MR Neurography: Diagnostic Imaging in the PNS

Surgical Management of Chronic Neuropathic Burn Pain

Burn-related chronic neuropathic pain can contribute to a decreased quality of life. When medical and pharmacologic therapies prove ineffective, patients should undergo evaluation for surgical intervention, consisting of a detailed physical examination and elective diagnostic nerve block, to identify an anatomic cause of pain. Based on symptoms and physical examination findings, particularly Tinel's sign, treatments can vary, including a trial of laser therapies, fat grafting, or nerve surgeries (nerve decompression, neuroma excision, targeted muscle reinnervation, regenerative peripheral nerve interfaces, and vascularized denervated muscle targets). It is essential to counsel patients to establish appropriate expectations prior to treatment with a multidisciplinary team.

Evolution of peripheral nerve changes in early multiple sclerosis-a longitudinal MR neurography study

Objectives

Multiple sclerosis (MS) is a demyelinating disorder of the central nervous system. Increasing evidence indicates additional peripheral nerve involvement in early and chronic disease stages. To investigate the evolution of peripheral nerve changes in patients first diagnosed with MS using quantitative MR neurography.

Materials and methods

This prospective study included 19 patients with newly diagnosed MS according to the revised McDonald criteria (16 female, mean 30.2 ± 7.1 years) and 19 age-/sex-matched healthy volunteers. High-resolution 3 T MR neurography of the sciatic nerve using a quantitative T2-relaxometry sequence was performed, which yielded the biomarkers of T2 relaxation time (T2app) and proton spin density (PSD). Follow-up scans of patients were performed after median of 12 months (range 7-16). Correlation analyses considered clinical symptoms, intrathecal immunoglobulin synthesis, nerve conduction study, and lesion load on brain and spine MRI.

Results

Patients showed increased T2app and decreased PSD compared to healthy controls at initial diagnosis and follow-up (p < 0.001 each). Compared to the initial scan, T2app further increased in patients at follow-up (p = 0.003). PSD further declined by at least 10% in 9/19 patients and remained stable in another 9/19 patients. Correlation analyses did not yield significant results.

Conclusion

Peripheral nerve involvement in MS appears at initial diagnosis and continues to evolve within 1 year follow-up with individual dynamics. Quantitative MRN provides non-invasive biomarkers to detect and monitor peripheral nerve changes in MS.

Unveiling the power of imaging techniques: comparing high-resolution ultrasound and functional MR neurography in peripheral nervous system pathology: a short communication

MRI and ultrasonography are used for diagnosing and helping manage peripheral nervous system pathologies. Multiple studies have compared the diagnostic accuracy of these two modalities, but the results can vary depending on the specific conditions being evaluated. In general, high-resolution ultrasound is considered a reliable and accurate tool for evaluating peripheral nerves, with high sensitivity and specificity. High-resolution ultrasound and functional MR neurography are both noninvasive imaging techniques used to evaluate nerve structures in the body. However, they differ in several technical aspects like imaging modality, spatial resolution, field of view, image quality, and accessibility. Establishing consensus on image acquisition techniques, and reporting formats to facilitate effective communication and comparison of results will further enhance the outcomes. The use of advanced ultrasound techniques, such as contrast-enhanced ultrasound, elastography, and ultrasound biomicroscopy, should be promoted for better visualization and characterization of nervous tissues, like transcranial Doppler for cerebrovascular evaluation.

Biomarkers in 5q-associated spinal muscular atrophy-a narrative review

5q-associated spinal muscular atrophy (SMA) is a rare genetic disease caused by mutations in the SMN1 gene, resulting in a loss of functional SMN protein and consecutive degeneration of motor neurons in the ventral horn. The disease is clinically characterized by proximal paralysis and secondary skeletal muscle atrophy. New disease-modifying drugs driving SMN gene expression have been developed in the past decade and have revolutionized SMA treatment. The rise of treatment options led to a concomitant need of biomarkers for therapeutic guidance and an improved disease monitoring. Intensive efforts have been undertaken to develop suitable markers, and numerous candidate biomarkers for diagnostic, prognostic, and predictive values have been identified. The most promising markers include appliance-based measures such as electrophysiological and imaging-based indices as well as molecular markers including SMN-related proteins and markers of neurodegeneration and skeletal muscle integrity. However, none of the proposed biomarkers have been validated for the clinical routine yet. In this narrative review, we discuss the most promising candidate biomarkers for SMA and expand the discussion by addressing the largely unfolded potential of muscle integrity markers, especially in the context of upcoming muscle-targeting therapies. While the discussed candidate biomarkers hold potential as either diagnostic (e.g., SMN-related biomarkers), prognostic (e.g., markers of neurodegeneration, imaging-based markers), predictive (e.g., electrophysiological markers) or response markers (e.g., muscle integrity markers), no single measure seems to be suitable to cover all biomarker categories. Hence, a combination of different biomarkers and clinical assessments appears to be the most expedient solution at the time.

