointment. P values of less than 0.2 were considered as confounder and adjusted by inverse probability of treatment weighting (IPTW) via propensity score. The effect of botulinum toxin on 48-hour response and duration of response was tested using weighted chi-square test and weighted Kaplan-Meier analysis.

RESULTS

There was a total of 97 patients in the study, and 111 injections, as some patients had bilateral injections. Patients in the Botox group had more 48-hour response than patients in the non-botulinum toxin group (P < 0.001 with IPTW, P = 0.005 without IPTW). Median pain-free survival was 30 days for Botox group and 1 day for non-Botox group (P = 0.059 with IPTW, P = 0.10 without IPTW).

CONCLUSION

CT-guided injections with botulinum toxin for patients with piriformis syndrome are more likely to lead to a positive response and a longer duration of response than patients who receive a CT-guided injection without botulinum toxin. We hope that this study facilitates future prospective randomized blind trials for patients with suspected piriformis syndrome.

Visualizing the autonomic and somatic innervation of the female pelvis with 3D MR neurography: a feasibility study

BACKGROUND

Treatment of female pelvic malignancies often causes pelvic nerve damage. Magnetic resonance (MR) neurography mapping the female pelvic innervation could aid in treatment planning.

PURPOSE

To depict female autonomic and somatic pelvic innervation using a modified 3D NerveVIEW sequence.

MATERIAL AND METHODS

Prospective study in 20 female volunteers (n = 6 normal, n = 14 cervical pathology) who underwent a modified 3D short TI inversion recovery (STIR) turbo spin-echo (TSE) scan with a motion-sensitive driven equilibrium (MSDE) preparation radiofrequency pulse and flow compensation. Modifications included offset independent trapezoid (OIT) pulses for inversion and MSDE refocusing. Maximum intensity projections (MIP) were evaluated by two observers (Observer 1, Observer 2); image quality was scored as 2 = high, 1 = medium, or 0 = low with the sciatic nerve serving as a reference. Conspicuity of autonomic superior (SHP) and bilateral inferior hypogastric plexuses (IHP), hypogastric nerves, and somatic pelvic nerves (sciatic, pudendal) was scored as 2 = well-defined, 1 = poorly defined, or 0 = not seen, and inter-observer agreement was determined.

RESULTS

Images were of medium to high quality according to both observers agreeing in 15/20 (75%) of individuals. SHP and bilateral hypogastric nerves were seen in 30/60 (50%) of cases by both observers. Bilateral IHP was seen in 85% (34/40) by Observer 1 and in 75% (30/40) by Observer 2. Sciatic nerves were well identified in all cases, while pudendal nerves were seen bilaterally by Observer 1 in 65% (26/40) and by Observer 2 in 72.5% (29/40). Agreement between observers for scoring nerve conspicuity was in the range of 60%-100%.

CONCLUSION

Modified 3D NerveVIEW renders high-quality images of the female autonomic and pudendal nerves.

Magnetic resonance neurography of the lumbosacral plexus at 3 Tesla - CSF-suppressed imaging with submillimeter resolution by a three-dimensional turbo spin echo sequence

PURPOSE

To investigate magnetic resonance neurography (MRN) of the lumbosacral plexus (LSP) with cerebrospinal fluid (CSF) suppression by using submillimeter resolution for three-dimensional (3D) turbo spin echo (TSE) imaging.

MATERIALS AND METHODS

Using extended phase graph (EPG) analysis, the signal response of CSF was simulated considering dephasing from coherent motion for frequency-encoding voxel sizes ranging from 0.3 to 1.3 mm and for CSF velocities ranging from 0 to 4 cm/s. In-vivo MRN included 3D TSE data with frequency encoding parallel to the feet/head axis from 15 healthy adults (mean age: 28.5 ± 3.8 years, 5 females; acquisition voxel size: 2 × 2 × 2 mm³) and 16 pediatric patients (mean age: 6.7 ± 4.1 years, 7 females; acquisition voxel size: 0.7 × 0.7 × 1.4 mm³) acquired at 3 Tesla. Five of the adults were scanned repetitively with changing acquisition voxel sizes (1 × 2 × 2 mm³, 0.7 × 2× 2 mm³, and 0.5 × 2 × 2 mm³). Measurements of the bilateral ganglion of the L5 nerve root, averaged between sides, as well as the CSF in the thecal sac were obtained for all included subjects and compared between adults and pediatric patients and between voxel sizes, using a CSF-to-nerve signal ratio (CSFNR).

