high resolution neurography of the brachial plexus by ... · neurografía de alta resolución en...

Radiología. 2016;58(2):88---100

www.elsevier.es/rx

UPDATE IN RADIOLOGY

High resolution neurography of the brachial plexus

by 3 Tesla magnetic resonance imaging�

C. Cejas a,∗, C. Rollán a, G. Michelin a, M. Noguésb

a Departamento de Imágenes, Fundación para la lucha de las enfermedades neurológicas de la infancia Dr. Raúl Carrea (FLENI),

Buenos Aires, Argentinab Departamento de Neurología, Fundación para la lucha de las enfermedades neurológicas de la infancia Dr. Raúl Carrea (FLENI),

Buenos Aires, Argentina

Received 15 January 2015; accepted 16 December 2015

Available online 29 March 2016

KEYWORDSBrachial plexus;Magnetic resonanceimaging;Diseases of theperipheral nervoussystem

Abstract The study of the structures that make up the brachial plexus has benefited particu-

larly from the high resolution images provided by 3 T magnetic resonance scanners. The brachial

plexus can have mononeuropathies or polyneuropathies. The mononeuropathies include trau-

matic injuries and trapping, such as occurs in thoracic outlet syndrome due to cervical ribs,

prominent transverse apophyses, or tumors. The polyneuropathies include inflammatory pro-

cesses, in particular chronic inflammatory demyelinating polyneuropathy, Parsonage---Turner

syndrome, granulomatous diseases, and radiation neuropathy. Vascular processes affecting the

brachial plexus include diabetic polyneuropathy and the vasculitides.

This article reviews the anatomy of the brachial plexus and describes the technique for

magnetic resonance neurography and the most common pathologic conditions that can affect

the brachial plexus.

© 2016 SERAM. Published by Elsevier España, S.L.U. All rights reserved.

PALABRAS CLAVEPlexo braquial;Resonanciamagnética;Enfermedades delsistema nerviosoperiférico

Neurografía de alta resolución en resonancia magnética 3 Tesla del plexo braquial

Resumen El estudio de las estructuras que conforman el plexo braquial se ha visto par-

ticularmente beneficiado con las imágenes de alta resolución que brindan los equipos de

resonancia 3 T. El plexo braquial puede presentar mononeuropatías o polineuropatías. Entre

las primeras se distinguen los traumatismos, el atrapamiento, como el síndrome de la aber-

tura torácica por costillas cervicales, apófisis transversas prominentes o tumores. En el grupo

de las polineuropatías se encuentran los procesos inflamatorios, entre los que destacan la

� Please cite this article as: Cejas C, Rollán C, Michelin G, Nogués M. Neurografía de alta resolución en resonancia magnética 3 Tesla del

plexo braquial. Radiología. 2016;58:88---100.∗ Corresponding author.

E-mail address: [email protected] (C. Cejas).

2173-5107/© 2016 SERAM. Published by Elsevier España, S.L.U. All rights reserved.

Document downloaded from http://www.elsevier.es, day 03/11/2017. This copy is for personal use. Any transmission of this document by any media or format is strictly prohibited.Document downloaded from http://www.elsevier.es, day 03/11/2017. This copy is for personal use. Any transmission of this document by any media or format is strictly prohibited.

High resolution neurography of the brachial plexus 89

polineuropatía desmielinizante inflamatoria crónica, la plexitis autoinmunitaria (síndrome de

Parsonage Turner), enfermedades granulomatosas y la neuropatía por radiación. Entre los pro-

cesos vasculares se mencionan la polineuropatía diabética y las vasculitis.

En esta revisión se repasa la anatomía del plexo braquial y se describe la técnica de estudio

de la neurografía por resonancia magnética y las principales patologías que pueden afectar al

plexo braquial.

© 2016 SERAM. Publicado por Elsevier España, S.L.U. Todos los derechos reservados.

