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 crucial to determine when the symptoms began, how long they last, 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 hand. Instead, 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 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.” Still, usually, they are not quite so explicit unless prompted. Occasionally, 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 opening jars or turning doorknobs or may experience early fatigue or weakness with work requiring 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 a complaint of weakness. In this scenario, the patient complains that the little finger gets caught on the edge of the pants pocket when they try 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 the 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 inserted on the ulnar side of the joint. Typically, this muscle is opposed by ulnar-innervated muscles that flex the joints. However, in ulnar neuropathy, the muscle is relatively unopposed and pulls the finger up to the ulnar side. This is the perfect position for catching onto the edge of the pocket.
The patient may also express the weakness complaint 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 unimpaired muscles.
Sometimes, a patient notices that the thumb−index finger pincer grip is weak. Two 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 the examiner demonstrates it, it constitutes the Froment sign.
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:
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Check elbow range of motion, and examine the carrying angle; look for areas of tenderness or ulnar nerve subluxation
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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
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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
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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 at 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]
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Palpate the cubital tunnel region to exclude mass lesions
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Examine for intrinsic muscle weakness
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Examine for clawing or abduction of the small finger with extension (the Wartenberg sign)
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Assess the ability to cross the index and middle fingers
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Check for the Froment sign with a critical pinch
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Check grip and pinch strength
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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
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Check 2-point discrimination
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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
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Exclude other causes of dysesthesias and weakness along with 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, an inspection of the hand may reveal a clawed posture (main en griffe in French).
Several factors contribute to the clawed appearance. Wasting 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 ulnar nerve innervates the flexors. 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 inserted 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 solid muscle activity in either direction, leads to flexion. Because of the unopposed radial nerve innervation, the first three digits are extended at both the metacarpophalangeal joints and the interphalangeal joints. 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 when 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 generally 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 heavily uses the adductor pollicis to adduct the thumb and the first dorsal interosseous muscle to move the index finger.
In addition to the overt weakness of the pinch, the examiner also notes that the thumb flexes at the interphalangeal joint because the flexor pollicis longus activates to compensate for the weakness. Thus, in addition to the weakness, the examiner sees flexion of the tip of the thumb.
Suppose a Martin-Gruber anastomosis in the forearm or a Riche-Cannieu in the palm is present. In that case, the examiner may be deceived by the apparent functioning of ulnar-innervated muscles.
Ulnar neuropathy at elbow
Positive Tinel sign at the 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 pretty specific if appropriately performed (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. Palpating the nerve in the ulnar groove may produce a similar result.
Atrophy and muscle weakness
The most crucial 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) ones near 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 vital muscles with C8/T1, lower-trunk, and 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.
Suppose both the ulnar intrinsic hand muscles and the ulnar forearm muscles are involved. In that case, an ulnar nerve lesion should be suspected in the elbow region (or, very rarely, above the elbow region). 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. The forearm muscles are sometimes spared 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 several separate fascicles. In some instances, 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 the wrist
The following physical findings are significant for ulnar neuropathy at or distal to the wrist:
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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
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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
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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)
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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
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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 the motor examination helps localize the ulnar lesion. [105]
Although in some patients, the area of the palmar cutaneous sensory nerve can extend a bit farther proximally than 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. Again, 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. The patient might perceive compression at the canal of Guyon and might be detectable on examination only in the tips of the fingers. Thus, the compression would affect only the superficial terminal branch. [106, 107, 108]
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A schematic diagram of the elbow region with 5 main sites (as given by Posner) labeled 1-5; other sites and structures are also named. The main regions of interest are colored circles. Sites 2 and 3 are close together and cannot be distinguished by means of electromyography and nerve conduction studies. This location is referred to as ulnar (or epicondylar) groove.
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The diagram shows the ulnar nerve distal to the elbow region. The dorsal ulnar cutaneous nerve (lavender) branches off the main trunk (purple). Although the course is not followed in detail after that, the lavender region on the sensory dermatome diagram shows where this sensory nerve innervates skin. Similarly, the palmar cutaneous sensory nerve (yellow) branches off to innervate the skin area depicted in yellow. The superficial terminal branch is mostly sensory (see green-colored skin on palmar surface), though it also gives off a branch to the palmaris brevis. The deep terminal branch has no corresponding skin area, because it is solely motor-innervating the muscles shown, as well as others not explicitly depicted. A nerve could be pinched or injured anywhere, but sites labeled I-IV are more commonly involved.
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Inching technique used to isolate conduction block in left ulnar nerve. Note significant amplitude drop at 305 mm, which correlates with position 2 cm above medial epicondyle. This is example of supracondylar block. Image courtesy of A S Lorenzo, MD.
