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.