High Resolution Neurography of the Brachial Plexus by 3Tesla Magnetic

Home , Subclavian nerve

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Radiología. 2016;58(2):88---100

www.elsevier.es/rx

UPDATE IN RADIOLOGY

High resolution neurography of the brachial plexus

ଝ

by 3 Tesla magnetic resonance imaging

a,∗ a a b

C. Cejas , C. Rollán , G. Michelin , M. Nogués

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

Buenos Aires, Argentina

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

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

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

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

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

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

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

system 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.

PALABRAS CLAVE

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

Plexo braquial;

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

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

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

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

periférico 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

ଝ

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: ccejas@ﬂeni.org.ar (C. Cejas).

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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.

Introduction Roots C5-C6 make up the upper trunk, root C7 contin-

ues as the medial trunk and roots C8-T1 make up the lower

trunk. The three trunks go through the scalene anterior and

The study of the Peripheral Nervous System (PNS) through

13,14

medius muscles (interscalene triangle).

magnetic resonance imaging (MRI) dates back to the

1,2 The subclavian and suprascapular nerves come from the

1990’s. MR neurography (MRN) has coined the term thanks

upper trunk. The phrenic nerve originates from roots C3-C5,

to high-resolution techniques, in particular those provided

3,4 the dorsal scapular nerve stems from root C5 and the long

by 3 T equipment. These sequences have revolutionized

thoracic nerve from roots C5 to C7.

the study of plexuses and peripheral nerves because they

The trunks split to form three anterior and three poste-

provide us with a signiﬁcant improvement in the signal/noise

rior divisions, which in turn join to form three distal cords,

relation in shorter acquisition times, and they convey high

5 --- 7 located on the lateral edge of the ﬁrst rib. When it comes to

resolution and contrast images. Diagnosis of PNS disor-

their relation with the axillary artery, cords are classiﬁed as

ders was traditionally based on three pillars: medical history,

8 lateral, posterior and medial. The lateral cord is formed by

physical examination and electrophysiological studies. The

anterior divisions of the upper and medial trunks, gives rise

complex anatomy of the brachial plexus makes clinical and

to the lateral pectoral nerve (C5-7) and contributes to the

electrophysiological assessment difﬁcult; therefore, MRN

formation of the musculocutaneous and median nerves. The

can be placed as the fourth pillar among diagnostic stud-

posterior cord is made up of the posterior divisions of the

ies. Firstly, MRN images distinguish a normal plexus from

three trunks giving rise to the subscapular nerve. The lower

a pathological one; in addition, they determine accurately

trunk continues as the medial cord and originates the medial

the location of the lesion (root, trunk, division or cord), and

pectoral nerve (C8-T1), the medial cutaneous brachial nerve

whether it affects one or several of them (mononeuropathy

(T1) and the medial cutaneous nerve of the forearm (C8-T1).

vs polyneuropathy). On the other hand, MRN images outline

The cords end in ﬁve branches: the axillary, median, ulnar,

the extension of the lesion and it often speciﬁes the etiol-

8---11 musculocutaneous and radial nerves.

ogy of the plexus disorder. Electrophysiological studies,

The brachial plexus innervates the muscles of the shoul-

though very useful to determine the location and degree

der girdle, and its terminal branches, the muscles of the

of nerve compromise, do not deﬁne the exact location or

12 upper limbs. Table 1 describes the motor and sense innerva-

etiology of brachial plexus lesions.

14,15

tions of the brachial plexus.

The goals of this review are to study brachial plexus

In MRIs the normal brachial plexus has some sort of a fas-

anatomy, describe the study protocol for MRN and the main

cicular appearance and a continuous course. In T1-weighted

diseases that can affect it.

sequences, the signal is isointense to that of the mus-

cle and hyperintense with respect to it in the T2-weighed

Anatomic analysis of the brachial plexus

sequences. In T1 sequences, a thin fat plane is observed

through MRIs surrounding every plexus structure. The ganglion annexed

to the dorsal root is observed as a pseudo-nodular image

MRI anatomic analysis of the brachial plexus beneﬁted sig- thicker than the root and it shows enhancement after the

niﬁcantly from neurographic sequences. The anatomical injection of IV contrast. The three brachial plexus trunks

points used as reference to assess MRN images are the clav- usually have a similar diameter, they are symmetric between

icle, the ﬁrst rib, the subclavian artery and vein and the both sides and do not present enhancement after the injec-

