Ulnar Neuropathy Flashcards
Ulnar Neuropathy
The ulnar nerve is an extension of the medial cord of the brachial plexus. It is a mixed nerve that supplies innervation to muscles in the forearm and hand and provides sensation over the medial half of the fourth digit and the entire fifth digit (the ulnar aspect of the palm) and the ulnar portion of the posterior aspect of the hand (dorsal ulnar cutaneous distribution).
Entrapment of the ulnar nerve is the second most common entrapment neuropathy in the upper extremity (after entrapment of the median nerve).
The most common site of ulnar nerve entrapment is at or near the elbow region, especially in the region of the cubital tunnel or in the epicondylar (ulnar) groove; the second most likely site is at or near the wrist, especially in the area of the anatomic structure called the canal of Guyon.
i. However, entrapment can also occur in the forearm between these two regions, below the wrist within the hand, or above the elbow.
Pressure on or injury to the ulnar nerve may cause denervation and paralysis of the muscles supplied by the nerve. Affected patients often experience numbness and tingling along the little finger and the ulnar half of the ring finger. This discomfort is often accompanied by weakness of grip and, rarely, intrinsic wasting. One of the most severe consequences is loss of intrinsic muscle function in the hand. When the ulnar nerve is divided at the wrist, only the opponens pollicis, superficial head of the flexor pollicis brevis, and lateral 2 lumbricals are functioning.
Conservative nonsurgical treatment may play a useful role in management. If such treatment fails or the patient has severe or progressive weakness or loss of function, surgical treatment is warranted. Several surgical approaches have been employed, each of which has its advocates; results for all of them appear to be satisfactory.
Course of ulnar nerve
The ulnar nerve is the terminal branch of the medial cord of the brachial plexus and contains fibers from C8, T1, and, occasionally, C7. [8, 9] It enters the arm with the axillary artery and passes posterior and medial to the brachial artery, traveling between the brachial artery and the brachial vein.
At the level of the insertion of the coracobrachialis in the middle third of the arm, the ulnar nerve pierces the medial intermuscular septum to enter the posterior compartment of the arm. [10, 11] Here, the nerve lies on the anterior aspect of the medial head of the triceps, where it is joined by the superior ulnar collateral artery. The medial intermuscular septum extends from the coracobrachialis proximally, where it is a thin and weak structure, to the medial humeral epicondyle, where it is a thick, distinct structure.
The next important site along the course of the ulnar nerve is the arcade of Struthers. This structure is found in 70% of patients, 8 cm proximal to the medial epicondyle, and extends from the medial intermuscular septum to the medial head of the triceps. The arcade of Struthers is formed by the attachments of the internal brachial ligament (a fascial extension of the coracobrachialis tendon), the fascia and superficial muscular fibers of the medial head of the triceps, and the medial intermuscular septum.
It is important to distinguish the arcade of Struthers from the ligament of Struthers, which is found in 1% of the population and extends from a supracondylar bony or cartilaginous spur to the medial epicondyle. This supracondylar spur can be found on the anteromedial aspect of the humerus, 5 cm proximal to the medial epicondyle, and it can often be seen on radiographs. The ligament of Struthers may occasionally cause neurovascular compression, usually involving the median nerve or the brachial artery but sometimes affecting the ulnar nerve.
Next, the ulnar nerve passes through the cubital tunnel, which is the space bounded by the following:
- The medial epicondyle (medial border)
- The olecranon (lateral border)
- The elbow capsule at the posterior aspect of the ulnar collateral ligament (floor)
- The humeroulnar arcade (HUA), or Osborne fascia or ligament (roof)
The deep forearm investing fascia of the flexor carpi ulnaris and the arcuate ligament of Osborne, also known as the cubital tunnel retinaculum, form the roof of the cubital tunnel. The cubital tunnel retinaculum is a 4-mm-wide fibrous band that passes from the medial epicondyle to the tip of the olecranon. Its fibers are oriented perpendicularly to the fibers of the flexor carpi ulnaris aponeurosis, which blends with its distal margin.
