Peripheral Nerve Injuries: Diagnosis, Treatment, and Prognosis
Discover everything you need to know about peripheral nerve injuries, including diagnosis, treatment, and prognosis. Gain insights into the epidemiology, etiology, anatomy, classification, treatment options, and prognosis of peripheral nerve injuries. Achieve functional recovery and prevent chronic neuropathic pain with optimized treatment approaches.
Introduction
Peripheral nerve injuries encompass a range of reversible and irreversible impairments determined by injury level, axonal disruption, and time to treatment. This blog will provide information on the diagnosis, treatment, and prognosis of peripheral nerve injuries.
Epidemiology
| Incidence | Demographics | Risk factors |
|---|---|---|
| Major peripheral nerve injury sustained in 2% of patients with extremity trauma | Males = Females | Penetrating injuries, displaced fractures |
| Nerve injuries account for approximately 3% of injuries affecting the upper extremity and hand | Stretching injuries | |
| Compression/crush | ||
| Laceration |
Etiology
Peripheral nerve injuries can be caused by various mechanisms of injury, including stretching, compression or crush injuries, and lacerations. Stretching injuries can lead to neurapraxia or brachial plexus stretch injury, while compression injuries can cause local ischemia and poor axonal transport, ultimately leading to nerve dysfunction. Lacerations can have a better prognosis than crush injuries, as sharp transections have a better chance of repair compared to crush injuries that can also lead to neuroma formation at the proximal end.
| Pathophysiology | Mechanism of injury examples |
|---|---|
| Stretching injury | 'Stingers' refer to neurapraxia from brachial plexus stretch injury Suprascapular nerve stretching injuries in volleyball players Correction of valgus in TKA leading to common peroneal nerve palsy |
| Compression/crush | Fibers are deformed Local ischemia Increased vascular permeability Endoneurial edema leads to poor axonal transport and nerve dysfunction Fibroblasts invade if compression persists Scar impairs fascicular gliding Chronic compression leads to Schwann cell proliferation and apoptosis 30mm Hg can cause paresthesias Increased latencies 60 mm Hg can cause complete block of conduction |
| Laceration | Sharp transections have a better prognosis than crush injuries Continuity of nerve disrupted Ends retract Nerve stops producing neurotransmitters Nerve starts producing proteins for axonal regeneration |
Anatomy
Understanding the anatomy of the nerves can help in the diagnosis and treatment of peripheral nerve injuries. Peripheral nerves are surrounded by epineurium, perineurium, and endoneurium, with myelin made by Schwann cells that insulate the axons to increase conduction velocity. Additionally, several fiber types can affect the speed and function of the nerves.
| Nerve Structure | Fiber Type |
|---|---|
| Epineural sheath | Fiber Type A - 10-20 um diameter, heavy myelination, fast speed, touch |
| Epineurium | Fiber Type B - < 3 um diameter, moderate myelination, medium speed, autonomic nervous system (ANS) |
| Perineurium | Fiber Type C - < 1.3 um diameter, none myelination, slow speed, pain |
| Fascicles | |
| Endoneurium | |
| Myelin | |
| Neuron cell |
Classification
There are several classification systems used for peripheral nerve injuries, including the Seddon and Sunderland classifications. These systems categorize the extent of nerve damage based on the degree of injury to the axon, endoneurium, perineurium, and epineurium. The severity of the injury can affect the prognosis and treatment options for the patient.
| Seddon Classification | Sunderland Classification |
|---|---|
| Neurapraxia (same as Sunderland 1st degree, "focal nerve compression") Nerve contusion or stretch leading to reversible conduction block without Wallerian degeneration |
1st degree (same as Seddon's neurapraxia (loss of myelin sheath)) |
| Axonotmesis (same as Sunderland 2nd-4th degree) Incomplete nerve injury more severe than neurapraxia |
2nd degree included within Seddon's axonotmesis Intact endoneurium, perineurium and epineurium |
| Neurotmesis Encompasses Sunderland 5th degree Complete nerve division with disruption of endoneurium |
3rd degree included within Seddon's axonotmesis Endoneurium injured with endoneurial scarring Intact perineurium and epineurium |
| 4th degree included within Seddon's axonotmesis Endoneurium and perineurium injured Intact epineurium Nerve in continuity but at the level of injury there is complete scarring across the nerve |
|
| 5th degree Same as Seddon's neurotmesis Completely severed or transected nerve involving all layers Regeneration not possible without repair |
Treatment
The treatment of peripheral nerve injuries depends on the severity and location of the injury, as well as the patient's age and medical history. Non-operative treatment options may involve observation and sequential EMGs, while operative treatments may include nerve repair or reconstruction, nerve grafting, nerve transfer, or tendon transfer. The choice of treatment will depend on the extent of the injury, and the goals of the treatment are to achieve functional recovery and prevent neuroma formation.
| Non-operative Treatment | Operative Treatment |
|---|---|
| Observation with sequential EMG | Direct muscular neurotization |
| Surgical repair | |
| Nerve grafting | |
| Nerve transfer | |
| Tendon transfer |
Prognosis
The prognosis of peripheral nerve injuries can vary depending on several factors, including the extent and location of the injury, the patient's age, and the type of injury. Younger patients and those with distal level injuries have a more favorable prognosis, while those with crush injuries or a repair delay have a worse prognosis. With treatment, however, many patients can achieve functional recovery and avoid chronic neuropathic pain.
Peripheral Nerve Injuries: Causes, Diagnosis, and Treatment
Peripheral nerve injuries can cause various impairments that depend on the injury level, axonal disruption, and time to treatment. The following charts and information will help individuals understand the epidemiology, etiology, pathophysiology, associated conditions, and treatment options for peripheral nerve injuries.
Peripheral Nerve Injury Incidence
Risk Factors for Peripheral Nerve Injuries
- Penetrating injuries
- Displaced fractures
Peripheral Nerve Injury Etiology
Pathophysiology of Peripheral Nerve Injuries
- Stretching injury - 8% elongation will diminish the nerve's microcirculation, 15% elongation will disrupt axons.
- Compression/crush - fibers are deformed, local ischemia, endoneurial edema leads to poor axonal transport and nerve dysfunction.
- Laceration - sharp transections have a better prognosis than crush injuries, continuity of nerve disrupted.
Peripheral Nerve Injury Types and Treatment
Treatment Options for Peripheral Nerve Injuries
- Observation with sequential EMG
- Direct muscular neurotization
- Surgical repair
- Nerve grafting
- Nerve transfer
- Tendon transfer