Post on 22-May-2020
Traumatic and Non‐Traumatic Brachial Plexus Imaging: What the practicing radiologist needs to know
Pardeep Athwal, MD; Megan K. Mills, MD; Mark Mahan, MD; Kevin R. Moore, MD; Barry G. Hansford, MD; Chris J. Hanrahan, MD; Anna K. McGow, MD; Sarah E. Stilwill, MD
Disclosures
•No relevant financial relationship to disclose
Objectives
Review imaging protocol
Review brachial plexus (BP) anatomy
Illustrate direct and indirect imaging features of traumatic and non‐traumatic brachial plexus pathology
Demonstrate intra‐operative findings
Median Nerve
Ulnar Nerve
MR Imaging Protocol
Ax T2 Dixon FS:
Cor STIR:Cor T1: Cor T1 FS post :
Ax T1 FS post :
Routine BP MR Scan on 1.5T and 3T includes the following basic 6 sequences:Coronal T1 sequence is key for identifying normal anatomy, peri‐neural and interscalene fat planes, and base of neck muscles.Coronal STIR, and T2 FS sequences are useful for brachial plexus (bp) nerve size and signal with excellent contrast resolution for depicting pathology.Post Contrast sequence imperative for tumor evaluation, and active inflammation. * 3T imaging preferred for MR Neurography; we employ Dixon FS Technique to enhance BP evaluation / lesion conspicuity .
Sag T2 Dixon FS:
COR T2 Dixon FS (fat suppressed):
Sag T2 DIXON non FS:
Cor T1 FS Dixon PC (water suppressed) :
MR Imaging Protocol: Dixon FS Technique
Sag T2 Dixon FS:
Dixon technique: Modified spin echo sequence; separates water and fat images and generates fat suppressed (water only) and water suppressed (fat only) images. Allows for robust fat suppression and superior image quality, decreasing base of neck field inhomogeneity with enhanced nerve evaluation .
Sag T2 non FS sequence: included for enhanced depiction of muscle anatomy including variant muscle slips and fibromuscular bands ( eg. accessory middle scalene muscle slip and Sibon’s fascial band), with improved BP nerve evaluation
Brachial Plexus Anatomy• Originates from the C5‐T1 spinal nerve Roots
• Spinal nerves split into ventral and dorsal rami • Dorsal Rami (DR)‐Innervate the paraspinal muscles• Ventral Rami (VR)‐Form the Brachial Plexus Trunks located between the anterior (as) and middle scalene (ms) muscles
• C5+C6 ‐‐> Superior or “Upper” Trunk• C7 ‐‐> Middle Trunk• C8+T1 ‐‐> Inferior or “Lower “Trunk
*
More laterally within the posterior triangle of the neck each Trunk divides into 2 forming 3 anterior and 3 posterior Divisions
Ax T2 FS
*
C8 DRG
T1 Transverse Process
C5Ventral Rami C6
C7
*
Upper Trunk (C5 + C6 VR)
**
First rib
as
ms
StatDx
Brachial Plexus Anatomy• The 3 anterior and 3 posterior Divisions ‐‐> 3 Cords which form just distal to the lateral margin of the first rib• Lateral cord: Anterior divisions of upper and middle trunks
• Posterior cord: Posterior divisions of upper, middle and inferior trunks
• Medial cord: Anterior division of inferior trunk
• At lateral border of pectoralis minor the 3 cords divide into five Branches: • Median• Ulnar• Radial• Axillary• Musculocutaneous
CordsDivisions Trunks Roots
Wikipedia
Brachial Plexus Anatomy
The 6 Divisions form just lateral to the inter‐scalene triangle within the base of neck.
