high-resolution 3t mr neurography of radial neuropathy
TRANSCRIPT
Journal of Neuroradiology (2011) 38, 265—274
REVIEW
High-resolution 3T MR neurography of radialneuropathyNeurographie RM 3T haute resolution de la neuropathie radiale
Neda Faridian-Aragha, Majid Chaliana, Theodoros Soldatosa,Gaurav K. Thawaita, E. Gene Deuneb, Allan J. Belzbergc,John A. Carrinoa, Avneesh Chhabraa,∗
a The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Hospital,601 North Caroline Street, JHOC 3262, Baltimore, MD 21287, USAb Orthopedic Hand Division, Johns Hopkins Hospital, Baltimore, MD, USAc Department of Neurosurgery, Johns Hopkins Hospital, Baltimore, MD, USA
Available online 22 July 2011
KEYWORDSRadial nerve;
Summary The radial nerve is a continuation of the posterior cord of the brachial plexus andone of the major nerves that provide motor and sensory innervations to the forearm. MR imag-
Radial neuropathy;High-resolution MRI;MRI
ing evaluation of the radial nerve pathology has been described in scattered case reports.Current high-field MR scanners enable high resolution and high contrast imaging of the periph-eral nerves. This article reviews the 3 Tesla magnetic resonance neurography imaging of radial
path. All
aisvpt
nerve anatomy and various© 2011 Elsevier Masson SAS
Introduction
Radial neuropathy is relatively uncommon [1] and comesthird in the order of frequency among all the neuropathiesthat involve the large mixed nerves of the body [2]. Diagno-sis of radial neuropathy is often difficult due to the vaguepresenting symptoms and frequently inconclusive results ofthe electrodiagnostic studies [1,3]. High-resolution ultra-
sound (US) and magnetic resonance neurography (MRN) haveproven to be useful tools in confirming the presence of neu-ropathy and defining the source, region and extent of the∗ Corresponding author. Tel.: +410 382-3863; fax: +410 502-6454.E-mail addresses: [email protected],
[email protected] (A. Chhabra).
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0150-9861/$ – see front matter © 2011 Elsevier Masson SAS. All rights redoi:10.1016/j.neurad.2011.05.006
ologies affecting it with relevant case examples.rights reserved.
bnormality [4—6]. Although MRN is more expensive than US,t is less operator-dependent and can depict subtle abnormalignal intensity changes in the affected nerve and dener-ated muscles, thereby confirming neuropathy. This articlerovides an overview of radial nerve anatomy and a spec-rum of pathologies on 3 Tesla (T) MRN imaging.
natomy of the radial nerve
osterior cord of the brachial plexus, which has contribu-ions from C5 to T1 nerves, gives rise to the radial nerve.
he radial nerve courses posterior to the proximal seg-ent of the axillary artery. In the arm, it courses aroundhe posterior aspect of the humerus in the spiral grooverom medial to lateral (Fig. 1), and pierces the lateral
served.
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Figure 1 Anatomical diagram demonstrating the radial nerveand its sites of entrapment. Common sites of radial nerveentrapment are indicated by asterisks.
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Figure 2 Normal Nerve. a: axial T2 SPAIR image at the level of thnerve (large arrow). Notice the abnormal T2 hyperintensity and endenervation change (edema like T2 signal) in the surrounding bicepsneuropathy. b—d: sequential axial T2 SPAIR images from other healthnerve (large arrows) in the arm (b), at the elbow (c) and, dividing atmedian (small arrows) and ulnar nerve (arrowheads) have been also m
N. Faridian-Aragh et al.
ntermuscular septum (LIS) to traverse between therachialis and brachioradialis muscles (Fig. 2) [7]. At theevel of the elbow joint, it enters the radial tunnel thats approximately 5 cm long, extending from the capitellumo the lower border of the supinator muscle (Fig. 1) [8].ere, the radial nerve terminates into its superficial andeep branches. The superficial sensory branch runs deep tohe brachioradialis muscle and innervates the skin of theadial side of the dorsum of the hand. The deep motorranch, the posterior interosseous nerve, travels to the backf the forearm (Fig. 2) and descends on the interosseousembrane, anterior to the extensor pollicis longus to theack of the hand. The radial nerve innervates the triceps,nconeus and brachioradialis muscles. The extensor carpiadialis longus and brevis may be innervated by the radialr the interosseous nerve [3]. All the other muscles of theorsolateral aspect of the forearm are supplied by the pos-
erior interosseous nerve [7]. In approximately 80% of theases, the brachialis has a dual innervation from the muscu-ocutaneous and radial nerves and the radial nerve usuallynnervates the inferolateral portion of the muscle [9].e spiral groove shows normal intermediate signal of the radiallargement of the musculocutaneous nerve (small arrow) and
brachii muscle for comparison in this case of musculocutaneousy volunteers show normal course and appearance of the radial
the lower part of the radial tunnel (d). The relative positions ofarked. Notice normal appearance of biceps muscle in the Fig 2b.