Introduction

The study of the Peripheral Nervous System (PNS) throughmagnetic resonance imaging (MRI) dates back to the1990’s.1,2 MR neurography (MRN) has coined the term thanksto high-resolution techniques, in particular those providedby 3 T equipment.3,4 These sequences have revolutionizedthe study of plexuses and peripheral nerves because theyprovide us with a significant improvement in the signal/noiserelation in shorter acquisition times, and they convey highresolution and contrast images.5---7 Diagnosis of PNS disor-ders was traditionally based on three pillars: medical history,physical examination and electrophysiological studies.8 Thecomplex anatomy of the brachial plexus makes clinical andelectrophysiological assessment difficult; therefore, MRNcan be placed as the fourth pillar among diagnostic stud-ies. Firstly, MRN images distinguish a normal plexus froma pathological one; in addition, they determine accuratelythe location of the lesion (root, trunk, division or cord), andwhether it affects one or several of them (mononeuropathyvs polyneuropathy). On the other hand, MRN images outlinethe extension of the lesion and it often specifies the etiol-ogy of the plexus disorder.8---11 Electrophysiological studies,though very useful to determine the location and degreeof nerve compromise, do not define the exact location oretiology of brachial plexus lesions.12

The goals of this review are to study brachial plexusanatomy, describe the study protocol for MRN and the maindiseases that can affect it.

Anatomic analysis of the brachial plexusthrough MRIs

MRI anatomic analysis of the brachial plexus benefited sig-nificantly from neurographic sequences. The anatomicalpoints used as reference to assess MRN images are the clav-icle, the first rib, the subclavian artery and vein and thescalene anterior and medius muscles. The brachial plexusis formed from the primary ventral branches of the spinalnerves that originate in the cervical (C) 5, 6, 7, 8 and thoracic(T) segments 1. In some individuals smaller ventral brachesC4 and T2 participate.13

Topographically, the brachial plexus is divided in five seg-ments: roots, trunks, divisions, cords and terminal branches(Fig. 1).

The ventral roots exit through the intervertebral foramenof the cervical spine and they are divided into pre- and post-ganglionic with respect to the ganglion annexed to the dorsalroot.

Roots C5-C6 make up the upper trunk, root C7 contin-ues as the medial trunk and roots C8-T1 make up the lowertrunk. The three trunks go through the scalene anterior andmedius muscles (interscalene triangle).13,14

The subclavian and suprascapular nerves come from theupper trunk. The phrenic nerve originates from roots C3-C5,the dorsal scapular nerve stems from root C5 and the longthoracic nerve from roots C5 to C7.

The trunks split to form three anterior and three poste-rior divisions, which in turn join to form three distal cords,located on the lateral edge of the first rib. When it comes totheir relation with the axillary artery, cords are classified aslateral, posterior and medial. The lateral cord is formed byanterior divisions of the upper and medial trunks, gives riseto the lateral pectoral nerve (C5-7) and contributes to theformation of the musculocutaneous and median nerves. Theposterior cord is made up of the posterior divisions of thethree trunks giving rise to the subscapular nerve. The lowertrunk continues as the medial cord and originates the medialpectoral nerve (C8-T1), the medial cutaneous brachial nerve(T1) and the medial cutaneous nerve of the forearm (C8-T1).The cords end in five branches: the axillary, median, ulnar,musculocutaneous and radial nerves.14

The brachial plexus innervates the muscles of the shoul-der girdle, and its terminal branches, the muscles of theupper limbs. Table 1 describes the motor and sense innerva-tions of the brachial plexus.14,15

In MRIs the normal brachial plexus has some sort of a fas-cicular appearance and a continuous course. In T1-weightedsequences, the signal is isointense to that of the mus-cle and hyperintense with respect to it in the T2-weighedsequences. In T1 sequences, a thin fat plane is observedsurrounding every plexus structure. The ganglion annexedto the dorsal root is observed as a pseudo-nodular imagethicker than the root and it shows enhancement after theinjection of IV contrast. The three brachial plexus trunksusually have a similar diameter, they are symmetric betweenboth sides and do not present enhancement after the injec-tion of IV contrast.16,17

Protocol for the study of the brachial plexusthrough MRIs

The study protocol of the brachial plexus in our centeris done using a Signa HDxt 3.0 T machine (GE, Milwau-kee, Wi), with an eight-channel neurovascular coil (HDNVArray) simultaneously including both sides of the brachialplexus. The sequences used are T1- and T2-weighted coronalIDEAL (Iterative Decomposition of water and fat with Echo


90 C. Cejas et al.

Scalene medius muscles

C5

C6

C7

C8

T1

TI

TM

TS

Scalene anterior muscles

Interscalene triangle

Brachial plexus

Clavicle

First rib

A

C

B

Figure 1 (A) Diagram of the topographic division of the brachial plexus. (B) IDEAL Sequence water-weighted and with fat sup-

pression; maximum intensity reconstruction of projection on coronal plane where we can see all the elements that make up the

brachial plexus (UT: Upper trunk; MT: Medial trunk; LT: lower trunk). (C) 3 D GRE sequence in axial slice where we can see the exit

of ventral and dorsal roots until the entry of the intervertebral foramen.

