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A simplified approach to MR imaging of the brachial plexus
Poster No.:
C-2218
Congress:
ECR 2012
Type:
Educational Exhibit
Authors:
I. Rehman , N. Uddin , F. Khosa ; Lahore/PK, Atlanta, GA/US
Keywords:
Trauma, Tissue characterisation, Education, Diagnostic procedure,
MR, Neuroradiology peripheral nerve, Head and neck
DOI:
10.1594/ecr2012/C-2218
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Page 1 of 24
Learning objectives
To illustrate the role of MR in imaging the brachial plexus; simplifying:•
•
•
•
The indications of the study.
MRI protocol.
Interpretation of normal findings.
Characterisation of brachial plexus pathology.
Background
Characterization of the presence and type of brachial plexus pathology can be a daunting
task for the radiologist. Clinical history and examination is limited most of the time,
furthermore, the option of "sticking a needle in" is high risk. MRI provides a multiplanar
non-invasive approach for baseline evaluation, and hence can be crucial in dictating
further management in both trauma and oncology setting.
Normal Anatomy
Brachial plexus is formed by the ventral rami of C5 -T1 (Fig 1) lying between anterior and
middle scalene muscles in the posterior triangle of neck. Upper two rami unite to form
the upper trunk and the lower two unite to form the lower trunk while the C7 nerve root
continues as middle trunk; at the lateral border of interscalene triangle. The trunks divide
into anterior and posterior divisions just behind the clavicle, which in turn, unite to form
the cords at or just lateral to the outer border of first rib (Fig 2). The cords are named as
medial, lateral and posterior according to their relation to subclavian/axillary artery; these
in turn divide into the five terminal branches at the lateral border of pectoralis minor.
MRI protocol
Sagittal plane is invaluable for imaging the nerves in cross section (Fig 3) whereas
coronal images not only show the nerves in continuity but are also used for right to left
comparisons. Axial sequences are obtained for evaluating the nerve roots at their origin
(Fig 4); another indication being evaluation of the pathology seen on other two planes.
Post contrast imaging is performed for characterization of tumours and in trauma setting.
Nevertheless, selection of sequences has to be tailored to individual study to get the best
result.
Page 2 of 24
A commonly employed protocol is to perform Coronal T1 and T2 weighted images (WI)
with fat saturation (fat sat) as well as sagittal T1 and T2 WI of the affected/abnormal side,
followed by axial T1 and T2 WI as and where required. Similarly, post contrast T1 weighted
fat sat imaging is performed when initial imaging has shown a local mass or thickening
of nerves and in trauma setting.
Images for this section:
Fig. 1: Brachial plexus illustration. Text in green marks the anatomical landmarks for
division. Roots form trunks at the lateral border of interscalene triangle, trunks subdivide
into divisions just posterior to clavicle, and divisions in turn, form cords at the outer border
of first rib. Terminal branches are formed at the lateral border of pectoralis minor muscle.
Page 3 of 24
Fig. 2: Normal Anatomy: Coronal T2 WI showing the cords and trunks of brachial plexus
lying between Middle scalene (MSM) in A and Anterior scalene (ASM) muscles in B.
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Fig. 3: Sagittal Anatomy: T2 WI showing the three cords of brachial plexus lying in
retropectoralis minor space. (SA: subclavian artery, SV: subclavian vein, MC: medial
cord, PC: posterior cord, LC: lateral cord)
Page 5 of 24
Fig. 4: Normal Anatomy: Axial T2 (A) and T1 WI (B) showing brachial plexus roots
emerging from neural foramina.
Page 6 of 24
Imaging findings OR Procedure details
Traumatic plexopathy
The basic concern of imaging in trauma setting is to differentiate between pre and post
ganglionic injury. MRI is indispensible for demonstrating injury to the cord itself, not shown
by any other imaging modality. Findings may include focal edema, focal hemorrhage in
acute phase and myelomalacia in the chronic phase. Avulsion of the cord, though rare,
is also well seen.
Traumatic pseudomeningoceles are well appreciated on T2 weighted sequences (Fig 5),
coexistence of a nerve root avulsion remains difficult to decide and indirect signs should
be taken into account. These include:
1.
2.
3.
4.
Non-visualization of the nerves on the affected side with normal visualization
on the contralateral side; and/or
Displacement of cord to the contralateral side owing to the absence of
normal traction provided by the intact nerves. (Fig 5)
Post contrast imaging may show enhancement of intradural nerves where
despite anatomical continuity, functional impairment has set in.
Enhancement of paraspinal muscles especially multifidus is also an indirect
sign.
Post ganglionic injuries may manifest in the form of edema (Fig 6); anatomic discontinuity
with or without nerve retraction ball; involvement of plexus in local hematoma which may
or may not be associated with fracture of clavicle etc. (Fig 7-9)
Radiation plexopathy
Post Radiation (XRT) thickening and fibrosis of the brachial plexus can present as a
diagnostic dilemma. Few key points include:
1.