The elbow capsule and the posterior and transverse portions of the medial collateral ligament form the floor of the cubital tunnel. The medial epicondyle and olecranon form the walls.
Upon entering the cubital tunnel, the ulnar nerve gives off an articular branch to the elbow. It then passes between the humeral and ulnar heads of the flexor carpi ulnaris and descends into the forearm between the flexor carpi ulnaris and the flexor digitorum profundus. About 5 cm distal to the medial epicondyle, the ulnar nerve pierces the flexor-pronator aponeurosis, the fibrous common origin of the flexor and pronator muscles.
Ulnar Nerve path in the forearm
The ligament of Spinner is an additional aponeurosis between the flexor digitorum superficialis of the ring finger and the humeral head of the flexor carpi ulnaris. This septum is independent of the other aponeuroses and attaches directly to the medial epicondyle and the medial surface of the coronoid process of the ulna. With anterior transposition of the ulnar nerve, it is important to recognize and to release this structure to prevent kinking.
In the forearm, the ulnar nerve extends motor branches to the flexor carpi ulnaris and the flexor digitorum profundus of the ring and small fingers. The ulnar nerve may extend as many as 4 branches to the flexor carpi ulnaris, ranging from 4 cm above to 10 cm below the medial epicondyle. Proximal dissection of the first motor branch to the flexor carpi ulnaris from the ulnar nerve may be performed up to 6.7 cm proximal to the medial epicondyle, facilitating anterior transposition of the nerve.
Posterior branches of the medial antebrachial cutaneous nerves cross the ulnar nerve anywhere from 6 cm proximal to 4 cm distal to the medial epicondyle. These branches are often cut in the course of making the skin incision for a cubital tunnel release, creating an area of dysesthesia or resulting in potential neuroma formation.
As the ulnar nerve courses down the forearm toward the wrist, the dorsal ulnar cutaneous nerve leaves the main branch. A little further down, the palmar cutaneous branch takes off. Thus, neither of these two branches goes through the canal of Guyon. [1] The remainder of the ulnar nerve enters the canal at the proximal portion of the wrist. This is bounded proximally and distally by the pisiform bone and the hook of the hamate bone. It is covered by the volar carpal ligament and the palmaris brevis.
The following two nerve anomalies should be mentioned because they may confuse the diagnosis in the setting of ulnar neuropathy:
i. Martin-Gruber anastomosis in the forearm - In this anomaly, fibers that supply the intrinsic muscles are carried in the median nerve to the middle of the forearm where they leave the median nerve to join the ulnar nerve; functioning intrinsic muscles could be observed with injury above this anastomosis, though the ulnar nerve dysfunction is proximal
ii. Riche-Cannieu anastomosis - In this anomaly, the median and ulnar nerves are connected in the palm; even with an injury at the wrist, there is some intrinsic function
Blood supply for the Ulnar Nerve
The extrinsic blood supply to the ulnar nerve is segmental and involves the following three vessels:
- Superior ulnar collateral artery
- Inferior ulnar collateral artery
- Posterior ulnar recurrent artery
Typically, the inferior ulnar collateral artery (and often the posterior ulnar recurrent artery) is sacrificed with anterior transposition. At the level of the medial epicondyle, the inferior ulnar collateral artery is the sole blood supply to the ulnar nerve. In an anatomic study, no identifiable anastomosis was found between the superior ulnar collateral artery and the posterior ulnar recurrent arteries in 20 of 22 arms; instead, communication between the two arteries occurred through proximal and distal extensions of the inferior ulnar collateral artery.
The intrinsic blood supply is composed of an interconnecting network of vessels that run along the fascicular branches and along each fascicle of the ulnar nerve itself. The surface microcirculation of the ulnar nerve follows an anastomotic stepladder arrangement. The inferior ulnar collateral artery is consistently found 5 mm deep to the leading edge of the medial intermuscular septum on the surface of the triceps.