Asymmetry and Least-squares estimation), with a thicknessof 1---0.1 mm, coronal 3D FIESTA with a thickness of 0.6 mm,axial 3D FIESTA with a thickness of 1.4 mm, and T1-weightedcoronal sequences 3D IDEAL after the injection of IVcontrast (Table 2). The IDEAL sequence developed byGeneral Electric (GE) Healthcare, or 3D SPACE (Sampling Per-fection with Application Optimized Contrast), developed bySiemens Healthcare, takes three different echo times thatseparate the image of the water from that of the fat. Finally,T1- and T2-weighted images are obtained simultaneouslywith four saturation pulse combinations: fat and waterdecomposition, and in-phase and out-of-phase images. Thissequence has the advantage of generating an even fat sat-uration yet despite the geometric variations presented bythe area of study. The drawback is in the temporary cost ofthe acquisition.18

SSFP (Steady State Free Precession) sequence, known byits different acronyms such as FIESTA (GE) or CISS (Siemens),is an echo gradient sequence that provides a high sig-nal/noise relation. Though it has very few flow artifacts,

it is sensitive to respiratory and deglutition movements.The clinical usefulness of this sequence derives from itscapacity to generate an adequate tissue signal with a highT2/T1 relation.19 It provides a detailed analysis of theintradural tract of the roots since it creates a contrastwith the signals of the cerebrospinal fluid (CSF). It is espe-cially useful in cases of trauma lesions, where it is possibleto visualize the alterations of the roots at the pregan-glionic level, even in the absence of pseudomeningocele.Notably this sequence generates poor soft-tissue contrastso it lacks usefulness in assessing the signal from the restof the surrounding structures such as vertebral bodies andmuscles.19

Through the use of multiplane reconstructions (MPR) andmaximum intensity projection (MIP) images these sequencesshow the nerve tract and its anatomic relations. T1-weighted sequences along with fat signal suppression areuseful in the assessment of nerve anatomy, they outlinethe perineural fat tissues and stud adjacent structures. Inturn T2-weighted sequences are more suitable for the study



Table 1 Motor and sense innervation of the brachial plexus.

Nerve Origin Motor innervation (muscles) Sense innervation

Dorsal scapular nerve C4, C5 Elevator scapulae

and rhomboids

---

Long thoracic nerve C4, C5, C6 Anterior serratus muscle ---

Subclavian nerve Upper trunk (C4, C5, C6) Subclavian muscle ---

Suprascapular nerve Upper trunk (C4, C5, C6) Supraspinatus and

infraspraspinatus muscles

---

Pectoral lateral nerve Lateral fasciculus (C5,

C6, C7)

Major pectoral muscle

Cutaneous muscle nerve Lateral fasciculus (C5,

C6, C7)

Coracobrachialis, brachial

and brachial biceps muscles

Continuous like the forearm

lateral cutaneous nerve

Pectoral medial nerve Medial fasciculus (C8,

T1)

Major and minor pectoral

muscle

---

Subscapular upper nerve Posterior fasciculus (C5) Subscapular muscle (upper

region)

Thoracodorsal nerve Posterior fasciculus (C6,

C7, C8)

Wide dorsal muscle ---

Subscapular inferior

nerve

Posterior fasciculus Subscapular (lower region)

and major round muscle

---

Axillary nerve Posterior fasciculus (C5,

C6)

Anterior branch: deltoid

muscle. Anterior branch: minor

round muscle and deltoid

muscle

Shoulder region, arm side

region

Radial nerve Posterior fasciculus (C5,

C6, C7, C8, T1)

Triceps, supinator, anconeus,

forearm extension and

brachioradialis muscles

Arm posterior region

Lateral root of the

median nerve

Lateral fasciculus (C6,

C7)

