MRI - Right brachial plexus MRI
What does the pseudomeningocele likely indicate in this case?
The pseudomeningocele likely indicates a nerve root avulsion. Although a pseudomeningocele is a helpful indicator of preganglionic injury, up to 23% of root avulsions do not have an associated pseudomeningocele, and pseudomeningocele-like lesions are seen in the absence of root avulsion in up to 24% of cases.
What is a differential diagnosis for pseudomeningocele?
The differential diagnosis would include non-traumatic perineural cyst / extradural meningeal cyst. Peripheral nerve sheath tumors can occur in this location but would demonstrate enhancement.
MRI of the right brachial plexus without and with IV contrast was also performed on the same day as the cervical spine MRI. In addition to the right C8 pseudomeningocele, there is right glenoid dysplasia with glenoid retroversion and posterior subluxation at the right glenohumeral joint.
The brachial plexus is comprised of the C5, C6, C7, C8, and T1 nerve roots. The upper trunk, middle trunk, and lower trunk are slightly thickened / hyperintense in the region of the scalene triangle (in between the anterior scalene and middle scalene muscles). The divisions appear normal in morphology, forming a Christmas tree appearance over the subclavian artery.
The cords (lateral cord, posterior cord, medial cord) are seen more distally and give a paw print configuration over the subclavian artery in this region. The branches of the brachial plexus (including the median nerve, musculocutaneous nerve, ulnar nerve, radial nerve, and axillary nerve) are seen more distally near the level of the coracoid process.
No muscle edema or atrophy is seen in the field of view. There is atelectasis in the posterior right lung.