Radiologic abnormalities in patients with neuropathy

Elina Zakin MD (

Dr. Zakin of the NYU School of Medicine has no relevant financial relationships to disclose.

)
Susan C Shin MD (

Dr. Shin of the Icahn School of Medicine at Mount Sinai has no relevant financial relationships to disclose.

)
Howard W Sander MD (

Dr. Sander of the NYU School of Medicine received honorariums from CSL for consulting work.

)
Louis H Weimer MD, editor. (

Dr. Weimer of Columbia University has received consulting fees from Roche.

)
Originally released November 5, 2019; expires November 5, 2022

Overview

Peripheral nerve disorders are common chief complaints in neurologic practice. The history and clinical examination always guide the clinician toward lesion localization. With electrodiagnostic studies, the clinician can further classify peripheral nerve pathophysiology and offer prognostication. Given continuing improvements in both magnetic resonance neurography and neuromuscular ultrasound, the clinician is able to further localize, characterize, and visualize the anatomy, both normal and pathologic. In this article, the authors review these imaging tools for peripheral nerve visualization and discuss their utility in various peripheral nerve pathologies. Images from the presented cases are included. The various advantages and disadvantages of MR neurography and neuromuscular ultrasound are also reviewed.

Key points

 

• This article focuses on the utility of peripheral nerve ultrasound and MR neurography in various peripheral neuropathies.

 

• Nerve ultrasound allows for the determination of peripheral nerve anatomical course, echogenicity, vascularity, and degree of mobility; it can be performed in real-time and is cost effective and operator-dependent.

 

• Evaluation of peripheral nerve with ultrasound requires a high frequency (15 to 18 MHz) linear array transducer, which allows for visualization of subtle changes in nerve caliber and is often complementary to electrodiagnostic studies and MR neurography.

 

• MR neurography may display abnormal T2 hyperintensity and nerve nodularity, either focal or diffuse, with fascicular distortion or enlargement as well as contrast enhancement to assist with characterization of peripheral nerve abnormalities.

 

• In contrast to ultrasound, MR neurography is less operator-dependent and allows for visualization of higher soft-tissue contrast, which can depict milder abnormalities when there are subtle T2 signal abnormalities.

 

• MR neurography should combine high-resolution axial T1-weighted (anatomy) and T2-weighted (fat suppressed, for pathology) sequences to provide a detailed evaluation of the peripheral nerve.

 

• Indications for peripheral nerve imaging discussed in this article include common entrapment neuropathies, brachial plexopathy, nerve sheath tumors, diabetic polyneuropathy, and acquired immune-mediated demyelinating polyneuropathies.

Historical note and terminology

In the 1980s, MR neurography and neuromuscular ultrasound were introduced as noninvasive options to evaluate peripheral nerve anatomy. In patients who were unable to tolerate electrodiagnostic studies or were unable to have invasive testing, these options allowed for identification of abnormal nerve pathology (ie, neuroma, compressive mass lesions or perineural fibrosis) with accurate localization of the pathology (Martinoli et al 2000). Ultrasound is inexpensive, allows for dynamic nerve imaging, and can quickly differentiate vessels from nerves using Doppler imaging. Ultrasound, however, is operator-dependent, and nerve imaging may be degraded by scar tissue or acoustic shadowing from surrounding calcifications. Deep nerve structures may be difficult to visualize (ie, pelvis or lumbosacral plexus) (Gruber et al 2003). Both imaging modalities are being used as a complement to the electrodiagnostic data in the diagnosis of peripheral neuropathies.

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