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High-resolution 3T MR neurography of radial neuropathy
Etiopathogenesis
Radial neuropathy may be seen in isolation or in associationwith other peripheral neuropathies or brachial plexopathy.The etiopathogenesis encompasses two groups of causes,one being related to systemic etiologies, such as diabetesmellitus, collagen vascular disease, vasculitis, etc.; and theother to local-regional etiologies, such as brachial plexopa-thy, nerve injury or entrapment, peripheral nerve sheathtumors or other mass lesions in the vicinity of the nerve,bony fracture, thickened LIS, tight or thickened aponeu-rotic fascia of supinator muscle and diffuse peripheral nervelesions. MRN has a role in the evaluation of the latter groupentities.
Clinical findings
Radial nerve compression or injury at the level of thebrachial plexus, axilla or the proximal arm causes den-ervation changes of all muscles innervated by the radialnerve. Radial neuropathy at the level of the spiral grooverelatively preserves the triceps function (elbow extension)[10], but interferes with the rest of the functions as men-tioned above. Pain, paresthesia and/or sensory deficit inthe radial nerve distribution may be observed in radial neu-ropathy at any of these levels [11]. Compression of theradial nerve in the radial tunnel may result in two dif-ferent syndromes, namely the radial tunnel syndrome andposterior interosseus nerve (PIN) syndrome. Radial tunnelsyndrome occurs in subjects performing repeated supina-tion and pronation or forceful extension movement of theforearm [12]. Posterior interosseous nerve syndrome usu-ally results from trauma, mass lesions and inflammation[3]. Radial tunnel syndrome predominantly presents withpain, paresthesia and numbness in the radial distributionof the wrist and hand [11], whereas posterior interosseousnerve syndrome predominantly presents with weakness ofthe extensor muscles of the digits [1,10]. On physical exam,
positive Tinel sign may aid in localization of the anatomicsite of injury/compression. In spiral groove syndrome, pos-itive Tinel sign is noted at the site of the groove at thejunction of upper 2/3 and lower 1/3 of the arm. However,aihc
Table 1 3 T MR Neurography examination protocol for the evalua
MR sequence FOV Base resoluti
Axial T1 22 448
Axial T2 SPAIR TSE 22 448
Sagittal PD SPAIR 38 704
3D SPAIR Space 30 384
3D DW PSIF 38 384
MR: magnetic resonance; TSE: turbo spin echo; SPAIR: spectral adiabaweighted reversed fast imaging with steady state precession (fat suppreTF: Turbo factor; PD: Proton density.Space is a single slab three-dimensional sequence with variable excitatiousing variable flip angle evolutions, Siemens, Erlangen, Germany. FieTR/TE in ms.
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n the radial tunnel syndrome, it is usually positive overhe radial side of the forearm [10,13]. Compression of theuperficial radial nerve results in Wartenberg syndrome. Thisften happens at the site where the nerve pierces the deepascia to become subcutaneous between the tendons of thextensor carpi radialis longus and brachioradialis. It resultsrom athletic activities with repeated supination and prona-ion of the forearm, as well as, from direct trauma to therm [11].
