What is a peripheral nerve injury?
A peripheral nerve injury is damage or disruption to the peripheral nerves, which emerge from the spinal cord and brainstem and reach the ‘ends’ of the body, rather than congregating around the central nervous system. These injuries can manifest due to trauma, compression, disease, or inflammation of the nerves.
Peripheral nerve injuries result in the dysfunction of the peripheral nerves, causing pain, weakness, numbness, or tingling in the affected body part. The severity and type of symptoms differ according to the location and extent of the injury.
Types of peripheral nerve injuries include:
- Brachial plexus injury (shoulder and arm)
- Peroneal nerve injury (foot and leg)
- Ulnar nerve compression (ring and little finger)
- Spinal accessory injury (back)
- Carpal tunnel syndrome (hand)
- Sciatica (lower back to feet)
What are the peripheral nerves?
The peripheral nerves are a system of 43 pairs of nerves that manage motor control and sensory input. They carry information from the brain to the body (motor instructions) and vice versa (sensory processing). These nerves assist in more than just voluntary movement, but also in basic, unconscious functions like breathing and digesting.
What causes peripheral nerve injury?
Peripheral nerve injuries can arise due to a variety of causes and factors. Any damage or disruption to the peripheral nerve system can become an injury, such as:
- Lacerations (cuts or tears)
- Bruising and blunt trauma (contusions)
- Gunshot wounds or impalement
- Stretching
- Electrical injuries
There are four kinds of peripheral nerve injuries
- Neuropraxia (stretching and contusion of the nerves)
- Rupture (stress and tearing of the nerves)
- Neuroma (tissue damage or scarring leading to compression)
- Avulsion (nerve root is torn from the spinal cord)
Symptoms of peripheral nerve injuries
Common symptoms of peripheral nerve injuries include:
- Numbness and loss of sensation in the limbs
- Weakness or paralysis (inability to move) in the limbs
- Burning or stinging pain in the limbs
Peripheral nerve injuries are evaluated according to the Sunderland classification system, which assigns the injury to one of five different degrees:
- First: reversible injury from neuropraxia. Does not require surgery and will recover within a few weeks
- Second: disruption of muscular electrical communication, but may not need surgery
- Third: damage to the axons (points of bioelectrical transmission in the nerves), which may need surgical intervention such as debriding the nerve (neurolysis) or even grafting.
- Fourth: damage to the axons has created scarring that prevents regeneration. Surgery is necessary.
- Fifth: more common in extreme rupture or stretch cases. Surgery is necessary.
Diagnosing peripheral nerve injuries
Peripheral nerve injuries are typically diagnosed through a combination of physical examination, medical history, scans, and other diagnostic tests.
The physical examination will serve to assess for any signs of injury (swelling, tenderness, redness, weakness, or lesions), as well as nerve response via testing reflexes, sensation, and muscle strength.
Diagnostic tests used during the investigation could be:
- Electromyography (EMG) and nerve conduction studies, which measure the electrical activity in muscles and nerves
- Magnetic resonance imaging (MRI), which uses powerful magnets and radio waves to produce detailed images of the body
- Computed tomography (CT) scan, which uses X-rays and computer technology to produce detailed images of the body
- Ultrasound, which uses high-frequency sound waves to produce images of internal organs and tissues
Treatment for peripheral nerve injuries.
Treatment for peripheral nerve injuries will depend on the location, cause, and severity. Ideally, conservative approaches are explored before surgery is considered, as in some cases the injury requires observation and rest, particularly for neurapraxic injuries.
Medications are used in treatment thought they are not curative. Their main purpose is to abate the pain and inflammation, if need be. NSAIDs like ibuprofen or naproxen are one such type of medication.
Physical rehabilitation is beneficial for patients post-peripheral nerve injury as it helps to strengthen muscles, coordination, and flexibility in a way that promotes regeneration or prevents future injury through nervous system adaptation. Acupuncture and massage therapy may also benefit patients.
Transcutaneous electrical nerve stimulation (TENS) can be explored for nerve regeneration and improving muscle function.
Surgical options for treatment are used particularly in cases of rupture and avulsion. There are different procedures for different injury sites and the extent of damage, such as:
- Nerve repair
- Nerve graft, where a healthy nerve from elsewhere in the body is used to bridge the two ends of a severed or torn nerve
- Nerve transfer, where a healthy nerve is permanently implanted where the damaged nerve is
- Nerve entrapment surgery
- Open decompression surgery
- Tendon and muscle grafts, to assist with arm movement and function
Peripheral nerve injuries are treated by physicians who specialise in the nervous system, which encompasses orthopaedic surgeons, neurologists, and neurosurgeons.
