What is neuropraxia?

What is Neuropraxia?

Neuropraxia is the mildest form of peripheral nerve injury characterized by temporary nerve conduction block without structural disruption of the nerve, resulting in transient loss of motor and/or sensory function that typically recovers completely. 1

Classification and Mechanism

Neuropraxia represents the first category in Seddon's classification of nerve injuries, which includes three types of increasing severity: neuropraxia, axonotmesis, and neurotmesis. 1

Key Pathophysiologic Features:

• The nerve remains structurally intact with preservation of the axon and surrounding connective tissue structures 1
• Injury results from blunt trauma, compression, or stretch mechanisms rather than transection 2
• The nerve that appears structurally intact may not be functionally intact, which is why visual assessment alone during surgery can be misleading 2

Clinical Presentation

Electrophysiological Characteristics:

• Distal to the injury site: Compound muscle action potentials (CMAP) and sensory nerve action potentials (SNAP) remain elicitable 3
• Proximal to the injury site: Stimulation demonstrates conduction block, confirming the diagnosis 3
• No Wallerian degeneration occurs, distinguishing neuropraxia from more severe injuries 3

Recovery Pattern:

• Sensory and motor function typically returns completely 1
• Recovery time is highly variable, ranging from days to months:
  • In liver transplantation patients: median 5 days (range up to 187 days) 4
  • In digital nerve injuries: 12 days to 6 months 5
• Approximately 32% of neuropraxia cases may require specific treatment such as physical therapy or medications during recovery 4

Common Clinical Contexts

Surgical Settings:

• Thyroid surgery: Stretch at the ligament of Berry is the most common cause of neuropraxic injury to the recurrent laryngeal nerve during thyroidectomy 2
• Liver transplantation: 8.3% incidence, predominantly affecting upper extremities (60%), left-sided (82%), and in males (84%) 4
• Digital nerve trauma: 12% of patients with isolated digital nerve injuries have neuropraxia rather than complete transection 5

Spinal Cord Neuropraxia:

• Occurs following cervical hyperextension or hyperflexion trauma 6
• Presents with neurological symptoms in both arms and legs lasting up to 15 minutes with complete recovery 6
• Strongly associated with preexisting cervical canal stenosis (present in 4 of 5 reported cases) 6

Critical Clinical Pitfalls

Intraoperative Detection Challenges:

• Surgeons visually identify only 10-14% of injured nerves intraoperatively 2
• In bilateral nerve injuries, injury is suspected in only 16% of cases by visual inspection alone 2
• Intraoperative nerve monitoring (IONM) can detect neuropraxic injury that is not visibly apparent, with negative predictive values of 92-100% 2

Risk Factors in Surgical Patients:

• Male gender 4
• Longer duration of surgery 4
• Procedures involving significant tissue manipulation 4

Prognostic Implications

The key distinguishing feature of neuropraxia is complete functional recovery, making accurate diagnosis essential to avoid unnecessary surgical exploration. 1, 5 However, the prolonged recovery period in some cases (up to 6 months) requires patient education and appropriate follow-up planning. 5

In surgical contexts where bilateral nerves are at risk (such as bilateral thyroid surgery), identifying neuropraxia on the first side can alter surgical strategy to prevent bilateral injury, which occurred in 17% of cases when monitoring information was ignored. 2