RESULTS

According to simulations, the CSF signal is reduced along the echo train for moving spins. Specifically, it can be reduced by over 90% compared to the maximum simulated signal for flow velocities above 2 cm/s, and could be most effectively suppressed by considering a frequency-encoding voxel size of 0.8 mm or less. For in-vivo measurements, mean CSFNR was 1.52 ± 0.22 for adults and 0.10 ± 0.03 for pediatric patients (p < .0001). Differences in CSFNR were significant between measurements using a voxel size of 2 × 2 × 2 mm³ and measurements in data with reduced voxel sizes (p ≤ .0012), with submillimeter resolution (particularly 0.5 × 2 × 2 mm³) providing highest CSF suppression.

CONCLUSIONS

Applying frequency-encoding voxel sizes in submillimeter range for 3D TSE imaging with frequency encoding parallel to the feet/head axis may considerably improve MRN of LSP pathology in adults in the future because of favorable CSF suppression.

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.

Update in the evaluation of peripheral nerves by MRI, from morphological to functional neurography

Imaging studies of peripheral nerves have increased considerably in the last ten years. In addition to the classical and still valid study by ultrasound, new neurographic techniques developed from conventional morphological sequences (including 3D isotropic studies with fat suppression) are making it possible to assess different peripheral nerves and plexuses, including small sensory and/or motor branches, with great precision. Diffusion-weighted sequences and diffusion tensor imaging have opened a new horizon in neurographic studies. This new approach provides morphological and functional information about the internal structure and pathophysiology of the peripheral nerves and diseases that involve them. This update reviews the different MR neurography techniques available for the study of the peripheral nerves, with special emphasis on new sequences based on diffusion.

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.

Diffusion tensor imaging of diabetic amyotrophy

OBJECTIVE

To qualitatively and quantitatively characterize the nerves of patients with diabetic amyotrophy (DA) using magnetic resonance neurography (MRN) with diffusion tensor imaging (DTI).

MATERIALS AND METHODS

Forty controls and 13 DA cases were analyzed. 1.5-Tesla and 3.0-Tesla MRN with DTI was used. Qualitative data from 13 patient records were recorded. Region of interest (ROI) measurements were taken of bilateral L3 through S2 lumbosacral nerve roots, femoral nerves, and sciatic nerves. An ANOVA and multiple linear regression analysis were performed. An intraclass correlation coefficient (ICC) was calculated between two readers.

RESULTS

In DA cases, abnormalities of the lumbosacral nerve roots (n = 11 patients), sciatic (n = 10), femoral (n = 13), and obturator nerves (n = 4) were seen; denervation changes of the abdominopelvic muscles were also identified. Quantitatively, minimum and mean nerve signals on B600 were significantly less than controls (p < 0.001). Minimum and mean ADC values were significantly greater in cases than in controls (p < 0.001 and p = 0.002 respectively). Mean fractional anisotropy (FA) values were significantly lower in cases than in controls (p = 0.041). There were no significant differences in the minimum FA values between cases and controls. Minimum and mean ADCs correlated positively with highest recorded hemoglobin A1 (HbA1c) while controlling for sex, age, and BMI (β = 0.518, p < 0.001 and β = 0.302, p = 0.020 respectively). ICCs were 0.892 (B600), 0.717 (ADC), and 0.730 (FA).

CONCLUSION

Neuromuscular lesions secondary to DA are qualitatively and quantitatively identified on MRN with DTI, and a positive correlation of ADC levels with serum HbA1c levels exists. Thus, MRN with DTI can be employed as a non-invasive diagnostic tool, if DA is suspected.

Quantitative assessment of diabetic amyotrophy using magnetic resonance neurography-a case-control analysis

OBJECTIVES

To quantitatively characterize diabetic amyotrophy (DA), or diabetic lumbosacral radiculoplexopathy, and compare with controls using magnetic resonance neurography (MRN).