The Peripheral Nerve Surgeon's Role in the Management of Neuropathic Pain

Neuropathic pain (NP) underlies significant morbidity and disability worldwide. Although pharmacologic and functional therapies attempt to address this issue, they remain incompletely effective for many patients. Peripheral nerve surgeons have a range of techniques for intervening on NP. The aim of this review is to enable practitioners to identify patients with NP who might benefit from surgical intervention. The workup for NP includes patient history and specific physical examination maneuvers, as well as imaging and diagnostic nerve blocks. Once diagnosed, there is a range of options surgeons can utilize based on specific causes of NP. These techniques include nerve decompression, nerve reconstruction, nerve ablative techniques, and implantable nerve-modulating devices. In addition, there is an emerging role for preoperative involvement of peripheral nerve surgeons for cases known to carry a high risk of inducing postoperative NP. Lastly, we describe the ongoing work that will enable surgeons to expand their armamentarium to better serve patients with NP.

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

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

MRI correlates of motoneuron loss in SMA

BACKGROUND

Magnetic resonance imaging (MRI) is currently explored as supplemental tool to monitor disease progression and treatment response in various neuromuscular disorders. We here assessed the utility of a multi-parametric magnetic resonance imaging (MRI) protocol including quantitative water T₂ mapping, Dixon-based proton density fat fraction (PDFF) estimation and diffusion tensor imaging (DTI) to detect loss of spinal motor neurons and subsequent muscle damage in adult SMA patients.

METHODS

Sixteen SMA patients and 13 age-matched controls were enrolled in this prospective, longitudinal study. All participants underwent MRI imaging including measurements of Dixon-based PDFF and DTI of the sciatic nerve. SMA patients furthermore underwent measurements of muscle water T₂ (T_2w) of the biceps femoris muscle (BFM) and quadriceps femoris muscle (QFM). Ten participants returned for a second scan six months later. MRI parameter were correlated with clinical data. All patients were on nusinersen treatment.

RESULTS

There were significantly higher intramuscular fat fractions in the BFM and QFM of SMA patients compared to healthy controls at baseline and after 6 months. Furthermore, T2 values significantly correlated positively with intramuscular fat fractions. The Hammersmith functional motor scale significantly correlated with the QFM's intramuscular fat fractions. DTI scans of the sciatic nerve were not significantly different between the two groups.

CONCLUSION

This study demonstrates that, water T₂ mapping and Dixon-based PDFF estimation may distinguish between adult SMA patients and controls, due to massive intramuscular fat accumulation in SMA. More extensive long-term studies are warranted to further evaluate these two modalities as surrogate markers in SMA patients during treatment.

Quantification and Proximal-to-Distal Distribution Pattern of Tibial Nerve Lesions in Relapsing-Remitting Multiple Sclerosis : Assessment by MR Neurography

PURPOSE

Recent studies suggest an involvement of the peripheral nervous system (PNS) in multiple sclerosis (MS). Here, we characterize the proximal-to-distal distribution pattern of peripheral nerve lesions in relapsing-remitting MS (RRMS) by quantitative magnetic resonance neurography (MRN).

METHODS

A total of 35 patients with RRMS were prospectively included and underwent detailed neurologic and electrophysiologic examinations. Additionally, 30 age- and sex-matched healthy controls were recruited. 3T MRN with anatomical coverage from the proximal thigh down to the tibiotalar joint was conducted using dual-echo 2‑dimensional relaxometry sequences with spectral fat saturation. Quantification of PNS involvement was performed by evaluating microstructural (proton spin density (ρ), T2-relaxation time (T2_app)), and morphometric (cross-sectional area, CSA) MRN markers in every axial slice.

RESULTS

In patients with RRMS, tibial nerve lesions at the thigh and the lower leg were characterized by a decrease in T2_app and an increase in ρ compared to controls (T2_app thigh: p < 0.0001, T2_app lower leg: p = 0.0040; ρ thigh: p < 0.0001; ρ lower leg: p = 0.0098). An additional increase in nerve CSA was only detectable at the thigh, while the semi-quantitative marker T2w-signal was not altered in RRMS in both locations. A slight proximal-to-distal gradient was observed for T2_app and T2-signal, but not for ρ.

CONCLUSION

PNS involvement in RRMS is characterized by a decrease in T2_app and an increase in ρ, occurring with proximal predominance at the thigh and the lower leg. Our results indicate microstructural alterations in the extracellular matrix of peripheral nerves in RRMS and may contribute to a better understanding of the pathophysiologic relevance of PNS involvement.

Dorsal Root Ganglion Volumetry by MR Gangliography

BACKGROUND AND PURPOSE

Dorsal root ganglion MR imaging (MR gangliography) is increasingly gaining clinical-scientific relevance. However, dorsal root ganglion morphometry by MR imaging is typically performed under the assumption of ellipsoid geometry, which remains to be validated.

