The most common causes of brachial plexus palsy in neonates are intrauterine trauma, chicken pox infection, soft tumors of the brachial plexus or surrounding structures, extrauterine trauma, and bony exostosis.
is the most common cause of brachial plexus injury. Trauma may occur during
pregnancy prior to the onset of labor (intrauterine trauma), during labor,
or at the time of delivery. The term obstetrical brachial plexus injury
is used for brachial plexus palsy that occur during labor or at the time
of delivery. Obstetrical brachial plexus injury is more frequent than
brachial plexus palsy due to intrauterine trauma.
trauma prior to the onset of labor
Figure 260.1.— Fixed right arm position with decreased movements.
during labor and delivery (obstetrical brachial plexus palsy)
Figure 260.2.— Fetal ultrasound 18-20 weeks gestation demonstrating a thin fixed right arm with decreased movements.
Decreased fetal arm movements during pregnancy leading to weakening of the forces that protect the brachial plexus may contribute to obstetrical brachial plexus palsy. (Click on clip)
Neonates born with intrauterine evidence of decreased arm movements such as anatomical deformities, thinner arm (Figure 260.3), or evidence of intrauterine arm injury that in addition have a brachial plexus injury during delivery show no fibrillation potentials during the the first week of life and do so at a later day.
Figure 260.3.— Brachial plexus palsy due to intrauterine factors predisposing for obstetrical brachial plexus palsy. Left arm is thinner.
Obstetrical brachial plexus injury occurs because the brachial plexus is pulled in a direction that causes the angle formed by the spinal cord and the plexus to increase beyond the stretching capacity of the nerve fibers (Figure 260.4).
Figure 260.4.— Brachial plexus palsy due to intrauterine compression. [A] Fixed anatomical deformity; [B] left arm is thinner.
brachial plexus injury is due to acute trauma as witnessed by the presence
of swelling of the brachial plexus on MRI for several days after the injury
(Figure 260.5). Evidence of trauma in other areas may be present. Frequent
structures involved are the scalp (caput cephalohematoma), facial and
phrenic nerve (diaphragmatic paralysis), oculosympathetic nerve fibers
(Horner syndrome), clavicle (fracture), shoulder (posterior dislocation
of the head of the humerus), and humerus (fracture).
Specific investigations may be required to diagnose these injuries.
The cornerstone of the treatment of obstetrical brachial plexus injury is to avoid: (1) muscular atrophy in the affected muscles, and (2) muscular contractures of the healthy muscles. Atrophy of the affected muscles renders them unsuitable for reinnervation. Contracture of the healthy muscles produces muscle group imbalance and joint deformities. Muscular atrophy is prevented with physical therapy. Physical therapy involving the shoulder is recommended after 7 to 10 days of age. The waiting period is recommended to avoid stretching the plexus during a time when the plexus is vulnerable to further injury. Physical therapy should include active and passive exercises. Splinting is generally contraindicated unless low-weight splints are used, and only to arrest or reverse deformities. Some authors recommend electrical stimulation.