Ax T2 FS
Subclavian Artery(SA)
1st rib
Sag T2 FS
Divisions
*
Branches
Roots*
*
Trunks
Divisions
Cords
Cor STIR
Case of a 35 yo F with NF‐1
Brachial Plexus Anatomy
The 3 Cords form just distal to the lateral margin of the 1st rib, named with respect to nerve proximity to the coursing axillary artery (AA)
*
Branches
Roots*
*
Trunks
Divisions
Cords
Cor STIR
Case of a 35 yo F with NF‐1
Proximal Cords
Lateral Posterior
Medial
SAG T2 FS
SA
Distal Cords
AA
Lateral
Medial
Posterior
SAG T2 FS
Cords
Ax T2 FS
Brachial Plexus Anatomy
The 5 terminal branches of the brachial plexus form at the border of the pectoralis minor muscle and include: the median, ulnar, musculocutaneous, axillary, and radial nerves. Sag T2 FS Sag T2 FS
Ax nerve
Anatomist90Wikipedia
Cor T1
SA
AC joint
Humerus
Outline:• Traumatic brachial plexus pathology:
• Nerve root avulsion • Pre ganglionic nerve avulsion• Post ganglionic nerve avulsion
• Obstetric brachial plexus palsy
• Non‐traumatic brachial plexus pathology• Radiation plexopathy• Idiopathic neuritis (aka parsonage turner syndrome)• Thoracic outlet syndrome• Tumors
• Neurofibromatosis / Neurofibroma / MPNST• Desmoid
Traumatic nerve avulsion: Pre‐ganglionic injury
Coronal STIR
C7
T1
Subacute pre‐ganglionic nerve avulsions of the C7and C8 nerves with pseudomeningocele formation at the C7/T1 level, lateralization of the C7 and C8 dorsal root ganglion (DRG), enlargement and edema of the avulsed nerve stump and indirect right hemi‐cord atrophy and edema.
Axial T2 FS
Axial T2 FS
45 yo M s/p MVA with proximal rib and transverse process fx’s at C‐T junction
Axial T2 FS
Traumatic nerve avulsion: Pre‐ganglionic injury
Axial T2 FS
Axial T2 FS
Axial T2 FS
Key Facts
• Traumatic BPI most commonly due to motor vehicle accidents >> gun shot wounds > sports injuries
• M >>F • Pre‐ganglionic BPI ‐‐> signifies avulsion of nerve roots and cannot be repaired
• Muscle functions are restored with nerve transfers; restoration of biceps muscle function and shoulder function is critical
MRI • Direct findings: lateralized DRG with downstream BP edema, enlargement and signal heterogeneity.
• Enhancement of the intradural nerve / nerve root signifies functional nerve impairment
• Indirect findings: Pseudomeningocele formation at level of avulsion; acute soft tissue denervation edema/ enhancement and chronic fatty muscle atrophy; acute spinal cord edema and chronic myelomalacia
Traumatic nerve avulsion: Post‐ganglionic injury
Axial T1 FS post contrast
Sub‐acute post‐ganglionic nerve injury with focal neurotemesis of C6 with post‐traumatic neuroma formation.Post‐contrast enhancement of the C6 nerve and proximal most segment of the upper trunk signifies focal inflammation and scarring.
35 yo M s/p motorcycle crash with T1 TP Fx presenting with neuropathic pain in shoulder and upper back
Coronal STIR
Traumatic nerve avulsion: Post‐ganglionic injury
Denervation edema is present within the rotator cuff muscles which are supplied by nerve branches of the upper trunk of the brachial plexus.
35 yo M s/p motorcycle crash with T1 TP Fx presenting with neuropathic pain in shoulder and upper back
Coronal STIR
Key Facts
• Post‐ganglionic BPI ‐‐> Focal nerve fiber / nerve fascicle disruption distal to the DRG
• Injury ranges from stretch injury to full thickness laceration
• Most commonly due to MVA’s +/‐ C‐spine or clavicle fractures
• Nerve fiber disruptions are repaired with nerve grafting (damaged nerve excision and autograft between two ends)
MRI • Direct findings: edema and enlargement along any segment of the BP distal to the DRG +/‐ focal discontinuity, +/‐hematoma and +/‐ resultant neuroma formation
• Indirect findings: acute denervation edema and chronic fatty muscle atrophy within the paraspinous muscles and/or shoulder girdle muscles.
