Brachial plexus MRI

MRI - Imaging modality of first choice for depicting the anatomy and pathology of the brachial plexus.

MRI - very well demonstrate the anatomy due to its inherent contrast differences between the nerves with low signal intensity and the surrounding hyperintense fat on T1-weighted images.

Challenges:
Large field of view
Other heterogeneous tissue distribution including fat, muscles, and bones.

1. Imaging in Brachial Plexus Presenter: Dr. Parameshwar Keerthi B H. Moderators: Dr. Anil Kumar Sakalecha

2. Contents Introduction Anatomy of Brachial Plexus Imaging protocol How to identify Brachial plexus in imaging Brachial plexus pathology – Classification Imaging in Brachial plexus pathologies Conclusion

3. Introduction Brachial plexus - sensory and motor innervation of the upper extremity. Involved in a variety of traumatic and non-traumatic pathologies. MRI - diagnosis and in localization of these lesions. Significant impact on the management .

4. Introduction MRI - Imaging modality of first choice for depicting the anatomy and pathology of the brachial plexus. MRI - very well demonstrate the anatomy due to its inherent contrast differences between the nerves with low signal intensity and the surrounding hyperintense fat on T1-weighted images . Challenges: Large field of view Other heterogeneous tissue distribution including fat, muscles, and bones.

5. Q-1 Option B

6. Anatomy of Brachial Plexus The brachial plexus originates from the cervical spinal nerves C5–C8 and the first thoracic spinal nerve T1 . The spinal nerves split into anterior (ventral) and posterior (dorsal) rami just distally of the dorsal root ganglion . The dorsal rami innervate the paraspinal muscles. The five ventral rami C5, C6, C7, C8 and T1 form the brachial plexus.

7. Anatomy of Brachial Plexus C5 and C6 join to form the upper trunk, C7 continues as the middle trunk, and the inferior trunk is formed by C8 and T1. All three trunks divide into an anterior and posterior division. The six divisions intermingle and form the three cords: the lateral, posterior and medial cord. The anterior divisions of the upper and middle trunks form the lateral cord, the anterior division of the lower trunk continues as the medial cord, and the posterior divisions of all trunks unite to form the posterior cord.

8. Anatomy of Brachial Plexus The individual cords - named according to their relationship to the adjacent subclavian artery: lateral, posterior, and medial. Inferior to the clavicle – cord divide into individual branches providing motor and sensory innervation to the upper extremity Lateral border of the pectoralis minor muscle - the cords divide into the five peripheral nerves which innervate the shoulder and arm: the median, ulnar, radial, axillary and musculocutaneous nerves.

9. Anatomy of Brachial Plexus

10. MR Brachial Plexus - Protocol Coronal 3D STIR (include both shoulders) FOV - 350mm. Coronal MIP FOV- 350mm. Coronal T1 (include both shoulders) FOV - 320mm. Axial STIR (C5 to inferior axilla, single-side ) FOV - 200mm . Axial T1 (single-side) FOV - 200mm. Sagittal T2 (C-spine to midpoint of arm) FOV - 240mm.

11. MR Brachial Plexus – Specific Sequences Intravenous Gadolinium: Administered in patients with tumors or mass lesions. Not administered in patients with traumatic brachial plexopathy . Traumatic brachial plexus injury – sagittal T2‑weighted images are obtained through the cervical spine followed by axial T2‑weighted images from C4 to T2 levels. 3D gradient echo ( GRE) sequence with thin slices - to look for the nerve root avulsion.

12. MR Brachial Plexus – Specific Sequences Thoracic outlet syndrome - sagittal T1‑weighted images are obtained through the symptomatic side extending from midline to the axilla with arm in hyperabducted position. These are compared with similar sagittal T1‑weighted images obtained with arm in neutral position by the side of body.

