Erb-Duchenne paralysis results from injury to the upper brachial plexus, most commonly occurring during birth. The incidence of neonatal brachial plexus injury is estimated at 1 in 1000 live births and is often associated with prolonged or difficult labor, fetal macrosomia, and/or shoulder dystocia.

Clinically, an upper plexus injury can be recognized by an adducted arm with internal rotation at the shoulder and extension with pronation at the elbow. Wrist extension is weak or absent, and fingers are often partially flexed or fisted. Biceps and triceps reflexes are absent. The Moro reflex is asymmetric.

If the injury extends higher than the C4 segment, associated ipsilateral diaphragmatic paralysis is present.

If there is involvement of the complete plexus (C5 to T1), there will be flaccid weakness of the limb. There may be an associated Horner syndrome.

The severity of the injury can vary widely depending on the extent of the injury (stretching versus avulsion).

Brachial plexus injuries also occur in older children and adults, primarily via traction and pressure injuries.