Traumatic nerve avulsion: Intra‐op correlation
Posterior cord
Discolored lateral cord
Medial cord
40 yo M s/p motorcycle crash with left sided clavicle fracture and C6 deficits ‐‐> laceration of the lateral cord
Traumatic nerve avulsion: Intra‐op correlation40 yo M s/p motorcycle crash with left sided clavicle fracture and C6 deficits‐‐> laceration of the lateral cord
Full thickness laceration of lateral cord
Obstetric brachial plexus palsy (OBPP) – Case #1
Key Facts • Downward traction on the shoulder girdle during vaginal birth in setting of shoulder dystocia ‐‐> OBPP ‐‐> risk of permanent disability and limb deformity
• Upper level injuries (C5‐C7) are the most common; inferior extension of nerve injury occurs with more severe traction
MRI • Pseudomeningocele with lateralized DRG when pre‐ganglionic • Neuroma formation when traction injury distal to the DRG
• Range of pathology from stretch injury, to partial or complete nerve avulsion• Muscle denervation edema and subsequent fatty atrophy
Cor T2 FS
3 month old with right arm Erb palsy since birth. Case shows C6 and C7 nerve root avulsions with pseudomeningocele formation.
Ax T2 FS
Obstetric brachial plexus palsy (OBPP)‐ Companion Case #2
Cor STIR
Focal Neuroma of the Upper Trunk
Ax STIR
5 month old baby girl born full term weighing 9 lbs. who “got stuck”. Baby delivered after “manipulation”, and immediately had no movement of right arm. No functional recovery since birth. Mom reports baby has mild motion of hand and wrist but remains in ulnar deviated position.
Erb Palsy: occurs with upper trunk C5 & C6 lesions ‐‐> loss of shoulder abduction, shoulder external rotation, elbow flexion, and forearm supination.
Involvement to middle trunk (C5–C7) ‐‐> additional loss of wrist extension ‐‐> waiter’s‐tip posture of extended Erb palsy.
Involvement of the entire brachial plexus (C5– T1) ‐‐> flail arm that can be associated with Horner syndrome if the T1 contribution to the sympathetic chain is disrupted
Obstetric brachial plexus palsy: Intra‐op correlation
Right upper extremity
Phrenic nerve
Omohyoid muscle
Neuroma of the upper trunk
Supraclavicular nerves
Anterior scalene muscle (divided)
Middle scalene muscle
Case #2 : Baby went on to surgical neurolysis, and decompression of the upper trunk with neuroma resection and grafting.
Obstetric brachial plexus palsy: Intra‐op correlation
Normal view of the brachial plexus upper trunks from contralateral left upper extremity.
Middle trunk
Anterior scalene m.
Sternocleidomastoid
Supraclavicular nerves (loop)
Upper trunk
Left upper extremity
Non‐traumatic pathology: Radiation plexopathy
COR STIR
Key Facts • Most commonly occurs following axillary, lung apical or base of neck XRT treatment for breast cancer, lung cancer and /or lymphoma
• Sx’s of pain, parathesias, hyperthesias and weakness usually occur in an upper trunk distribution ‐‐> weakness of the arm flexors and shoulder abductors
MRI • MR findings include: diffuse uniform swelling, thickening and mild enhancement of the involved BP without focal mass; +/‐ soft tissue denervation changes
• T2 FS and STIR ‐‐> show hyperintense signal of the BP within the XRT field• Low signal on T1 and T2 FS ‐‐> suggests BP fibrosis ‐‐> downward BP traction/tethering • Mild enhancement can be seen in both XRT plexopathy and tumor recurrence; tumor recurrence ‐‐> focal mass or asymmetric “mass like” enhancement of the BP
65 year old M with RUL lung cancer s/p XRT with right arm pain, neck pain and weakness
COR T1 PC FS Lung Mass
MR neurogramimages show abnormal supra‐ and infra‐clavicluar BP enhancing edema, enlargement /thickening and downward tethering consistent with XRTfibrosis.