13. T1 Sagittal Images – Neutral & Hyperabducted State

14. How to Identify Brachial Plexus on MRI ???

15. Identification of Roots The brachial plexus is predominantly formed by the ventral rami of the spinal nerves of C5 through T1. They exit the neural exit foramina and form the roots. On the sagittal images the proximal part of the first rib is used to identify the C8 and T1 nerve roots, with C8 above and T1 below the first rib.

16. Identification of Roots

17. Identification of Roots

18. Interscalene Triangle The nerve roots and the subclavian artery enter the interscalene triangle. It is formed by the anterior scalene and middle scalene muscles. Just lateral of the interscalene triangle the three trunks are formed

19. Interscalene Triangle

20. Identification of Trunks

21. The divisions are located at the level where the brachial plexus crosses the clavicle. The cords are positioned above and around the axillary artery and they are named after their position relative to the axillary artery. On sagittal MRI images the lateral cord is located most anterior, the posterior cord most superior and the medial cord most posterior. Identification of Divisions

22. Identification of Divisions

23. Identification of Cords

24. Brachial Plexus – Coronal Images On the coronal images the T1 nerve root can always be easily identified as a horizontal linear structure surrounded by fat close to the lung apex. At this level the stellate ganglion can also be identified. The C8 nerve root is also usually surrounded by fat and easily seen. On the T2-STIR images the nerves have a slightly increased signal intensity compared to the surrounding tissues.

25. Brachial Plexus – Coronal

26. Brachial Plexus – Coronal

27. Brachial Plexus – Coronal Images The roots C5–C7 are surrounded by less fat and have contact with the scalene muscles. To identify the trunks on the coronal images the dorsal scapular artery can be used as a landmark. It is a branch of the subclavian artery supplying the rhomboid muscles. This small artery runs between the superior and middle, or middle and inferior trunk

28. Brachial Plexus – Coronal

29. Classification of Brachial Plexus Pathologies

30. Classification of Brachial Plexus Pathologies Brachial Plexus - Pathologies Non - Traumatic Traumatic Infective Inflammatory Neoplasm Radiation Vascular Extrinsic compression

31. Traumatic Brachial Plexopathy There are two distinctive populations affected by traumatic brachial plexopathy . Neonates sustain a traction injury due to shoulder dystocia during vaginal delivery. The second population is young men in the second and third decades – fall from a height motorcycle or motor vehicle crash penetrating injury from a gunshot

32. Traumatic Brachial Plexopathy - Classification It is important to differentiate between preganglionic and postganglionic injuries. Post ganglionic injuries are associated with good prognosis. Post ganglionic injuries - surgery: nerve grafting MRI of preganglionic injuries can show nerve root avulsions, with or without pseudomeningoceles.

33. Pseudomeningocele - Imaging Cerebrospinal fluid collections due to a dural tear. The presence of a pseudomeningocele is highly indicative for a preganglionic lesion, seen in 80% of avulsions. It is not pathognomonic. Spinal cord abnormalities like edema , haemorrhage and myelomalacia are seen in ~ 20 % of patients with preganglionic injuries.

34. Preganglionic Injury Enhancement of intradural nerve roots and root stumps suggests functional impairment of nerve roots despite morphologic continuity. Features of denervation/atrophy in the paraspinal muscles is an accurate indirect sign of root avulsion injury

35. Postganglionic Injury MRI of show thickened nerves with hypointensity on T1- and hyperintensity on T2-weighted images. Nerve contiguity can be assessed; there may be discontinuity with distal nerve contraction. Increased T2 signal and enhancement of intact nerves suggests damage or impairment despite contiguity . Haematoma, fracture fragment or callus formation may also cause brachial plexopathy.

36. Pseudomeningocele - Imaging

37. Traumatic Plexopathy - Complication Brachial plexus injuries may be associated with injuries to the subclavian artery due to their anatomical proximity to each other. Also post-traumatic pseudoaneurysm of subclavian artery may present with delayed brachial plexus paralysis due to compression of the brachial plexus.

