Carpal Tunnel Syndrome
S. Brent Brotzman, MD
Background
Carpal tunnel syndrome (CTS) is relatively common (the most common peripheral neuropathy), affecting 1% of the general population. It occurs most frequently during middle or advanced age, with 83% of 1215 study patients older than 40 years with a mean age of 54 years. Women are affected twice as frequently as men.
The carpal tunnel is a rigid, confined fibro-osseous space that physiologically acts as a “closed compartment.” CTS is caused by compression of the median nerve at the wrist. The clinical syndrome is characterized by pain, numbness, or tingling in the distribution of the median nerve (the palmar aspect of the thumb, index, and long finger). These symptoms may affect all or a combination of the thumb, index, long, and ring fingers. Pain and paresthesias at night in the palmar aspect of the hand (median nerve distribution) are common symptoms.
The prolonged flexion or extension of the wrists under the patient’s
head or pillow during sleep is believed to contribute to the prevalence of nocturnal symptoms. Conditions that alter fluid balance (pregnancy, use of oral contraceptives, hemodialysis) may predispose to CTS. CTS associated with pregnancy is transitory and typically resolves spontaneously. Therefore surgery should be avoided during pregnancy.
Typical Clinical Presentation
Paresthesias, pain, and numbness or tingling in the palmar surface of the hand in the distribution of the median nerve (Fig. 1–39) (i.e., the palmar aspect of the three and one-half radial digits) are the most common symptoms. Nocturnal pain is also common. Activities of daily living (such as driving a car, holding a cup, and typing) of ten aggravate pain. Pain and paresthesias are sometimes relieved by the patient massaging or shaking the hand.
Provocative Testing Maneuvers (Table 1–5)
Phalen Maneuver (Fig. 1–40)
The patient’s wrists are placed in complete (but not forced) flexion.
If paresthesias in the median nerve distribution occur within the 60-second test, the test is positive for CTS.
Gellman and associates (1986) found this to be the most sensitive (sensitivity, 75%) of the provocative maneuvers in their study of CTS.
Tinel Sign (Median Nerve Percussion)
Tinel sign may be elicited by lightly tapping the patient’s median nerve at the wrist, moving from proximal to distal.
The sign is positive if the patient complains of tingling or electric shock-like sensation in the distribution of the median nerve.
Sensory Testing of the Median Nerve Distribution
Decreased sensation may be tested by:
Threshold tests: Semmes-Weinstein monofilament; vibrometry perception of a 256-cps tuning fork.
Innervation density tests: two-point discrimination.
Sensory loss and thenar muscle weakness often are late findings.
Electrodiagnostic Tests
Electrodiagnostic studies are a useful adjunct to clinical evaluation, but do not supplant the need for a careful history and physical examination.
These tests are indicated when the clinical picture is ambiguous or there is suspicion of other neuropathies.
The criterion for a positive electrodiagnostic test is a motor latency greater than 4.0 M/sec and a sensory latency of greater than 3.5 M/sec.
The interpretation of findings in patients with CTS is classified in Table 1–6.
Special Tests for Evaluation
Phalen maneuver (60 seconds).
Tinel sign at carpal tunnel (percussion test).
Carpal tunnel direct compression (60 seconds).
Semmes-Weinstein monofilament sensory testing.
Palpation of pronator teres/Tinel’s (rule out pronator syndrome).
Spurling’s test of the neck (rule out cervical radiculopathy). (See Chapter 3, Shoulder Injuries.)
Radicular testing (motor, sensory, reflexes) of involved extremity (rule out radiculopathy).
Inspection for weakness or atrophy of thenar eminence (a late finding of CTS).
Exploration for possible global neuropathy on history and examination (e.g., diabetic).
If gray area, electromyographic/nerve conduction velocity (EMG/NCV) testing of entire involved upper extremity to exclude cervical radiculopathy versus CTS versus pronator syndrome.
Evaluation
Patients with systemic peripheral neuropathies (e.g., diabetes, alcoholism, hypothyroidism) typically have sensory abnormality distribution that is not solely isolated to the median nerve distribution.
More proximal compressive neuropathies (e.g., C6 cervical radiculopathy) will produce sensory deficits in the C6 distribution (well beyond median nerve distribution); plus weakness in the C6 innervated muscles (biceps) and an abnormal biceps reflex.
Electrodiagnostic tests are helpful in distinguishing local compressive neuropathies (such as CTS) from peripheral systemic neuropathies (such as diabetic neuropathy).
Treatment
All patients should undergo initial conservative management, unless the presentation is acute and associated with trauma (such as CTS associated with acute distal radius fracture).
All patients with acute CTS should have the wrist taken out of flexion in the cast and placed in neutral (see section on distal radius fractures).
Circumferential casts should be removed or bivalved, and icing and elevation above the heart should be initiated.
Close serial observation should check for possible “emergent” carpal tunnel release if symptoms do not improve.
Some authors recommend measurement of wrist compartment pressure.
Nonoperative Management
Pregnant women are all treated nonoperatively because of spontaneous resolution after delivery of the baby.
Nonoperative treatment may include:
The use of a prefabricated wrist splint, placing the wrist in a neutral position, worn at night; daytime splinting if patient’s job allows.
Activity modification (discontinuing vibratory machinery or placing a support under unsupported arms at the computer).
Cortisone injection of the carpal tunnel (Fig. 1–41) (not the actual median nerve). Studies have shown that fewer than 25% of patients who had cortisone injection into the carpal tunnel were symptom free at 18 months after injection. As many as 80% of patients do have temporary relie with cortisone injection and splinting. Green found that symptoms typically recurred 2 to 4 months after cortisone injection, leading to operative treatment in 46% of patients.
The technique for injection is shown in Figure 1–41. If injection creates paresthesias in the hand, the needle should be immediately withdrawn and redirected; injection should not be into the median nerve.
Vitamin B6 has not been shown in clinical trials to have any therapeutic effect on CTS, but may help “missed” neuropathies (pyridoxine deficiency).
Nonsteroidal anti-inflammatory drugs (NSAIDs) can be used for control of inflammation.
Any underlying systemic disease (such as diabetes, rheumatoid arthritis, or hypothyroidism) must be controlled.
Surgical Treatment
Indications for surgical treatment of CTS include:
Thenar atrophy or weakness.
Sensation loss on objective measures.
Fibrillation potentials on electromyelograms.
Symptoms that persist more than a year despite appropriate conservative measures.
The goals of carpal tunnel release are:
Decompression of the nerve.
Improvement of excursion.
Prevention of progressive nerve damage.
Our recommendation is open carpal tunnel release (complication rate of 10 to 18%) rather than endoscopic release (complication rate up to 35% in some studies). In our experience, the times to return to work and sporting activities have not been different enough between the two procedures to warrant the differences in complication rate (dramatically increased frequency of digital nerve lacerations with endoscopic technique).
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