Wrist drop
Encyclopedia
Wrist drop, also known as radial nerve
palsy, or Saturday night palsy, is a condition where a person cannot extend their wrist
and it hangs flaccidly. To demonstrate wrist drop, hold your arm out in front of you with your forearm parallel to the floor. With the back of your hand facing the ceiling (i.e. pronated), let your hand hang limply so that your fingers point downward. A person with wrist drop would be unable to move from this position to one in which the fingers are pointing up towards the ceiling.
is the part of the body which extends from the elbow to the wrist and is not to be confused with the arm which extends from the shoulder to the elbow. The extensor muscles in the forearm are extensor carpi ulnaris, extensor digiti minimi, extensor digitorum, extensor indicis, extensor pollicis longus, extensor pollicis brevis, extensor carpi radialis brevis, extensor carpi radialis longus. These extensor muscles are supplied by the radial nerve
. Other muscles in the forearm also innervated by the radial nerve are supinator and abductor pollicis longus. Note that all these muscles are situated in the posterior half of the forearm (posterior when in the anatomical position). Also, brachioradialis
, anconeus, triceps brachii, and extensor carpi radialis longus are all innervated by muscular branches of the radial nerve in the arm.
s in the forearm
contracting, pulling on tendon
s that attach distal to (beyond) the wrist. If the tendons, the muscles, or the nerve
s supplying these muscles, are not working as they should be, wrist drop may occur. The following situations may result in wrist drop:
Stab wounds to the chest at or below the clavicle may result in wrist drop. The radial nerve is the terminal branch of the posterior cord of the brachial plexus
. A stab wound may damage the posterior cord and result in neurological deficits including an inability to abduct the shoulder beyond 15 degrees, an inability to extend the forearm, reduced ability to supinate the hand, reduced ability to abduct the thumb and sensory loss to the posterior surface of the arm and hand.
The radial nerve can be damaged if the humerus
(the bone of the arm) is broken, because it runs through the radial groove on the lateral border of this bone.
Wrist drop is also associated with lead poisoning
because of the effect of lead
on the radial nerve.
Persistent injury to the nerve is also a common cause through either repetitive motion or by applying pressure externally along the route of the radial nerve as in the prolonged use of crutches or extended leaning on the elbows.
1) Weakness of brachioradialis, wrist extension and finger flexion = radial nerve lesion
(2) weakness of finger extension and radial deviation of the wrist on extension = posterior interossious nerve lesion
(3) weakness of triceps, finger extensors and flexors = c7,8 lesion
(4) generalised weakness of upper limb marked in deltoid, triceps, wrist extension and finger extension = corticospinal lesion
for wrist drop frequently includes nerve conduction velocity
studies to isolate and confirm the radial nerve as the source of the problem. Plain films
can help identify bone spurs and fractures that may have injured the nerve. Sometimes MRI imaging is required to differentiate subtle causes.
or physical therapy
. In some cases surgical removal of bone spurs or other anatomical defects that may be impinging on the nerve might be warranted.
Radial nerve
The radial nerve is a nerve in the human body that supplies the upper limb. It supplies the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial compartment of the forearm and the associated joints and overlying skin.It...
palsy, or Saturday night palsy, is a condition where a person cannot extend their wrist
Wrist
In human anatomy, the wrist is variously defined as 1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand;...
and it hangs flaccidly. To demonstrate wrist drop, hold your arm out in front of you with your forearm parallel to the floor. With the back of your hand facing the ceiling (i.e. pronated), let your hand hang limply so that your fingers point downward. A person with wrist drop would be unable to move from this position to one in which the fingers are pointing up towards the ceiling.
Anatomy of the forearm
In anatomical parlance, the forearmForearm
-See also:*Forearm flexors*Forearm muscles...
is the part of the body which extends from the elbow to the wrist and is not to be confused with the arm which extends from the shoulder to the elbow. The extensor muscles in the forearm are extensor carpi ulnaris, extensor digiti minimi, extensor digitorum, extensor indicis, extensor pollicis longus, extensor pollicis brevis, extensor carpi radialis brevis, extensor carpi radialis longus. These extensor muscles are supplied by the radial nerve
Radial nerve
The radial nerve is a nerve in the human body that supplies the upper limb. It supplies the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial compartment of the forearm and the associated joints and overlying skin.It...
