Brachial plexus root avulsion

Case contributed by Shu Su


4 weeks post motorbike accident. Initially flaccid left upper limb, whole upper limb numbness and left side of neck up to angle of jaw and lower earlobes.

Patient Data

Age: 41
Gender: Male

T2 hyperintense pseudomeningoceles are seen at C6/C7  and C7/T1 around avulsed C7 and T1 nerve roots on the left. No intrinsic cord signal abnormality.There appears to be complete disruption of the roots of the left brachial plexus immediately beyond the scalene muscles.  Redundant brachial plexus is seen beyond this. Moderate amount of edema within the soft tissues of the lateral neck on the left, particularly involving the scalenes musculature. The cervical spine demonstrates no evidence of malalignment or abnormal bone marrow signal. Small left shoulder joint effusion.  Denervation edema seen in the muscles around the scapula.

Conclusion: Complete disruption of the roots of the left brachial plexus.  Left C6/C7 and C7/T1 pseudo-meningocoeles around avulsed left C7 and T1 nerve roots.

Case Discussion

Preganglionic lesions of the brachial plexus are proximal to the dorsal root ganglion and typically have a poor prognosis. Pseudomeningocoeles are common after nerve root avulsion but can also be present with intact nerve roots. They represent CSF collections in dural sac outpouchings due to dural/perineural tear. Retracted distal nerve roots or a nerve retraction ball may also be visible. Other associated signs include:

  • spinal cord abnormalities: edema, hemorrhage, myelomalacia, syringomyelia, contralateral cord displacement
    • signal intensity changes in spinal cord in 20% of preganglionic injury patients 
  • T2-weighted hyperintensity of denervated paraspinal muscles (especially multifidus muscle) due to dilatation of vascular bed and enlargement of extracellular space

Case courtesy of A/Prof Pramit Phal.

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