MATERIALS AND METHODS

Sixty-four healthy volunteers (37 [57.8%] men; mean age, 31.5 [SD, 8.3] years) underwent MR gangliography of the bilateral L4-S2 levels (3D-T2WI TSE spectral attenuated inversion recovery-sampling perfection with application-optimized contrasts by using different flip angle evolution, isotropic voxels = 1.1 mm³, TE = 301 ms). Ground truth dorsal root ganglion volumes were bilaterally determined for 96 dorsal root ganglia (derivation cohort) by expert manual 3D segmentation by 3 independent raters. These ground truth dorsal root ganglion volumes were then compared with geometric ellipsoid dorsal root ganglion approximations as commonly practiced for dorsal root ganglion morphometry. On the basis of the deviations from ellipsoid geometry, improved volume estimation could be derived and was finally applied to a large human validation cohort (510 dorsal root ganglia).

RESULTS

Commonly used equations of ellipsoid geometry underestimate true dorsal root ganglion volume by large degrees (factor = 0.42-0.63). Ground truth segmentation enabled substantially optimizing dorsal root ganglion geometric approximation using its principal axes lengths by deriving the dorsal root ganglion volume term of [Formula: see text]. Using this optimization, the mean volumes of 510 lumbosacral healthy dorsal root ganglia were as follows: L4: 211.3 (SD, 52.5) mm³, L5: 290.7 (SD, 90.9) mm³, S1: 384.2 (SD, 145.0) mm³, and S2: 192.4 (SD, 52.6) mm³. Dorsal root ganglion volume increased from L4 to S1 and decreased from S1 to S2 (P < .001). Dorsal root ganglion volume correlated with subject height (r = . 22, P < .001) and was higher in men (P < .001).

CONCLUSIONS

Dorsal root ganglion volumetry by measuring its principal geometric axes on MR gangliography can be substantially optimized. By means of this optimization, dorsal root ganglion volume distribution was estimated in a large healthy cohort for the clinically most relevant lumbosacral levels, L4-S2.

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

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

Magnetic Resonance Neurography: Improved Diagnosis of Peripheral Neuropathies

Peripheral neuropathies account for the most frequent disorders seen by neurologists, and causes are manifold. The traditional diagnostic gold-standard consists of clinical neurologic examinations supplemented by nerve conduction studies. Due to well-known limitations of standard diagnostics and atypical clinical presentations, establishing the correct diagnosis can be challenging but is critical for appropriate therapies. Magnetic resonance neurography (MRN) is a relatively novel technique that was developed for the high-resolution imaging of the peripheral nervous system. In focal neuropathies, whether traumatic or due to nerve entrapment, MRN has improved the diagnostic accuracy by directly visualizing underlying nerve lesions and providing information on the exact lesion localization, extension, and spatial distribution, thereby assisting surgical planning. Notably, the differentiation between distally located, complete cross-sectional nerve lesions, and more proximally located lesions involving only certain fascicles within a nerve can hold difficulties that MRN can overcome, when basic technical requirements to achieve sufficient spatial resolution are implemented. Typical MRN-specific pitfalls are essential to understand in order to prevent overdiagnosing neuropathies. Heavily T2-weighted sequences with fat saturation are the most established sequences for MRN. Newer techniques, such as T2-relaxometry, magnetization transfer contrast imaging, and diffusion tensor imaging, allow the quantification of nerve lesions and have become increasingly important, especially when evaluating diffuse, non-focal neuropathies. Innovative studies in hereditary, metabolic or inflammatory polyneuropathies, and motor neuron diseases have contributed to a better understanding of the underlying pathomechanism. New imaging biomarkers might be used for an earlier diagnosis and monitoring of structural nerve injury under causative treatments in the future.

MRI DTI and PDFF as Biomarkers for Lower Motor Neuron Degeneration in ALS

Objective

To evaluate the utility of nerve magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), and muscle MRI multi-echo Dixon for assessing lower motor neuron (LMN) degeneration in amyotrophic lateral sclerosis (ALS).

Methods

In this prospective observational cohort study, 14 patients with ALS and 13 healthy controls underwent a multiparametric MRI protocol, including DTI of the sciatic nerve and assessment of muscle proton density fat fraction of the biceps femoris and the quadriceps femoris muscles by a multi-echo Dixon sequence.

Results

In ALS patients, mean fractional anisotropy values of the sciatic nerve were significantly lower than those of healthy controls. The quadriceps femoris, but not the biceps femoris muscle, showed significantly higher intramuscular fat fractions in ALS.

Interpretation

Our study provides evidence that multiparametric MRI protocols might help estimate structural nerve damage and neurogenic muscle changes in ALS.

[Imaging of the hand : What should be considered regarding the nerves?]

BACKGROUND

Peripheral nerve disorders of the hand and wrist are most commonly caused by entrapment neuropathies, while traumatic nerve injuries and neoplasms are less common.

OBJECTIVES

The indication for additional imaging methods and different imaging options, especially in patients with atypical symptoms or remaining unclear etiology of symptoms after completion of standard diagnostics, are presented.

MATERIALS AND METHODS

The imaging methods magnetic resonance (MR) neurography and neurosonography are introduced, and typical findings as well as diagnostic pitfalls are presented.