16,17

scalene anterior and medius muscles. The brachial plexus tion of IV contrast.

is formed from the primary ventral branches of the spinal

nerves that originate in the cervical (C) 5, 6, 7, 8 and thoracic

Protocol for the study of the brachial plexus

(T) segments 1. In some individuals smaller ventral braches

C4 and T2 participate. through MRIs

Topographically, the brachial plexus is divided in ﬁve seg-

ments: roots, trunks, divisions, cords and terminal branches The study protocol of the brachial plexus in our center

(Fig. 1). is done using a Signa HDxt 3.0 T machine (GE, Milwau-

The ventral roots exit through the intervertebral foramen kee, Wi), with an eight-channel neurovascular coil (HDNV

of the cervical spine and they are divided into pre- and post- Array) simultaneously including both sides of the brachial

ganglionic with respect to the ganglion annexed to the dorsal plexus. The sequences used are T1- and T2-weighted coronal

root. IDEAL (Iterative Decomposition of water and fat with Echo

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90 C. Cejas et al.

A B

Scalene medius muscles C7 Scalene anterior muscles C8

Interscalene triangle T1 TS TM

Brachial plexus TI

First rib

Clavicle

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 thickness it is sensitive to respiratory and deglutition movements.

of 1---0.1 mm, coronal 3D FIESTA with a thickness of 0.6 mm, The clinical usefulness of this sequence derives from its

axial 3D FIESTA with a thickness of 1.4 mm, and T1-weighted capacity to generate an adequate tissue signal with a high

coronal sequences 3D IDEAL after the injection of IV T2/T1 relation. It provides a detailed analysis of the

contrast (Table 2). The IDEAL sequence developed by intradural tract of the roots since it creates a contrast

General Electric (GE) Healthcare, or 3D SPACE (Sampling Per- with the signals of the cerebrospinal ﬂuid (CSF). It is espe-

fection with Application Optimized Contrast), developed by cially useful in cases of trauma lesions, where it is possible

Siemens Healthcare, takes three different echo times that to visualize the alterations of the roots at the pregan-

separate the image of the water from that of the fat. Finally, glionic level, even in the absence of pseudomeningocele.

T1- and T2-weighted images are obtained simultaneously Notably this sequence generates poor soft-tissue contrast

with four saturation pulse combinations: fat and water so it lacks usefulness in assessing the signal from the rest

decomposition, and in-phase and out-of-phase images. This of the surrounding structures such as vertebral bodies and

sequence has the advantage of generating an even fat sat- muscles.

uration yet despite the geometric variations presented by Through the use of multiplane reconstructions (MPR) and

the area of study. The drawback is in the temporary cost of maximum intensity projection (MIP) images these sequences

the acquisition. show the nerve tract and its anatomic relations. T1-

SSFP (Steady State Free Precession) sequence, known by weighted sequences along with fat signal suppression are

its different acronyms such as FIESTA (GE) or CISS (Siemens), useful in the assessment of nerve anatomy, they outline

is an echo gradient sequence that provides a high sig- the perineural fat tissues and stud adjacent structures. In

nal/noise relation. Though it has very few ﬂow artifacts, turn T2-weighted sequences are more suitable for the study

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High resolution neurography of the brachial plexus 91

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, Major pectoral muscle

C6, C7)

Cutaneous muscle nerve Lateral fasciculus (C5, Coracobrachialis, brachial Continuous like the forearm

C6, C7) and brachial biceps muscles lateral cutaneous nerve

Pectoral medial nerve Medial fasciculus (C8, Major and minor pectoral ---

T1) muscle

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

region)

Thoracodorsal nerve Posterior fasciculus (C6, Wide dorsal muscle ---

C7, C8)

Subscapular inferior Posterior fasciculus Subscapular (lower region) ---

nerve and major round muscle

Axillary nerve Posterior fasciculus (C5, Anterior branch: deltoid Shoulder region, arm side

C6) muscle. Anterior branch: minor region

round muscle and deltoid

muscle

Radial nerve Posterior fasciculus (C5, Triceps, supinator, anconeus, Arm posterior region