Denervation muscle edema
Dr. J Crim Dr. J Crim
Coronal STIR
Non‐traumatic pathology: Parsonage Turner Syndrome (PTS)
Sagittal PD FS
MR images show smooth, uniform edema of the bilateral BP worse on the left with downstream multi‐focal denervation muscle edema in the supraspinatus >>> triceps muscle , deltoid and cranial subscapularis muscles.
45 year old F with sudden onset L >R shoulder pain.
Key Facts • PTS is a painful, non‐traumatic self‐limiting disorder involving the shoulder girdle• Most patients present with sudden onset of pain +/‐ weakness, paresthesias and paralysis• The etiology is unknown although recent viral illness, immunizations and auto‐immune disease has been implicated
• The suprascapular nerve is almost always involved >>> axillary and subscapular nerves
MRI • Smooth enlargement and hyperintense edema signal of the BP on T2 or STIR, most commonly involving the C5‐C6 roots and upper trunk with downstream changes in the cords and peripheral nerves
• Multi‐focal denervation muscle edema involving more than one nerve distribution
SS
SSc
IS
TricepsDr. J Crim
Non‐traumatic pathology: Thoracic outlet syndrome (TOS)
TOS Imaging protocol: We perform a dedicated MR Neurogram of the BP, in combination with an MRA. Both are performed with dynamic maneuvers.
MRA dynamic maneuvers: Patient is imaged in neutral position with the arms at the side and injected with ½ dose of gadolinium contrast. Subsequently, patient is imaged with the arms in abduction (placed over head) and given the remaining ½ dose of contrast to complete the MRA portion of the study.
The non‐contrast portion of the BP includes a Sag T2 non‐FS which is obtained with the arms in neutral position at the patients side, AND again with the patients arms abducted, placed overhead. The Sag non‐FS demonstrates nicely anatomy of the costo‐clavicular (CC) space with clear definition of the coursing first rib, subclavian artery and subclavian vein and BP. The SCV normally compresses when then arms are abducted, however the SCA remains patent.
Rib
MRA MIP with arms abducted Sag T2 non FS with arms abductedSag T2 non FS in neutral
ClavicleClavicle
RibSCV
Image at level of BP distal trunks / divisions, just distal to inter‐scalene triangle
SCVSCA
SCA
SCV compressed within narrowed CC interval but SCA is patent
Non‐traumatic pathology: Thoracic outlet syndrome (TOS)35 y/o F with history of numbness and tingling during overhead maneuvers
Coronal MRA with arms In neutral position
KeyFacts
• Dynamically induced compression of the neural, arterial, or venous structures crossing the interscalene triangle,costoclavicular space or retropectoralis minor space leads to thoracic outlet syndrome (TOS).
• Contributing soft tissue abnormalities include: Anterior scalene muscle hypertrophy, common origin of anterior and middle scalene muscles, broad middle scalene, post traumatic or post treatment scarring.
• Contributing osseous abnormalities include: cervical rib, elongated transverse process of C7, or abnormal first rib or clavicle deformity.
MRI
• Look for focal filling defect in SCV and SCA on Sag T2 FS and Sag T2 non‐FS sequences and on concurrently performed MRA in setting of vascular compression.
