Brachial plexopathy can be categorized as either traumatic or nontraumatic. Traumatic cases vary in severity and require imaging for prognosis and surgery decisions. Nontraumatic cases includes neuritis from many factors (radiation, inflammation, infection, metabolic disorders, compression and benign/malignant tumors).

Traumatic plexopathies [2, 5-7]

Traumatic brachial plexus injuries can be devastating and may result in life-altering functional disability. The location of the injury is crucial for the management. Preganglionic lesions are devastating injuries that are commonly irreparable. In contrast, postganglionic injuries can be potentially repaired or treated with surgical graft replacement.

• Preganglionic lesions:
  

  Fig 15: A 43-year-old male patient who suffered a motorcycle accident. Clinically, he is unable to move his right upper limb. Axial T2 TSE images (A, B) and coronal 3D FIESTA images (C, D) show post-traumatic pseudomeningoceles at the C6-C7 and T1-T2 right neural foramina (preganglionic injury of the right C7 and T1 roots). Department of Radiology. Hospital Universitario Virgen de la Arrixaca, Murcia, Spain.

They result from nerve rootlets avulsion from the spinal cord, a condition that is not surgically repairable. The gold standard diagnosis is surgical exploration. MRI has a sensitivity of 93% and specificity of 72% for diagnosing preganglionic injury.

Signs of preganglionic injury: a) direct: discontinuity of the ventral or dorsal root of the spinal cord; b) indirect: pseudomeningocele, spinal cord edema, displacement of the spinal cord and denervation of the ipsilateral paravertebral muscles (dorsal branch of the spinal nerve).

In cases of suspected traumatic brachial plexus injury, an MRI should ideally be performed 3-4 weeks after the traumatic event, once acute edema and subarachnoid hemorrhage have resolved, leading to pseudomeningocele formation.

Although pseudomeningocele is a very reliable indicator of preganglionic injury, the main differential diagnosis should include extradural meningeal cysts, although they are rare in the cervical and thoracic spine.

Fig 16: A 37-year-old woman presents with cervical pain, with no known traumatic history. Axial T2 FSE images (A), sagittal T2 FSE (B), and coronal 3D FIESTA (C) show a small cystic lesion at the C7-T1 right neural foramen, suggestive of an extradural meningeal cyst. Department of Radiology. Hospital Universitario Virgen de la Arrixaca, Murcia, Spain.

• Postganglionic lesions:

They manifest as focal changes in nerve caliber, loss of fascicular architecture, nerve discontinuity, neuromas, or signal abnormalities.

Fig 17: A 22-year-old male who suffered a motorcycle accident with left upper limb paralysis. 3D CUBE STIR sequence with IV contrast in coronal (A), axial (B), and sagittal (C) planes, shows distortion of the upper, middle, and lower trunks, as well as hyperintensity at the level of the divisions and cords (red arrows), suggestive of post-ganglionic injury. A soft tissue mass (red dashed circle) is seen in relation to a hematoma. No preganglionic involvement of the brachial plexus was observed. Department of Radiology. Hospital Universitario Virgen de la Arrixaca, Murcia, Spain.

Fig 18: CT with IV contrast in axial (A), coronal (B), and sagittal (C) planes of the same patient as in Figure 17, shows a left supraclavicular hematoma extending from C6 to T2. It affects the scalene muscles and extends into the costoclavicular space and retropectoral area, accompanying the axillary-subclavian neurovascular bundle. In these cases, MRI of the brachial plexus is recommended due to suspicion of traumatic injury. Department of Radiology. Hospital Universitario Virgen de la Arrixaca, Murcia, Spain.

Nontraumatic plexopathies [2, 8, 9]

• Acute brachial neuritis (Parsonage-Turner syndrome):

It is an idiopathic neuralgia with an acute onset (post-viral, minor trauma, exercise, childbirth, etc.). It is usually unilateral and more common in males. The most frequently affected root is C5, as well as the lateral cord.