C6, C7, C8, T1) forearm extension and

brachioradialis muscles

Lateral root of the Lateral fasciculus (C6, Articular branches: ﬂexor carpi Tenar and palmar region

median nerve C7) radialis, round pronator, long of hand, elbow and wrist,

palmar, superﬁcial and deep thumbs, index ﬁnger,

common ﬂexor (lateral half) medial ﬁnger and half the

of ﬁngers, square pronator, ring ﬁnger

palmar cutaneous muscles

Medial root of the Medial fasciculus (C8, Terminals branches: muscles

median nerve T1) of thenar eminence (except

for the thumb adductor), ﬁrst

and second lumbrical muscles

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

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

skin

Medial cutaneous nerve Medial fasciculus (C7, C8 Flexor carpi ulnaris muscle, Medial region of the hand,

of the cubital forearm and T1) two medial bellies of the deep one and a half ﬁngers of the

ﬂexor of ﬁngers---intrinsic to palmar side and two and a

the hand (except for the thenar half ﬁngers of the dorsal

eminence) and the two more side

lateral lumbrical muscles)

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

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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 intensity Diseases affecting the brachial plexus

abnormalities.

Also the combination of both sequence pulses allows us

Mononeuropathy

to observe denervation changes of the affected muscles.

T2-weighted sequences allow us to ﬁnd the presence of

muscular edema/inﬂammation related to acute dener- Neuropathy due to trauma

vations. T1-weighted sequences show adipose inﬁltra- Brachial plexus traumatic pathology presents different eti-

20,21

tion---ﬁnding associated with chronic denervation. ologies based on the age group.

IV contrast sequences are reserved for the study of In pediatric populations, the most frequent cause is

neoplastic or inﬂammatory diseases and during the late post- excessive traction during childbirth, that can cause proximal

27,28

operative period to differentiate the presence of ﬁbrous and/or distal paralysis of the brachial plexus.

tissue. Erb-Duchenne palsy or proximal paralysis of the brachial

In cases of plexus brachial entrapment, it is necessary to plexus results from lesion of nerve roots C5-C6, sometimes

evaluate vascular structures by angiographic sequences and C7 too, or of the entire upper trunk. In 25% of the cases, the

29,30

3D SPGR (Spoiled Gradient Recalled) T1 through an eight- phrenic nerve is also compromised.

channel coil CTL Array (Torso PA Signa---GE, Milwaukee, Wis), Klumpke’s palsy or distal paralysis occurs due to the avul-

with IV contrast. sion of roots C8 and T1; on some occasions it can affect root

Functional sequences are still in the pipeline. C7. It is less common than the proximal variant.

Diffusion weighted images (DWI) assess both qualitative In adults, trauma is the most common cause of brachial

and quantitatively the movement of water in the tissue. plexus injury usually due to trafﬁc accidents, on motorcycle

High b values (1000 to 1400) are suggested for the study of accidents in particular. Based on clinical and electrophys-

diffusivity of peripheral nerve lesions, with quantification iological findings, it is difficult to determine the pre- or

of the diffusion coefﬁcient (ADC map). This sequence in post-ganglionic origin of the lesions. The value of these dis-

particular obtains speciﬁc images of nerves with excellent tinctions is in the fact that postganglionic lesions can be

fat and vascular signal suppression. Diffusion tensor images repaired with nerve graft or transposition and prognosis is

32,33

(DTI) derive from DWI and its 3D representation is tractogra- more favorable. Neurographic sequences have proven to

phy. These techniques assess the structure and disposition of be effective in this distinction.

neural tracts in normal situations, as well as their displace- In preganglionic lesions, the MRN shows the avulsion

ment, disruption, inﬁltration or disorganization of ﬁbers due of the root or roots with end-retractions associated with

to tumors within or along the brachial plexus. Vargas et al. the presence of pseudomeningocele (Fig. 2). These ﬁnd-

studied tractography images in patients with benign and ings are usually accompanied by changes in T2-weighted

malignant neural tumors. In benign tumors, they showed signals of the spinal cord expressed by a hyperintense sig-

that the ﬁbers surrounded or went through the tumor with- nal area due to edema in acute period and myelomalacia or

out any disruptions whatsoever. In malignant tumors, they syringomyelia in chronic periods. The spinal cord can also

found disruption/destruction and disorganization of nerve show changes of morphology due to displacement or trac-

