The document provides details on radiological imaging of brachial plexus pathology. It begins with an overview of brachial plexus anatomy including its origin, course, branches and functions. It then discusses various pathologies that can affect the brachial plexus including traumatic injuries, infections, inflammation, benign and malignant neoplasms, radiation plexopathy, compression and vascular abnormalities. For each pathology, it describes relevant imaging findings such as edema, enhancement patterns, masses, pseudomeningoceles and atrophy that help in diagnosis. Example images demonstrate various brachial plexus injuries and conditions.

1. Radiological Imaging of Brachial plexuses pathology.
Dr/ ABD ALLAH NAZEER. MD.

2. The brachial plexus is a complex neural network formed by lower cervical and upper
thoracic ventral nerve roots which supplies motor and sensory innervations to the
upper limb and pectoral girdle. It is located in the neck extending into the axilla
posterior to the clavicle.
Summary
origin: ventral rami of C5 to T1
course: emerges between anterior and middle scalenes, courses through the posterior
triangle of neck posterior to the clavicle before becoming closely associated with
the axillary artery in the axilla before giving up its terminal branches or alternatively
the roots emerge from behind the anterior scalenes to form 3 trunks which pass
between anterior and medial scalenes, then each trunk divides into an anterior and
posterior division which pass behind the clavicle, the divisions combine to form 3 cords
which surround the second part of the axillary artery, and finally the cords terminate
as the 5 major nerves
major (terminal) branches
median nerve
ulnar nerve
radial nerve
axillary nerve
musculocutaneous nerve
motor supply: upper limb and pectoral girdle
sensory supply: upper limb and part of the upper thorax

3. Gross anatomy
The brachial plexus consists of roots, trunks, divisions, cords and terminal
branches as it travels from proximal to distal upper limb. This mnemonic describes
the order of these subdivisions.
Roots
Roots are formed between the scalenes anterior and scalenus medius muscles by
the anterior rami of C5-C8 and T1 nerve roots. Three branches arise from the roots
directly 2:
dorsal scapular nerve: arises from the posterior aspect of the C5 root and supplies
the rhomboids
subclavian nerve: arises from the C5 and C6 roots anteriorly to supply subclavius
(although some texts describe this nerve arising from the superior trunk)
long thoracic nerve: arises from the posterior aspects of C5-C7 and supplies
serratus anterior
In addition, the scaleni and longus colli muscles are supplied by multiple variable
unnamed muscular branches that arise from all or some of the roots.
It is important to remember that although not part of the brachial plexus:
the dorsal rami course posteriorly into the spinal extensors (erector spinae) and do
not contribute to the brachial plexus.
the ventral rami of C4 and C5 also contribute to the phrenic nerve
the ventral ramus of T1 also contributes to the first intercostal nerve

4. Trunks
Trunks form from the roots as they pass between scalenus anterior and medius muscles, then go
on to traverse the posterior triangle:
C5 and C6 roots combine to form the upper or superior trunk
C7 root makes up the middle trunk
C8 and T1 roots combine to form the lower or inferior trunk
One branch arises from the trunks:
suprascapular nerve: arises from the upper trunk and supplies the supraspinatus
and infraspinatus muscles, and sensation to the glenohumeral and acromioclavicular joints
Divisions
Each trunk divides to form an anterior and posterior division posterior to the mid clavicle.In
general anterior divisions supply muscles of the anterior compartments (flexors) whereas the
posterior divisions supply muscles of the posterior compartments (extensors). No branches arise
from the divisions.
Cords
The divisions then combine to form cords, which are named for their relation to the second part
of the axillary artery:
lateral cord is formed by the union of the upper two anterior divisions at the lateral border of
the first rib
medial cord is a continuation of the lower anterior division
posterior cord consists of the united three posterior divisions
The prevertebral fascia of the neck extends down to ensheath the axillary artery and cords.
It is into this axillary sheath that local anaesthetic is injected when performing a brachial
plexus block.

5. Peripheral nerves (branches)
Various peripheral nerves, also termed "branches", then branch from these cords.
Branches from the lateral cord are:
lateral pectoral nerve
terminal branches
musculocutaneous nerve
lateral root of the median nerve
Branches from the posterior cord are:
upper subscapular nerve
thoracodorsal nerve
lower subscapular nerve
terminal branches
radial nerve
axillary nerve
Branches from the medial cord are:
medial pectoral nerve
medial cutaneous nerve of the arm
medial cutaneous nerve of the forearm
terminal branches
medial root of the median nerve
ulnar nerve

7. Coronal MRI scan shows the normal appearance of the brachial plexus – you can see the C5, C6 and C7 nerve
roots emerging from the vertebrae and converging further down into the trunks, divisions and roots.