RESULTS

The diagnostic gold standard, which comprises a past medical history, neurologic examination and electrophysiology, can often establish the diagnosis. Imaging methods, especially MR neurography and neurosonography, are gaining increasing importance in the diagnostic workup of atypical neuropathies, as well as in the determination of the exact lesion location and spatial lesion extension, especially for surgical planning. Recent technical advances allow high-resolution depiction of small distal terminal nerve branches.

CONCLUSIONS

MR neurography allows for the high-resolution depiction of peripheral nerves of the hand and wrist. It can confirm the diagnosis of neuropathy, identify the exact lesion location, and rule out any differential diagnoses. Neurosonography is a time- and cost-efficient alternative diagnostic method.

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.

MR imaging of venous malformations: sciatic nerve infiltration patterns and involved muscle groups

The aim of this retrospective cross-sectional study was to provide an MRI-based examination framework of venous malformations (VMs) infiltrating the sciatic nerve and determine the frequency of nerve infiltration patterns and muscle involvement in correlation to the patients’ quality of life. Pelvic and lower limb MR images of 378 patients with vascular malformations were examined retrospectively. Pain levels and restriction of motion were evaluated with a questionnaire. Cross-sectional areas of affected nerves were compared at standardized anatomical landmarks. Intraneural infiltration patterns and involvement of muscles surrounding the sciatic nerve were documented. Sciatic nerve infiltration occurred in 23/299 patients (7.7%) with VM. In all cases (23/23; 100%), gluteal or hamstring muscles surrounding the nerve were affected by the VM. Infiltrated nerves were enlarged and showed signal alterations (T2-hyperintensity) compared to the unaffected side. Enlarged nerve cross-sectional areas were associated with elevated pain levels. Three nerve infiltration patterns were observed: subepineurial (12/23; 52.2%), subparaneurial (6/23; 26.1%) and combined (5/23; 21.7%) infiltration. This study provides a clinically relevant assessment for sciatic nerve infiltration patterns and muscle involvement of VMs, while suggesting that VMs in gluteal and hamstring muscles require closer investigation of the sciatic nerve by the radiologist.

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

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

Fascicular torsions of the anterior and posterior interosseous nerve in 4 cases: neuroimaging methods to improve diagnosis

Diagnosis of spontaneous fascicular nerve torsions is difficult and often delayed until surgical exploration is performed. This case series raises awareness of peripheral nerve torsions and will facilitate an earlier diagnosis by using nerve ultrasound (NUS) and magnetic resonance neurography (MRN). Four patients with previously ambiguous upper-extremity mononeuropathies underwent NUS and 3T MRN. Neuroimaging detected proximal torsions of the anterior and posterior interosseous nerve fascicles within median or radial nerve trunks in all patients. In NUS, most cases presented with a thickening of affected nerve fascicles, followed by an abrupt caliber decrease, leading to the pathognomonic sausage-like configuration. MRN showed T2-weighted hyperintense signal alterations of fascicles at and distal to the torsion site, and directly visualized the distorted nerves. Three patients had favorable outcomes after being transferred to emergency surgical intervention, while 1 patient with existing chronic muscle atrophy was no longer eligible for surgery. NUS and MRN are complementary diagnostic methods, and both can detect nerve torsions on a fascicular level. Neuroimaging is indispensable for diagnosing fascicular nerve torsions, and should be applied in all unclear cases of mononeuropathy to determine the diagnosis and if necessary, to guide surgical therapies, as only timely interventions enable favorable outcomes.

Magnetization transfer ratio quantifies polyneuropathy in hereditary transthyretin amyloidosis

Objective

To quantify peripheral nerve lesions in symptomatic and asymptomatic hereditary transthyretin amyloidosis with polyneuropathy (ATTRv‐PNP) by analyzing the magnetization transfer ratio (MTR) of the sciatic nerve, and to test its potential as a novel biomarker for macromolecular changes.

Methods

Twenty‐five patients with symptomatic ATTRv‐PNP, 30 asymptomatic carriers of the mutant transthyretin gene (mutTTR), and 20 age‐/sex‐matched healthy controls prospectively underwent magnetization transfer contrast imaging at 3 Tesla. Two axial three‐dimensional gradient echo sequences with and without an off‐resonance saturation rapid frequency pulse were conducted at the right distal thigh. Sciatic nerve regions of interest were manually drawn on 10 consecutive axial slices in the images without off‐resonance saturation, and then transferred to the corresponding slices that were generated by the sequence with the off‐resonance saturation pulse. Subsequently, the MTR and cross‐sectional area (CSA) of the sciatic nerve were evaluated. Detailed neurologic and electrophysiologic examinations were conducted in all ATTRv‐PNP patients and mutTTR‐carriers.

Results

Sciatic nerve MTR and CSA reliably differentiated between ATTRv‐PNP, mutTTR‐carriers, and controls. MTR was lower in ATTRv‐PNP (26.4 ± 0.7; P < 0.0001) and in mutTTR‐carriers (32.6 ± 0.8; P = 0.0005) versus controls (39.4 ± 2.1), and was also lower in ATTRv‐PNP versus mutTTR‐carriers (P = 0.0009). MTR correlated negatively with the NIS‐LL and positively with CMAPs and SNAPs. CSA was higher in ATTRv‐PNP (34.3 ± 1.7 mm³) versus mutTTR‐carriers (26.0 ± 1.1 mm³; P = 0.0005) and versus controls (20.4 ± 1.2 mm³; P < 0.0001). CSA was also higher in mutTTR‐carriers versus controls.