Articular branches: flexor carpi

radialis, round pronator, long

palmar, superficial and deep

common flexor (lateral half)

of fingers, square pronator,

palmar cutaneous muscles

Tenar and palmar region

of hand, elbow and wrist,

thumbs, index finger,

medial finger and half the

ring finger

Medial root of the

median nerve

Medial fasciculus (C8,

T1)

Terminals branches: muscles

of thenar eminence (except

for the thumb adductor), first

and second lumbrical muscles

Arm medial

cutaneous nerve

Medial fasciculus (C8-T1) --- Front and anterior arm skin

Medial fasciculus (C8-T1) --- Front and anterior forearm

skin

Medial cutaneous nerve

of the cubital forearm

Medial fasciculus (C7, C8

and T1)

Flexor carpi ulnaris muscle,

two medial bellies of the deep

flexor of fingers---intrinsic to

the hand (except for the thenar

eminence) and the two more

lateral lumbrical muscles)

Medial region of the hand,

one and a half fingers of the

palmar side and two and a

half fingers of the dorsal

side

Table 2 Protocol for the study of the brachial plexus neuropathy.

Sequence FOV Cutting thickness RT/ET Matrix NEX

Axial 3D FIESTA 27 1.4/0.0 5/1.9 320 × 320 0.8

Coronal 3D FIESTA 35 0.6/0.0 4.3/1.8 320 × 320 0.8

Coronal T2-weighted IDEAL 35 1.0/0.1 7080/92.7 320 × 256 3

Coronal T1-weighted IDEAL 40 1.0/0.1 1320/10.2 320 × 224 3


92 C. Cejas et al.

Figure 2 Trauma: 17-year-old male patient who had a motorcycle accident. He shows traumatic preganglionic lesion of the brachial

plexus. (A) Water T2-weighted IDEAL sequence on the coronal plane. (B) 3D GRE Sequence on the axial plane. Pseudomeningoceles

can be observed (arrows) at the level of the right intervertebral foramens C7-T1 and T1-T2 in relation to the avulsion of roots C8

and T1, respectively. Observe the changes of morphology and the displacement of the spinal cord in B. The patient did not undergo

surgery since the MRN determined preganglionic lesion (data that electrophysiological studies cannot provide).

of nerve course and to discard caliber and signal intensityabnormalities.

Also the combination of both sequence pulses allows usto observe denervation changes of the affected muscles.T2-weighted sequences allow us to find the presence ofmuscular edema/inflammation related to acute dener-vations. T1-weighted sequences show adipose infiltra-tion---finding associated with chronic denervation.20,21

IV contrast sequences are reserved for the study ofneoplastic or inflammatory diseases and during the late post-operative period to differentiate the presence of fibroustissue.22

In cases of plexus brachial entrapment, it is necessary toevaluate vascular structures by angiographic sequences and3D SPGR (Spoiled Gradient Recalled) T1 through an eight-channel coil CTL Array (Torso PA Signa---GE, Milwaukee, Wis),with IV contrast.23

Functional sequences are still in the pipeline.Diffusion weighted images (DWI) assess both qualitative

and quantitatively the movement of water in the tissue.High b values (1000 to 1400) are suggested for the study ofdiffusivity of peripheral nerve lesions, with quantificationof the diffusion coefficient (ADC map).24 This sequence inparticular obtains specific images of nerves with excellentfat and vascular signal suppression. Diffusion tensor images(DTI) derive from DWI and its 3D representation is tractogra-phy. These techniques assess the structure and disposition ofneural tracts in normal situations, as well as their displace-ment, disruption, infiltration or disorganization of fibers dueto tumors within or along the brachial plexus.25 Vargas et al.studied tractography images in patients with benign andmalignant neural tumors. In benign tumors, they showedthat the fibers surrounded or went through the tumor with-out any disruptions whatsoever. In malignant tumors, theyfound disruption/destruction and disorganization of nervefibers.26 In our institutio, we have not had the results wewere expecting with using these sequences and this is whywe do not include them in the standard protocol. Howeverwe continue working in its optimization.

Diseases affecting the brachial plexus

Mononeuropathy

Neuropathy due to trauma

Brachial plexus traumatic pathology presents different eti-ologies based on the age group.