Sites of nerve entrapment
As diagnostic and surgical methodologies have evolved over the past century, physicians’ ability to recognize and describe sites of entrapment has improved. However, the terminology used to describe ulnar nerve entrapment has become confusing, in that not all clinicians use the same words for the same things. This confusion can be illustrated by examining the terms applied to ulnar nerve entrapment in the elbow region, [15] of which the two most commonly used (and misused) are tardy ulnar palsy [16] and cubital tunnel syndrome.
In 1878, Panas first described what is now often called tardy ulnar palsy, in which either prior trauma or osteoarthritis gradually caused damage to the ulnar nerve. [18] Additional cases were reported over the ensuing decades, [19, 20] usually associated with trauma (eg, fractures in the elbow region) and typically occurring in the epicondylar groove. [21, 22] Initially denoting time (ie, appearing years after trauma), the term came to have an anatomic connotation (ie, usually seen in or very near the epicondylar groove). [23]
From 1922 on, physicians began to recognize ulnar entrapments in the HUA. [24, 25] In 1958, the term cubital tunnel syndrome was coined to describe the effects of the ulnar nerve entrapment [26] at the HUA. Numerous other reports ensued.
Although the current state of knowledge is still incomplete, it is possible to identify approximately five sites in the elbow region at which the ulnar nerve is most likely to be compressed. (Five is not a firm figure; some of the sites are so close together that certain authorities categorize them differently to get a different number.)
This article principally follows Posner’s classification, which lists the following sites:
- Above the elbow in the region of the intermuscular septum
- The medial epicondylar region
- The epicondylar (ie, ulnar) groove
- The region of the cubital tunnel
- The region where the ulnar nerve exits from the flexor carpi ulnaris, at which the usual cause of compression is the deep flexor-pronator aponeurosis
Ulnar Neuropathy
Etiology
Cubital tunnel syndrome may be caused by constricting fascial bands, subluxation of the ulnar nerve over the medial epicondyle, cubitus valgus, bony spurs, hypertrophied synovium, tumors, ganglia, or direct compression. Occupational activities may aggravate cubital tunnel syndrome secondary to repetitive elbow flexion and extension. Certain occupations are associated with the development of cubital tunnel syndrome; however, a definite relation to occupational activities is not well defined. [65, 66, 67]
Factors that may cause ulnar neuropathy at or near the elbow include the following:
- Compression during general anesthesia
- Blunt trauma
- Deformities (eg, rheumatoid arthritis)
- Metabolic derangements (eg, diabetes)
- Transient occlusion of the brachial artery during surgery
- Subdermal contraceptive implant
- Venipuncture
- Hemophilia leading to hematomas
- Malnutrition leading to muscle atrophy and loss of fatty protection across the elbow and other joints
- Cigarette smoking
Factors that may cause ulnar neuropathy at or distal to the wrist (ie, at the canal of Guyon) include the following:
- Ganglionic cysts
- Tumors
- Blunt injuries, with or without fracture
- Aberrant artery
- Idiopathic
Ulnar Neuropathy
Prognosis
A favorable surgical outcome is more likely for sensory function than for motor function. Overall, however, a favorable outcome occurs in 85-95% of cases.
The following factors are relevant to the prognosis:
1. A motor amplitude of 10% of normal or a greatly reduced recruitment of motor units indicates a low likelihood of significant or full recovery
- In some cases, nerve regeneration is accompanied by pain and paresthesias, which are thought to be secondary to random ectopic impulse generation of affected nerves
- A diameter greater than 3.5 mm on the initial sonogram of the ulnar nerve at the elbow is associated with persistent symptoms or signs, regardless of whether conservative treatment or surgical treatment is provided
- The outcome is not correlated either with the clinical features noted at baseline or with the duration of symptoms before treatment
- The presence of motor conduction velocity slowing or pure conduction block across the elbow signifies a favorable outcome; these are considered independent prognostic factors
Unfavorable or poor surgical outcome is associated with the following:
- Age older than 50 years
- Coexisting diabetes or other causes of peripheral polyneuropathy
- Atrophy and ongoing denervation of ulnar-derived muscles
- Absent ulnar sensory responses
- Postoperative position of the ulnar nerve in relation to the medial epicondyle
Ulnar Neuropathy Clinical History
Both the onset and the progress of the symptoms can be variable. Presenting symptoms of ulnar nerve entrapment can range from mild transient paresthesias in the ring and small fingers to clawing of these digits and severe intrinsic muscle atrophy.