8. Common presenting symptoms
Presenting symptoms referable to the BP can range from vague and nonspecific
(e.g., regional shoulder pain, upper extremity weakness, or altered upper
extremity/shoulder sensorium) to symptoms with specific nerve distribution (e.g.,
pain or motor/sensory deficit). More specific symptoms such as scapular winging
(due to long thoracic nerve injury), diaphragmatic dysfunction (involvement of the
phrenic nerve C3-C5), or Horner’s syndrome (postganglionic C8-T1 involvement)
can also be presenting complaints.
Pathology categorization
Disease processes affecting the brachial plexus can be subdivided into the
following broad categories: traumatic injury and several nontraumatic subtypes,
including: infection, inflammatory brachial neuritis/neuropathy, benign or
malignant neoplasms, radiation-induced plexopathy, vascular abnormalities, and
compression of the plexus.
Traumatic injury
Perhaps the most significant utility of brachial plexus MR in the setting of trauma
is to differentiate pre and post ganglionic injury, a distinction that has significant
management implications. Identification of a preganglionic injury can be difficult
and often requires recognition of a combination of direct (e.g., high resolution 3D
MRI or CT myelography) and indirect imaging characteristics.

9. Direct signs
High-resolution 3D T2- and CT myelography images can show anatomical
continuity or lack thereof of intradural nerve rootlets. The course of the
rootlets should be followed from the root entry zone to the DRG in the
neural foramen. In the setting of a structurally intact yet injured nerve
root, post contrast sequences may show abnormal enhancement of the
injured nerve root relative to the control side.
Indirect signs
A traumatic pseudomeningocele may be present on T2-weighted images.
The pseudomeningocele will usually show invagination into the affected
neural foramen, with or without the detached nerve root within it.
Contralateral deviation of the spinal cord is another indirect sign.
Normally, the nerve rootlets anchor the spinal cord in the middle of the
thecal sac, much like the taut ropes attached to large tents. Avulsion of
nerve rootlets results in unopposed traction by the contralateral, intact
nerve rootlets. Postganglionic traumatic injuries can demonstrate focal
edema (hyperintense T2 signal) involving any part of the plexus distal to
the DRG, anatomic discontinuity with or without clumping/retraction,
or a peri-plexus hematoma.

10. Infection
Infection of the brachial plexus can arise from a variety of sources, but it usually
spreads directly from an adjacent structure such as an extension of spinal
osteomyelitis, empyema/pulmonary parenchymal infections, glenohumeral
septic arthritis, overlying soft tissue infection, or iatrogenic introduction of
pathogens.2,15,16 Imaging characteristics of brachial plexus infections are similar
to infectious processes elsewhere in that they result in T2 hyperintense edema,
variable enhancement pattern (non-mass like), surrounding soft tissue
inflammation and presence or absence of a demonstrable source collection.
Inflammation
Spontaneous brachial plexitis, also known as Parsonage Turner Syndrome, typically
presents with the constellation of spontaneous acute severe burning shoulder pain,
subsequent sensory disturbance, and delayed weakness and atrophy. The
inflammatory processes involving structures adjacent to the brachial plexus can
also secondarily involve the brachial plexus. The imaging characteristics of brachial
plexus inflammation are nonspecific but consistent with inflammatory conditions
elsewhere in the body. Commonly encountered features include T2 hyperintensity,
thickening and variable enhancement of brachial plexus components, as well as
enlargement of the affected shoulder girdle muscle with enhancement and
hyperintense T2 signal (signs of acute/subacute denervation).

11. Benign neoplasms
A variety of benign lesions can involve the brachial plexus. Specifically, these
entities include fibromatosis, proliferative fasciitis, lipoma, hemangioma, brachial
cleft cyst, lymphangioma, and benign neural and nerve sheath neoplasms .
Fibromatosis (extra-abdominal desmoid) and proliferative fasciitis can both
present as rather large masses involving the brachial plexus, with the former
usually presenting as painless, and the latter as exquisitely tender. Both of these
lesions typically demonstrate T1 isointensity to surrounding muscle/soft tissue,
heterogeneous T2 hyperintensity, with mild enhancement in the case of
proliferative fasciitis and avid enhancement in fibromatosis.
Lesions such as lymphangiomas, lipomas, brachial cleft cysts, and hemangiomas
occur rarely in the BP and demonstrate similar imaging characteristics as they
would in other areas of the body. Lipomas are usually easily discernible from non
fatty lesions, as they characteristically demonstrate T1 and T2 hyperintensity, with
signal dropout on fat-saturated sequences. One potential pitfall is differentiating
benign lipoma from low-grade liposarcoma. In the setting of large lesions (>10
cm), significant non-fatty components, numerous septae, or heterogeneous
enhancement, PET-CT can be performed for better characterization.
Benign nerve sheath tumors have been described in a plethora of prior
publications. Briefly, they are commonly observed as T2 hyperintense lesions in the
neural foramen, sometimes resulting in expansion and osseous remodeling.