ﬁbers. In our institutio, we have not had the results we tion. Associated with the preganglionic lesion, it is possible

were expecting with using these sequences and this is why to ﬁnd a lesion of the posterior roots which in the images it

we do not include them in the standard protocol. However can be translated as the presence of edema in paravertebral

we continue working in its optimization. muscles especially the multiﬁdus muscle. In acute cases,

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High resolution neurography of the brachial plexus 93

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 IV Thoracic outlet syndrome

21,30---33

contrast. Thoracic outlet syndrome is neuropathy due to compression

In postganglionic lesion, the MRN shows a wide spectrum in which the brachial plexus can show compressions at three

of abnormalities ranging from root thickening to the com- speciﬁc anatomic levels: the interscalene triangle, medially

21,30,32,33

plete separation of the ﬁbers and end-retraction located, whose base is made up by the subclavian artery,

(Fig. 3). where the brachial plexus trunks are located posterior and

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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- and costoclavicular triangles are the spaces that are usually

dial location, and the minor retro-pectoral space, lateral to compromised.

the others. In the two latter spaces the subclavian vein is the Brachial plexus entrapment can be due to the presence

most anterior structure, the homonymous artery is located of prominent transverse process of C7 vertebra, or that of

posterior to the vein. The three brachial plexus cords are cervical ribs or accessory scalene muscles. Other less com-

located above and posterior to the subclavian vessels. At mon causes are post-traumatic ﬁbrosis of scalene muscles,

these three levels, the brachial plexus can get trapped along compression due to ‘‘backpack’’ activities or one massive

with the subclavian artery and/or vein. The interscalene bone 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).

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High resolution neurography of the brachial plexus 95

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 such homogeneous enhancement after the injection of IV con-

as swimming, weight lifting, sports where the arm is the trast. Several signs have been described that allow us to

dominating limb such as tennis or even surgical positions. suspect the presence of neurogenic tumors. Presentation in

Other causes of entrapment are tumors from surrounding ‘‘onion layers’’ describes a fascicular pattern of fusiform

34,35

structures such as lipomas. morphology, the ‘‘target sign’’ in T2-weighted sequences

Based on the entrapment location the MRN of the shows one hypointense center due to the presence of ﬁbro-

brachial plexus can show alteration in the roots, trunks sis and a peripheral ring associated with the presence of

or cords. The affected nerves can show displacement, myxoid material. The maximum tumor diameter is not usu-

39---41

thickening and increase of the T2-weighted signal inten- ally greater than 5 cm (Fig. 5). However they can be

sity. Similarly the neurography allows us to determine the heterogeneous due to the presence of necrosis, cystic

presence of anatomic variants or other lesions resulting degeneration or calciﬁcations which makes differential diag-

from entrapment (Fig. 4), and provide additional data such nosis difﬁcult with the malignant variant.

as post-denervation changes in the adjacent muscles. In Half of malignant tumors originate de novo and the

these patients, as it was explained in the section about other half due to the malignant degeneration of a neuroﬁ-

the study techniques, the protocol must be completed broma. Approximately 10% of neuroﬁbromas show malignant

with 3D SPGR sequences after the injection of IV con- transformation, hence the special interest of performing

trast and with dynamic manoeuvers: one phase with the an image follow-up of patients with neuroﬁbromatosis.

arms by both sides of the body and another phase with Both malignant schwannomas and neuroﬁbromas are usu-

the arms raised. The MRN plays an important role in the ally greater than 5 cm in its maximum diameter, they show

entrapment syndromes of the brachial plexus because other irregular edges and a very heterogeneous enhancement

than determining the cause and the exact location of the after the injection of IV contrast due to the presence of

43,44

lesion it also allows the surgeon to improve the strategy of necrotic areas.

