The distinct innervation of the hand usually enables diagnosis of an ulnar nerve impingement by symptoms alone. Ulnar nerve damage that causes paralysis to these muscles will result in a characteristic ulnar claw position of the hand at rest. Clinical tests such as the card test for Froment's sign, can be easily performed for assessment of ulnar nerve. However, a complete diagnosis should identify the source of the impingement, and radiographic imaging may be necessary to determine or rule-out an underlying cause. Imaging studies, such as ultrasound or MRI, may reveal anatomic abnormalities or masses responsible for the impingement. Additionally, imaging may show secondary signs of nerve damage that further confirm the diagnosis of impingement. Signs of nerve damage include flattening of the nerve, swelling of the nerve proximal to site of injury, abnormal appearance of nerve, or characteristic changes to the muscles innervated by the nerve. Differential diagnoses Symptoms of ulnar neuropathy or neuritis do not necessarily indicate an actual physical impingement of the nerve; any injury to the ulnar nerve may result in identical symptoms. In addition, other functional disturbances may result in irritation to the nerve and are not true "impingement". For example, anterior dislocation and "snapping" of ulnar nerve across the medial epicondyle of the elbow joint can result in ulnar neuropathy. Entrapment of other major sensory nerves of the upper extremities result in deficits in other patterns of distribution. Entrapment of the median nerve causes carpal tunnel syndrome, which is characterized by numbness in the thumb, index, middle, and half of the ring finger. Compression of the radial nerve causes numbness of the back of the hand and thumb, and is much rarer. A simple way of differentiating between significant median and ulnar nerve injury is by testing for weakness in flexing and extending certain fingers of the hand. Median nerve injuries are associated with difficulty flexing the index and middle finger when attempting to make a fist. However, with an ulnar nerve lesion, the pinky and ring finger cannot be unflexed when attempting to extend the fingers. Some people are affected by multiple nerve compressions, which can complicate diagnosis. Classification<unk>  is classified by location of entrapment. The ulnar nerve passes through several small spaces as it courses through the medial side of the upper extremity, and at these points the nerve is vulnerable to compression or entrapment—a so-called "pinched nerve". The nerve is particularly vulnerable to injury when there has been a disruption in the normal anatomy. The most common site of<unk>  is at the elbow, followed by the wrist. Causes or structures which have been reported to cause<unk>  include: * Problems originating at the neck: thoracic outlet syndrome, cervical spine pathology, compression by anterior scalene muscles * Problems originating in the chest: compression by pectoralis minor muscles * Brachial plexus abnormalities * Elbow: fractures, growth plate injuries, cubital tunnel syndrome, flexorpronator aponeurosis, arcade of Struthers * Forearm: tight flexor carpi ulnaris muscles * Wrist: fractures, ulnar tunnel syndrome, hypothenar hammer syndrome * Artery aneurysms or thrombosis * Other: Infections, tumors, diabetes, hypothyroidism, rheumatism, and alcoholism Cubital tunnel syndrome The most common location of ulnar nerve impingement at the elbow is within the cubital tunnel, and is known as cubital tunnel syndrome. The tunnel is formed by the medial epicondyle of the humerus, the olecranon process of the ulna and the tendinous arch joining the humeral and ulnar heads of the flexor carpi ulnaris muscle. While most cases of injury are minor and resolve spontaneously with time, chronic compression or repetitive trauma may cause more persistent problems. Commonly cited scenarios include: * Sleeping with the arm folded behind neck, elbows bent. * Pressing the elbows upon the arms of a chair while typing. * Resting or bracing the elbow on the arm rest of a vehicle. * Bench pressing. * Intense exercising and strain involving the elbow. Compression of the ulnar nerve at the medial elbow may occasionally be caused by an epitrocheloanconeus muscle, an anatomical variant. Ulnar tunnel syndrome Ulnar nerve impingement along an anatomical space in the wrist called the ulnar canal is known as ulnar tunnel syndrome. Recognized causes of ulnar nerve impingement at this location include local trauma, fractures, ganglion cysts, and classically avid cyclists who experience repetitive trauma against bicycle handlebars. This form of ulnar neuropathy comprises two work-related syndromes: so-called "hypothenar hammer syndrome," seen in workers who repetitively use a hammer, and "occupational neuritis" due to hard, repetitive compression against a desk surface.
Ulnar nerve entrapment
Median nerve palsy
Ulnar tunnel syndrome
Radial tunnel syndrome
Calpainopathy
Anterior cutaneous nerve entrapment syndrome
Carpal tunnel syndrome
Injury of axillary nerve