agnetic resonance neurography imagingvaluation of radial neuropathy
he protocol used for MRN of the upper extremity in author’snstitution has been outlined in Table 1. Depending upon theeld of view, a 4—8 channel flex coil or a dedicated elbowoil is commonly employed for imaging of the radial nerve on3-T magnet. Axial T1 weighted and axial T2 spectral adia-atic inversion recovery (SPAIR) imaging techniques tailoredo the site of abnormality are used for primary interpre-ation of nerve size and signal characteristics. The SPAIRequence is a frequently applied sequence on 3 T MRN imag-ng [14,15]. It uses varying flip angles and is thereby, morepecific absorption rate (SAR) favorable than the short taunversion recovery (STIR) sequence. It also provides bet-er fat saturation than frequency selective fat suppressedpin echo image, while maintaining higher signal to noiseatio (SNR) than the STIR image [16,17]. The radial nerveemonstrates isointense signal intensity to the muscle onll imaging sequences, as opposed to the ulnar nerve, whichay have an artifactual mild increased T2 signal intensity
SI) even in asymptomatic subjects (Fig. 2). A coronal pro-on density sequence is used to exclude space-occupyingesions along the length of the nerve and to detect anyajor internal derangement of the elbow joint. Isotropic 3D
dimensional) sequences, such as SPAIR SPACE (sample per-ection with application optimized contrasts using varyingip angle evolutions, Siemens, Erlangen, Germany) and 3DW-PSIF are used as problem solving techniques as they
llow isotropic multiplanar reconstructions and maximumntensity projections. SPACE is a spin-echo 3D sequence withigher SNR than the 3D gradient echotype sequence, whichan be acquired in acceptable time period of 5—6 minutestion of radial neuropathy.
on Slice thickness TR/TE/TF
3 657/11/5
3 4500/84/15
6 4880/40/13
0.8 1020/91/119
0.9 10/5/7
tic inversion recovery; 3D DW-PSIF: three-dimensional diffusion-ssed sequence with a diffusion moment-b value of 80—90 s/mm2);
n pulse (sampling perfection with application optimized contrastsld of view (FOV) is presented in cm, slice thickness in mm, and
268 N. Faridian-Aragh et al.
Figure 3 a—c: entrapment neuropathy. Sequential axial T2 SPAIR images (a, b) in a 34-year-old man, with acute onset andprogressive pain in the left arm and weakness in the extensor muscles of the wrist and digits for the last few months. EMG showedabsent radial nerve conduction at the spiral groove. MR images showed the proximal nerve enlargement (large arrow in a) withdistal entrapment at the spiral groove (large arrow in b). Notice denervation muscle edema like signal in the brachialis muscle(short arrows in a and b). Oblique coronal reconstruction image from 3D DW PSIF sequence (c) with advantages of vascular signalsuppression nicely depicts focal radial nerve entrapment and narrowing at the spiral groove with a twist (arrow) due to thickenedl ringi -PSIF
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ateral intermuscular spetum. The findings were confirmed dusointense signal and size of the radial nerve (arrows) on 3D DW
nd provides sub 1 mm in-plane resolution. 3D DW-PSIF alsoreates nerve selective images with vascular suppressionue to its steady state nature and a low diffusion momentFig. 3). It is an isotropic steady state sequence (0.9 mmn-plane resolution) with low diffusion moment (b value-0 mm/s2), which suppresses the signal from the flowingrotons, creating nerve specific images. The normal nerveshow isointense SI on this sequence and the abnormal nerveshow increased SI similar to T2 SPAIR sequence, while the SIf the adjacent hyperintense vessels is nulled. It is primar-ly for anatomic imaging with application of a low diffusionoment to keep enough SNR in the image. Use of higher b
alues (1000 mm/s2) for functional imaging, such as diffusion
ensor imaging and tractography is currently in feasibilitytages. The authors do not use intravenous contrast forntrapment and traumatic neuropathies in their practice.ut, contrast enhanced scans are useful for characterizationtpof
surgical release of the nerve. For comparison, notice normalfrom a healthy volunteer (d).
nd better delineation of pathology in cases of inflamma-ions, diffuse polyneuropathies and suspected mass lesions.
ntrapment neuropathy
ommon sites of radial nerve entrapment include areas ofpiral groove and the radial tunnel; with the latter beingore commonly observed (Fig. 1). At the spiral groove, the
erve may be entrapped by thickened lateral intermuscu-ar septum (> 2 mm) or prominent/tight tendinous arch ofhe lateral head of the triceps muscle [18]. The nerve maylso get compressed at this level against the humerus in
he classic syndrome of Saturday night palsy, where theatient, sometimes intoxicated with alcohol, sleeps on theutstretched arm or dangles the arm on the back of a chairor prolonged hours (Fig. 3) [19].
