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

Abstract

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.

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

“…In this pilot study, we have demonstrated the feasibility of obtaining reliable MTR measurements in the proximal lumbar plexus in healthy volunteers using a 3 T MRI system and commercially available software and hardware; the acquisition and analysis protocol presented in this work maybe easily translated to the clinical settings to study a large number of pathological conditions affecting the lumbar plexus 20,21 . The rationale behind this study was the lack of quantitative MRI protocols that can be used to obtain more specific information about the underlying pathophysiological processes involved in common pathologies affecting the lumbar plexus.…”

“…Furthermore, in the first reported clinical application of MTR in patients with Charcot-Marie-Tooth disease, it was demonstrated that MTR was significantly decreased in the proximal sciatic nerve of patients as compared to controls suggesting that MTR measurements may be a viable biomarker of proximal nerve pathology 19 . The ability to obtain reliable MTR measurements in the peripheral nerves of the lower extremities as well as other anatomical locations such as the lumbar plexus for example, which is known to be affected by a plethora of neurological conditions 20,21 , can have profound clinical implications both in terms of diagnosis and approach to treatment.…”

Coronal STIR sequence, a simple adjustment to routine MRI protocol for extra-spinal sciatica and sciatica-like symptoms

“…The MR neurography imaging of lumbosacral plexus has also utilized STIR besides T1 sequences in axial and coronal planes; and the revolutionized MR neurography techniques in the era of 3-Tesla MRI scanners introduced high-resolution images of the nerve plexus through three dimensional (3D) isotropic acquisition imaging with the advantage of maximum intensity projection (MIP) as well as curvilinear reconstructed images. High-resolution images allow detection of signal changes along the nerves and small neuromas and may help to point to sites of entrapment [21][22][23][24][25]. While MR neurography provides visual analysis of the nerves, diffusion-weighted imaging can provide further quantitative assessment through measurement of the apparent diffusion coefficient value (ADC) and fraction anisotropy (FA) of entrapped nerves and nerve roots and using ADC values for differentiating benign from malignant neurogenic tumors [26][27][28][29][30].…”

T2 mapping of the distal sciatic nerve in healthy subjects and patients suffering from lumbar disc herniation with nerve compression

“…Magnetic resonance neurography (MRN) of the peripheral nervous system (PNS), the application of magnetic resonance imaging (MRI) for the depiction and study of peripheral nerves of the human body, is increasingly applied in vivo. Advances in protocols and MRI scanner techniques now allow depicting even small or highly oblique nerves originating from the brachial plexus or lumbosacral plexus (LSP) [ 1 – 3 ]. A prominent nerve originating from the LSP is the sciatic nerve, which has been routinely under investigation in studies using MRN in the past.…”