The nerve supply to the arm is from nerve roots C5-T1 via the brachial plexus. The nerves pass under the clavicle and end in the axilla.
Signs and symptoms
Traumatic injury mostly occurs in severe road traffic accidents (especially on a motorcycle) and falls from heights. Young men are most commonly affected. The position of the arm (as the injury occurs) will determine the levels involved.
If the arm was held at the side, a C8-T1 injury is usual. However, if the arm is abducted, C7 is commonly involved.
Symptoms are often associated with:
- Broken clavicle.
- Swelling around the shoulder.
- Neck and shoulder pain.
- Paraesthesiae and weakness in the arm.
- Horner's syndrome, which indicates complete lesion in the lower plexus, ie C5-C7.
See also the separate Neurological Examination of the Upper Limbs article.
Pinch the nail base, pull the finger outwards and ask about feeling anything. A burning feeling indicates continuity in the following nerves; absence does not necessarily mean the nerve is divided but may be due to neurapraxia instead.
- Thumb - tests the median nerve supplied by C6.
- Middle finger - tests the median nerve supplied by C7.
- Little finger - tests the ulnar nerve suppled by C8.
Examination can be made difficult by anomalous nerve distribution, including C4 contributing to the brachial plexus and also because many muscles are supplied by more than one motor neuron. Assessment of loss of motor function at the cervical root:
- C5: shoulder movement in all directions, flexion of elbow (to some degree).
- C6: flexion of elbow, rotation of forearm, flexion of wrist (to some degree).
- C7: mainly a sensory trunk. (Produces generalised loss of movement in the arm, without total paralysis in any given muscle group. Always supplies the latissimus dorsi.)
- C8: extension and flexion of fingers, flexion of wrist, hand movement.
- T1: intrinsic muscles of the hand - eg adduction or abduction of fingers.
Many cases are temporary, with full function recovering within one week. However, permanent injury is not uncommon. See also the separate Birth Injuries to the Baby article.
- There are two types of brachial plexus paralysis in neonates: the upper plexus injury is called Erb's palsy; the lower plexus injury is called Klumpke's palsy.
- In the UK the incidence is 0.42 per 1,000 live births.
- They can occur when the head is pulled away from the shoulder during delivery. A small proportion is unrelated to delivery.
- Large birth weight and/or maternal diabetes.
- Shoulder dystocia (increases the risk for brachial plexus injury 100-fold).
- Breech presentation.
- Second stage of labour lasting more than 60 minutes.
- Assisted delivery.
- Intrauterine torticollis.
Examine 48 hours after delivery for a more reliable assessment.
- Erb's palsy (C5-C6 injury) - the arm is characteristically held adducted and internally rotated with the forearm pronated, hand and wrist flexed ('waiter's tip' position). The infant is unable to move the arm or shoulder. See the separate Erb's Palsy article.
- Klumpke's palsy - Horner's syndrome is present, ie meiosis, ptosis, anhydrosis.
- High-resolution MRI requires no radiation exposure, is non-invasive and provides more detail than CT myelography.
- Plain X-rays can be useful to diagnose hemidiaphragm paralysis from phrenic nerve involvement, or fractures of the clavicle or humerus.
- Nerve conduction studies.
- Adult trauma: rehabilitation may play an important role in reducing disability.
- Neonatal: spontaneous recovery usually occurs and can start within days but can take months:
- Physiotherapy can help.
- Other treatments include botulinum toxin injection and electrical stimulation.
- Neuromuscular electrical stimulation (NMES) is a treatment used in an older child, where muscles are stimulated by pulsating alternating currents. It should be titrated with guidance from the child to allow muscle contraction without pain.
- Prevention of obstetric injury is not always possible, as a significant proportion of injuries may occur in utero.
- Specialist surgical repair in tertiary centres: options include nerve transfers, nerve grafting, muscle transfers and neurolysis of scar around the brachial plexus.
- Phrenic nerve transfer has shown useful recovery of arm function in some patients; however, there is very little information about long-term functional and quality-of-life outcomes. There is also some evidence of consequent impairment of respiratory function. However, because patients with brachial plexus injuries are often very disabled and treatment options may be limited, the National Institute for Health and Care Excellence (NICE) recommends that phrenic nerve transfer may be considered as a treatment option.
- In neonates, surgery is recommended as an early intervention, as outcome is best if repair is undertaken within three months.
- Progressive contractures.
- Deafferentation pain; this occurs when the nerve roots are avulsed in preganglionic lesions. The cells in the dorsal column are robbed of their nerve supply. After the injury (days to weeks), spontaneous signals are generated by these cells, which result in intractable pain for the patient.
- Bony deformities.
- Posterior shoulder dislocation.
- Agnosia of the affected limb.
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