In pediatric populations, the most frequent cause isexcessive traction during childbirth, that can cause proximaland/or distal paralysis of the brachial plexus.27,28

Erb-Duchenne palsy or proximal paralysis of the brachialplexus results from lesion of nerve roots C5-C6, sometimesC7 too, or of the entire upper trunk. In 25% of the cases, thephrenic nerve is also compromised.29,30

Klumpke’s palsy or distal paralysis occurs due to the avul-sion of roots C8 and T1; on some occasions it can affect rootC7. It is less common than the proximal variant.31

In adults, trauma is the most common cause of brachialplexus injury usually due to traffic accidents, on motorcycleaccidents in particular. Based on clinical and electrophys-iological findings, it is difficult to determine the pre- orpost-ganglionic origin of the lesions. The value of these dis-tinctions is in the fact that postganglionic lesions can berepaired with nerve graft or transposition and prognosis ismore favorable.32,33 Neurographic sequences have proven tobe effective in this distinction.

In preganglionic lesions, the MRN shows the avulsionof the root or roots with end-retractions associated withthe presence of pseudomeningocele (Fig. 2). These find-ings are usually accompanied by changes in T2-weightedsignals of the spinal cord expressed by a hyperintense sig-nal area due to edema in acute period and myelomalacia orsyringomyelia in chronic periods. The spinal cord can alsoshow changes of morphology due to displacement or trac-tion. Associated with the preganglionic lesion, it is possibleto find a lesion of the posterior roots which in the images itcan be translated as the presence of edema in paravertebralmuscles especially the multifidus muscle. In acute cases,



Figure 3 Trauma: 21-year-old male patient who had a motorcycle accident. He shows traumatic postganglionic lesion of the

brachial plexus. (A and B) Water-weighted IDEAL sequence. It is possible to observe avulsion of the roots and retraction of the ends

(arrows). Notice hyperintensity and increase in root thickness with lesion due to stretching. The patient underwent surgery with

nerve transposition and kinesic treatment. His evolution was not the one expected.

Figure 4 Lesion by entrapment. Thoracic outlet syndrome in a 9-year-old girl with paresthesia of the right upper limb.

(A) Computed Tomography (CT) in coronal reconstruction showing prominent transverse bilateral apophysis and right rudimen-

tary cervical rib with inferolateral inclination causing decrease of space for the lower trunk of the brachial plexus. (B) T2-weighted

IDEAL sequence showing thickening and course deviation of the right root C8. The patient underwent surgery with resection of

cervical rib, with excellent clinical evolution.

the muscle can show enhancement after the injection of IVcontrast.21,30---33

In postganglionic lesion, the MRN shows a wide spectrumof abnormalities ranging from root thickening to the com-plete separation of the fibers and end-retraction21,30,32,33

(Fig. 3).

Thoracic outlet syndrome

Thoracic outlet syndrome is neuropathy due to compressionin which the brachial plexus can show compressions at threespecific anatomic levels: the interscalene triangle, mediallylocated, whose base is made up by the subclavian artery,where the brachial plexus trunks are located posterior and


94 C. Cejas et al.

Figure 5 Neurofibromatosis; 24-year-old male patient in follow-up of his baseline disease. Study for the screening of malignant

transformation of neurofibromas. T2-weighted IDEAL sequence. (A---C) Coronal cuts. (D) Axial cut. (E) Curvilinear reconstruction.

It is possible to see ‘‘bundle’’ thickening of the brachial plexus roots, trunks, divisions and cords. In the present study no signs of

malignant transformation were observed.

superior to the artery; the costoclavicular space, of interme-dial location, and the minor retro-pectoral space, lateral tothe others. In the two latter spaces the subclavian vein is themost anterior structure, the homonymous artery is locatedposterior to the vein. The three brachial plexus cords arelocated above and posterior to the subclavian vessels. Atthese three levels, the brachial plexus can get trapped alongwith the subclavian artery and/or vein. The interscalene

and costoclavicular triangles are the spaces that are usuallycompromised.34

Brachial plexus entrapment can be due to the presenceof prominent transverse process of C7 vertebra, or that ofcervical ribs or accessory scalene muscles. Other less com-mon causes are post-traumatic fibrosis of scalene muscles,compression due to ‘‘backpack’’ activities or one massivebone callus due to the fracture of the clavicle. It can also be

Figure 6 Pancoast Tumor; 55-year-old male patient with right three month old progressive omalgia and palpebral ptosis. An expan-

sive, solid lesion is observed in the right supraclavicular fossa that contacts the pleural dome while compromising the homolateral

roots from C6 to T1, and extension onto the lower trunk and divisions. (A) T2 IDEAL sequence on the coronal plane showing one

hyperintense and heterogeneous neo-formation with irregular edges (long arrow). T1-weighted 3D IDEAL sequence after injection of

contrast. (B) Coronal plane. (C) On the parasagittal plane we can see an intense heterogeneous enhancement of mass (long arrows).