• Look for loss of peri‐neural fat surrounding the BP within the interscalene triangle and/or CC space, +/‐ close proximity of nerves to bony structures and any anomalous muscle slip or fibrous band ( Cor T1, Sag T2 FS and Sag T2 non‐FS are key)
CXR with between the 1st ‐2nd rib
Focal thrombus within the SCA
Non‐traumatic pathology: Thoracic outlet syndrome (TOS)35 y/o F with history of numbness and tingling during overhead maneuvers
CXR with between the 1st ‐2nd rib
Sag T2 with arms in neutral Sagittal T2 with arms abducted
Sag T2 FS images show a filling defect within the SCA with progressive CC space impingement / narrowing during arm abduction due to abnormal fusion mass between the 1st and 2ndribs. The coursing distal BP trunks and proximal divisions are getting compressed just distal to the interscalene triangle ‐‐> upper extremity neurologic deficits. Cor T1 post contrast image demonstrates non‐enhancing thrombus within the left SCA
SCV
Abnl rib ankylosis
Cor T1 FS PC
Non‐traumatic, tumor pathology: Neurofibroma
Key Facts • Neurofibromas are the most common benign neural tumor to involve the BP • 1/3 of these tumors occur in patients with NF‐1; 2/3’s of cases are sporadic• The majority are multiple, plexiform and diffusely involve the BP
• Plexiform neurofibromas are pathopneumonic for NF‐1, with increased risk of malignant txf
MRI • MR best to characterize & define total extent; lesions are most conspicuous on STIR and T2 FS• Focal neurofibroma‐‐> well circumscribed fusiform mass, hypointense on T1, hyperintense on T2 +/‐central low signal “target sign” with either avid or patchy/heterogeneous post contrast enhancement
• Plexiform neurofibroma‐‐>Trans‐spatial, multi‐lobulated, “rope‐like” expansion along a long nerve segment and its branches with T2 hyperintensity and heterogeneous post‐contrast enhancement
• MPNST ‐‐> less common, usually > 5 cm, with heterogeneous T2 signal and heterogeneous contrast enhancement, +/‐ progressive invasion/infiltration into adjacent soft tissues.
60 yo F with history of neurofibromatosis and a left sided BP plexiform neurofibroma
C5 NR
C6 NR
Cor T1 FS PC Cor T1 FS PC
MR images show an avidly enhancing plexiform neurofibroma involving the distal C5 and C6 nerve roots, upper trunk, anterior division and proximal cords.
35 yo F with NF‐1 and diffuse involvement of the BP
MR image show marked enlargement, edema and stippled nodularity of the entire brachial plexus consistent with neurofibromatosis with multiple small nerve sheath tumors.DDx for diffuse nerve thickening includes chronic inflammatory demyelinating neuropathy and Charcot‐Marie‐tooth disease.
Cor STIR
Companion tumor cases: Neurofibromatosis and MPNST
MR demonstrate a lobulated MPNST (dashed arrow) engulfing the BP (solid arrow) inferolaterally & invading the upper mediastinum (white curved arrow).** Imaging findings of benign vs. malignant nerve sheath tumors are difficult to distinguish. However, patients usually have increased pain with malignant tumor degeneration.
Coronal T1WI C+ FS StatDx
40 yo F with NF‐1 and MPNST
22 yo female with left upper extremity numbness, tingling and palpable neck mass Pre contrast: classic iso‐/hypointense T1 signal, and heterogeneous hyperintense T2/STIR signal with scattered low signal bands representing a mix of spindle cells and collagen stroma.
Post contrast: desmoid tumors typically show avid post‐contrast enhancement on MRI.
Coronal T1 Coronal STIR
Coronal T1 FS PC Ax T1 FS PC
Non‐traumatic, tumor pathology: Desmoid
Desmoid tumors are a locally invasive, benign soft tissue tumor typically seen involving the abdominal wall; extra‐abdominal desmoids in the head and neck can encase, and distort the BP ‐‐> neurologic deficits
Treatment includes tamoxifen +/‐ NSAIDS, surgery, and/or XRTSuccessful tx response ‐‐> decreased tumor size/volume, with decreased T2 hyperintensity and enhancement
Summary• Understanding the complex anatomy of the brachial plexus is key to interpretation on MRI
• The brachial plexus provides both sensory and motor innervation to the upper extremity
• Recognizing location, and severity of brachial plexus traumatic injuries and non‐traumatic pathology aids in early diagnosis, and significantly impacts patient management
References• Brandão S, et al. Comparing T1‐weighted and T2‐weighted three‐point Dixon technique with
conventional T1‐weighted fat‐saturation and short‐tau inversion recovery (STIR) techniques for the study of the lumbar spine in a short‐bore MRI machine. Clin Radiol. 2013 Nov;68(11):e617‐23.