36---38

treatment. Lymphomas do not often affect the brachial plexus and

are usually due to primary lymphomas of the central ner-

45---47

Brachial plexus tumors vous system. Tumor lesions of lipoma origin even in

The most common primary tumors of the brachial their benign variants, can cause neuropathy due to extrin-

plexus are benign tumors of the nerve sheath such as sic compression. The pancoast tumor is a tumor of the

schwannomas, neuroﬁbromas and their malignant vari- pulmonary apex that characteristically invades the brachial

ants. Neuroﬁbromas are usually found in the context of plexus, and on some occasions neuropathic pain makes the

39 49

neuroﬁbromatosis. patient go to see the doctor (Fig. 6).

In the MRN, schwannomas and neuroﬁbromas show char- The MRN allows us to determine the location and

acteristics in common. They are homogeneous lesions, compromise of brachial plexus structures, and at the same

isointense to the nerve and the muscle in T1-weighted time provides us with data about the characteristics of the

sequences and hyperintense in T2-weighted sequences, with tumor in a more accurate way than other modalities.

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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 polyneuropathies, a reduction of muscle trophism and adi-

20,21

pose inﬁltration can be observed.

Polineuropathies of inﬂammatory origin

Chronic idopathic demyelinating polyneuropathy

Parsonage Turner Chronic idiopathic demyelinating polyneuropathy (CIDP) is

Parsonage Turner syndrome or amyotrophic neuralgia is of the most common cause of demyelinating polyneuropathy.

unknown etiology, although an inﬂammatory/autoimmune It shows chronic progressive or recurrent course, with pre-

origin is presumed. It occurs more often in middle-aged dominance of motor affectation of the proximal and distal

men, with affectation of the right brachial plexus, and in muscles of the limbs. Although there are clinical criteria for

nearly 30% of the cases it is bilateral. It debuts with severe, the diagnosis of CIDP set by the American Academy of Neu-

sudden-onset pain and muscular weakness. In most cases rology, in practice diagnosis is usually difﬁcult to conﬁrm due

it resolves in two months; however, it can persist for up to the heterogeneity of its clinical and electrophysiological

to 2 or 3 years. In its acute/subacute stage, the MRN presentation. It is often necessary to resort to the biopsy of

shows diffuse thickening and an increase of signal inten- the peripheral nerve that conﬁrms the selective loss of the

sity in the T2-weighted sequences of the affected nerves myelin sheath.

(Fig. 7). It also allows us to determine the extent of the The MRN allows us to determine the extent of the disease

lesions which is very often greater than the clinical one at its onset and during the follow-up. It is possible to observe

and that of the data provided by electrophysiological stud- the diffuse thickening of the brachial plexus branches, which

ies. It is also possible to conﬁrm postdenervation changes acquires a fusiform morphology that allows us to distinguish

that usually compromise the muscles of the shoulder it from other plexopathies of inﬂammatory origin. Tazawa

girdle especially the serratus anterior, the supraspinatus and et al compared the diameter of roots C6 and C7 in CIDP

infraspraspinatus muscles. In its chronic stage, as in other patients and in normal subjects. They determined a 5 mm

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High resolution neurography of the brachial plexus 97

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. Another observe diffuse, symmetric thickening of the plexus, which

ﬁnding made by the MRIs is the increase of signal intensity acquires a geographic disposition in relation to the irradia-

in T2-weighted sequences of compromised nerves. Also it tion ﬁeld with an absence of tumor lesions. It is not common

is possible to observe focal or diffuse enhancement after to observe enhancement after the injection of IV contrast.

the injection of IV contrast which translates into the rup- In chronic periods, it is possible to observe tortuosities of

ture of the hematoneural barrier. Enhancement can persist plexus branches with stratiﬁcation of perineural fat due to

54 59

after the treatment and remission of symptoms. It is usu- the presence of ﬁbrosis (Fig. 9).

ally accompanied by affectation of the lumbosacral plexus

so its study is convenient (Fig. 8).

Diabetic polyneuropathy

Radiation

Post-actinic neuropathy has an incidence of 10---20% and it Diabetes

occurs in patients who have received high doses of radiation Diabetic polyneuropathy is the most common neuropathy in

(>60 Gy). It is necessary to differentiate tumor recurrence diabetic patients, with a prevalence as high as 54% in type I

from post-radiation inﬂammation when there is brachial diabetes and 45% in type II diabetes. It occurs in a diffuse

plexus compromise in the context mentioned above. or focal/multifocal manner and it can be classiﬁed as having

Post-actinic neuropathy occurs between 30 months and a typical or an atypical presentation.