(D) T2 IDEAL sequence on the coronal plane. Notice the acute denervation signs of the muscles of the rotator cuff (short arrow).



Figure 7 Inflammatory Plexitis. Parsonage Turner syndrome in a 22-year-old woman with 15 day old pain in shoulder and right

upper limb. T2-weighted IDEAL sequence. (A) Coronal plane. (B) Right parasagittal plane. We can see the thickening of right roots

C5, C6, C7, C8 and left roots C6, C7 and C8 (arrowheads), the upper, medial and lower trunks and the anterior and posterior cords

in right predominance (arrow). Although the clinical manifestation was on the right side, the findings in the images were bilateral.

She had a good evolution after therapy with corticoid and immunoglobulin pulses.

due to muscular hypertrophy associated with activities suchas swimming, weight lifting, sports where the arm is thedominating limb such as tennis or even surgical positions.35

Other causes of entrapment are tumors from surroundingstructures such as lipomas.34,35

Based on the entrapment location the MRN of thebrachial plexus can show alteration in the roots, trunksor cords. The affected nerves can show displacement,thickening and increase of the T2-weighted signal inten-sity. Similarly the neurography allows us to determine thepresence of anatomic variants or other lesions resultingfrom entrapment (Fig. 4), and provide additional data suchas post-denervation changes in the adjacent muscles. Inthese patients, as it was explained in the section aboutthe study techniques, the protocol must be completedwith 3D SPGR sequences after the injection of IV con-trast and with dynamic manoeuvers: one phase with thearms by both sides of the body and another phase withthe arms raised. The MRN plays an important role in theentrapment syndromes of the brachial plexus because otherthan determining the cause and the exact location of thelesion it also allows the surgeon to improve the strategy oftreatment.36---38

Brachial plexus tumors

The most common primary tumors of the brachialplexus are benign tumors of the nerve sheath such asschwannomas, neurofibromas and their malignant vari-ants. Neurofibromas are usually found in the context ofneurofibromatosis.39

In the MRN, schwannomas and neurofibromas show char-acteristics in common. They are homogeneous lesions,isointense to the nerve and the muscle in T1-weightedsequences and hyperintense in T2-weighted sequences, with

homogeneous enhancement after the injection of IV con-trast. Several signs have been described that allow us tosuspect the presence of neurogenic tumors. Presentation in‘‘onion layers’’ describes a fascicular pattern of fusiformmorphology, the ‘‘target sign’’ in T2-weighted sequencesshows one hypointense center due to the presence of fibro-sis and a peripheral ring associated with the presence ofmyxoid material. The maximum tumor diameter is not usu-ally greater than 5 cm39---41 (Fig. 5). However they can beheterogeneous due to the presence of necrosis, cysticdegeneration or calcifications which makes differential diag-nosis difficult with the malignant variant.42

Half of malignant tumors originate de novo and theother half due to the malignant degeneration of a neurofi-broma. Approximately 10% of neurofibromas show malignanttransformation, hence the special interest of performingan image follow-up of patients with neurofibromatosis.Both malignant schwannomas and neurofibromas are usu-ally greater than 5 cm in its maximum diameter, they showirregular edges and a very heterogeneous enhancementafter the injection of IV contrast due to the presence ofnecrotic areas.43,44

Lymphomas do not often affect the brachial plexus andare usually due to primary lymphomas of the central ner-vous system.45---47 Tumor lesions of lipoma origin even intheir benign variants, can cause neuropathy due to extrin-sic compression.48 The pancoast tumor is a tumor of thepulmonary apex that characteristically invades the brachialplexus, and on some occasions neuropathic pain makes thepatient go to see the doctor49 (Fig. 6).