Interpretation

MTR is a novel imaging marker that can quantify macromolecular changes in ATTRv‐PNP and differentiate between symptomatic ATTRv‐PNP and asymptomatic mutTTR‐carriers and correlates with electrophysiology.

A study of diffusion tensor imaging of median nerve in diabetic peripheral neuropathy

Objective

To evaluate the role of diffusion tensor imaging (DTI) in the evaluation of diabetic peripheral neuropathy (DPN) compared to clinical scores and nerve conduction studies (NCS).

Patients and methods

We included 30 patients with diabetes mellitus complaining of neuropathy symptoms and 15 healthy volunteers. All subjects underwent evaluation using 1.5-T DTI of median nerves and NCS. Patients underwent clinical evaluation using the Neuropathy Deficit Score (NDS), Neuropathy Impairment Score in the Lower Limbs (NIS-LL), and Diabetic Neuropathy Examination (DNE) score.

Results

We found statistically significant differences between healthy volunteers and patients in fractional anisotropy (FA) of the distal segment (P = 0.016) and whole median nerve (P = 0.024), apparent diffusion coefficient (ADC) of proximal (P = 0.027) and distal (P < 0.001) segments, and whole median nerve (P = 0.019). Distal segment FA was significantly correlated with NDS (P = 0.003), DNEs (P = 0.003), sensory amplitude (P = 0.048), and motor CV (P = 0.020). Distal segment ADC was significantly correlated with NDS (P = 0.007), NIS-LL (P = 0.003), DNEs (P = 0.01), and sensory amplitude (P = 0.032). The best cut-off value of distal segment for FA was 0.45 (87% sensitivity, 80% specificity) and of distal segment ADC was 1.217 (80% sensitivity and specificity).

Conclusions

Our results suggest that 1.5-T DTI examination of the median nerve can provide useful non-invasive information in patients with DPN.

Trial registration

ClinicalTrials.gov, NCT03934970. Registered on May 1, 2019

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.

Magnetic Resonance Imaging as a Biomarker in Rodent Peripheral Nerve Injury Models Reveals an Age-Related Impairment of Nerve Regeneration

Assessment of myelin integrity in peripheral nerve injuries and pathologies has largely been limited to post-mortem analysis owing to the difficulty in obtaining biopsies without affecting nerve function. This is further encumbered  by the small size of the tissue and its location. Therefore, the development of robust, non-invasive methods is highly attractive. In this study, we used magnetic resonance imaging (MRI) techniques, including magnetization transfer ratio (MTR), to longitudinally and non-invasively characterize both the sciatic nerve crush and lysolecithin (LCP) demyelination models of peripheral nerve injury in rodents. Electrophysiological, gene expression and histological assessments complemented the extensive MRI analyses in young and aged animals. In the nerve crush model, MTR analysis indicated a slower recovery in regions distal to the site of injury in aged animals, as well as incomplete recovery at six weeks post-crush when analyzing across the entire nerve surface. Similar regional impairments were also found in the LCP demyelination model. This research underlines the power of MTR for the study of peripheral nerve injury in small tissues such as the sciatic nerve of rodents and contributes new knowledge to the effect of aging on recovery after injury. A particular advantage of the approach is the translational potential to human neuropathies.

Feasibility of Diffusion Tensor and Morphologic Imaging of Peripheral Nerves at Ultra-High Field Strength

Supplemental digital content is available in the text.

Objectives

The aim of this study was to describe the development of morphologic and diffusion tensor imaging sequences of peripheral nerves at 7 T, using carpal tunnel syndrome (CTS) as a model system of focal nerve injury.

Materials and Methods

Morphologic images were acquired at 7 T using a balanced steady-state free precession sequence. Diffusion tensor imaging was performed using single-shot echo-planar imaging and readout-segmented echo-planar imaging sequences. Different acquisition and postprocessing methods were compared to describe the optimal analysis pipeline. Magnetic resonance imaging parameters including cross-sectional areas, signal intensity, fractional anisotropy (FA), as well as mean, axial, and radial diffusivity were compared between patients with CTS (n = 8) and healthy controls (n = 6) using analyses of covariance corrected for age (significance set at P < 0.05). Pearson correlations with Bonferroni correction were used to determine association of magnetic resonance imaging parameters with clinical measures (significance set at P < 0.01).