2.
3.
Is there a mass? Presence of mass is can be an indicator of a recurrence.
How much time has elapsed since XRT? Post XRT thickening occurs at
5-30 months after radiation to the axilla with a peak incidence at 10 months.
Changes occurring years after XRT are more likely to be a recurrence rather
than post radiation fibrosis.
What is the signal intensity on T2 weighted images? Fibrosis maintains low
signal intensity on both T1 and T2 WI. (Fig 10, 11)
Inflammatory plexopathy
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Brachial plexus may get secondarily involved in infection/inflammation of the
supraclavicular fossa or axilla with resulting weakness and/or pain and paraesthesia
along the involved nerve's distribution (Fig 12, 13).
Neoplastic plexopathy
Commonest benign tumours involving brachial plexus include neurofibroma &
schwannoma. Multiple neurofibromas are seen in cases of neurofibromatosis type 1.
Both of these have an oval orientation parallel to the long axis of the involved nerve
with schwannoma maintaining an eccentric relation to the nerve as it "displaces and
compresses" adjacent nerve fascicles rather than "infiltrating" them like a plexiform
neurofibroma. (Fig 14)
Benign nerve sheath tumours usually demonstrate high signal intensity on T2-WI and
some central areas of inhomogeneity (the target sign-fig 15). Avid uniform post contrast
enhancement is most common. It's not usually possible to differentiate between a
schwannoma and neurofibroma on imaging alone; few differentiating features between
the two bein:1.
2.
3.
The orientation of the lesion with the nerve of origin
Multiplicity
History of neurofibromatosis or presence of other signs like dural ectasia etc.
Malignant peripheral nerve sheath tumours do not show any specific imaging features in
contrast to the benign lesions. Some imaging features which may help in differentiation
include: absence of target sign on T2-WI, poorly defined margins, infiltration into
surrounding tissues etc.
Brachial plexus may also get involved in lymphomatous adenopathy in the axilla or rarely
get involved in neurolyphomatosis as an extension of the primary CNS lymphoma or as
a primary lymphoma of peripheral nerves (Fig 16).
Secondary malignancies involving the brachial plexus are more common than the primary
tumours of the plexus. Commonest tumours being the breast and lung cancers, followed
by melanoma etc (Fig 17-19).
Images for this section:
Page 8 of 24
Fig. 5: Post traumatic meningocoele: Coronal T1 and T2 WI with fat sat (A & B) showing
a meningocoele in relation to C8 cervical nerve root at C7-D1 interspace. Axial T2 WI
(C) through the same interspace re-demonstrates the meningocoele. Cervical cord is
displaced to the right, with intact right sided nerve roots. Left sided nerve roots are not
visualized, indirectly denoting avulsion injury. Oblique and Coronal 3D reconstructions
(D & E) demonstrate different profiles of the meningocoele.
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Fig. 6: Post traumatic edema. Coronal (A & B)and axial (C & D) T2 WI with fat sat showing
extensive edema involving the brachial plexus in the root of neck extending down into
axilla along the cords of brachial plexus.
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Fig. 7: Post traumatic hematoma: Coronal T1 WI (A) and T2 WI with fat sat (B) showing
a heterogeneous low signal intensity (SI) on T1 WI and high SI on T2 WI involving the left
brachial plexus in the supraclavicular fossa, representing a partly organized hematoma.
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Fig. 8: Fracture of clavicle: AP projection of clavicle showing a fracture of left clavicle
with inferior displacement of the lateral fragment.
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Fig. 9: Fracture of clavicle with surrounding hematoma in the same patient. Coronal T1
WI (A) and T2 WI with fat sat (B) through the clavicle show the fractured depressed lateral
segment of left clavicle with a soft tissue mass of low signal intensity (SI) on T1 WI and
heterogeneously high SI on T2 WI consistent with hematoma. Edema extends along the
cords of brachial plexus into the axilla consistent with injury to the plexus. Axial T1 and
T2 WI (C & D) showing the hematoma along left clavicle.
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Fig. 10: Radiation Plexopathy. Coronal T2 WI with fat sat through the plexus show
thickening and edema of the cords bilaterally without any discrete mass. This patient had
H/O local xrt for Burkit lymphoma.
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Fig. 11: Radiation plexopathy: Coronal T1 (A) and T2 WI (B) showing thickening of the left
sided brachial plexus which maintains low signal intensity on all sequences, representing
post radiation fibrosis.