Many patients complain of sensory changes in the fourth and fifth digits. Rarely, a patient notices that the unusual sensations are mainly in the medial side of the ring finger (fourth digit) rather than the lateral side, corresponding to the textbook sensory distribution. Sometimes the third digit is also involved, especially on the ulnar (ie, medial) side. The sensory changes can include numbness, tingling, or burning. If the patient rests on the elbows at work, increasing numbness and paresthesias may be noticed throughout the day.
Pain rarely occurs in the hand. Complaints of pain tend to be more common in the arm, up to and including the elbow area. Indeed, the elbow is probably the most common site of pain in an ulnar neuropathy.
Occasionally, patients specifically say “I have pain in my elbow,” “I have pain in my funny bone,” or even “I have pain in this little groove in my elbow,” but usually they are not quite so explicit unless prompted. On occasion, severe pain at the elbow or wrist may radiate into the hand or up into the shoulder and neck.
Patients rarely notice specific muscle atrophy, but when they do, they often complain that their hands “look older.”
Weakness may also be a presenting complaint. For example, patients may report difficulty in opening jars or turning doorknobs or may experience early fatigue or weakness with work that requires repetitive hand motions.
The complaint of weakness may also be expressed in more subtle ways. For example, one traditional sign of ulnar neuropathy, the Wartenberg sign, is actually a complaint of weakness. In this scenario, the patient complains that the little finger gets caught on the edge of the pants pocket when he or she tries to place the hand into the pocket.
At first, this complaint may be surprising, because most physicians, remembering that finger abduction is governed by the ulnar nerve, are probably inclined to assume that a patient who has an ulnar neuropathy would be less, rather than more, likely to have the little finger abducted and thus caught on the edge of the pocket. However, adduction is also mediated by the ulnar nerve. In essence, the patient cannot abduct the fifth digit tightly against the fourth because of weakness of the interosseous muscles.
Ulnar Neuropathy Clinical History
Both the onset and the progress of the symptoms can be variable. Presenting symptoms of ulnar nerve entrapment can range from mild transient paresthesias in the ring and small fingers to clawing of these digits and severe intrinsic muscle atrophy.
Many patients complain of sensory changes in the fourth and fifth digits. Rarely, a patient notices that the unusual sensations are mainly in the medial side of the ring finger (fourth digit) rather than the lateral side, corresponding to the textbook sensory distribution. Sometimes the third digit is also involved, especially on the ulnar (ie, medial) side. The sensory changes can include numbness, tingling, or burning. If the patient rests on the elbows at work, increasing numbness and paresthesias may be noticed throughout the day.
Pain rarely occurs in the hand. Complaints of pain tend to be more common in the arm, up to and including the elbow area. Indeed, the elbow is probably the most common site of pain in an ulnar neuropathy.
Occasionally, patients specifically say “I have pain in my elbow,” “I have pain in my funny bone,” or even “I have pain in this little groove in my elbow,” but usually they are not quite so explicit unless prompted. On occasion, severe pain at the elbow or wrist may radiate into the hand or up into the shoulder and neck.
Patients rarely notice specific muscle atrophy, but when they do, they often complain that their hands “look older.”
Weakness may also be a presenting complaint. For example, patients may report difficulty in opening jars or turning doorknobs or may experience early fatigue or weakness with work that requires repetitive hand motions.
