Aetiology

Brachial plexus injuries are quite rare and can result from a variety of causes. In adults, the majority of traumatic brachial plexus injuries are related to motor vehicle accidents, gunshot or stab wounds, contact sport accidents, or workplace accidents during heavy physical labour.[5]

Lesser degrees of injury can be seen in other traumatic situations, such as improper positioning during surgery, inflammatory conditions such as Parsonage-Turner syndrome, and primary and metastatic tumours.[11][12] The Pancoast tumour of the lung apex results in typical lower root symptoms, such as pain and paralysis of the hand, and is common enough that it should be considered in any case of significant hand pain without another obvious cause.[13]

Some metabolic disorders including diabetes mellitus, liver diseases, and renal disease may result in nerve injury.[14]

Pathophysiology

The many causes of brachial plexus injury have in common an eventual discontinuity of nerve function. This may occur by:

  • Physical discontinuity of axons, as with penetrating injuries

  • Extrinsic compression of the nerve fibres by primary tumours, metastatic tumours, or limb positioning, or by a cervical rib or first rib abnormalities

  • Metabolic causes that can disrupt internal metabolic active transport systems within the axon and result in loss of electrical conductivity.

Since all somatic nerves, including those of the brachial plexus, subserve voluntary movement and skin sensibility, these will be the functions that are lost with brachial plexus injury. There can be additional vascular changes due to sympathetic nerve involvement but these are generally milder in presentation and consequence.[15]

Although most reconstructive surgeries are done for physical discontinuity of nerves following direct trauma, severe longstanding compressions and inflammations may equally require surgical management.[16]

Classification

Sunderland classification[3]

Based on anatomical boundaries within the nerves that are transgressed by increasing force of trauma. There are 5 degrees of injury from simple stretch/compression to complete transaction:

  • First-degree injury: axon remains intact; includes conduction blocks

  • Second-degree injury: axon is severed, but endoneurium, perineurium, and epineurium are intact

  • Third-degree injury: axon and endoneurium damaged leaving fascicular pattern intact

  • Fourth-degree injury: axon, endoneurium, and perineurium damaged

  • Fifth-degree injury: complete injury.

Seddon classification[4]

Based on clinical findings with increasing force of trauma. There are 3 degrees of injury from simple stretch/compression to complete transaction:

  • Neurapraxia (first-degree Sunderland)

  • Axonotmesis (second-degree Sunderland)

  • Neurotmesis (fifth-degree Sunderland).

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