METHODS

Forty controls and 23 DA cases were analyzed qualitatively and quantitatively. Cross-sectional areas (CSAs) of bilateral L3 through S2 lumbosacral nerve roots, femoral nerves, and sciatic nerves (proximal and distal measurements) were measured. A linear model was used to assess the nerve location and case/control effect on angle-corrected CSAs. Intra- and inter-reader analysis was performed using intraclass correlation (ICC).

RESULTS

In DA cases, abnormalities of the lumbosacral nerve roots, sciatic, femoral, and obturator nerves were seen in 21/23, 16/23, 21/23, and 9/23, respectively. Denervation abnormalities of multiple abdominopelvic muscles were seen. Quantitatively, the CSA of all measured LS plexus nerve roots and bilateral femoral nerves were significantly larger in DA cases vs. controls by 45% (95% CI, (30%, 49%); p < 0.001). The ICC was moderate for inter-rater analysis = 0.547 (95% CI, 0.456-0.626) and excellent for intra-rater analysis = 0.90 (95% CI, 0.89-92).

CONCLUSIONS

Multifocal neuromuscular lesions related to diabetic amyotrophy were qualitatively and quantitatively detected on MRN. Qualitative abnormalities distinguished cases from controls, and nerve CSAs of cases were significantly larger than those of controls. Therefore, MRN may be employed as a non-invasive diagnostic tool for the evaluation of diabetic amyotrophy.

KEY POINTS

• Qualitative abnormalities of lumbosacral nerve roots, their peripheral branches, and muscles are seen in DA. • The lumbosacral nerve roots and their peripheral branches in diabetic amyotrophy cases are significantly larger in cross-sectional area than non-diabetic subjects by 45% (95 CI, 30%, 49%; p < 0.001). • The ICC was moderate for inter-rater analysis = 0.547 (95% CI, 0.456-0.626) and excellent for intra-rater analysis = 0.90 (95% CI, 0.89-92).

Retrospective study of the interlaminar approach for percutaneous endoscopic lumbar discectomy with the guidance of pre-operative magnetic resonance neurography

Background

To measure the direct effects of pre-operative magnetic resonance neurography (MRN), and analyze the procedure and clinical outcomes of the percutaneous endoscopic interlaminar discectomy, in order to demonstrate the feasibility and safety of the interlaminar approach.

Methods

In this study, 127 patients who underwent percutaneous endoscopic lumbar discectomy (PELD) and were followed up by more than 12 months, were retrospectively evaluated. The pre-operative demographic data were collected. In addition, the coronal scan and the reconstruction of the lumbosacral plexus were examined to measure the distance between the nerve root and the dural sac at the coronal plane. Furthermore, the post-operative and pre-operative visual analog scale (VAS) scores and Oswestry Disability Index (ODI) were compared.

Results

The mean and minimum values of distance T between the nerve root and dural sac of L5/S1 to L2/3 on the operation side of the MRN images were all larger than 7.3 mm which is the diameter of the working canal. During the follow-up, VAS and ODI data improved significantly compared with their corresponding pre-operative scores (P<0.01). Regarding the post-operative complications, there were 2 (1.57%) cases of hypesthesia and 3 (2.36%) cases of neuropathic pain, which were transient and alleviated in 3 months. In addition, there was 1 (0.79%) case of intervertebral space infection and 1 (0.79%) dural tear. No relapse of disc herniation and iatrogenic instability occurred by the end of the last follow-up.

Conclusions

The MRN indicates that the incidence of herniated disc impingement increases over the distance between the nerve root and the dural sac, thus making the interlaminar approach more suitable for the treatment of herniation. The procedures and clinical outcomes of the IL-PELD demonstrate the safety and advantages of the interlaminar approach.

Diffusion tensor imaging of the sciatic nerve in Charcot-Marie-Tooth disease type I patients: a prospective case-control study

OBJECTIVES

This study aimed to evaluate whether diffusion tensor imaging (DTI) parameters and cross-sectional area (CSA) can differentiate between the sciatic nerve of Charcot-Marie-Tooth (CMT) disease type I (demyelinating form) patients and that of controls.