The complaint of weakness may also be expressed in more subtle ways. For example, one traditional sign of ulnar neuropathy, the Wartenberg sign, is actually a complaint of weakness. In this scenario, the patient complains that the little finger gets caught on the edge of the pants pocket when he or she tries to place the hand into the pocket.
At first, this complaint may be surprising, because most physicians, remembering that finger abduction is governed by the ulnar nerve, are probably inclined to assume that a patient who has an ulnar neuropathy would be less, rather than more, likely to have the little finger abducted and thus caught on the edge of the pocket. However, adduction is also mediated by the ulnar nerve. In essence, the patient cannot abduct the fifth digit tightly against the fourth because of weakness of the interosseous muscles.
Furthermore, the muscle that extends the fifth digit at the metacarpal phalangeal joint (the extensor digiti quinti) is radially innervated and inserts on the ulnar side of the joint. Normally, this muscle is opposed by ulnar-innervated muscles that flex the joints. In the setting of an ulnar neuropathy, however, the muscle is relatively unopposed and thus pulls the finger up and to the ulnar side. This is the perfect position for catching onto the edge of the pocket.
The patient also may express the complaint of weakness by saying, “My grip is weak.” Many of the grip muscles are ulnar. Also, when someone tries to grip powerfully, the hand usually deviates in the ulnar direction under the influence of the flexor carpi ulnaris. If this ulnar deviation is impaired, the grip mechanism does not work optimally, even for the muscles that are unimpaired.
Sometimes, a patient notices that the thumb−index finger pincer grip is weak. Two of the key muscles involved in this movement are the adductor pollicis (adducting the thumb) and the first dorsal interosseous muscle (adducting the index finger). In addition to the weak pincer grip, the median-innervated flexor pollicis longus partially compensates for the weakened adductor pollicis, and the thumb flexes at the distal joint. This flexion usually goes unnoticed by the patient, but when it is demonstrated by the examiner, it constitutes the Froment sign.
Ulnar Neuropathy Physical Exam
Typically, the clinical examination begins at the neck and shoulder and moves down the affected extremity to the elbow. The physical examination should include the following steps:
1. Check elbow range of motion, and examine the carrying angle; look for areas of tenderness or ulnar nerve subluxation
- Check for the Tinel sign - This sign is typically present in individuals with cubital tunnel syndrome; however, as many as 24% of the asymptomatic population also present with the sign
- Perform an elbow flexion test - This test, generally considered the best diagnostic test for cubital tunnel syndrome involves having the patient flex the elbow past 90°, supinate the forearm, and extend the wrist; results are positive if discomfort is reproduced or paresthesia occurs within 60 seconds
- Consider a shoulder internal rotation test - In this test, the upper extremity is kept at 90° of shoulder abduction, maximal internal rotation, and 10° of flexion, with the elbow flexed 90°, the wrist in neutral, and the fingers extended; a result is considered positive if any symptom attributed to cubital tunnel syndrome appears within 10 seconds; this test appears specific to cubital tunnel syndrome and may be more sensitive for the syndrome than the 10-second elbow flexion test is
- Palpate the cubital tunnel region to exclude mass lesions
- Examine for intrinsic muscle weakness
- Examine for clawing or abduction of the small finger with extension (the Wartenberg sign)
- Assess ability to cross the index and middle fingers
- Check for the Froment sign with key pinch
- Check grip and pinch strength
- Check vibratory perception and light touch with Semmes-Weinstein monofilaments - This is more important than static and moving 2-point discrimination tests, which reflect innervation density, as the initial changes in nerve compression affect threshold
- Check 2-point discrimination
- Evaluate sensation, especially the area on the ulnar dorsum of the hand supplied by the dorsal ulnar sensory nerve - Hypoesthesia in this area suggests a lesion proximal to the canal of Guyon
- Exclude other causes of dysesthesias and weakness along the C8-T1 distribution (eg, cervical disk disease or arthritis, thoracic outlet syndrome, and ulnar nerve impingement at the canal of Guyon)
Description of possible physical presentation for Ulnar Neuropathy
Several factors contribute to the clawed appearance. Wasting of the intrinsic muscles of the hand makes it look bonier. The fourth and fifth digits extend at the metacarpal phalangeal joint because the extensors at that joint are radially innervated, whereas the flexors are innervated by the ulnar nerve. Also, the fifth digit deviates slightly in the medial direction because the muscle that extends the fifth digit at the metacarpophalangeal joint is radially innervated and inserts on the ulnar side of the joint.