38. Subclavian Artery - Pseudoaneurysm

39. Neonatal Brachial Plexopathy Occurs in approximately 1 in 1000 neonates. Downward traction on the shoulder girdle produces stereotyped patterns of plexus injury . Nerve lesions occur first at higher levels, with more severe traction progressive inferior extension of lesion occur. Superior nerve injury is typically extraforaminal , at the level of the superior trunks, because a welldeveloped investing fascia protects the upper nerve roots from proximal traction.

40. Classification of Neonatal Brachial Plexus Injury Superior Nerve Injury Inferior Nerve Injury Extraforaminal Intraforaminal Well-developed investing fascia protects the upper nerve roots from proximal traction. Partial or complete avulsion of the nerve root

41. Obstetrics Brachial Palsy – Naraka’s Classification Types Nerve Root involved Deformity Type I (Erb-Duchenne type) C5 and C6 deficits Loss of shoulder abduction, shoulder external rotation, elbow flexion, and forearm supination. Type II (Extended Erb’s ) C5 to C7/C8 deficits Type I with loss of wrist extension Type IIII C5 to C8/T1 deficits Total palsy with no Horner syndrome Type IV C5 to T1 and the sympathetic chain Total palsy with Horner syndrome

42. Neoplasm Four types of neurogenic tumors of the brachial plexus. Schwannoma Neurofibroma Plexiform neurofibroma Malignant Peripheral Nerve Sheath Tumor (MPNST) Plexiform neurofibroma and one third of the neurofibromas are associated with neurofibromatosis type I Schwannomas - capsuled and are eccentric nerve sheath tumors which displace the nerve fascicles and can be resected without damaging the nerve

43. Neurogenic Tumors Neurofibromas do not have a capsule and invade the nerve fascicles. Neurogenic tumors characteristically have an ovoid form , and the nerve can often be seen entering and leaving the tumor. In schwannomas the nerve enters or leaves the related tumor eccentrically, while in neurofibromas the nerve passes through the center of the tumor.

44. Imaging Findings in Neurogenic Tumors Neurogenic tumors will have signal intensities similar to muscles and T2 heterogeneously hyperintesne . They enhance with intravenous gadolinium. Cystic parts may be present in schwannomas . Neurogenic tumors may present as an apical lung tumor. MPNST’s – poorly defined margins, cystic degeneration, peripheral enhancement, perilesional edema and bone destruction

45. Neurogenic Tumors - MRI

46. Large Schwannoma - MRI

47. Other Neurogenic Tumors Neurogenic tumors of nerves in the vicinity of the brachial plexus include those of the vagal nerve, phrenic nerve and sympathetic trunk. The course of those tumors is in a more vertical direction. Sympathetic chain can also have a ganglion cell origin: neuroblastoma , ganglioneuroblastoma and ganglioneuroma

48. Ganglioneuroma - Imaging

49. Q-2 Option - D

50. Superior Sulcus Tumor Also known as Pancoast tumor. Non-small cell lung carcinomas that arise from the lung apex and invade the thoracic inlet. Tumor infiltration of the stellate ganglion causes Horner’s syndrome, which is characterized by miosis, ptosis and anhidrosis . Pancoast’s syndrome - Pain in the shoulder and arm Weakness and atrophy of the muscles of the hand Horner’s syndrome .

51. Pancoast Syndrome

52. Pancoast Tumor – Imaging MRI useful to assess the extension of tumors towards the brachial plexus, vertebral bodies, intervertebral foramina and the subclavian vessels . Infection may radiographically mimic a malignant superior sulcus tumor . Especially Nocardia is known to invade the thoracic wall. Contra-indications for surgery: Brachial plexus involvement above C8. Vertebral body invasion of more than 50 % Extensive mediastinal involvement with invasion of oesophagus or trachea.

53. Interscalene Fat Pad - Importance The earliest sign of extrathoracic and brachial plexus involvement is invasion of the interscalene fat pad by the tumor This fat pad lies between the anterior and the middle posterior scalene muscles and cephalad to the lung apex. The trunks of the brachial plexus are found in this fat pad. In advanced disease there is direct extension and invasion of the brachial plexus, intercostal nerves, stellate ganglion, neighbouring ribs, and vertebrae.

