Definition: A preganglionic brachial plexus injury occurs when the
spinal roots are avulsed directly from the spinal cord or the rootlets rupture
proximal to the dorsal root ganglion. An injury distal to the dorsal root
ganglion is called postganglionic
Etiology: Adult brachial plexus injury can result from penetrating
injuries, falls, and motor vehicle accidents, causing fracture or compression.
Obstetric brachial plexus injury is associated with shoulder dystocia, which occurs
more frequently with fetal macrosomia.
Incidence: The true incidence of adult brachial plexus injuries
is undetermined due to significant underreporting, but they account for 5% of
peripheral injuries. However, obstetric palsies complicate 1% of all births.
Age and Gender: Most adult traumatic brachial plexus injuries occur in
males aged 15 to 25 years. Obstetric brachial plexus palsy occurs more
frequently in males due to their greater mean birth weight.
Signs and Symptoms: Acute pain over a nerve suggests a rupture, whereas
lack of percussion tenderness indicates an avulsion. The classic Erb’s palsy
occurs at C5-6, producing a classic “waiters tip” with the forearm adducted,
internally rotated, and the elbow extended. Total brachial palsy is
characterized by complete arm paralysis, decreased sensation, and a pale extremity.
The suprascapular nerve supplies the supraspinatus and infraspinatus muscles,
so injury can be assessed by lack of shoulder external rotation and abduction
and the presence of infraspinatus atrophy. Loss of shoulder flexion, internal
rotation, and abduction may be caused by injury to the axillary nerve that
supplies the deltoid. Horner’s syndrome suggests C8-T1 root avulsion. Injury to
the long thoracic nerve that innervates the serratus anterior causes scapular winging
on arm flexion. The dorsal scapular nerve is derived from C4-5 roots and
innervates the rhomboids; studies indicate that injury to this nerve causes
rhomboid atrophy.
Diagnostic: Plain
radiographs of the cervical spine, shoulder, and chest should be done after a traumatic injury. Transverse process fractures
suggest root avulsion at that level. Clavicle or first
and second rib fracture may indicate brachial plexus injury. With avulsion
of a cervical root, the dural sheath heals
with development of a pseudomeningocele that is evident on CT myelogram at 3 to 4 weeks. MRI can visualize much of the
brachial plexus, large neuromas, and inflammation or
edema. Electromyogram and nerve conduction velocity studies help confirm a
diagnosis, localizing lesions, defining the
severity of axon loss, and revealing subclinical recovery.
Treatment: Surgery
should be performed in the absence of clinical or electrical evidence of recovery
or when spontaneous recovery is impossible. Nerve grafting using
interpositional grafts such as the sural nerve and other cutaneous nerves can
be performed with rupture or postganglionic neuromas that do not conduct across
the lesion. Neurotization or nerve transfer in which a nerve of lesser
importance such as the spinal accessory nerve, intercostal nerves, or medial
pectoral nerves can be transferred to the denervated distal nerve. Free
functioning muscle transfer is the transplantation of a muscle and its neurovascular
pedicle to a new location. The latissimus dorsi, rectus femoris, and the
gracilis are most commonly used to provide reliable elbow flexion.
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