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ULNAR NERVE PALSY


Introduction

The ulnar nerve is derived from the C8 and T1 nerve roots. It is a terminal branch of the medial cord of the brachial plexus. In the midportion of the arm, it passes from the anterior to the posterior part of the arm, piercing the intermuscular septum approximately 10 cm above the medial epicondyle. The nerve then passes through a fascial tunnel bounded laterally by the internal brachial ligament and inferiorly by an accessory origin of the medial head of the triceps from the medial intermuscular septum




Ulnar Nerve Palsy is paralysis caused by damage, compression or trapping of the ulnar nerve as it makes its way down the length of the arm. This occurs due to nerve compression at the elbow (cubital tunnel) or at the wrist (Guyon’s canal). Muscle weakness and atrophy predominate the clinical presentation. The cubital tunnel is in this region commonly referred to as the 'funny bone', the area where the ulnar nerve crosses the elbow joint. The wrist is made up of a number of small bones. Two of these bones and their associated ligaments form a canal that runs through the wrist (Guyon's canal). As the ulnar nerve crosses the wrist, it passes through this canal before it branches to supply some of the fingers in the hand.


Causes

Ulnar nerve dysfunction is a common form of peripheral neuropathy. It occurs when there is damage to the ulnar nerve, which travels down the arm. The ulnar nerve is near the surface of the body where it crosses the elbow, so prolonged pressure on the elbow may cause damage. The damage involves the destruction of the covering of the nerve (myelin sheath) or part of the nerve (axon). This damage slows or prevents nerve signaling.
A problem with one single nerve group (such as the ulnar nerve) is called mononeuropathy. The usual causes are direct injury, prolonged external pressure on the nerve, or compression of the nerve caused by swelling or injury of nearby body structures. Entrapment involves pressure on the nerve where it passes through a narrow structure.
The ulnar nerve is commonly injured at the elbow because of elbow fracture or dislocation. Prolonged pressure on the base of the palm may also cause damage to part of the ulnar nerve. In some cases, no detectable cause can be identified.

Symptoms

Ø Abnormal sensations in the 4th or 5th fingers
Ø Numbness, decreased sensation
Ø Tingling, burning sensation
Ø Pain
Ø Weakness of the hand
Ø Pain or numbness may awaken the patient from sleep. The condition is made worse by activities such as tennis or golf.
Lesions at the wrist are characterized by hypothenar wasting and paralysis of the intrinsic muscles of the hand and consequent clawing of the hand. There is weakness of finger abduction and there is loss of adduction of the thumb. There is loss of sensation over the ulnar one and a half fingers.
The clawing of the hand is less marked with a high lesion because the ulnar half of flexor digitorum profundus is paralysed and so the terminal interphalangeal joints are not flexed. In other respects the motor and sensory losses are the same as a low lesion.

Cubital Tunnel Syndrome

Ulnar nerve entrapment is a condition where the ulnar nerve becomes trapped or pinched due to some physiological abnormalities and the Compression at the elbow, known as cubital tunnel syndrome

Causes

· Bending of the elbow causes the nerve to stretch several millimeters.
· Frequent bending of the elbow in activities such as pulling levers, reaching or lifting causes the nerve to become irritated and inflamed.
· When the nerve is stretched over the elbow the nerve can sometimes move or actually snap over the medial epicondyle causing irritation.
· Leaning on the elbow, resting it on an elbow rest during a long distance drive or running machinery may cause repetitive pressure and irritation on the nerve.
· A direct hit on the cubital tunnel may damage the ulnar nerve.

Symptoms

The symptoms of Cubital Tunnel Syndrome primarily involve numbness and tingling in the ring and little finger and the sides and back of the hand. These complaints or symptoms worsen when the elbow is bent i.e. when holding a telephone, resting the head on the hand and crossing the arms over the chest. The hand may become weaker resulting in trouble opening bottles or jars. The hand may not perform as well as it did before and there may be a tendency to drop things. Clawing may occur in the ring and little fingers.

Guyon’s canal Syndrome

On the palm, the ulnar nerve passes under a ligament between two small wrist bones, the pisiform and hamate. The tunnel formed by the bones and ligaments is called Guyon's canal. The Ulnar Nerve supplies sensation to the little finger and half of the ring finger. It is critical that the area of compression be localized to either the wrist (Guyon's canal), or the elbow (cubital tunnel), or the neck (thoracic outlet syndrome, cervical radiculopathy) by physical examination and electrical studies prior to embarking on a treatment. All three may cause numbness and tingling in the same ring and small fingers

Symptoms

Symptoms begin with a feeling of pins and needles in ring and little finger. This is followed by decreased sensation and eventually weakness and clumsiness in the hand as the small muscles of the hand are involved.


Causes

Pressure on the ulnar nerve in the Guyon's canal is usually caused by a cyst in the canal, clotting of the ulnar artery from repetitive trauma, or a fracture of the bony process called the hook of the hamate bone in a golfer's from hitting the ground instead of the golf ball, or in a baseball player from heavy batting.

Site of lesion

The ulnar nerve may be damaged at a number of sites


-at the elbow behind the medial epicondyle - commonly due to cubitus valgus, or bony thickening secondary to arthritis or the result of an old fracture in the cubital tunnel - due to entrapment of the nerve in the tunnel formed by the tendinous arch connecting the two heads of the flexor carpi ulnaris; the entrapment is aggravated by pressure on the fully flexed forearm which commonly occurs when sleeping in the prone position
-at the wrist - due to pressure in Guyon's canal from a deep ganglion or laceration
-in the hand - due to compression of the deep motor branch against the pisiform and hamate; this is usually seen in individuals whose occupation involves prolonged pressure upon the outer part of the palm, for example, motorcyclists and road workers using vibrating drills.


Investigation

An exam of the hand and wrist can reveal ulnar nerve dysfunction. There may be weakness of wrist and hand bending and difficulty moving the fingers. Severe cases may display wasting of the hand muscles or a characteristic "claw-like" deformity. A detailed history may be needed to determine the possible cause of the neuropathy.
Tests that reveal ulnar nerve dysfunction may include an EMG (a recording of electrical activity in muscles) and NERVE CONDUCTION TEST. Other tests may include blood tests, X-rays, and imaging scans.


Treatment

A wrist splint may be worn to decrease the pins and needles sensation. If symptoms persist in spite of these treatment modalities, surgical decompression of the nerve is needed. This procedure involves cutting the ligament that stretches over the top of the ulnar nerve and forms the roof of Guyon's canal.


And of course to gain full ROM physiotherapy treatment includes Passive movements, strengthening exercises, Electrical nerve stimulation and Rehabilatation managements.

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