emb
High-resolution 3T MR neurography of radial neuropathy
Within the radial tunnel, the radial nerve and/or itsbranches, most commonly the posterior interosseous nerve,may be compressed at any of the following locations: (1)
the radiocapitellar joint by fibrous bands; (2) the tendinousedge of the extensor carpi radialis brevis muscle; (3) theradial recurrent artery and branches (leash of Henry); (4)the arcade of Frohse, representing the proximal tendinousdaio
Figure 4 a—e: traumatic radial and PIN neuropathy. Forty-six-yeadue to motor vehicle accident, presented 2 weeks later with weakinterosseus component of the left radial nerve. In addition, there wulnar neuropathy at the elbow. Sequential axial T2 SPAIR images (a,at the elbow (arrow in a), which could be traced to the abnormally ein b). Oblique coronal reconstruction from STIR image (c) nicely dediscontinuity (arrows) in keeping with a stretch injury. Axial T2 SPselective posterior compartment denervation edema like T2 SI withtraumatic PIN neuropathy from recent trauma. The patient subsequ
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dge of the supinator muscle [20], which is the most com-on of all (1); and (5) the distal end of the supinator muscley a fibrous band (Fig. 1) [3,21]. On MRN, the neuropathy is
emonstrated as focal or diffuse enlargement of the nerve,s well as increased T2 hyperintensity approaching the signalntensity of the adjacent vessels (Fig. 3). The highest degreef T2 hyperintensity is noted in the vicinity of the entrap-r-old man with multiple soft tissue injuries and bone fracturesness in digits extension. EMG showed injury to the posterioras evidence of bilateral median neuropathies at the wrist andb) show abnormally enlarged and T2 hyperintense radial nervenlarged and T2 hyperintense posterior interosseus nerve (arrowpicts the whole course of the abnormal radial nerve without
AIR (d) and corresponding axial T1 weighted (e) images showout muscle atrophy (arrows) confirming the diagnosis of acuteently improved on conservative treatment.
270 N. Faridian-Aragh et al.
Figure 5 Locoregional Space occupying lesion. Axial T2 fatsaturated image in a 16-year-old boy presenting with shoulderar
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Figure 7 Schwannomatosis. Twenty-two-year-old man diag-nosed with schwannomatosis (INI1 mutation) in adolescencewith both central and peripheral tumors as well as both thecentral and peripheral symptoms. Coronal STIR image showsthe peripheral nerve sheath tumor with classic target and tailsigns related to proximal and distal radial nerve enlargement intk
a
nd arm pain. Notice abnormal T2 hyperintensity of the encasedadial nerve (arrow) by a biopsy proven osteosarcoma.
ent site with distal gradual normalization of the SI. Thisbnormal SI is related to various hypothesized mechanisms,.g. proximal axoplasmic flow blockade, venous congestionnd distal Wallerian degeneration changes. MRN can dif-erentiate compressive from adhesive lesions. Radial nerve
ourse deviations due to the adjacent mass lesions may alsoe noted. In our experience, focal twist in the nerve courseue to fibrous bands or thickened intermuscular septum isest demonstrated on images reconstructed along the longigure 6 Benign peripheral nerve sheath tumor. Coronal STIRmage in a 72-year-old man with chronic intermittent left armain. EMG study shows the presence of bilateral median neu-opathies at the wrists and patchy brachial plexopathy. MRmage shows an incidental benign peripheral nerve sheath tumorschwannoma) arising from the radial nerve. Notice the clas-ic target sign (small arrow) and tail sign related to minimalnlarged of the proximal radial nerve (larger arrow).
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he right arm (large arrow). Also, notice additional tumors ineeping with history of schwannomatosis (small arrows).
xis of the nerve (Fig. 3c). Although electrodiagnostic stud-es may confirm the presence of neuropathy, cross-sectionalmaging is essential to detect the underlying cause of entrap-
ent. Regional muscle denervation changes on MRN alsoerve as important secondary findings confirming neuro-athy.
igure 8 Diffuse neuropathy in neurofibromatosis type I (NF-). Axial STIR image in a 41-year-old man, previously diagnosedith NF-I presenting with right elbow pain. Notice enlarged andbnormally T2 hyperintense radial (large arrow), median (smallrrow) and ulnar (arrowhead) nerves with preserved fascicu-ar appearance. No focal mass was detected in these diffuselynlarged nerves.
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High-resolution 3T MR neurography of radial neuropathy
Traumatic neuropathy
Trauma is the most common cause of radial nerve injuryat the level of the arm [11,12]. Common examples includedisplaced humeral bone fractures, improper use of axil-lary crutches, prolonged use of tourniquet at the upperarm, lateral or posterior intramuscular injections to thearm [3], and open surgery for reduction of humeral frac-tures [22]. Approximately 12% of humeral fractures resultin radial neuropathy. This incidence is higher in fracturesof the midshaft and significantly higher in open fractures[23,24]. Direct trauma can also affect the interosseous andsuperficial branches of the radial nerve.