METHODS

This prospective comparison study included 18 CMT type I patients and 18 age/sex-matched volunteers. Magnetic resonance imaging including DTI and axial T2-weighted Dixon sequence was performed for each subject. Region of interest analysis was independently performed by two radiologists on each side of the sciatic nerve at four levels: hamstring tendon origin (level 1), lesser trochanter of the femur (level 2), gluteus maximus tendon insertion (level 3), and mid-femur (level 4). Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were calculated. The CSA of the sciatic nerve bundle was measured using axial water-only image at each level. Comparisons of DTI parameters between the two groups were performed using the two-sample t test and Mann-Whitney U test. Interobserver agreement analysis was also conducted.

RESULTS

Interobserver agreement was excellent for all DTI parameter analyses. FA was significantly lower at all four levels in CMT patients than controls. RD, MD, and CSA were significantly higher at all four levels in CMT patients. AD was significantly higher at level 2 in CMT patients.

CONCLUSION

DTI assessment of the sciatic nerve is reproducible and can discriminate the demyelinating nerve pathology of CMT type I patients from normal nerves. The CSA of the sciatic nerve is also a potential parameter for diagnosing nerve abnormality in CMT type I patients.

KEY POINTS

• Diffusion tensor imaging parameters of the sciatic nerve at proximal to mid-femur level revealed significant differences between the Charcot-Marie-Tooth disease patients and controls. • The cross-sectional area of the sciatic nerve was significantly larger in the Charcot-Marie-Tooth disease patients. • Interobserver agreement was excellent (intraclass coefficient > 0.8) for all diffusion tensor imaging parameter analyses.

Role of MR Neurography in Groin and Genital Pain: Ilioinguinal, Iliohypogastric, and Genitofemoral Neuralgia

OBJECTIVE

Chronic neuralgia of the border nerves (ilioinguinal, iliohypogastric, and genitofemoral) is difficult to diagnose and treat clinically. We examined the role of MR neurography (MRN) in the evaluation of border nerve abnormalities and the results of treatments directed at the MRN-detected nerve abnormalities.

MATERIALS AND METHODS

This retrospective cross-sectional study included 106 subjects with groin or genital pain (mean [± SD] age, 50.7 ± 15.4 years) who showed mono- or multifocal neuropathy of the border nerves at 3-T MRN. Subjects who underwent CT-guided perineural injection were assessed for pain response. Injection responses were categorized as positive, possible positive, and negative. Subjects who received hyaluronidase, continuous radiofrequency ablation, or surgery were also evaluated for treatment outcomes.

RESULTS

One hundred forty abnormal nerves were positive for neuropathy in 106 studies. Eighty of 106 subjects had single neuropathy, and 26 had multifocal neuropathy. Fifty-eight subjects underwent CT-guided perineural injections, with five receiving bilateral injections (63 injections). Improvement in subjective pain was seen in 53 of 63 cases (84.2%). A statistically significant improvement in pain response was noted in the isolated ilioinguinal nerve block group as compared with the isolated genitofemoral nerve block group (p = 0.0085). Thirteen of 58 subjects received multiple nerve injections at the same sitting. Both groups receiving single or multiple nerve injections had similar improvement in pain scores of 84% and 85%, respectively, although this difference was not statistically significant.

CONCLUSION

Our retrospective analysis showed improved pain relief in subjects who underwent CT-guided nerve blocks on the basis of a positive MRN.

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.

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.

A step towards stereotactic navigation during pelvic surgery: 3D nerve topography

Background

Long-term morbidity after multimodal treatment for rectal cancer is suggested to be mainly made up by nerve-injury-related dysfunctions. Stereotactic navigation for rectal surgery was shown to be feasible and will be facilitated by highlighting structures at risk of iatrogenic damage. The aim of this study was to investigate the ability to make a 3D map of the pelvic nerves with magnetic resonance imaging (MRI).

Methods

A systematic review was performed to identify a main positional reference for each pelvic nerve and plexus. The nerves were manually delineated in 20 volunteers who were scanned with a 3-T MRI. The nerve identifiability rate and the likelihood of nerve identification correctness were determined.