. Other muscles in the forearm also innervated by the radial nerve are supinator and abductor pollicis longus. Note that all these muscles are situated in the posterior half of the forearm (posterior when in the anatomical position). Also, brachioradialis
Brachioradialis
Brachioradialis is a muscle of the forearm that acts to flex the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm...
, anconeus, triceps brachii, and extensor carpi radialis longus are all innervated by muscular branches of the radial nerve in the arm.
Causes
Wrist extension is achieved by muscleMuscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
s in the forearm
Forearm
-See also:*Forearm flexors*Forearm muscles...
contracting, pulling on tendon
Tendon
A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...
s that attach distal to (beyond) the wrist. If the tendons, the muscles, or the nerve
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...
s supplying these muscles, are not working as they should be, wrist drop may occur. The following situations may result in wrist drop:
Stab wounds to the chest at or below the clavicle may result in wrist drop. The radial nerve is the terminal branch of the posterior cord of the brachial plexus
Brachial plexus
The brachial plexus is a network of nerve fibers, running from the spine, formed by the ventral rami of the lower four cervical and first thoracic nerve roots...
. A stab wound may damage the posterior cord and result in neurological deficits including an inability to abduct the shoulder beyond 15 degrees, an inability to extend the forearm, reduced ability to supinate the hand, reduced ability to abduct the thumb and sensory loss to the posterior surface of the arm and hand.
The radial nerve can be damaged if the humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
(the bone of the arm) is broken, because it runs through the radial groove on the lateral border of this bone.
Wrist drop is also associated with lead poisoning
Lead poisoning
Lead poisoning is a medical condition caused by increased levels of the heavy metal lead in the body. Lead interferes with a variety of body processes and is toxic to many organs and tissues including the heart, bones, intestines, kidneys, and reproductive and nervous systems...
because of the effect of lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
on the radial nerve.
Persistent injury to the nerve is also a common cause through either repetitive motion or by applying pressure externally along the route of the radial nerve as in the prolonged use of crutches or extended leaning on the elbows.
1) Weakness of brachioradialis, wrist extension and finger flexion = radial nerve lesion
(2) weakness of finger extension and radial deviation of the wrist on extension = posterior interossious nerve lesion
(3) weakness of triceps, finger extensors and flexors = c7,8 lesion
(4) generalised weakness of upper limb marked in deltoid, triceps, wrist extension and finger extension = corticospinal lesion
Diagnosis
The workupMedical test
A diagnostic test is any kind of medical test performed to aid in the diagnosis or detection of disease. For example:* to diagnose diseases, and preferably sub-classify it regarding, for example, severity and treatability...
for wrist drop frequently includes nerve conduction velocity
Nerve conduction velocity
Nerve conduction velocity is the speed at which an electrochemical signal propagates down a neural pathway. Many things can affect this, including axon diameter, myelination, the internal resistance of the axon, and temperature. Nerve conduction velocity differs from species to species, and to a...
studies to isolate and confirm the radial nerve as the source of the problem. Plain films
Projectional radiography
Projectional radiography or plain film radiography is the practice of producing two-dimensional images using x-ray radiation. Radiographic exams are typically performed by Radiologic Technologists, highly trained medical professionals who specialize in the usage of radiographic equipment, patient...
can help identify bone spurs and fractures that may have injured the nerve. Sometimes MRI imaging is required to differentiate subtle causes.
Treatment
Initial management includes splinting of the wrist for support along with occupationalOccupational therapy
Occupational therapy is a discipline that aims to promote health by enabling people to perform meaningful and purposeful activities. Occupational therapists work with individuals who suffer from a mentally, physically, developmentally, and/or emotionally disabling condition by utilizing treatments...
or physical therapy
Physical therapy
Physical therapy , often abbreviated PT, is a health care profession. Physical therapy is concerned with identifying and maximizing quality of life and movement potential within the spheres of promotion, prevention, diagnosis, treatment/intervention,and rehabilitation...
. In some cases surgical removal of bone spurs or other anatomical defects that may be impinging on the nerve might be warranted.