Results

The 7 T acquisitions with high in-plane resolution (0.2 × 0.2mm) afforded detailed morphologic resolution of peripheral nerve fascicles. For diffusion tensor imaging, single-shot echo-planar imaging was more efficient than readout-segmented echo-planar imaging in terms of signal-to-noise ratio per unit scan time. Distortion artifacts were pronounced, but could be corrected during postprocessing. Registration of FA maps to the morphologic images was successful. The developed imaging and analysis pipeline identified lower median nerve FA (pisiform bone, 0.37 [SD 0.10]) and higher radial diffusivity (1.08 [0.20]) in patients with CTS compared with healthy controls (0.53 [0.06] and 0.78 [0.11], respectively, P < 0.047). Fractional anisotropy and radial diffusivity strongly correlated with patients' symptoms (r = −0.866 and 0.866, respectively, P = 0.005).

Conclusions

Our data demonstrate the feasibility of morphologic and diffusion peripheral nerve imaging at 7 T. Fractional anisotropy and radial diffusivity were found to be correlates of symptom severity.

Three-Dimensional In vivo Magnetic Resonance Imaging (MRI) of Mouse Facial Nerve Regeneration

MRI (magnetic resonance imaging) is an indispensable tool in the diagnosis of centrals nervous system (CNS) disorders such as spinal cord injury and multiple sclerosis (MS). In contrast, diagnosis of peripheral nerve injuries largely depends on clinical and electrophysiological parameters. Thus, currently MRI is not regularly used which in part is due to small nerve calibers and isointensity with surrounding tissue such as muscles. In this study we performed translational MRI research in mice to establish a novel MRI protocol visualizing intact and injured peripheral nerves in a non-invasive manner without contrast agents. With this protocol we were able to image even very small nerves and nerve branches such as the mouse facial nerve (diameter 100–300 μm) at highest spatial resolution. Analysis was performed in the same animal in a longitudinal study spanning 3 weeks after injury. Nerve injury caused hyperintense signal in T₂-weighted images and an increase in nerve size of the proximal and distal nerve stumps were observed. Further hyperintense signal was observed in a bulb-like structure in the lesion site, which correlated histologically with the production of fibrotic tissue and immune cell infiltration. The longitudinal MR representation of the facial nerve lesions correlated well with physiological recovery of nerve function by quantifying whisker movement. In summary, we provide a novel protocol in rodents allowing for non-invasive, non-contrast agent enhanced, high-resolution MR imaging of small peripheral nerves longitudinally over several weeks. This protocol might further help to establish MRI as an important diagnostic and post-surgery follow-up tool to monitor peripheral nerve injuries in humans.

MR microneurography and quantitative T2 and DP measurements of the distal tibial nerve in CIDP

OBJECTIVE

In this study we investigated the potential of magnetic resonance (MR) micro-neurography to detect morphological and relaxometric changes in distal tibial nerves in patients affected with chronic inflammatory demyelinating polyneuropathy (CIDP), and their associations with clinical and electrophysiological features.

MATERIALS AND METHODS

10 subjects affected with CIDP and 10 healthy subjects were examined. Multiple MR parameters, including the number of fascicles (N), fascicles diameter (FD), total fascicles area (FA), epineurium area (EA), total nerve area (NA), fascicles to nerve ratio (FNR) and quantitative T2 and proton density (PD) were investigated on high resolution MR images of the distal tibial nerve. Those parameters were correlated with clinical scores, age of onset, disease duration and electrophysiologic data.

RESULTS

Median NA and FA were significantly increased in the CIDP population (median values for NA in cm² in CIDP: 0.185; controls: 0.135; p: 0.028; for FA in CIDP 0.136; controls 0.094; p: 0.021). There was no correlation between the parameters investigated and clinical or electrophysiologic features.

CONCLUSION

MR microneurography can detect increased total nerve and fascicle area in distal tibial nerves in CIDP and may be useful for diagnosing CIDP.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The Role of the Peripheral Nerve Surgeon in the Treatment of Pain

Pain is a frequent cause of physician visits. Many physicians find these patients challenging because they often have complicated histories, emotional comorbidities, confusing examinations, difficult problems to fix, and the possibility of factitious complaints for attention or narcotic pain medications. As a result, many patients are lumped into the category of chronic, centralized pain and relegated to pain management. However, recent literature suggests that surgical management of carefully diagnosed generators of pain can greatly reduce patients' pain and narcotic requirements. This article reviews recent literature on surgical management of pain and four specific sources of chronic pain amenable to surgical treatment: painful neuroma, nerve compression, myofascial/musculoskeletal pain, and complex regional pain syndrome type II.

MRI biomarkers of proximal nerve injury in CIDP

Objective

To evaluate the utility of nerve diffusion tensor imaging (DTI), nerve cross‐sectional area, and muscle magnetic resonance imaging (MRI) multiecho Dixon for assessing proximal nerve injury in chronic inflammatory demyelinating polyneuropathy (CIDP).

Methods

In this prospective observational cohort study, 11 patients with CIDP and 11 healthy controls underwent a multiparametric MRI protocol with DTI of the sciatic nerve and assessment of muscle proton‐density fat fraction of the biceps femoris and the quadriceps femoris muscles by multiecho Dixon MRI. Patients were longitudinally evaluated by MRI, clinical examination, and nerve conduction studies at baseline and after 6 months.