The MRN allows us to determine the location andcompromise of brachial plexus structures, and at the sametime provides us with data about the characteristics of thetumor in a more accurate way than other modalities.50


96 C. Cejas et al.

Figure 8 Chronic inflammatory demyelinating polyradiculoneuropathy. 32-year-old woman with symptoms of lumbosacral

polyneuropathy who had been diagnosed with chronic idiopathic demyelinating polyneuropathy through clinical examination and

neurography of lumbosacral plexus. She did not show any clinical manifestations of brachial plexus compromise. T2-weighted IDEAL

sequence. (A) Coronal Plane. (B) Right parasagittal plane. (C) Curvilinear reconstruction. We can see significant hypertrophy and

signal increase of the brachial plexus roots, trunks, divisions and cords from C4 to T1 both bilaterally and symmetrically.

Brachial polyneuropathy

Polineuropathies of inflammatory origin

Parsonage Turner

Parsonage Turner syndrome or amyotrophic neuralgia is ofunknown etiology, although an inflammatory/autoimmuneorigin is presumed. It occurs more often in middle-agedmen, with affectation of the right brachial plexus, and innearly 30% of the cases it is bilateral. It debuts with severe,sudden-onset pain and muscular weakness. In most casesit resolves in two months; however, it can persist for upto 2 or 3 years.51 In its acute/subacute stage, the MRNshows diffuse thickening and an increase of signal inten-sity in the T2-weighted sequences of the affected nerves(Fig. 7). It also allows us to determine the extent of thelesions which is very often greater than the clinical oneand that of the data provided by electrophysiological stud-ies. It is also possible to confirm postdenervation changesthat usually compromise the muscles of the shouldergirdle especially the serratus anterior, the supraspinatus andinfraspraspinatus muscles.52 In its chronic stage, as in other

polyneuropathies, a reduction of muscle trophism and adi-pose infiltration can be observed.20,21

Chronic idopathic demyelinating polyneuropathy

Chronic idiopathic demyelinating polyneuropathy (CIDP) isthe most common cause of demyelinating polyneuropathy.It shows chronic progressive or recurrent course, with pre-dominance of motor affectation of the proximal and distalmuscles of the limbs. Although there are clinical criteria forthe diagnosis of CIDP set by the American Academy of Neu-rology, in practice diagnosis is usually difficult to confirm dueto the heterogeneity of its clinical and electrophysiologicalpresentation. It is often necessary to resort to the biopsy ofthe peripheral nerve that confirms the selective loss of themyelin sheath.53

The MRN allows us to determine the extent of the diseaseat its onset and during the follow-up. It is possible to observethe diffuse thickening of the brachial plexus branches, whichacquires a fusiform morphology that allows us to distinguishit from other plexopathies of inflammatory origin.54 Tazawaet al55 compared the diameter of roots C6 and C7 in CIDPpatients and in normal subjects. They determined a 5 mm



Figure 9 Postradiotherapy Plexopathy. 74-year-old woman with a history of breast cancer who had been undergone surgery

and radiotherapy 15 years ago. (A) T2-weighted IDEAL sequence shows distal nodular thickening of left roots C8 and T1 (arrow).

(B) T1-weighted 3 D IDEAL sequences with contrast, where nodular reinforcement is observed (discontinued arrow). (C) T2-weighted

IDEAL sequence shows signs of pectoral muscle edema (thick arrow). (D) T2-weighted IDEAL sequence with water suppression.

Infraclavicular soft tissue fibrosis can be seen (arrowhead).

cut-off point from which it can be defined as CIDP. Anotherfinding made by the MRIs is the increase of signal intensityin T2-weighted sequences of compromised nerves. Also itis possible to observe focal or diffuse enhancement afterthe injection of IV contrast which translates into the rup-ture of the hematoneural barrier. Enhancement can persistafter the treatment and remission of symptoms.54 It is usu-ally accompanied by affectation of the lumbosacral plexusso its study is convenient56 (Fig. 8).

Radiation

Post-actinic neuropathy has an incidence of 10---20% and itoccurs in patients who have received high doses of radiation(>60 Gy).57 It is necessary to differentiate tumor recurrencefrom post-radiation inflammation when there is brachialplexus compromise in the context mentioned above.

