True or False: Pins and needles or tingling sensations in the fourth and fifth digits of the hand suggest the median nerve is injured.

Answer: False. This symptom actually indicates an injury to the ulnar nerve.

The median nerve innervates the palmar side of the thumb, the second digit, the third digit and half of the fourth digit, but does not innervate any portion of the fifth digit. The ulnar nerve innervates the fifth digit and half of the fourth digit, on both the palmar and the dorsal surfaces. A person who experiences tingling in these two fingers likely is to have an injury to the ulnar nerve or to the nerve root in the neck where the ulnar nerve ultimately originates.

People commonly sustain minor injuries to the ulnar nerve by banging their "funny bone" - the point on the elbow where the ulnar nerve runs close to the surface of the skin. Hitting this sensitive spot against a hard surface causes sharp tingling running down the forearm into the two small fingers. If the ulnar nerve is bruised, tingling in these two fingers might continue for quite some time. In addition, severe damage to the ulnar nerve can cause weakness in wrist and hand flexion and difficulty with controlled movements of the fingers.

Apart from accidents, there also are other factors that can make a person vulnerable to straining the ulnar nerve. The nerve is located within a protective tunnel known as the olecranon or epicondylar groove. In some people, this groove is congenitally shallow, so the nerve does not lie securely within it. Other people might experience stress on the ulnar nerve due to the specific activities they perform. During elbow flexion, the olecranon groove flattens as the ligament superior to it stretches. Types of work calling for continuous or repetitive full elbow flexion might place continual pressure on the ulnar nerve.

Once the ulnar nerve or its nerve root has been injured, moving the affected area might make the symptoms worse. If the problem originates in the elbow, using the elbow might exacerbate the symptoms; if the problem originates in the neck, movements of the head and neck might exacerbate the symptoms.