Diagnosis of the common forms of nerve injury of the extremities.

(I) Cutting and laceration. (2) Stretching, which may be sudden (e.g. stretching of the sciatic by jumping upon the extended foot) causing fibre rupture and haemorrhage, or prolonged (e.g. lying with the arm extended for hours above the head) causing ischaemia. (3) Contusion. (4) Concussion (including that produced by a "near miss" when a missile passes through neighbouring tissues without touching the nerve). (5) Pressure (e.g. crutch and "Saturday-night" palsies). (6) Puncture (e.g. by an injection needle). (7) Local poisoning by injected substances; and (8) Freezing.