Results

The analysis included 61 studies on pelvic nerve anatomy. A main positional reference was defined for each nerve. On MRI, the sacral nerves, the lumbosacral plexus, and the obturator nerve could be identified bilaterally in all volunteers. The sympathetic trunk could be identified in 19 of 20 volunteers bilaterally (95%). The superior hypogastric plexus, the hypogastric nerve, and the inferior hypogastric plexus could be identified bilaterally in 14 (70%), 16 (80%), and 14 (70%) of the 20 volunteers, respectively. The pudendal nerve could be identified in 17 (85%) volunteers on the right side and in 13 (65%) volunteers on the left side. The levator ani nerve could be identified in only a few volunteers. Except for the levator ani nerve, the radiologist and the anatomist agreed that the delineated nerve depicted the correct nerve in 100% of the cases.

Conclusion

Pelvic nerves at risk of injury are usually visible on high-resolution MRI with dedicated scanning protocols. A specific knowledge of their course and its application in stereotactic navigation is suggested to improve quality of life by decreasing the likelihood of nerve injury.

Electronic supplementary material

The online version of this article (10.1007/s00464-018-6086-3) contains supplementary material, which is available to authorized users.

Demystifying MR Neurography of the Lumbosacral Plexus: From Protocols to Pathologies

Magnetic resonance neurography is a high-resolution imaging technique that allows evaluating different neurological pathologies in correlation to clinical and the electrophysiological data. The aim of this article is to present a review on the anatomy of the lumbosacral plexus nerves, along with imaging protocols, interpretation pitfalls, and most common pathologies that should be recognized by the radiologist: traumatic, iatrogenic, entrapment, tumoral, infectious, and inflammatory conditions. An extensive series of clinical and imaging cases is presented to illustrate key-points throughout the article.

Quantitative magnetic resonance (MR) neurography for evaluation of peripheral nerves and plexus injuries

Traumatic conditions of peripheral nerves and plexus have been classically evaluated by morphological imaging techniques and electrophysiological tests. New magnetic resonance imaging (MRI) studies based on 3D fat-suppressed techniques are providing high accuracy for peripheral nerve injury evaluation from a qualitative point of view. However, these techniques do not provide quantitative information. Diffusion weighted imaging (DWI) and diffusion tensor imaging (DTI) are functional MRI techniques that are able to evaluate and quantify the movement of water molecules within different biological structures. These techniques have been successfully applied in other anatomical areas, especially in the assessment of central nervous system, and now are being imported, with promising results for peripheral nerve and plexus evaluation. DWI and DTI allow performing a qualitative and quantitative peripheral nerve analysis, providing valuable pathophysiological information about functional integrity of these structures. In the field of trauma and peripheral nerve or plexus injury, several derived parameters from DWI and DTI studies such as apparent diffusion coefficient (ADC) or fractional anisotropy (FA) among others, can be used as potential biomarkers of neural damage providing information about fiber organization, axonal flow or myelin integrity. A proper knowledge of physical basis of these techniques and their limitations is important for an optimal interpretation of the imaging findings and derived data. In this paper, a comprehensive review of the potential applications of DWI and DTI neurographic studies is performed with a focus on traumatic conditions, including main nerve entrapment syndromes in both peripheral nerves and brachial or lumbar plexus.

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.

3 Tesla magnetic resonance imaging study of the normal canine femoral and sciatic nerves

Understanding the normal course and optimizing visualization of the canine peripheral nerves of the lumbar plexus, in particular the sciatic and the femoral nerves, is essential when interpreting images of patients with suspected peripheral neuropathies such as inflammatory or neoplastic conditions. The purpose of this prospective, anatomic study was to describe the magnetic resonance imaging (MRI) anatomy of the normal canine femoral and sciatic nerves and to define the sequences in which the nerves are best depicted. A preliminary postmortem cadaver study was performed to determine optimal sequences and imaging protocol. In a second step the optimized technique was implemented on 10 healthy Beagle dogs, included in the study. The applied protocol included the following sequences: T1-weighted, T2-weighted, T2-Spectral Attenuated Inversion Recovery, T1-weighted postcontrast and T1-Spectral Presaturated Inversion Recovery postcontrast. All sequences had satisfactory signal-to-noise ratio and contrast resolution in all patients. The sciatic and femoral nerves were seen in all images. They were symmetric and of homogeneous signal intensity, being iso- to mildly hyperintense to muscle on T2-weighted, mildly hyperintense in T2-Spectral Attenuated Inversion Recovery, and iso- to mildly hypointense in T1-weighted images. No evidence of contrast enhancement in T1-weighted and T1-Spectral Presaturated Inversion Recovery postcontrast sequences was observed. The anatomic landmarks helpful to identify the course of the femoral and sciatic nerves are described in detail. This study may be used as an anatomical reference, depicting the normal canine femoral and sciatic nerves at 3 Tesla MRI.

