What presentation is characteristic of ulnar neuropathy?

Updated: Jun 08, 2018
  • Author: Charles F Guardia, III, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Answer

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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