• Bowen BC, Verma A, Brandon AH, Fiedler JA. Radiation induced brachial plexopathy: MR imaging with clinical correlation. AJNR Am J Neuroradiol 1996; 17:1932‐1936.
• Brandao S, Seixas D, Ayres‐Basto M, et al. Comparing T1‐weighted and T2‐weighted three‐point Dixon technique with conventional T1‐weighted fat‐saturation and short‐tau inversion recovery (STIR) techniques for the study of the lumbar spine in a short‐bore MRI machine. Clinical Radiology 2013; 68:617‐623.
• Chappell KE, Robson MD, Stonebridge‐Foster A, et al. Magic angle effects in MR neurography. AJNR 2004; 25:431–440
• Chhabra A, Andreisek G, Soldatos T, et al. MR Neurography: Past, Present and Future. AJR 2011; 197: 583‐591.
• Chhabra A et al. High‐Resolution 3T MR Neurography of the Brachial Plexus and Its Branches, with Emphasis on 3D Imaging. AJNR 2013, 34: 486‐497.
• Demondion X, and Herbinet P et al. Imaging Assessment of Thoracic Outlet Syndrome. Radiographics 2006; Vol 26, Issue 6.
• Freund W, Brinkmann A, Wagner F, et al. MR neurography with multiplanar reconstruction of 3D MRI datasets: an anatomical study and clinical applications. Neuroradiology 2007; 49:335–341.
• Grant GA, Britz GW, Goodkin R, Jarvik JG, Maravilla K, Kliot M. The utility of magnetic resonance imaging in evaluating peripheral nerve disorders. Muscle Nerve 2002; 25:314–331.
• Husarik DB, Saupe N, Pfirrmann CW, Jost B, Hodler J, Zanetti M. Elbow nerves: MR findings in 60 asymptomatic subjects—normal anatomy, variants, and pitfalls. Radiology 2009; 252:148–156.
• Iyer VR et al. Malignant Brachial plexopathy: A pictorial essay of MRI findings. Indian J Radiol Imaging. 2010 Nov; 20(4): 274–278.
• Menashe, SJ et al. Brachial Plexus Birth Palsy: Multimodality Imaging of Spine and Shoulder Abnormalities in Children. AJR. February 2015, Volume 204, Number 2.
• Van Es H, Bollen T, van Heesewijk H. MRI of the brachial plexus: A pictorial review. European Journal of Radiology 2010; 74: 391‐402.
• Vargas MI, Viallon M, Nguyen D, Beaulieu JY, Delavelle J, Becker M. New approaches in imaging of the brachial plexus. Eur J Radiol 2010; 74:403–410.
• Viallon M, Vargas MI, Jlassi H, Lövblad KO, Delavelle J. High‐resolution and functional magnetic resonance imaging of the brachial plexus using an isotropic 3D T2 STIR (short term inversion recovery) SPACE sequence and diffusion tensor imaging. Eur Radiol 2008; 18:1018–1023.
• Wasa J, and Nishida Y et al.. MRI Features in the Differentiation of Malignant Peripheral Nerve Sheath Tumors and Neurofibromas. AJR, June 2010, Volume 194, Number 6.
• Wittenberg, KH and Adkins, MC. MR Imaging of Nontraumatic Brachial Plexopathies: Frequency and Spectrum of Findings. Radiographics, July 2000, Volume 20, Issue 4.
• Yoshikawa, T et al. Brachial Plexus Injury: Clinical Manifestations, Conventional Imaging Findings and the Latest Imaging Techniques . Radiographics, October 2006 Vol 26. Issue suppl 1.
References
Thank you!
• Contact Information:
• Sarah Stilwill MDSarah.stilwill@hsc.utah.edu
• Pardeep Athwal MD Pardeep.athwal@hsc.utah.edu