54. Interscalene Triangle - Invasion Pancoast tumours will be involving the interscalene triangle (middle compartment ). Connective-tissue sheath , covering the brachial plexus will initially displace the nerve roots or trunks superiorly without actually invading them. Sensory dysfunction may occur because of extrinsic nerve compression Loss of motor function is more likely to be indicative of frank invasion of the nerve

55. Pancoast Tumor – MRI

56. Pancoast Tumor – MRI

57. Other Tumors of Brachial Plexus Can be benign or malignant soft tissue tumors, bone tumors or metastatic disease. The most common benign soft tissue tumors is lipoma followed by aggressive fibromatosis . Malignant soft tissue tumors include various types of sarcomas, such as Liposarcoma Leiomyosarcoma Malignant fibrous histiocytoma Synovial cell sarcoma.

58. Other Tumors of Brachial Plexus All kind of bone tumors of the first rib, clavicle, scapula and vertebral bodies may involve the brachial plexus. In this group bone metastases are the most common cause. Other rare causes include plasmocytoma, chondrosarcoma and osteochondroma.

59. Lipoma – MRI

60. Non-Hodgkin's Lymphoma - MRI

61. Synovial Sarcoma – MRI

62. Nocardia Infection – MRI

63. Metastatic vs Radiation Brachial Plexopathy

64. Case Scenario A 56-year-old woman with a history of a left-sided breast carcinoma was treated with surgery and irradiation. The patient was doing well until about 7 months after termination of radiation therapy Then she developed weakness and pain in the left upper extremity. An MRI examination was performed

65. MRI – Brachial Plexus

66. Q - 3 Option - B

67. Radiation vs Metastatic Brachial Plexopathy Important to differentiate brachial plexopathy due to metastasis and radiation. Most common with the radiation dose of 6,000 cGy or more. How to differentiate???

68. Radiation vs Metastatic Brachial Plexopathy Imaging Features Radiation Brachial Plexopathy Metastatic Brachial Plexopathy Location Upper brachial plexus – C5& C6. Lower brachial plexus – Horner’s syndrome (C7,C8 & T1). Pain Absent Present Latency Period < 1 year > 1 year Lesion Diffuse In Radiation fibrosis – T1/T2 hypointense. No enhancement on T1 post contrast. Multiple nodules or masses. Metastatic lesion – T1 hypointense, T2 – heterogeneously hyperintense. Heterogeneous enhancement on post contrast.

69. Radiation Fibrosis - MRI

70. Metastatic Tumours Breast carcinoma - most common source of metastatic disease causing brachial plexopathy. Other metastatic sources include lung carcinoma and head and neck cancers. Metastatic lymphadenopathy - surround the neurovascular bundle, resulting in vascular or neural compromise. Metastatic disease from all causes - T1 hypointense and T2 heterogeneously hyperintense lesion.

71. Metastatic Tumours - MRI

72. Thoracic outlet syndrome Dynamically induced compression of neural and/or arterial structures crossing the cervicothoracobrachial junction . The three spaces that are evaluated on sagittal T1‑weighted images are, Interscalene triangle Costoclavicular region Retropectoralis minor spaces MRI - important role in, Demonstrating neurovascular compression. Localizing the cause of compression. Identifying the structure causing the compression.

73. 3 Spaces in Thoracic Outlet syndrome

74. Costoclavicular Space

75. Retropectoral Region - MRI

76. Causes of Thoracic Outlet Syndrome The costoclavicular space is the most common site of compression followed by interscalene triangle. The lesions causing compression may be, Bony abnormalities (cervical rib, long transverse process of C7 vertebra, callus or osteochondroma of clavicle or first rib) Soft tissue pathologies (fibrous band, hypertrophy of scalenus anterior muscle, scalenus minimus muscle, and fibrous scarring). Contrast‑enhanced MR angiography may be performed with the arm in elevated position to demonstrate narrowing of subclavian artery.