12. Malignant neoplasms
Malignant lesions can either primarily arise within the brachial plexus or
spread to the brachial plexus secondarily. Primary malignant lesions involving
the brachial plexus are predominately sarcomatous (low grade sarcoma,
radiation induced sarcoma, osteosarcoma, Ewing Sarcoma, leiomyosarcoma,
liposarcoma). These soft tissue masses often demonstrate overlapping
imaging characteristics and can be difficult to differentiate based on imaging
alone. Primary mesothelioma, malignant nerve sheath tumors and
involvement from primary vertebral tumors such as chondrosarcoma or
chordoma are also rarely seen involving the brachial plexus.
In regards to metastatic disease, the most common primary malignancies are
breast, lung, lymphoma, and head/neck cancer. Lung adenocarcinoma
typically secondarily involves the brachial plexus via direct extension in the
setting of a Pancoast tumor involving the superior sulcus. Breast carcinoma
(Figure 8), lymphoma, and head/neck malignancies usually involve the
brachial plexus via metastatic regional lymphatic spread In the setting of
primary or metastatic brachial plexus involvement it is important to
determine presence or absence of leptomeningeal enhancement/spread,
relation to the ipsilateral vertebral artery, and extent of nerve root
involvement.

13. Radiation plexopathy
Radiation plexopathy typically manifests as T2 hypointense thickening of the brachial
plexus components without focal mass. In the setting of prior malignancy and local
radiation to the brachial plexus, it is crucial for the clinician to attempt to differentiate
tumor progression/recurrence from benign radiation-induced plexopathy changes. Time
course is key to discerning these entities, as radiation induced plexopathy occurs between 5
and 30 months post radiation therapy (peak incidence 10-20 months post
radiation). Furthermore, details of clinical presentation can help aid in diagnosis. For
example, increasing/new pain or new Horner syndrome are more likely to reflect tumor
recurrence/progression; while unilateral edema or parasthesia is more likely to reflect
radiation-induced plexopathy.
Compression of the brachial plexus
The neurovascular bundle can be compressed at several areas along the brachial plexus,
resulting in a clinical constellation of symptoms commonly referred to as thoracic outlet
syndrome. Particularly, the brachial plexus components can be affected at the interscalene
triangle, costoclavicular space, or less commonly, the pectoralis minor space. Clinically, this
syndrome can result in ulnar distribution hand weakness, hand/arm/neck
pain/parasthesias, and upper extremity muscle atrophy. Symptomatology is often
exacerbated/reproducible by arm raise. The syndrome is typically caused by anatomic
variants such as a cervical rib, prominent lower cervical transverse processes,
posttraumatic fibrous bands, or pectoralis muscle hypertrophy. MRI can be used to identify
any of the aforementioned causative factors, and should include provocative testing in
order to reproduce Symptomatology during the time of the scan.

14. Vascular abnormalities
A variety of space-occupying vascular
abnormalities can result in brachial plexus
compression, including but not limited to pseudo
aneurysm, arteriovenous fistula (AVF), or
arteriovenous malformation (AVM).2 The involved
vessels include the subclavian, axillary, common
carotid, and vertebral arteries. A variety of
predisposing conditions can result in these lesions,
which are best characterized on dedicated vascular
studies such as CT angiography, MR angiography,
and/or conventional angiography.

15. The Axial T2FS and Coronal STIR SPACE images: Pseudomeningoceles of C3-4 to C6-7 levels with avulsed nerve roots
(arrows). Coronal STIR SPACE image: Asymmetrical atrophy of the distal right brachial plexus segments (arrows).

16. Avulsion injuries in 26-year-old man with weakness and pain in upper extremity after motorcycle crash. Coronal fat-
suppressed T2-weighted image shows bright fluid filled pseudomeningoceles (arrows) in course of C8 and T1 nerve roots.

17. Avulsion injuries in 26-year-old man. Coronal post gadolinium T1-weighted
image (A) and parasagittal T2-weighted image (B) show posttraumatic
pseudomeningoceles (arrows) involving C7 and C8 nerve roots.