Fig 19: A 28-year-old woman with pain, weakness, and paresthesia in the left upper limb following traumatic effort. Coronal 3D CUBE STIR image with IV contrast shows hyperintensity and thickening of the left C5 root. Department of Radiology. Hospital Universitario Virgen de la Arrixaca, Murcia, Spain.

Fig 20: Axial DP FS sequence (A), coronal DP FS (B), oblique sagittal DP FS (C), and oblique sagittal T1 FSE (D) of the same patient as in Figure 19, show hyperintensity of the muscle fibers in the deltoid, teres minor, and subscapularis muscles (red arrows), consistent with edema due to acute denervation. No atrophy was seen. These findings, along with those in Figure 20, suggest Parsonage-Turner syndrome.

• Postirradiation brachial plexopathy.

It occurs with tumors of the head and neck, breast or pulmonary apex, because of radiation exposure to the suprascapular or axillary region. It is crucial to distinguish between postirradiation plexopathy or local recurrence of the underlying disease, for which PET-CT may sometimes be necessary. On MRI, it appears as thickening and hyperintensity on T2 sequences, with fine longitudinal enhancement.

• Brachial plexus tumors.

Note that primary and secondary brachial plexus tumors exist, although this is not the poster´s main subject. Primary tumors divide into benign (neurofibromas or schwannomas) and malignant (malignant peripheral nerve sheath tumors or neurolymphomatosis).

Fig 21: A 19-year-old patient with type 1 neurofibromatosis and a suspicious mass in the right arm. Axial T1 FSE images (A), axial T2 FSE (B), axial DP FS (C), axial T1 FS with IV contrast (D), and sagittal DP FS (E) show a solid nodular lesion in the axillary region, arising from the terminal branch of the median nerve (yellow arrow), consistent with a neurofibroma. Department of Radiology. Hospital Universitario Virgen de la Arrixaca, Murcia, Spain.

Fig 22: A 56-year-old patient with bilateral masses in both axillary regions. Coronal T1 FSE sequence shows three solid bilateral axillary masses related to tumors of neural origin (diagnosis confirmed by pathological examination). Department of Radiology. Hospital Universitario Virgen de la Arrixaca, Murcia, Spain.

Among the malignant tumors that secondarily affect the brachial plexus, metastases are notable because of their high frequency.

Fig 23: A 61-year-old woman with no relevant medical history presents with cervical pain, weakness in shoulder abduction, and right arm flexion. Sagittal STIR images (A), axial T1 FS with IV contrast (B), and PET-CT (C) reveal a pre- and paravertebral soft tissue mass at C5-C6 right neural foramen, with high 18F-FDG uptake suggestive of malignancy. Further evaluation demonstrated a locally advanced cervical cancer. Department of Radiology. Hospital Universitario Virgen de la Arrixaca, Murcia, Spain.

Fig 24: 3D CUBE STIR image with IV contrast from the same patient as in Figure 23, showing mild hyperintensity and thickening of the C5 and C6 roots, and the upper trunk, all suggestive of infiltrative plexopathy secondary to metastasis. Department of Radiology, Hospital Universitario Virgen de la Arrixaca, Murcia, Spain.

Fig 25: A 57-year-old woman with metastatic breast cancer presents with progressive paresis of the right upper limb. Sagittal T1 FSE (A), axial T2 FSE (B, C), and coronal 3D CUBE STIR with IV contrast (D) images reveal diffuse metastatic infiltration of cervical-thoracic vertebral bodies and posterior elements (red asterisk), along with a soft tissue mass obliterating the right C5-C6, C6-C7, C7-T1, and T1-T2 neural foramina (red arrow and circle). Thickening and hyperintensity of the C5 to T1 roots (red bracket) and the upper, middle, and lower trunks (red dashed brackets) suggesting infiltrative plexopathy. Department of Radiology. Hospital Universitario Virgen de la Arrixaca, Murcia, Spain.