Include these maneuvers in the physical exam
A thorough evaluation of the neck, shoulder, elbow, and wrist is crucial for all patients with signs and symptoms associated with CTS. Provocative maneuvers (TABLE 1)7,13 are also important as an aid to diagnosis. The results of the following tests should be viewed with caution, however, as studies have found wide variations in their sensitivity and specificity:
TABLE 1
Diagnosing carpal tunnel syndrome, using physical maneuvers7,13
| Test | Technique | Positive test | Sensitivity (%) | Specificity (%) |
|---|---|---|---|---|
| Phalen’s | Patient holds wrist flexed 90° with elbow in full extension | Pain or paresthesia ≤60 sec | 68 | 73 |
| Tinel’s | Clinician repetitively taps wrist over transverse carpal ligament | Pain or paresthesia | 50 | 77 |
| Median nerve compression* (MNC) | Clinician applies direct pressure over the transverse carpal ligament | Pain or paresthesia ≤30 sec | 64 | 83 |
| MNC + Phalen’s | Same as above | Same as above | 80 | 92 |
| *also known as Durkan’s test. | ||||
Phalen’s maneuver. The patient flexes his or her wrist with the elbow in full extension to increase pressure on the median nerve, and holds the position for 60 seconds. The onset of pain or paresthesia is a positive test. A meta-analysis found the sensitivity and specificity of a positive Phalen’s sign to be 68% and 73%, respectively.7
Tinel’s test. Tap the volar surface of the patient’s wrist just proximal to, or on top of, the carpal tunnel. Pain or paresthesia in the fingers innervated by the median nerve as a result of the percussion constitutes a positive result. Tinel’s test is less sensitive than the Phalen’s maneuver, but has a similar specificity.13
The median nerve (Durkan’s) compression test. Apply pressure over the transverse carpal ligament; the test is positive if pain or paresthesia develops within 30 seconds.7
The hand elevation test. The patient raises both hands overhead for 60 seconds; here, too, pain or paresthesia is a positive result.14
Combining results of provocative maneuvers may increase sensitivity and specificity. Positive results in both the Phalen’s and median nerve compression tests, for example, have a collective sensitivity and specificity of 80% and 92%, respectively.13
When (or whether) to order electrodiagnostic studies
While some clinicians consider EDS to be the gold standard in CTS diagnosis,6 evidence is limited. One issue is the lack of universally accepted reference standards; another is that most studies have been affected by “spectrum bias.”15 What’s more, EDS—which include nerve conduction studies (NCS) and electromyography (EMG)—do not always correlate directly with symptoms, and 16% to 34% of mild cases can be missed.16
EDS are useful in many instances, however. EMG can rule out other causes of CTS symptoms (TABLE 2 details the differential diagnosis),7,11 while NCS can aid in diagnosing CTS, gauging its severity, and arriving at a prognosis. Specifically, NCS can detect delayed distal latencies and slowed conduction velocities that can occur when the myelin sheath is damaged by prolonged compression of the median nerve.17 With more severe compression, axonal damage occurs, as evidenced by reduced action potential amplitudes on NCS. Results of the nerve conduction tests are compared to age-dependent normal values and to results from other nerves on either the same or the contralateral hand. In a 2002 systemic review, the sensitivity of NCS for CTS was 56% to 85% and the specificity was 94% to 99%.18
TABLE 2
Differential diagnosis for CTS7,11
| Condition | Characteristics |
|---|---|
| Carpometacarpal arthritis of thumb | Thumb is painful when in motion; radiographic findings |
| Cervical radiculopathy | Neck pain, nerve root distribution (eg, C6), positive Spurling’s test |
| DeQuervain’s tenosynovitis | Painful resisted thumb dorsiflexion, tender at base of thumb |
| Hypothyroidism | Fatigue, cold intolerance, dry skin, hair loss, abnormal thyroid function tests |
| Peripheral neuropathy | History of DM, lower extremity involvement |
| Pronator syndrome (median nerve compression at the elbow) | Tenderness at proximal forearm |
| Ulnar compressive neuropathy | Compression and positive Tinel’s sign: ulnar nerve at elbow or wrist produces pain or paresthesias in 4th and 5th fingers |
| Vibration white finger | History of use of power drill or other hand-held vibratory tool; symptoms of Raynaud’s syndrome |
| Wrist arthritis | Painful wrist ROM, radiographic findings |
| CTS, carpal tunnel syndrome; DM, diabetes mellitus; ROM, range of motion. | |
Before and after surgery. The American Academy of Orthopedic Surgeons (AAOS) recommends EDS when CTS surgery is being considered. 7 EDS may also be used after surgery, to verify neurologic improvement.
Ultrasound. In patients with CTS, ultrasound reveals an increased cross-sectional area of the median nerve, a finding that has prompted studies of this modality as a diagnostic tool.19 Although evidence suggests that ultrasound’s sensitivity and specificity for CTS would be similar to that of EDS, the optimal cutoff for an abnormal test has not been defined,19 and ultrasound does not provide information on prognosis or alternate causes.