In general, trauma can result in mild (neuropraxia—stretch injury), moderate (axonotmesis — partial or com-plete discontinuity of axons) or severe (neurotmesis—partialor complete discontinuity of nerve) nerve injuries [16,17].
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Figure 9 a—c: lymphoma. Fifty-five-year-old woman with 1 year hisof the digits. EMG showed multifocal sensorimotor peripheral neuropdiffuse enlargement and abnormal T2 hyperintensity of all nervescompared to median (small arrows) and ulnar (arrowheads) nerves.right (c) and left (not shown) showed abnormal enhancement of the
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rogress in the degree of nerve abnormality, often resultsn increased T2 signal abnormality and neuroma formation.ild-moderate nerve abnormalities (Fig. 4) on MRN shoulde distinguished from focal neuromas and nerve discontinu-ty of severe nerve injury, which frequently require surgery.lectrodiagnostic studies cannot distinguish nerve in conti-uity from discontinuity and MRN is useful for preoperativelanning.
umors and tumor-like lesions
eoplasms, such as peripheral nerve sheath tumors (PNST)nd lymphoma, as well as tumor-like conditions such as
myloidosis and perineurioma, can result in radial neuropa-hy apart from encasement or displacement by locoregionaleoplastic space occupying lesions (Fig. 5) [25—27]. PNSTsre divided into benign peripheral nerve sheath tumorstory of pain in arms, hands, and feet and weakness in extensionathy. Axial STIR images of the right (a) and left (b) arms showwith most abnormality of the radial nerves (long arrows) asCoronal fat saturated post contrast T1 weighted images of theradial (long arrow) and median (short arrow).
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BPNSTs), which are more common, and malignant periph-ral nerve sheath tumors (MPNSTs). These tumors mayccur sporadically or in association with neurocutaneousyndromes. The most common subtypes of BPNST arechwannomas and neurofibromas. Schwannomas are moreommon in the third to sixth decades of life. They mostlyresent as solitary tumors and may be seen as an inci-ental finding (Fig. 6). Multiple schwannomas of the radialerve and other peripheral nerves usually occur in asso-iation with neurocutaneous syndromes (Fig. 7) [28,29].eurofibromas, however, occur at a younger age. Solitaryeurofibromas involve the subcutaneous nerves and show noreference for a particular region of the body [30]. MPN-Ts are more common in the third to sixth decade of life.hese tumors comprise 10% of soft-tissue sarcomas. Theyre more common and occur at an earlier age in patientsith neurofibromatosis. In these patients, as compared to
he general population, tumors tend to be larger and ofigher grade. MPNSTs are more likely to involve the majorerves, such as the brachial or sacral plexus and are usu-lly located in the deeper soft tissues [31]. Currently, MRs the best imaging method for the diagnosis of PNSTs, withRN showing a potential for better depiction of fasicularontinuity or neural origin of the mass lesion. It not onlyifferentiates the normal from abnormal nerves, but it alsoan depict the focal mass lesion, its relationship to the nervend its fascicles, the extension to the surrounding bony andoft tissues as well as, diffusely thickened nerves (Fig. 8)30]. Benign lesions typically appear as ovoid, round orusiform masses with well-defined margins. On T2-weightedmages, they demonstrate low signal intensity in the cen-ral portion and high signal intensity in the periphery, aign referred to as ‘‘target sign’’ (Fig. 6) or a ‘‘fascicularign’’, as multiple rings with lower signal at the center. Aail sign depicting the proximity or abnormality of the adja-
ent nerve may be evident (Fig. 7). A ‘‘split fat sign’’ whichan be seen on longitudinal T1-weighted images, when theell-defined tumor is surrounded by a layer of fat. Theseesions may show variable or homogeneous enhancement on
im
i
igure 10 Inflammatory neuropathy. Forty-one-year-old womanadial nerve conduction at the spiral groove, clinically suspicious fmage from 3D STIR SPACE sequence (a) shows normal symmetricabnormal arm nerves, with most abnormality of the radial nerve (lonedian nerves (small arrow) with preserved fascicular appearance i
N. Faridian-Aragh et al.
ost-contrast imaging. MRN imaging can also demonstrateven mild degrees of atrophy in the innervated muscles.resence of a mass lesion close to a nerve and atrophyf the regional muscles are suggestive of neural origin ofhe tumor. However, these signs may also be variably seenn MPNSTs. Malignancy is highly suspected when there arelinical findings of new onset pain/neurologic deficits andpon the presence of two or more of the following MRndings: ill-defined/invasive margins, peritumoral edema,
argest diameter over 5 cm and heterogenous signal intensityn T1 and T2-weighted images [32,33].
