pathogenesis of peripheral nerve diseases

Last reviewed 12/2022

Two pathological processes predominate in diseases of peripheral nerves:

• axonal degeneration:
• severely damaged axons degenerate distally
• within a week the nerve becomes electrically inert
• muscle fibres supplied by damaged motor nerves atrophy
• EMG records show fibrillation potentials
• axons may regrow at about 1 mm/day
• undamaged motor fibres sprout to supply more muscle fibres

• demyelination:
• demyelination of peripheral nerve fibres initially leaves the axon intact
• the result is blockage or slowing of conduction
• pressure or entrapment neuropathies are primarily caused by demyelination
• inflammatory processes e.g. Guillan-Barre are caused by demyelination