**2.2 Pathophysiology**

Nerve entrapment can be acute or chronic. Acute nerve compression is the development of acute and sensory-motor paralysis in the innervation area as a result of irritation with external pressure where the peripheral nerve is superficial [1]. Chronic compression occurs when the nerve passes through a fibro-osseous canal and is continuously subjected to microtrauma and distortion. According to the Seddon's classification, chronic nerve entrapment is divided into 3 subgroups as neuropraxia, axonotmesis and neurometsis. Neuropraxia is the mildest form characterized by myelin sheath injury or ischemia in which axon and connective tissue are preserved. Improvement occurs within weeks and months. Axonotmesis is

more severe than neuropraxia. There is injury to the axon itself. Although it takes a long time, nerve regeneration is possible. However, there is no complete recovery in patients. Neurometsis is the most severe of them and involves the complete disruption of the axon, which is unlikely to heal [1, 16, 17].
