Imaging of non-neurogenic peripheral nerve malignancy-a case series and systematic review

A neuromuscular clinician's guide to magnetic resonance neurography

Magnetic resonance neurography (MRN) is increasingly used in clinical practice for the evaluation of patients with a wide spectrum of peripheral nerve disorders. This review article discusses the technical aspects of MRN highlighting the core sequences performed for clinical care. A robust, high-resolution, heavily T2-weighted fluid-sensitive sequence performed on a 3.0 Tesla magnet system remains the main workhorse MRN sequence. In specific clinical scenarios, adjunct techniques such as diffusion-weighted imaging can be added to a protocol for disease characterization. In addition, gadolinium-based contrast material can also be administered for the purposes of image optimization (suppress adjacent vascular signal) and disease characterization. Technical modifications to field of view and planes of imaging can be made based on the clinical question and discussion with the radiologist(s). On fluid-sensitive MRN sequences, a normal peripheral nerve exhibits iso- to minimally hyperintense signal relative to skeletal muscle with a predictable trajectory, preserved "fascicular" architecture, and tapered caliber from proximal to distal. Peripheral nerve abnormalities on MRN include alterations in signal, caliber, architecture, diffusion characteristics as well as enhancement and provide information regarding the underlying etiology. Although some MRN findings including nerve hyperintensity and long-segmental enlargement are nonspecific, there are certain diagnoses that can be made with high certainty based on imaging including benign peripheral nerve tumors, high-grade peripheral nerve injury, and intraneural ganglia. The purpose of this article is to familiarize a neuromuscular clinician with fundamentals of MRN acquisition and interpretation to facilitate communication with the neuromuscular radiologist and optimize patient care.

Novel MRI signs for differentiating neurogenic and non-neurogenic peripheral nerve Tumors: Insights from Contrast-Enhanced magnetic resonance neurography

OBJECTS

To investigate the specific manifestations of neurogenic and non-neurogenic tumors involving peripheral nerves on contrast-enhanced magnetic resonance neurography (CE-MRN) and explore the potential of CE-MRN in aiding differential diagnosis.

MATERIALS AND METHODS

Twenty-nine patients with neurogenic tumors and 23 with non-neurogenic tumors involving peripheral nerves were enrolled in this study. Both routine MRI and CE-MRN scanning were performed on all subjects. The location, pattern of involvement, classical MRI signs, and novel CE-MRN signs of nerve involvement were evaluated and compared between the two groups. The novel CE-MRN signs included "Enhanced target sign", "Nerve effacing sign", "Nerve wrapping sign", "Nerve compressing sign", "Nerve tail sign", and morphological changes of nerves. Diagnostic confidence in identifying nerve involvement and lesion conspicuity were assessed and compared between routine MRI and CE-MRN.

RESULTS

The majority of neurogenic tumors were schwannoma (79.3 %) and involved a single nerve (75.9 %), whereas the majority of non-neurogenic tumors were malignant tumors (78.3 %) and involved multiple nerves (78.3 %) (P < 0.001). In terms of classical MRI signs, neurogenic tumors exhibited a significantly higher incidence of the "Tail sign" (75.9 % vs 13 %), "Dumbbell sign" (31 % vs 4.3 %), "Target sign" (51.7 % vs 8.7 %), and "Split fat sign" (55.2 % vs 4.3 %), while showing a lower incidence of the "Effacement of fat plane" (3.4 % vs 60.9 %) compared to non-neurogenic tumors (all p < 0.05). Regarding novel CE-MRN signs, neurogenic tumors demonstrated a significantly higher incidence of the "Enhanced target sign" (65.6 % vs 13 %) and the "Nerve tail sign" (100 % vs 13 %), while exhibiting a lower incidence of the "Nerve effacing sign" (0 % vs 52.2 %) and the "Nerve wrapping sign" (0 % vs 17.4 %) compared to non-neurogenic tumors (all p < 0.05). CE-MRN yielded significantly higher diagnostic confidence scores (2.87 ± 0.35 vs 1.75 ± 0.84), but lower lesion conspicuity scores (2.35 ± 0.71 vs 2.92 ± 0.27) compared to routine MRI (all P < 0.001).