The fourth and fifth interphalangeal joints flex because the extensor muscles for these joints are also ulnar and because the natural tension of the muscles and tendons, in the absence of strong muscle activity in either direction, leads to flexion. The first three digits are extended at both the metacarpophalangeal joints and the interphalangeal joints because of the unopposed radial nerve innervation. All these factors make the hand look somewhat like a claw.
A different interpretation of the posture is that it looks like the hand gesture that a priest makes in the process of conferring a blessing. For this reason, it is sometimes called the benediction sign or the benediction hand.
The Froment sign is an observable sign that correlates with the complaint of a weakened ability to pinch normally between the first and second digits. This sign is sometimes elicited by asking the patient to grasp a piece of paper between the thumb and index finger. Ordinarily, the grasp is tight, and the patient makes heavy use of the adductor pollicis to adduct the thumb and the first dorsal interosseous muscle to move the index finger.
Ulnar neuropathy at elbow
Clinical Presentation
- Positive Tinel sign at elbow
To test for the Tinel sign, the examiner taps with a reflex hammer over the ulnar nerve in the ulnar groove and a little further distally over the cubital tunnel. The test is considered to yield a positive result if the patient experiences definite paresthesias in the ulnar portion of the hand, especially in the last two digits.
This test is not regarded as highly sensitive, but it is quite specific if performed properly (ie, if the examiner does not hit too hard). With a sufficiently hard tap, many normal individuals will experience paresthesias in the fourth and fifth digits. On the assumption that the complaint is unilateral, the opposite side serves as a good control for this. Sometimes, palpating the nerve in the ulnar groove may produce a similar result. - Atrophy and muscle weakness
The most important ulnar hand muscles to test are the first dorsal interosseous muscle and the abductor digiti minimi (abductor digiti quinti). In the forearm, the flexor digitorum profundus of the fourth and fifth digits (which flexes the distal phalanges of those fingers) and the flexor carpi ulnaris (which controls flexion at the wrist in the ulnar direction) are valuable to examine.
It is not uncommon for the flexor carpi ulnaris to be spared in ulnar lesions near the elbow, especially in lower (more distal) lesions close to the elbow. Sparing occurs because the branch to the flexor carpi ulnaris splits off from the main trunk before (ie, above or proximal to) the compression.
The ulnar muscles should not be examined in isolation from other muscles. In particular, several key muscles with C8/T1, lower-trunk, medial-cord innervation should be examined, especially the abductor pollicis brevis (a thenar muscle typically involved with carpal tunnel syndrome, the major compressive median nerve neuropathy) and the median-innervated long thumb and index finger flexors.
If both the ulnar intrinsic hand muscles and the ulnar forearm muscles are involved, then an ulnar nerve lesion in the region of the elbow (or, very rarely, above the elbow region) should be suspected. If the ulnar forearm muscles are spared, it is reasonable to consider the possibility of a lesion at the wrist, but extra caution is warranted in this case. Sometimes, the forearm muscles are spared with a lesion near the elbow, especially if the lesion is in the lower elbow region in or around the cubital tunnel.