Both T-cell and B-cell lymphomas have been reported tonvolve peripheral nerves and may cause peripheral neu-opathy. There are scattered reports of involvement of theadial nerve with the resultant neuropathy and MR imagingas proven to be of value in the evaluation of these caseFig. 9) [34—36]. Other neoplastic or non-neoplastic massesions, which originate from the tissues adjacent to theadial nerve, e.g. soft tissue sarcoma, lipoma, ganglion cyst,nlarged lymph nodes and aneurysm, can also cause radialeuropathy [37—44]. The high contrast and spatial resolu-ion of MRN can help in the differentiation of PNSTs fromther mass lesions, which are in proximity to the nerve.he PNSTs usually show an abnormal fascicular continuityith the mass lesion, which is not appreciated with extrin-
ic lesions. MRN studies in cases of suspected mass lesionshould be performed with intravenous contrast for betterelineation and characterization of the pathology.
iscellaneous conditions
rachial plexopathy may secondarily cause radial neuropa-hy. It may occur as a result of degenerative cervicalpondylotic changes, trauma [45], primary and secondaryeoplastic disorders, radiation, brachial neuritis, chronic
nflammatory demyelinating polyneuropathy and multifocalotor neuropathy [46,47].The radial nerve may also be involved in infectious ornflammatory conditions, especially autoimmune disorders
with left humeral pain and left wrist drop and no detectableor brachial versus radial neuritis. Coronal MIP reconstructionl brachial plexuses. Axial T2 SPAIR image (b) shows diffuselyg arrow) and milder abnormality of the ulnar (arrowhead) and
n this case of autoimmune neuritis.
High-resolution 3T MR neurography of radial neuropathy
Figure 11 Radiation neuropathy. Forty-eight-year-oldwoman, status post-radical resection and radiation therapy forthe treatment of soft tissue sarcoma in the forearm presentedfor routine follow up. Axial STIR image at the level of theelbow shows mildly enlarged radial nerve (large arrow) as wellas mildly T2 hyperintense median nerve (small arrow) as a sideeffect of radiation treatment. Patient was asymptomatic at
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this time. Also, notice post-radiation changes with edema likeT2SI in the anterior subcutaneous, fascial and muscular planes.
[48]. Diagnosis is usually reached through history and clinicalas well as laboratory findings. Imaging may be sometimesperformed to exclude space occupying lesions or to confirmneuropathy in atypical cases. MRN shows the abnormal nerveas diffusely T2 hyperintense with or without mild diffuseenlargement (Fig. 10). Generally, no focal contour changesare observed. Bursitis secondary to inflammatory disorders,such as rheumatoid arthritis may also compress the posteriorinterosseous nerve [49,50].
Finally, radial neuropathy may result from radiation tothe upper limb for the treatment of sarcoma [51,52], ormay occur secondary to damage to brachial plexus follow-ing radiation therapy for the treatment of cancers of breastor the head and neck [53—55]. In general, the developmentof radiation-induced neuropathy as well as its timing andseverity, depend on the total radiation dose, dose per frac-tion and the extent of the radiation field. MRN is capable ofdepicting the abnormal change in signal intensity and size ofthe nerve; the presence of muscle edema, fatty infiltrationand atrophy as well as edema and fibrosis in the surround-ing tissues (Fig. 11). However, it is worth mentioning thatthe nerve changes demonstrated by MRN may not be accom-panied by clinical symptoms and therefore, to prevent thefalse-positive diagnosis, MRN findings should be interpretedin light of clinical findings.
Conclusion
Involvement of the radial nerve and its branches can occurdue to many different types of pathology. The results of clin-ical examination and electrodiagnostic tests may not alwaysbe helpful in the diagnosis of radial neuropathy. By defining
[
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he source, region and extent of the disorder, MRN providesseful additional information and should be considered inhe diagnostic protocol of patients with suspected radialeuropathy.
isclosure of interest
he authors declare that they have no conflicts of interestoncerning this article.
cknowledgment
he authors gratefully acknowledge Tim Phelps, Associaterofessor and Medical Illustrator in the Department of Arts Applied to Medicine, The Johns Hopkins University, Bal-imore, MD, for his great contribution in the illustration ofhe radial nerve.
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