= most severe nerve injury of extremities

Cause: severe traction force on upper limb at birth / in traffic accident (motorcycle)

1. Erb-Duchenne palsy: adduction injury affecting C5-6 ← downward displacement of shoulder
   • paralysis of shoulder muscles + biceps
2. Klumpke palsy: abduction injury at C7, C8, T1 ← arm stretched over head
   • paralysis of forearm flexors + intrinsic hand muscles

CT myelography (preferred method):

• Shoulder artifacts may be problematic at C8–T1 level
• displacement of spinal cord to contralateral side ← absence of normal nerve root traction on cord
• pouchlike nerve root sleeve at site of avulsion
• asymmetric slightly deformed root sleeve + nerve roots
• obliteration of tip of root sleeve
• traumatic meningocele
• contrast extravasation collecting in axilla
• metrizamide in neural foramina

MR:

◊Conventional MR only in 50% accurate!

Pitfalls: partial root avulsion, intradural fibrosis, traumatic meningocele, movement artifacts (respiration, swallowing, blood flow)

• focal T2-hyperintense cord changes ← edema of acute phase / myelomalacia in chronic phase
• focal T2-hypointense cord changes ← hemosiderin
• enhancement of morphologically normal intradural nerve root / root stump ← functional impairment (mostly preganglionic)
• abnormal enhancement of paraspinal (multifidus) muscle ← muscle denervation = indirect sign of root avulsion
• thickening of postganglionic brachial plexus ← edema + fibrosis