20 years after radiotherapy, and in usually compromises The typical diabetic polyneuropathy is usually of chronic,

the infraclavicular region. In turn, tumor recurrence occurs symmetric evolution, with sensitive-motor affectation and

within the ﬁrst year of treatment and it usually affects the it is the most common form of presentation. The atypi-

supraclavicular region. cal variant can occurs any time during the course of the

The MRN is the modality of choice to differentiate disease; its evolution is acute or chronic, it is usually asym-

both entities. In post-radiation neuropathy it is common to metric, monophasic and it can alternate nerve structure

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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. Compromise of the brachial plexus is usually Conclusion

less frequent than that of the lumbosacral plexus, but

when it is present, it usually coexists with lumbosacral The brachial plexus is an anatomically complex region home

polyradiculopathy. of mononeuropathies and polyneuropathies of different eti-

The MRN is particularly useful for the atypical forms, ologies. The MRN in high-ﬁeld equipment accompanied by

where an accurate diagnosis of neuropathy has not been high-resolution sequences has become one of the pillars

obtained yet. The most common ﬁndings are mild to mod- together with clinical examination and electrophysiological

erate increase of signal intensity in T2-weighted sequences, studies for the diagnosis and follow-up of brachial plexus

as well as variable thickening of the roots, trunks and cords lesions.

compromised. It is common to ﬁnd asymmetric distribu-

tion, even when the electromyographic examination shows

Ethical responsibilities

neuropathy of one nerve only. As it happens in other plex-

opathies, postdenervation changes will be observed in the

63 Protection of people and animals. The authors declare that

muscles of the region (Fig. 10).

no experiments with human beings or animals have been

performed while conducting this investigation.

Vasculitis

Isolated vasculitis of the peripheral nervous system is an Data conﬁdentiality. The authors conﬁrm that in this article

uncommon cause of brachial plexopathy. This polyneu- there are no data from patients.

ropathy shows an asymmetric, progressive pattern of

distribution. During the anatomopathological examination

Right to privacy and informed consent. The authors con-

the multifocal neural ischemic lesion due to inﬂammation

ﬁrm that in this article there are no data from patients.

of the small- and mid-caliber epineural blood vessels is

described, and less frequently the lesions located in the

perineurium and endoneurium. The clinical, electromyo- Author contributions

graphic and pathological ﬁndings are similar both in the

neuropathy due to vasculitis and in the diabetic neuropathy. 1. Manager of the integrity of the study: CC and MN.

The status of non-diabetic patient is the way to differen- 2. Study Idea: CC, CR, GM and MN.

tiate both entities. In the MRN, the ﬁndings have similar 3. Study Design: CC, CR, GM and MN.

characteristics to those of other inﬂammatory neuropathies. 4. Data Mining: CC, CR and GM.

As it happens to be the case with other polyneuropathies, 5. Data Analysis and Interpretation: CC, CR and GM.

the MRN is capable of showing a greater compromise 6. Statistical Analysis: NA.

to both the clinical presentation and electrophysiological 7. Reference Search: CC, CR and GM.

studies. 8. Writing: CC, CR, GM and MN.

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High resolution neurography of the brachial plexus 99

9. Critical review of the manuscript with intellectually rel- 15. Martinez Benia F, Pinazzo S. Anatomía del sistema nervioso per-

evant remarks: CC, CR, GM and MN. iférico. Parte 1: inervación del miembro superior. In: Socolovsky

10. Approval of ﬁnal version: CC, CR, GM and MN. M, editor. Introducción a la cirugía de los nervios periféricos.

Buenos Aires: Journal; 2013. p. 3---5.

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Conﬂict of interests Neuroimaging Clin N Am. 2014;24:91---108.

17. Rubin JA, Wesolowski JR. Neck MR imaging anatomy. Magn Reson

Imaging Clin N Am. 2011;19:457---73.

The authors declare no conﬂict of interests associated with

18. Cha J, Hong H, Park J, Paik S, Lee H. Practical application of

this article whatsoever.

iterative decomposition of water and fat with echo asymme-

try and least-squares estimation (IDEAL) imaging in minimizing

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