Nerve entrapment syndromes are caused by chronic injury to a nerve as it travels through a bony or ligamentous tunnel. Repetitive compression, rubbing or sliding of the nerve within the canal, or against a bony prominence, results in chronic injury to the nerve. Immobilisation of the affected area with a splint can reduce this form of damage.
Entrapment neuropathies can also be caused by systemic disorders such as rheumatoid arthritis, pregnancy, acromegaly or hypothyroidism.
Repetitive injury to a nerve may result in ischaemia, oedema and damage to the myelin sheath of the nerve.
Focal segmental demyelination at the site of compression is the key patho-physiological feature of all nerve entrapment syndromes.
Complete recovery of function after surgical decompression reflects re-myelination of the injured nerve. Incomplete recovery in more chronic and severe cases of entrapment is due to Wallerian degeneration of the axons and permanent fibrotic changes in the neuromuscular junction, which prevent re-innervation and restoration of function.