Imaging of progressive weakness or numbness of central or peripheral origin

Weakness and numbness occur in a variety of patterns that reflect injury to different parts of the central and peripheral nervous system. Progressive symptoms most often signify an underlying structural or degenerative problem. Familiarity with the major descending motor and ascending sensory tracts of the central nervous system, as well as radicular (dermatome and myotome) and peripheral nerve anatomy, is essential. Damage to these tracts and nerve fibers produces characteristic clinical symptoms and signs. Imaging, when used in a hypothesis-driven way, can be a valuable adjunct to the clinical history and physical examination. One of the most useful aspects of imaging is that it allows for differentiation of edema and inflammation from gliosis and atrophy, both of which can be associated with progressive weakness or numbness. Compression of nervous system structures by nonnervous system tissue can also be easily detected. The spectrum of diseases and imaging abnormalities associated with progressive weakness and numbness is highlighted in this review via a series of illustrative cases. In each case, anatomic localization and the key imaging findings are emphasized.

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.

Magnetic Resonance Neurography of the Pelvic Nerves

Chronic pelvic pain syndrome is commonly caused by nerve injury, inflammation, or entrapment. Owing to the complex anatomy and branching patterns of pelvic nerves, pelvic neuropathies are often difficult to illustrate and diagnose. High-resolution 3-T magnetic resonance neurography is a promising technique for the evaluation of peripheral neuropathy. In this article, the authors discuss the normal anatomy of major pelvic nerves, technical considerations of high-resolution imaging, and normal and abnormal imaging appearances with relevant case examples.

Magnetic resonance neurography in the diagnosis of neuropathies of the lumbosacral plexus: a pictorial review

Magnetic resonance neurography (MRN) is an important tool to detect abnormalities of peripheral nerves. This pictorial review demonstrates the MRN features of a variety of neuropathies affecting the lumbosacral plexus (LSP) and lower extremity nerves, drawn from over 1200 MRNs from our institution and supplemented by the literature. Abnormalities can be due to spinal compression, extraspinal compression, malignancy, musculoskeletal disease, iatrogenesis, inflammation, infection, and idiopathic disorders. We discuss indications and limitations of MRN in diagnosing LSP neuropathies. As MRN becomes more widely used, physicians must become familiar with the differential diagnosis of abnormalities detectable with MRN of the LSP.

3D MR Neurography of the Lumbosacral Plexus: Obtaining Optimal Images for Selective Longitudinal Nerve Depiction

BACKGROUND AND PURPOSE

The number of centers currently performing 3D fat-suppressed isotropic imaging is limited. If the angular orientations of the major lumbosacral plexus nerves on 3D isotropic MR neurography could be determined, similar planes could be prescribed during acquisition of 2D or 3D nonisotropic techniques for optimal depiction of various nerves. Our aim was to determine oblique sagittal and coronal angular measurements for longitudinal depiction of lumbosacral plexus nerves. Interobserver and intraobserver performance and mean calibers of sciatic and femoral nerves were also determined.

MATERIALS AND METHODS

A consecutive series of lumbosacral plexus MR neurography examinations with 3D nerve-selective imaging performed during a 10-month period on a 3T scanner were evaluated. Two observers performed reconstructions and angular measurements. Sciatic and femoral nerve diameters were measured. Descriptive statistics and intraclass correlation coefficient correlations were used.