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Normal median and ulnar patterns are compared with those of 3 commonly recognized types of Martin-Gruber anomaly.
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First 3 traces correspond to ulnar compound muscle action potential (CMAP) amplitude during recording at abductor digiti quinti (ADQ) and stimulating at wrist, below elbow, and above elbow, respectively. Fourth trace corresponds to stimulation of median nerve at elbow during recording at ADQ. Although CMAP amplitude is reduced markedly above elbow, this is compensated for by adding response seen after stimulation of median nerve; this represents Martin-Gruber anastomosis.
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First 3 traces correspond to stimulation of ulnar nerve during recording at first dorsal interosseous (FDI) muscle at wrist, below elbow, and above elbow, respectively. Fourth trace corresponds to stimulation of median nerve at elbow during recording at FDI muscle; this represents Martin-Gruber anastomosis.
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In those with Martin-Gruber anomaly who have no other significant neuropathy or nerve compression, stimulation of specific nerves at different sites yields differing results. With the median nerve, stimulation at the elbow yields larger compound muscle action potential (CMAP) at hypothenar muscles, first dorsal interosseous (FDI) muscle, or thenar muscles (or combination thereof) than does stimulation at the wrist. With the ulnar nerve, stimulation at the wrist yields larger CMAP at hypothenar muscles, FDI muscle, or thenar muscles (or combination thereof) than does stimulation at the elbow. In this context, "larger" and "smaller" generally refer to amplitude differences ≥1.0 mV.
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Riche-Cannieu anastomosis is communication between the recurrent branch of the median nerve and the deep branch of the ulnar nerve in the hand. Although it is present in 77% of hands, it yields highly variable degrees of detectable physiologic difference. In many hands, it contributes little and does not affect diagnostic findings at all. The most common effect is probably to give ulnar innervation to some muscles usually innervated by the median nerve, median innervation to muscles usually innervated by the ulnar nerve, or both. The most extreme version is the so-called all-ulnar hand (very rare). Two examples of confusion this might cause are as follows: (1) a median lesion could cause denervation in typically ulnar muscle, such as adductor digiti minimi (adductor digiti quinti) or first dorsal interosseous muscle, and (2) an ulnar lesion could cause denervation in typically median muscle, such as flexor pollicis brevis or abductor pollicis brevis.
Tables
Type |
Anatomy |
Most Characteristic Finding |
Confirmation |
Additional Verification |
Potential Clinical Confusion |
I |
Crossover fibers innervate hypothenar muscles |
Ulnar stimulation at wrist* produces larger hypothenar CMAP than stimulation at elbow |
Stimulation of median nerve at elbow† produces response at hypothenar muscles |
Hypothenar CMAP from ulnar stimulation at wrist is equal to hypothenar CMAP from ulnar stimulation at elbow plus hypothenar CMAP from median stimulation at elbow |
Smaller response from proximal stimulation could be mistaken for conduction block |
II |
Crossover fibers innervate FDI muscle |
Ulnar stimulation at wrist produces larger FDI CMAP than stimulation at elbow |
Stimulation of median nerve at elbow produces response at FDI |
FDI CMAP from ulnar stimulation at wrist is equal to FDI CMAP from ulnar stimulation at elbow plus FDI CMAP from median stimulation at elbow |
Usually none, because FDI muscle is not usually recording site; if it is used, conduction block could be suspected, as in type I |
III |
Crossover fibers innervate thenar muscles (typically ADP and FPB) |
Elbow stimulation of median nerve produces greater thenar response than wrist stimulation |
Ulnar stimulation produces thenar CMAP with initial positive deflection; it is higher with wrist stimulation than with elbow stimulation |
For thenar CMAP amplitudes, median elbow stimulation amp is equal to median wrist stimulation amplitude plus ulnar wrist stimulation amplitude minus ulnar elbow stimulation amplitude |
Can complicate median nerve studies, especially when carpal tunnel syndrome is involved |
ADP—adductor pollicis; CMAP—compound motor (or muscle) action potential; FDI—first dorsal interosseous; FPB—flexor pollicis brevis. *Ulnar stimulation at the wrist yields larger CMAP at hypothenar muscles, FDI, or thenar muscles (or sometimes a combination of these) than stimulation at the elbow. †Median stimulation at the elbow yields larger CMAP at hypothenar muscles, FDI, or thenar muscles (or sometimes a combination of these) than stimulation at the wrist. Note: "Larger" and "smaller" generally mean amplitude difference ≥1.0 mV. |
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