77. Thoracic Outlet Syndrome - Imaging

78. Brachial Plexus Neuritis Acute brachial plexitis presents with shoulder and upper arm pain lasting for few days to weeks followed by upper arm weakness. Idiopathic brachial neuritis is of unknown cause but an immune‑mediated inflammatory reaction. Probable etiologies - viral infection, vaccination, surgery, pregnancy , etc. Brachial plexitis is seen on MRI as focal or diffuse hyperintense signal in brachial plexus.

79. Brachial Plexus Neuritis – Clinical Features Affects the lower brachial plexus. Presents with acute onset of unilateral shoulder pain followed by flaccid paralysis of the shoulder and para -scapular muscles. Often a self-limiting course.

80. Immune Mediated Brachial Neuritis Includes, MMN – Multifocal Motor Neuropathy CIDP - Chronic Inflammatory Demyelinating Polyradiculoneuropathy MIDN - Multifocal Inflammatory Demyelinating Neuropathy MMN is characterized by slowly progressive, asymmetrical weakness of the limbs without sensory loss . CIDP causes a symmetrical weakness of the limbs with sensory loss.

81. Imaging MRI of the affected peripheral nerves can be abnormal. The nerves are enlarged and have an increased signal intensity on T2-weighted images. T2-weighted images with fat suppression are very useful in these patients. The lesions may, but often do not enhance after the administration of intravenous gadolinium.

82. MIDN - Imaging

83. Multifocal motor neuropathy Rare autoimmune peripheral neuropathy. Predominantly affects the upper limbs with a distal asymmetrical pattern. Lower motor neuron signs are always seen, with fasciculations sometimes present . It is mediated by anti-GM1 ganglioside IgM antibody .

84. MMN – Imaging Asymmetrical focal or diffuse signal hyperintensity and enlargement of the brachial plexus is classical . The increased signal intensity is believed to be due to demyelination, while inflammation and oedema might lead to swelling in nerves . MRI is considered to be of help to differentiate MMN from lower motor neuron disease, with brachial plexus MRI being normal in the latter.

85. CIDP - Chronic Inflammatory Demyelinating Polyradiculoneuropathy Acquired demyelinating disease involving peripheral nerves. Generally considered the chronic counterpart to Guillain-Barre syndrome (GBS ). Clinical Features - gradual and protracted (> 2 month) weakness of both proximal and distal musculature associated with areflexia and sensory changes.

86. CIDP - Pathology Affected nerves demonstrate segmental infiltration with inflammatory cells (lymphocytes) and demyelination. Over time there is proliferation of Schwann cells and deposition of collagen resulting in thickening of the nerve and the characteristic onion bulb appearance. Denervation atrophy of the supplied muscles.

87. CIDP - Imaging

88. Sonography of Brachial Plexus Uses- Entrapment neuropathies due to - Cervical rib, elongated C7 transverse process. Nerve tumors from brachial plexus. Guiding interventions (i.e., biopsy & brachial plexus anesthesia ). Can detect root avulsion, nerve injury in form of a neuroma, and scar tissue formation.

89. Brachial Plexus – Nerve Block

90. Imaging Pearls 3 important spaces to be identified? 5 Roots – 3 trunks – Division – 3 Cord – Branches. Sequences – Coronal – T1 / STIR, Axial – T1 / STIR & Sagittal – T1 / STIR. Brachial Plexopathies – Traumatic & Non traumatic. Imaging – Prime role in differentiating metastatic brachial plexopathy from radiation plexopathy.

91. Conclusion Brachial plexus has a complex anatomy and long course. Various traumatic and non-traumatic pathologies affecting it can be evaluated optimally by MRI . Knowledge of the anatomy and proper planning of the scan are essential for complete evaluation of the brachial plexus.