RESULTS

There were 52 subjects, 11 men and 41 women. Mean sagittal thecal sac angles for coronal demonstration of lumbosacral plexus nerve roots from L1 to S1 for 2 independent observers measured 13.58° ± 2.87° and 13.61° ± 2.18°. Mean sagittal femoral nerve angles were 27.78° ± 4.81° and 28.94° ± 4.49°, and mean sagittal sciatic nerve angles were -10.7° ± 3.75° and -11.82° ± 2.87°. Coronal angular measurements of the femoral and sciatic nerves were similar. The intraclass correlation coefficient was moderate (0.582-0.671) for interobserver performance. For intraobserver performance among various angular measurements, the intraclass correlation coefficient was moderate to good (0.586-0.788). Femoral nerve caliber on MR imaging was almost half that of the sciatic nerve. Mean right femoral nerve thickness was 4.52 ± 1.11 mm and 4.85 ± 0.64 mm for the 2 observers, and mean left femoral nerve thickness was 4.48 ± 0.97 mm and 4.94 ± 0.57 mm. Mean right sciatic nerve thickness was 9.71 ± 1.76 mm and 9.94 ± 0.83 mm, and mean left sciatic nerve thickness was 10.03 ± 1.71 mm and 9.98 ± 0.99 mm.

CONCLUSIONS

Angular lumbosacral plexus measurements aid in the prescription of different planes on MR imaging for the optimal longitudinal demonstration of nerves.

Deep gluteal syndrome: anatomy, imaging, and management of sciatic nerve entrapments in the subgluteal space

Deep gluteal syndrome (DGS) is an underdiagnosed entity characterized by pain and/or dysesthesias in the buttock area, hip or posterior thigh and/or radicular pain due to a non-discogenic sciatic nerve entrapment in the subgluteal space. Multiple pathologies have been incorporated in this all-included "piriformis syndrome," a term that has nothing to do with the presence of fibrous bands, obturator internus/gemellus syndrome, quadratus femoris/ischiofemoral pathology, hamstring conditions, gluteal disorders and orthopedic causes. The concept of fibrous bands playing a role in causing symptoms related to sciatic nerve mobility and entrapment represents a radical change in the current diagnosis of and therapeutic approach to DGS. The development of periarticular hip endoscopy has led to an understanding of the pathophysiological mechanisms underlying piriformis syndrome, which has supported its further classification. A broad spectrum of known pathologies may be located nonspecifically in the subgluteal space and can therefore also trigger DGS. These can be classified as traumatic, iatrogenic, inflammatory/infectious, vascular, gynecologic and tumors/pseudo-tumors. Because of the ever-increasing use of advanced magnetic resonance neurography (MRN) techniques and the excellent outcomes of the new endoscopic treatment, radiologists must be aware of the anatomy and pathologic conditions of this space. MR imaging is the diagnostic procedure of choice for assessing DGS and may substantially influence the management of these patients. The infiltration test not only has a high diagnostic but also a therapeutic value. This article describes the subgluteal space anatomy, reviews known and new etiologies of DGS, and assesses the role of the radiologist in the diagnosis, treatment and postoperative evaluation of sciatic nerve entrapments, with emphasis on MR imaging and endoscopic correlation.

Diffusion-weighted MR neurography of the brachial and lumbosacral plexus: 3.0 T versus 1.5 T imaging

PURPOSE

To compare intraindividually the nerve conspicuity of the brachial and lumbosacral plexus on diffusion-weighted (DW) MR neurography (MRN) at two different field strengths.

MATERIALS AND METHODS

16 healthy volunteers were investigated at 3.0 T and 1.5 T applying optimized variants of a DW spin-echo echo-planar imaging sequence with short TI inversion recovery fat suppression. Full-volume (FV) and curved sub-volume (CSV) maximum intensity projection (MIP) images were reconstructed and nerve conspicuity was visually assessed. Moreover, visible length and sharpness of the nerves were quantitatively analyzed.

RESULTS

On FV MIP images, nerve conspicuity at 3.0 T compared to 1.5 T was worse for brachial plexus (P=0.00228), but better for lumbosacral plexus (P=0.00666). On CSV MIP images, nerve conspicuity did not differ significantly for brachial plexus, but was better at 3.0 T for lumbosacral plexus (P=0.00091). The visible length of the analyzed nerves did not differ significantly with the exception of some lumbosacral nerves, which were significantly longer at 3.0 T. The sharpness of all investigated nerves was significantly higher at 3.0 T by about 40-60% for cervical and 97-169% for lumbosacral nerves.

CONCLUSION

DW MRN imaging at 3.0 T compared to 1.5 T is superior for lumbosacral plexus, but not for brachial plexus.