Compression neuropathy, i.e. peripheral nerve compression, is caused by external pressure on the nerve that is often a one-time occurrence (e.g. a night's drunken sleep with the upper arm pinched), or occasionally intermittent (e.g. leaning on the elbow while on the telephone). Compression neuropathy usually recovers spontaneously once the external pressure is removed. Entrapment neuropathy, i.e. peripheral nerve entrapment, means that the nerve is compressed between surrounding anatomical structures. The pressure is usually persistent, although its severity may vary according to the extent of tissue oedema and strain on the limb. In order to recover completely, entrapment neuropathies generally require treatment (reduction of the oedema, surgical release of the nerve, etc.).