18. Stretching (“burning”) injury of right brachial plexus in 35-year-old man. Coronal fat-
suppressed T2-weighted image shows that there is high signal, indicating edema, and
thickening of divisions and cords (straight arrows) of right brachial plexus. Note effusion
(curved arrow) in ipsilateral shoulder joint due to traction injury of upper extremity.

23. 57-year-old woman who had undergone surgery and irradiation for treatment of left-sided
breast carcinoma and was doing well until about 7 months after termination of radiation
therapy, when she developed weakness and pain in left upper extremity. Coronal fat-
suppressed T2-weighted image shows diffuse thickening and increased signal intensity
(arrow) in region of left brachial plexus affecting trunks, divisions, and cords.

25. Coronal fat-suppressed T2-weighted image shows mild thickening and increased
signal in trunks for left brachial plexus in 45-year-old man who presented with sudden
onset of weakness in ipsilateral upper extremity. Symptoms resolved spontaneously
4 weeks later; this case was assumed to be a virus-induced plexopathy.

27. 65-year-old man presenting with left-sided mixed (i.e., motor and sensory) brachial plexopathy of 2 months'
duration. Patient also has history of cigarette smoking and persistent cough that developed 3 weeks earlier. Chest
radiography (not shown) revealed abnormal findings. Coronal T1-weighted image shows large left tumor (arrow);
note normal interscalene fat pad on right. Obliteration of this fat by tumor as seen here generally implies invasion
of brachial plexus at level of trunks that normally course between scalene muscles in interscalene fat pad.

28. Small left Pancoast's tumor in 60-year-old woman. Coronal T1-weighted image
shows small bilobed mass (white arrow) in left lung apex. Note preservation of
normal interscalene fat pad (black arrow), which on coronal images has
triangular appearance. Left brachial plexus (arrowhead) is nicely seen.

29. Schwannoma in 45-year-old woman. Coronal fat-suppressed T2-weighted image
shows mass with high signal intensity (lower arrow) in region of roots and trunks
of right brachial plexus. Note “tail” of mass extending into C7-T1 right neural
foramen (upper arrows). This finding is typical of nerve sheath tumors.

30. Lipoma in 44-year-old woman. Coronal T1-weighted image (A) and
corresponding fat-suppressed image (B) show well-defined fatty mass (arrows)
that typically loses all signal intensity after fat-suppression technique is applied.

31. Traumatic pseudoaneurysm in subclavian artery of 38-year-old man. Coronal
unenhanced (A) and axial enhanced (B) T2-weighted images show mass (arrows) in
region of right subclavian artery compressing brachial plexus. Note concentric rings
of varying signal intensities due to clot that forms walls of this pseudoaneurysm.

32. Charcot-Marie-Tooth disease in 18-year-old woman. Coronal fat-suppressed T2-
weighted image shows left brachial plexus to be thick and hyperintense.

33. Non-Hodgkin lymphoma in a 53-year-old man. Axial (a) and oblique sagittal (b) T1-
weighted images show multiple small masses (solid arrows) in the base of the neck and
involving the right brachial plexus (arrowheads). Also note the superior mediastinal
adenopathy (curved arrow in b). In b, open straight arrow = subclavian artery.

34. Malignant peripheral nerve sheath tumor (neurosarcoma)
of the upper trunk of the brachial plexus.

35. Neurofibromatosis type 1 (NF1) shows large plexiform neurofibromas
of both brachial plexuses, affecting nerve roots C5, C6, C8, T1 and T2.

36. MRI shows a patient who recently underwent neck surgery. The C5 and C6 nerve roots
have been completely severed (neurotmesis) and there is evidence of post-traumatic
neuroma formation at their ends. The patient was treated with nerve transfer surgery.

38. Melanoma in a 35-year-old man. Axial T1- (a) and T2-weighted (b) images show a large
mass in the right axilla (solid arrows in a) contiguous to and displacing the right brachial
plexus (arrowhead in a). Note the subtle areas of increased T1 signal intensity within the
mass that are characteristic of melanoma. Open arrow = subclavian artery.

39. Conclusion
The brachial plexus can be efficiently imaged and
effectively interpreted by the general radiologist when
approached from a practical standpoint. Optimization of
a practical BP imaging protocol is paramount to identify
normal anatomy and associated pathology. Practical and
useful information that can help the referring physician
include, pre- vs. post-ganglionic location of lesion, mass
vs. non-mass like enhancement, laterality or bilateral
nature of disease, location of injury/mass/abnormality in
BP segments (e.g. root, trunk, division, etc.), and
anatomical region and surrounding structures involved
(e.g., interscalene space, costoclavicular triangle,
relationship to subclavian/axillary vessels).

40. Thank You.