CONCLUSION

CE-MRN is a valuable imaging modality for the identification of tumor-related peripheral nerve involvement, as it offers supplementary indicators and enhances diagnostic confidence.

Recurrence of diffuse large B-cell lymphoma in sciatic and tibial nerves: A case report

Infiltration of peripheral or cranial nerves with lymphatic cells is a rare condition that is known as neurolymphomatosis (NL). The involvement could be primary or secondary and mostly occurs in patients with a history of B-cell lymphoma. The most common peripheral nerve involved is the sciatic nerve. Patients may present with painful or painless mononeuropathy or polyneuropathy, and MRI is the perfect modality to evaluate the suspicious clinical findings that may demonstrate enlargement, thickening, and enhancement of the involved nerve or an enhancing mass lesion in the course of the nerve. Biopsy can be safely performed to confirm the diagnosis. Few articles have reported the cases of peripheral nerve involvement by lymphoma as well as MRI features of this diagnosis. In this article, we report a case of NL using MRI, ultrasound, and pathologic features and also present a brief review of relevant literature.

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

BACKGROUND. A standardized guideline and scoring system would improve evaluation and reporting of peripheral neuropathy (PN) on MRI. OBJECTIVE. The objective of this study was to create and validate a neuropathy classification and grading system, which we named the Neuropathy Score Reporting and Data System (NS-RADS). METHODS. This retrospective study included 100 patients with nerve imaging studies and known clinical diagnoses. Experts crafted NS-RADS using mutually agreed-on qualitative criteria for the classification and grading of PN. Different classes were created to account for the spectrum of underlying pathologies: unremarkable (U), injury (I), neoplasia (N), entrapment (E), diffuse neuropathy (D), not otherwise specified (NOS), and postintervention state (PI). Subclasses were established to describe the severity or extent of the lesions. Validation testing was performed by 11 readers from 10 institutions with experience levels ranging from 3 to 18 years after residency. After initial reader training, cases were presented to readers who were blinded to the final clinical diagnoses. Interobserver agreement was assessed using correlation coefficients and the Conger kappa, and accuracy testing was performed. RESULTS. Final clinical diagnoses included normal (n = 5), nerve injury (n = 25), entrapment (n = 15), neoplasia (n = 33), diffuse neuropathy (n = 18), and persistent neuropathy after intervention (n = 4). The miscategorization rate for NS-RADS classes was 1.8%. Final diagnoses were correctly identified by readers in 71-88% of cases. Excellent inter-reader agreement was found on the NS-RADS pathology categorization (κ = 0.96; 95% CI, 0.93-0.98) as well as muscle pathology categorization (κ = 0.76; 95% CI, 0.68-0.82). The accuracy for determining milder versus more severe categories per radiologist ranged from 88% to 97% for nerve lesions and from 86% to 94% for muscle abnormalities. CONCLUSION. The proposed NS-RADS classification is accurate and reliable across different reader experience levels and a spectrum of PN conditions. CLINICAL IMPACT. NS-RADS can be used as a standardized guideline for reporting PN and improved multidisciplinary communications.

3D MR Neurography

High-resolution isotropic volumetric three-dimensional (3D) magnetic resonance neurography (MRN) techniques enable multiplanar depiction of peripheral nerves. In addition, 3D MRN provides anatomical and functional tissue characterization of different disease conditions affecting the peripheral nerves. In this review article, we summarize clinically relevant technical considerations of 3D MRN image acquisition and review clinical applications of 3D MRN to assess peripheral nerve diseases, such as entrapments, trauma, inflammatory or infectious neuropathies, and neoplasms.