Results

In sciatic nerves of CIDP patients, mean cross‐sectional area was significantly higher and fractional anisotropy value was significantly lower, compared to controls. In contrast, muscle proton‐density fat fraction was significantly higher in thigh muscles of patients with CIDP, compared to controls. MRI parameters showed high reproducibility at baseline and 6 months.

Interpretation

Advanced MRI parameters demonstrate subclinical proximal nerve damage and intramuscular fat accumulation in CIDP. Data suggest DTI and multiecho Dixon MRI might be useful in estimating axonal damage and neurogenic muscle changes in CIDP.

Novel pathomechanisms in inflammatory neuropathies

Inflammatory neuropathies are rare autoimmune-mediated disorders affecting the peripheral nervous system. Considerable progress has recently been made in understanding pathomechanisms of these disorders which will be essential for developing novel diagnostic and therapeutic strategies in the future. Here, we summarize our current understanding of antigenic targets and the relevance of new immunological concepts for inflammatory neuropathies. In addition, we provide an overview of available animal models of acute and chronic variants and how new diagnostic tools such as magnetic resonance imaging and novel therapeutic candidates will benefit patients with inflammatory neuropathies in the future. This review thus illustrates the gap between pre-clinical and clinical findings and aims to outline future directions of development.

Sural nerve injury in familial amyloid polyneuropathy: MR neurography vs clinicopathologic tools

OBJECTIVE

To detect and quantify lesions of the small-caliber sural nerve (SN) in symptomatic and asymptomatic transthyretin familial amyloid polyneuropathy (TTR-FAP) by high-resolution magnetic resonance neurography (MRN) in correlation with electrophysiologic and histopathologic findings.

METHODS

Twenty-five patients with TTR-FAP, 10 asymptomatic carriers of the mutated transthyretin gene (mutTTR), and 35 age- and sex-matched healthy controls were prospectively included in this cross-sectional case-control study. All participants underwent 3T MRN with high-structural resolution (fat-saturated, T2-weighted, and double-echo sequences). Total imaging time was ≈45 minutes per patient. Manual SN segmentation was performed from its origin at the sciatic nerve bifurcation to the lower leg with subsequent evaluation of quantitative microstructural and morphometric parameters. Additional time needed for postprocessing was ≈1.5 hours per participant. Detailed neurologic and electrophysiologic examinations were conducted in the TTR group.

RESULTS

T2 signal and proton spin density (ρ) reliably differentiated between TTR-FAP (198.0 ± 13.3, 429.6 ± 15.25), mutTTR carriers (137.0 ± 16.9, p = 0.0009; 354.7 ± 21.64, p = 0.0029), and healthy controls (90.0 ± 3.4, 258.2 ± 9.10; p < 0.0001). Marked differences between mutTTR carriers and controls were found for T2 signal (p = 0.0065) and ρ (p < 0.0001). T2 relaxation time was higher in patients with TTR-FAP only (p = 0.015 vs mutTTR carriers, p = 0.0432 vs controls). SN caliber was higher in patients with TTR-FAP vs controls and in mutTTR carriers vs controls (p < 0.0001). Amyloid deposits were histopathologically detectable in 10 of 14 SN specimens.

CONCLUSIONS

SN injury in TTR-FAP is detectable and quantifiable in vivo by MRN even in asymptomatic mutTTR carriers. Differences in SN T2 signal between controls and asymptomatic mutTTR carriers are derived mainly from an increase of ρ, which overcomes typical limitations of established diagnostic methods as a highly sensitive imaging biomarker for early detection of peripheral nerve lesions.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that MRN accurately identifies asymptomatic mutTTR carriers.

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.

Assessment of the synergic effect of immunomodulation on nerve repair using multiparametric magnetic resonance imaging

INTRODUCTION

The immune system plays a pivotal role in nerve injury. The aim of this study was to determine the role of multiparametric magnetic resonance imaging (MRI) in evaluation of the synergic effect of immunomodulation on nerve regeneration in neurotmesis.

METHODS

Rats with sciatic nerve neurotmesis and surgical repair underwent serial multiparametric MR examinations over an 8-week period after subepineurial microinjection of lipopolysaccharide (LPS) and subsequent subcutaneous injection of FK506 or subepineurial microinjection of LPS or phosphate-buffered saline (PBS) alone.

RESULTS

Nerves treated with immunomodulation showed more prominent regeneration than those treated with LPS or PBS alone and more rapid restoration toward normal T2, fractional anisotropy (FA), and radial diffusivity (RD) values than nerves injected with LPS or PBS.

DISCUSSION

Nerves treated with immunomodulation exert synergic beneficial effects on nerve regeneration that can be predicted by T2 measurements and FA and RD values. Muscle Nerve 57: E38-E45, 2018.

