Ulnar Neuropathy Clinical Presentation

Updated: May 23, 2017
  • Author: Charles F Guardia, III, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Presentation

History

A careful clinical history is imperative. 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. [18]

It is important to determine when the symptoms began, how long they are lasting, whether they are transient or continuous, and whether they are related to work, sleep, or recreation. In addition, although the answer will frequently be negative, one should ask specifically about trauma and pressure to the arm and wrist, especially the elbow, the medial side of the wrist, and other sites close to the course of the ulnar nerve.

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. [99, 100]

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.

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Physical Examination

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:

  • 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, [101, 102] 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 [103]
  • 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)

In addition to assessing sensation and testing individual muscle strength, inspection of the hand may reveal a clawed posture (main en griffe in French).

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.

In addition to overt weakness of the pinch, the examiner also notes that the thumb flexes at the interphalangeal joint because the flexor pollicis longus activates in an attempt to compensate for the weakness. Thus, in addition to the weakness, the examiner sees flexion of the tip of the thumb.

If a Martin-Gruber anastomosis in the forearm or a Riche-Cannieu anastomosis in the palm is present, the examiner may be deceived by the apparent functioning of ulnar-innervated muscles.

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Ulnar neuropathy at elbow

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. [104]

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.

Even for higher elbow lesions, there can be considerable selectivity regarding which muscles are affected because the ulnar nerve is organized into a number of separate fascicles. In certain cases, some fascicles are severely affected by whatever is pinching the nerve while other fascicles remain unaffected. If other C8/T1, lower-trunk, medial-cord muscles are affected, a C8/T1 radiculopathy or a brachial plexus lesion may be the cause.

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

Adding information from the sensory examination to that of the motor examination helps to localize the ulnar lesion. [105]

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. [106, 107, 108]

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