Pathophysiology of HNPP explored using axonal excitability.

Area of Science:

• Neuroscience
• Genetics
• Peripheral Nerve Disorders

Background:

• Hereditary liability to pressure palsies (HNPP) is an autosomal dominant disorder affecting peripheral nerve myelination.
• HNPP leads to increased susceptibility to nerve damage from compression or stretching.

Observation:

• Axonal excitability was assessed in HNPP patients at proximal and distal nerve sites.
• Comparisons were made with healthy controls and Charcot-Marie-Tooth type 1A (CMT1A) patients.

Findings:

• HNPP patients showed non-uniform axonal excitability changes along the nerve, with more significant alterations distally.
• Threshold electrotonus was notably altered at the wrist, while recovery cycles showed subtle changes at the elbow.
• CMT1A patients exhibited more pronounced and uniform excitability changes compared to HNPP patients.

Implications:

• Structural abnormalities at the nodes of Ranvier are sufficient to explain HNPP's axonal excitability alterations.
• These nodal abnormalities predispose nerves to conduction block under mechanical stress, clarifying HNPP pathophysiology.