Orthopaedics
Peripheral Nerve Injuries
Peripheral nerve injuries for MBBS and NEET-PG: Seddon classification, radial, ulnar, median and common peroneal palsies, carpal tunnel syndrome and regeneration, mapped to NMC code OR11.1.
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Peripheral Nerve Injuries
Peripheral nerve injuries for MBBS and NEET-PG: Seddon classification, radial, ulnar, median and common peroneal palsies, carpal tunnel syndrome and regeneration, mapped to NMC code OR11.1.
This chapter covers injuries to the peripheral nerves of the limbs. It sets out the Seddon and Sunderland grading of nerve injury and the way nerves regenerate, then works through the classic named palsies of the upper and lower limb, their clinical deformities, the sites at which they are injured and the principles of management.
High-yield: Peripheral Nerve Injuries
- Seddon classified nerve injury into neurapraxia, axonotmesis and neurotmesis in order of increasing severity.
- Neurapraxia is a temporary conduction block with an intact axon and a full recovery.
- Axonotmesis is loss of axon continuity with intact connective tissue sheaths, allowing recovery by regeneration at about a millimetre a day.
- Neurotmesis is complete division of the nerve and needs surgical repair for any chance of recovery.
- Radial nerve injury in the spiral groove causes wrist drop with preserved triceps.
- Ulnar nerve injury at the elbow produces a claw hand that is most marked, the ulnar paradox, when the injury is more distal.
- Median nerve injury at the wrist causes an ape thumb deformity with loss of thumb opposition.
- Carpal tunnel syndrome is compression of the median nerve at the wrist, giving night pain and tingling of the radial three and a half fingers.
- Tinel and Phalen signs support the clinical diagnosis of carpal tunnel syndrome.
- Common peroneal nerve injury at the neck of the fibula causes foot drop and a high stepping gait.
- The axillary nerve is injured at the surgical neck of the humerus and in shoulder dislocation, numbing the regimental badge area.
- The long thoracic nerve supplies serratus anterior, and its injury causes winging of the scapula.
- Nerve conduction studies and electromyography help localise the lesion and grade the severity of a nerve injury.
- The pattern of motor and sensory loss allows the level of a nerve injury to be worked out clinically before any investigation.
Classic peripheral nerve palsies
- **Radial nerve:** Spiral groove of humerus. Wrist drop with preserved triceps.
- **Ulnar nerve:** Elbow or wrist. Claw hand, ulnar paradox worse with distal lesions.
- **Median nerve:** Wrist. Ape thumb, loss of opposition. Carpal tunnel syndrome.
- **Common peroneal nerve:** Neck of fibula. Foot drop and high stepping gait.
NMC competencies in this chapter
- **OR11.1:** Peripheral nerve injuries: classification, clinical features and management
Frequently Asked Questions
What is the Seddon classification of nerve injury?
It grades injury into neurapraxia, a reversible conduction block, axonotmesis, loss of the axon with intact sheaths that recovers by regeneration, and neurotmesis, complete division needing surgical repair.
What deformity follows a radial nerve injury?
Wrist drop, an inability to extend the wrist and fingers, because the radial nerve supplies the extensor compartment of the forearm. Injury in the spiral groove spares the triceps.
What is the ulnar paradox?
A more distal ulnar nerve injury produces a more obvious claw hand than a proximal one, because the proximal lesion also paralyses the long finger flexors that would otherwise curl the fingers.
How fast does a nerve regenerate after axonotmesis?
Regenerating axons grow at roughly one millimetre per day, so recovery time can be estimated from the distance between the injury and the target muscle.
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