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Fig. 12: Inflammatory plexopathy. Coronal T2 WI with fat sat (A) and Axial T1 WI fat sat
pre (B) and post contrast (C) images showing an ill-defined enhancing soft tissue mass in
left supraclavicular region, consistent with cellulitis/early abscess formation in this patient
with H/O IV drug abuse. The brachial plexus is seen running through the mass.
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Fig. 13: Nodular Fasciitis. Coronal T1 (A) and T2 WI with fat sat (B) showing a
nodular rounded mass (not following the nerve) of low signal intensity (SI) on T1 and
heterogeneous high SI on T2 WI closely abutting the right sided brachial plexus. Axial
pre and post contrast T1 WI with fat sat (C & D) shows heterogeneous enhancement.
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Fig. 14: Benign tumour. Coronal T1 and T2 WI with fat sath (A & B)showing a fusiform
swelling involving the lateral cord of left brachial plexus. Note the low signal intensity (SI)
on T1 WI (A, C) and uniform high SI on T2 WI with fat sat (B). It shows avid uniform post
contrast enhancement (D) consistent with a benign tumour.
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Fig. 15: Brachial nerve sheath tumour. Coronal T2 WI with fat sat (A) showing a high
signal intensity (SI) dumb bell shaped mass arising from D1 nerve root. Sagittal T1 WI (B)
through the left parasagittal region demonstrates the mass with low SI. Axial T2 and T1
WI (C & D) showing the mass in left supraclavicular region extending into axillary apex.
Post contrast T1 WI with fat sat (E) showing heterogeneous central enhancement.
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Fig. 16: Lymphoma. Coronal STIR image (A) showing infiltrative mass encasing the
brachial plexus, extending along the plexus into the axilla. Sagittal T1 WI (B) through
left parasagittal region showing encasement of brachial plexus and left subclavian
artery in the retropectoralis minor space, without splaying, suggestive of lymphomatous
adenopathy. Axial T1 and T2 WI (C & D) showing lymphomatous mass in left axilla. Note
the normal appearing right subclavian artery.
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Fig. 17: Infiltrative plexopathy. Coronal T1 WI and T2 WI with fat sat showing thickening
of right C5 nerve root (white arrow) with edema. This patient had H/O right breast cancer.
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Fig. 18: Neoplastic plexopathy. Coronal STIR (A), T1 WI (B); Axial T2 (C) and T1 WI (D)
showing thickening and edema of the left sided brachial plexus. Note normal appearing
brachial plexus on the right side. This patient had a left lung mass with metastasis
extending along the left brachial plexus.
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Fig. 19: Neoplastic plexopathy. Axial T1 (A) and T2 (B) WI showing a right superior sulcus
mass involving adjacent rib as well as encasing the right brachial plexus.
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Conclusion
A knowledge of basic MRI anatomy of the brachial plexus and its various disease spectra
helps in narrowing down the diagnosis in this area where clinico-pathological options are
limited.
Personal Information
References
1.
Wittenberg KH, Adkins MC. MR imaging of nontraumatic brachial
plexopathies: Frequency and spectrum of findings. Radiographics. 2000; 20:
1023-32.
2.
Van Es WH, Bollen TL, Heeswijk HPMv. MRI of the brachial plexus: A
pictorial review. Eur Radiol. 2001; 74: 391-402.
3.
Saifuddin A. Imaging tumours of the brachial plexus. Skeletal Radiol. 2003;
32:375-87.
4.
Van Es HW. MRI of the brachial plexus. Eur Radiol. 2001; 11: 325-36.
5.
Amrami KK, Port JD. Imaging the brachial plexus. Hand Clin. 2005;
21:25-37.
6.
Sureka J, Cherian RA, Alexander M, Thomas BP. MRI of brachial
plexopathies. Clinical Radiology. 2009; 64:208-18.
7.
Demondion X, Boutry N, Drizenko A, Paul C, Francke JP, Cotton A.
Thoracic outlet: Anatomic correlation with MR imaging. AJR. 2000;
175:417-22.
8.
Bair DN, Rapopart S, Sostman HD, Blair OC. Normal brachial plexus: MR
imaging. Radiology. 1987; 165:763-7.
9.
Yoshikawa T, Hayashi N, Yamamoto S, Tajiri Y, Yoshioka N, Masumoto T
et al. Brachial plexus injury: clinical manifestations, conventional imaging
findings, and the latest imaging techniques. Radiographics. 2006; 26:
S133-43.
10. Wippold FJ, Lubner M, Perrin RJ, Lammle M, Perry A. Neuropathology for
the neuroradiologist: Antoni A and Anotoni B tissue patterns. AJNR AM J
Neuroradiol. 2007; 28: 1633-8.
11. Gerevini S, Mandelli C, Cadioli M, Scotti G. Diagnostic value and surgical
implications of the magnetic resonance imaging in the management of
adult patients with brachial plexus pathologies. Surg Radiol Anat. 2008;
30:91-101.
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