Crush or cut injuries to nerves that damage some or all of their conducting fibers. Tingling is a symptom of damage or irritation to a nerve or nerves. Numbness suggests that the affected nerve may be severed or dead. A brief tingling sensation, as when a person’s hand or foot “falls asleep,” is not a cause for concern. However, numbness or persistent tingling may indicate a significant nerve injury and require medical attention.
These have several causes. Continued or repeated severe pressure may damage a nerve seriously, as in the case of a crutch pressing into the armpit and causing drop-wrist. Bruising due to a blow which drives a superficially placed nerve against a bone may damage, say, the radial nerve behind the upper arm. A wound may sever nerves, along with other structures; this accident is specially liable to occur to the ulnar nerve in front of the wrist, for example when a person accidentally puts a hand through a pane of glass.