Post-actinic neuropathy occurs between 30 months and20 years after radiotherapy, and in usually compromisesthe infraclavicular region. In turn, tumor recurrence occurswithin the first year of treatment and it usually affects thesupraclavicular region.58

The MRN is the modality of choice to differentiateboth entities. In post-radiation neuropathy it is common to

observe diffuse, symmetric thickening of the plexus, whichacquires a geographic disposition in relation to the irradia-tion field with an absence of tumor lesions. It is not commonto observe enhancement after the injection of IV contrast.In chronic periods, it is possible to observe tortuosities ofplexus branches with stratification of perineural fat due tothe presence of fibrosis59 (Fig. 9).

Diabetic polyneuropathy

Diabetes

Diabetic polyneuropathy is the most common neuropathy indiabetic patients, with a prevalence as high as 54% in type I

diabetes and 45% in type II diabetes.60 It occurs in a diffuseor focal/multifocal manner and it can be classified as havinga typical or an atypical presentation.

The typical diabetic polyneuropathy is usually of chronic,symmetric evolution, with sensitive-motor affectation andit is the most common form of presentation. The atypi-cal variant can occurs any time during the course of thedisease; its evolution is acute or chronic, it is usually asym-metric, monophasic and it can alternate nerve structure


98 C. Cejas et al.

Figure 10 Diabetic Neuropathy. 64-year-old male patient with a 10 year old poorly controlled type II diabetic polyneuropathy.

He showed sensorimotor signs in the right upper limb. T2-weighted IDEAL sequence. (A) We can see an irregular thickening of the

right spinal nerves C6 to T1 from its exit from the intervertebral foramens and in distal direction. (B) Multiplane reconstruction and

magnification of image A.

in time.61 Compromise of the brachial plexus is usuallyless frequent than that of the lumbosacral plexus, butwhen it is present, it usually coexists with lumbosacralpolyradiculopathy.62

The MRN is particularly useful for the atypical forms,where an accurate diagnosis of neuropathy has not beenobtained yet. The most common findings are mild to mod-erate increase of signal intensity in T2-weighted sequences,as well as variable thickening of the roots, trunks and cordscompromised. It is common to find asymmetric distribu-tion, even when the electromyographic examination showsneuropathy of one nerve only. As it happens in other plex-opathies, postdenervation changes will be observed in themuscles of the region63 (Fig. 10).

Vasculitis

Isolated vasculitis of the peripheral nervous system is anuncommon cause of brachial plexopathy. This polyneu-ropathy shows an asymmetric, progressive pattern ofdistribution.64 During the anatomopathological examinationthe multifocal neural ischemic lesion due to inflammationof the small- and mid-caliber epineural blood vessels isdescribed, and less frequently the lesions located in theperineurium and endoneurium. The clinical, electromyo-graphic and pathological findings are similar both in theneuropathy due to vasculitis and in the diabetic neuropathy.The status of non-diabetic patient is the way to differen-tiate both entities.65 In the MRN, the findings have similarcharacteristics to those of other inflammatory neuropathies.As it happens to be the case with other polyneuropathies,the MRN is capable of showing a greater compromiseto both the clinical presentation and electrophysiologicalstudies.66

Conclusion

The brachial plexus is an anatomically complex region homeof mononeuropathies and polyneuropathies of different eti-ologies. The MRN in high-field equipment accompanied byhigh-resolution sequences has become one of the pillarstogether with clinical examination and electrophysiologicalstudies for the diagnosis and follow-up of brachial plexuslesions.

Ethical responsibilities

Protection of people and animals. The authors declare thatno experiments with human beings or animals have beenperformed while conducting this investigation.

Data confidentiality. The authors confirm that in this articlethere are no data from patients.

Right to privacy and informed consent. The authors con-firm that in this article there are no data from patients.

Author contributions

1. Manager of the integrity of the study: CC and MN.2. Study Idea: CC, CR, GM and MN.3. Study Design: CC, CR, GM and MN.4. Data Mining: CC, CR and GM.5. Data Analysis and Interpretation: CC, CR and GM.6. Statistical Analysis: NA.7. Reference Search: CC, CR and GM.8. Writing: CC, CR, GM and MN.



9. Critical review of the manuscript with intellectually rel-evant remarks: CC, CR, GM and MN.

10. Approval of final version: CC, CR, GM and MN.

Conflict of interests

The authors declare no conflict of interests associated withthis article whatsoever.

Acknowledgements

Thanks to Ms. Inés Escobar, M.D., for her design of thebrachial plexus scheme shown in Fig. 1.

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