Ulnar neuropathy at or distal to wrist
The following physical findings are significant with respect to ulnar neuropathy at or distal to the wrist:
- Weakness of the interosseous and hypothenar muscles only, with no sensory loss - This would most likely be due to compression of the deep motor branch in the hand after it had separated from the superficial terminal sensory branch but before the branch to the hypothenar muscles had taken off
- Interosseous muscle weakness only, with no sensory loss - This would most likely be due to compression of the deep motor branch after the branch to the hypothenar muscles had taken off
- Weakness of the interosseous and hypothenar muscles, with sensory involvement in the fifth digit - This would suggest involvement in the canal of Guyon with compression of both the deep motor branch and the superficial terminal sensory branch (ie, what might be considered the typical or classic Guyon canal pattern)
- Pure sensory loss, with normal dorsal ulnar cutaneous sensory nerve, normal palmar cutaneous sensory nerve, and normal motor responses - This would imply injury to the superficial terminal sensory branch alone, probably a compression distal to the canal of Guyon
- Interosseous weakness and sensory loss, with preserved function in the hypothenar and dorsal ulnar cutaneous territories - This would imply a compression of the deep motor branch and the superficial terminal sensory branch distal to the point where the subbranch to the hypothenar area (eg, the abductor digit minimi) had split off from the deep motor branch
Sensory Examination for Ulnar Nerve Neuropathy
Adding information from the sensory examination to that of the motor examination helps to localize the ulnar lesion.
Although in some patients, the area of the palmar cutaneous sensory nerve can extend a bit farther proximally than is usual, if the sensory involvement extends more than 2.5 cm above the wrist crease along the medial aspect of the forearm, involvement of the nerve roots (C8/T1) or the brachial plexus is likely (possibly in addition to an ulnar injury).
As noted (see Anatomy), both the palmar cutaneous sensory branch of the ulnar nerve and the dorsal ulnar cutaneous branch come off the main ulnar branch above (proximal to) the wrist. Thus, a lesion exclusively at the wrist (at the canal of Guyon) would miss these branches, and the only sensory involvement would be in the superficial terminal branch. However, a physician must be cautious in interpretation.
Typically, neuropathic damage, whether generalized or related to nerve compression, affects (or is perceived to affect) the most distal parts of the nerves preferentially. A compression at the canal of Guyon might be perceived by the patient and might be detectable on examination only in the tips of the fingers. Thus, the compression would appear to be affecting only the superficial terminal branch.
Lab Studies and Radiography for Ulnar Neuropathy
Laboratory Studies
Routine studies for ulnar nerve entrapment are ordered to rule out anemia, diabetes mellitus, and hypothyroidism and include the following:
- Complete blood cell (CBC) count
- Urinalysis
- Fasting blood glucose
Depending on the specific clinical situation, the following tests may be considered as well:
- Hemoglobin A 1C
- Antinuclear antibody
- Erythrocyte sedimentation rate
- Renal function tests
- Paraproteinemia workup (serum protein electrophoresis with immunofixation)
- Angiotensin-converting enzyme
- Lyme serology
- Thyroid function tests
- Vitamins B-12, B-1, and B-6
- Folate level
- Methylmalonic acid
- Tissue transglutaminase antibody
- Gliadin antibody
- HIV serology
- Hepatitis serologies
Radiography
Radiographs of the neck should be obtained if cervical disk disease is suspected and to rule out cervical ribs. Radiographs of the chest should be obtained if Pancoast tumor or tuberculosis is suspected.
Radiographs of both the elbow and the wrist are mandatory in ulnar nerve compression because double-crush syndrome may be present. Entrapment of the ulnar nerve may occur at more than one level.
Radiographs of the elbow reveal abnormal anatomy, such as a valgus deformity, bone spurs or bone fragments, a shallow olecranon groove, osteochondromas, and destructive lesions (eg, tumors, infections, or abnormal calcifications). If there is a history of trauma or arthritis, a cubital tunnel projection radiograph should be obtained to exclude medial trochlear lip osteophytes. If a supracondylar process on the medial aspect of the humerus is suspected, an elbow radiograph should be obtained 5 cm proximal to the medial epicondyle.
Radiographs of the wrist reveal fractures of the hook of the hamate, dislocations of the wrist bones, and, to a lesser extent, soft-tissue masses and calcifications.
