Brachial Plexus Birth Injury MRI — Assessing Nerve Root Avulsion

Brachial Plexus Birth Injury MRI

When a newborn has an arm that won’t move after a difficult delivery, the key surgical question is where the nerve is damaged — and MRI helps answer the hardest part.

Pre- vs postganglionic — the crucial split

Obstetric brachial plexus injury ranges from stretch (neurapraxia, often recovers) to rupture and, most severe, root avulsion from the spinal cord. The distinction between preganglionic (avulsion, at the cord) and postganglionic injury drives the surgical strategy.

Preganglionic avulsions cannot be repaired by direct grafting to the cord — they need nerve transfers — so identifying them changes the operation.

What MRI shows

Pseudomeningocoele: a CSF-filled outpouching at the neural foramen — a key marker of root avulsion.
Absent/displaced nerve roots on high-resolution heavily T2-weighted sequences.
Postganglionic changes: nerve thickening, neuroma, and secondary muscle denervation/atrophy.

High-resolution 3D sequences and often sedation/anaesthesia are needed to image these tiny structures in a baby.

Role in management

MRI complements clinical assessment and electrophysiology in deciding whether and when to operate in infants who fail to recover spontaneously, and in planning the reconstruction. It is performed in specialist centres within a defined window.

Reference: Somashekar D et al. High-resolution MRI evaluation of neonatal brachial plexus palsy. AJNR / Pediatr Radiol reviews.

Educational summary for clinicians; managed by specialist peripheral-nerve teams. Not medical advice.