Ouch! My Funny Bone! Trivia Quiz

Answer: False

Many older texts recommend looking for various static signs to identify which nerve is damaged, for example, the "hand of benediction", which is supposedly a sign of median nerve damage. This posture is similar to that of the Christian blessing, hence its name, with only the ring and little fingers bent when trying to make a fist.

However, such a posture can also result from damage to the ulnar nerve, leading to possible confusion. The best way to identify which nerve is damaged is to undertake tests that involve movements rather than static postures, for example, using thumb movements to test for median nerve injury rather than resting postures.

Answer: Ring and little fingers

The ulnar nerve has two sensory branches, the palmar branch and the dorsal branch, both of which arise from the main ulnar nerve just above the wrist. The branches provide sensation to the skin of the little finger and half of the ring finger (also called the fifth and fourth digits), and the area of the palm beneath these fingers.

Therefore if the nerve is damaged, these areas will lose sensation and/or become tingly. Sensation is most distinct in the sides of the fingers, so the clinician usually tests the sensory effects of ulnar nerve damage by touching the sides of the fourth and fifth digits.

Answer: Flexor carpi ulnaris

Often people are intimidated by the long Latin names of some muscles, but actually they are useful as they can tell you information about where the muscle is and what it does. Flexor carpi ulnaris (FCU) is a flexor of the wrist ("carpi") on the ulnar side ("ulnaris") or on the little finger side. When its actions are combined with flexor carpi radialis (FCR), the wrist flexes, and there are analogous extensors, i.e. extensor carpi ulnaris (ECU), extensor carpi radialis longus (ECRL) and extensor carpi radialis brevis (ECRB).

For sideways movements of the wrist, called radial deviation and ulnar deviation, these muscles work in particular combinations. For radial deviation, the radial flexor and extensors contract, while for ulnar deviation, the ulnar flexor and extensor contract. Because the ulnar flexor (FCU) is supplied by the ulnar nerve, if this nerve is damaged, ulnar deviation is no longer possible, and the wrist is pulled toward the radial side.

Answer: Guyon

Although Jean Casimir Félix Guyon (1831-1920) was more known for his work on the genitourinary system, he discovered the ulnar tunnel at the wrist, through which the ulnar nerve travels with accompanying blood vessels. If the ulnar nerve is impacted here, it is known as "Guyon's tunnel syndrome", which is more colloquially known as handlebar palsy, as impaction can be caused by leaning on the wrists when riding a mountain bike. Guyon's tunnel syndrome can also be caused a ganglion cyst inside the tunnel, which is usually treated by surgical removal of the cyst.

Answer: Froment's sign

Froment's sign looks for the action of the adductor pollicis muscle, which brings the thumb back from an outstretched (or "abducted") position, and is innervated by the ulnar nerve. The patient is asked to hold a piece of paper between his index finger and thumb. If the ulnar nerve and therefore adductor pollicis is working, the plane of the digits remains flat. If adductor pollicis is not working, the patient flexes his thumb instead to hold the paper, using flexor pollicis longus, which is supplied by the median nerve.

The other three signs are used to test for median nerve neuropathy.

Answer: Carpal tunnel syndrome

The carpal tunnel at the wrist carries the median nerve along with nine flexor tendons. When the flexor muscles are overused, these tendons can swell and impinge on and entrap the nerve, leading to carpal tunnel syndrome, which is a form of median nerve neuropathy. Treatment is often initially to rest the arms and hands, avoid overuse, or to use splints. Later on, if the condition becomes advanced, steroid injections can be performed, or the carpal tunnel can be surgically decompressed by releasing an overlying ligament.

There are various tests to look for carpal tunnel syndrome, including Tinel's sign, which involves tapping on the carpal tunnel to increase the pressure within, leading to high discomfort for the patient as the nerve becomes more compressed. Phalen's sign is more sensitive than Tinel's sign, and similarly involves increasing pressure within the carpal tunnel; the patient is asked to put the backs of his hands together and hold.

Answer: Opposition of the thumb

Opposition of the thumb describes the action of putting your thumb against the tips of the other fingers. To test for the action of the opponens pollicis muscle, which is innervated by the median nerve, the patient is asked to make an 'O' shape with his thumb and index finger. If the muscle is not working correctly, he will be unable to make a full 'O'.

The other movements are undertaken by different nerves. Supination of the forearm is achieved by the supinator muscle, which is supplied by the radial nerve. Extension of the fingers is also undertaken by the radial nerve, by action of extensor digitorum. The elbow is flexed primarily by biceps brachii, which is innervated by the musculocutaneous nerve.

Answer: Extension of the wrist is lost.

As mentioned above, the radial nerve supplies extensor muscles throughout the entire upper limb. Grip strength is markedly increased by extending the wrist, as this frees up the flexor tendons on the front of the wrist which act to clench the fingers, therefore if the wrist cannot extend, it follows that the grip strength will be decreased in the patient. Testing grip strength is one method to test for neuropathy of the radial nerve.

Answer: Humerus

The radial nerve travels down the back of the humerus in a groove in the bone called the radial sulcus. Along with the nerve, the deep brachial artery travels in this groove, and so fracturing the humerus mid-shaft can rupture the artery. Bleeding and oedema can impinge the nerve in the groove and cause symptoms of entrapment. Radial nerve neuropathy causes a loss of extension throughout the upper limb, so the arm is usually held in flexion. Extension is lost at the elbow, wrist, and fingers.

A nontraumatic cause of these symptoms is leaning on the back of the arm for a prolonged period - this is colloquially known as Saturday night palsy, as it often occurs in a person who sleeps while drunk with their arm draped over a chair.

Answer: True

The radial nerve branches various times in the arm, and the superficial branch supplies sensation to the skin on the back of the hand, and also to the web of skin between the index finger and thumb. The clinician can test for any abnormalities in sensation in these areas to detect damage to the radial nerve.

Although there are other areas of sensation supplied by the nerve, such as the side of the thumb, the web and back of the hand are more specific for testing purposes.