Predicting the Response to Intravenous Immunoglobulins in an Animal Model of Chronic Neuritis

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a disabling autoimmune disorder of the peripheral nervous system (PNS). Intravenous immunoglobulins (IVIg) are effective in CIDP, but the treatment response varies greatly between individual patients. Understanding this interindividual variability and predicting the response to IVIg constitute major clinical challenges in CIDP. We previously established intercellular adhesion molecule (ICAM)-1 deficient non-obese diabetic (NOD) mice as a novel animal model of CIDP. Here, we demonstrate that similar to human CIDP patients, ICAM-1 deficient NOD mice respond to IVIg treatment by clinical and histological measures. Nerve magnetic resonance imaging and histology demonstrated that IVIg ameliorates abnormalities preferentially in distal parts of the sciatic nerve branches. The IVIg treatment response also featured great heterogeneity allowing us to identify IVIg responders and non-responders. An increased production of interleukin (IL)-17 positively predicted IVIg treatment responses. In human sural nerve biopsy sections, high numbers of IL-17 producing cells were associated with younger age and shorter disease duration. Thus, our novel animal model can be utilized to identify prognostic markers of treatment responses in chronic inflammatory neuropathies and we identify IL-17 production as one potential such prognostic marker.

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

RATIONALE AND OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

The Prevalence and Management of Systemic Amyloidosis in Western Countries

BACKGROUND

Amyloidosis has been a mystery for centuries, but research of the last decennia has clarified many of the secrets of this group of diseases. A protein-based classification of amyloidosis helps to understand problems that were part of the obsolete clinical classification in primary, secondary, and familial amyloidosis. All types of amyloid are secondary to some underlying precursor-producing process: each type is caused by a misfolded soluble precursor protein that becomes deposited as insoluble amyloid fibrils.

SUMMARY

The incidence of amyloidosis is not well documented, but probably falls between 5 and 13 per million per year. Prevalence data are scarce, but one UK study indicates about 20 per million inhabitants. Amyloidosis can be localized (amyloid deposited in the organ or tissue of precursor production) or systemic (amyloid at one or more sites distant from the site of precursor production). The major systemic types of amyloidosis are AL (associated with a light chain-producing plasma cell dyscrasia), AA (associated with longstanding inflammation), wild-type ATTR (associated with normal transthyretin and old age), and hereditary ATTR (associated with a transthyretin mutation) amyloidosis. Imaging techniques, such as cardiac ultrasound, magnetic resonance imaging, bone scintigraphy, and serum amyloid P component scintigraphy, are useful both for diagnosing amyloidosis and for assessing disease severity. Serologic markers are useful for detecting organ disease and disease monitoring during follow-up. Current treatment modalities are directed against the ongoing supply of precursor proteins and thereby aim to stop further accumulation of amyloid. Novel treatment modalities, such as interference with amyloid formation and even removal of amyloid, are being studied. A well-thought and planned monitoring during follow-up helps to assess the effect of treatment and to early detect possible progression of amyloidosis.

KEY MESSAGES

Clinical management comprises histologic proof of amyloid, evidence of systemic deposition, reliable typing, precursor assessment, severity of organ disease, risk assessment and prognosis, choice of treatment, and planned monitoring during follow-up.

FACTS FROM EAST AND WEST

(1) AL amyloidosis is the most prevalent type of amyloidosis accounting for 65% of the amyloidosis-diagnosed patients in the UK and for 93% of the amyloidosis-diagnosed patients in China. The predisposition of men over women to develop AL amyloidosis might be higher in China than in Western countries (2:1 vs. 1.3:1). Both in the East and West, incidence increases with age. At the time of diagnosis, edema is twice as frequent and the proportion of renal involvement is higher in Chinese compared to Western patients. (2) Melphalan followed by autologous stem cell transplantation (ASCT) is the current standard therapy but is restricted to eligible patients. The efficacy and safety of bortezomib combined with dexamethasone were proven in Western patients and recently confirmed in a Chinese cohort. Recent studies in China and the US indicate that bortezomib induction prior to ASCT increases the response rate. Thalidomide and lenalidomide have shown benefit, but toxicity and lack of clinical evidence exclude these agents from first-line therapy. The green tea extract epigallocatechin-3-gallate is under investigation as an inhibitor of AL amyloid formation and a compound that might dissolve amyloid.

Pain Examination and Diagnosis

Pain is a clinical challenge to health care providers who care for hand disorders. Pathologic pain that prevents recovery leads to dissatisfaction for both patients and providers. Despite pain being common, the root cause is often difficult to diagnose. This article reviews the examination and diagnostic tools that are helpful in identifying pathologic and neuropathic pain. This article provides tools to speed recognition of these processes to allow earlier intervention and better patient outcomes.

MR anatomy and pathology of the ulnar nerve involving the cubital tunnel and Guyon's canal

Ulnar neuropathy is a common and frequent reason for referral to hand surgeons. Ulnar neuropathy mostly occurs in the cubital tunnel of the elbow or Guyon's canal of the wrist, and it is important for radiologists to understand the imaging anatomy at these common sites of impingement. We will review the imaging and anatomy of the ulnar nerve at the elbow and wrist, and we will present magnetic resonance imaging examples of different causes of ulnar neuropathy, including trauma, overuse, arthritis, masses and mass-like lesions, and systemic diseases. Treatment options will also be briefly discussed.