Carpal Tunnel Syndrome
DEFINITION
Carpal tunnel syndrome is compression of the median nerve in the wrist as it passes within the carpal tunnel, which is a structure bordered by the carpal bones and roofed by the transverse carpal ligament.
SYNONYMS
None in common usage. Carpal tunnel syndrome is a diagnosis often incorrectly used by clinicians for a variety of other hand conditions involving pain.
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ETIOLOGY
Carpal tunnel syndrome occurs when either the volume of the carpal tunnel decreases or the volume of the contents increases, resulting in increased pressure within the tunnel. The increased pressure leads to ischemia or axonal compression of the median nerve, experienced by the patient as pain, paresthesias, and/or numbness in the volar aspect of the radial three digits.Advanced cases may include weakness and atrophy in the thenar muscles and lumbrical muscles to the index and middle fingers, or hypohidrosis (decreased sweating) as a result of involvement of the sympathetic nerves.
EPIDEMIOLOGY AND
DEMOGRAPHICS
• The prevalence of carpal tunnel syndrome is approximately 50 cases per 1000 population in the United States(US).
• Peak age of onset is 45 to 60 years.
• Prevalence is 3 to 10 times as high in women as in men; prevalence is higher in whites than nonwhites.
Carpal-Tunnel-Syndrome
MECHANISM OF INJURY
• Compression of the median nerve often results from sleeping with the wrists positioned in full flexion.
• Activitiesinvolving prolonged repetitive activity of the hands (e.g.,keyboarding),vibration (e.g., riveting), or physical pressure over the volar wrist can cause or worsen nerve compression.
COMMON SIGNS AND
SYMPTOMS
• The symptom pattern for carpal tunnel syndrome is specific and characteristic. Pain and paresthesias/numbness are felt in the volar aspect of the index and middle fingers and in the radial aspect of the ring fingers and the thumb, as well as the dorsum of these digits distal to the DIP joint.
• The palm is not involved.
• If there is weakness, it will be noted as decreased strength for thumb opposition.
• In addition to these symptoms, patients may complain of pain in the volarforearm,anterior upper arm,and even shoulder.
• Sympathetic nerve involvement may manifest as decreased sweating in the involved area.
• Patients may report difficulty manipulating small objects such as earrings or buttons.
Carpal-Tunnel-Syndrome
AGGRAVATING ACTIVITIES
• Carpal tunnel syndrome is aggravated by prolonged positioning in wrist flexion or extension or with the weight of the hand producing pressure on the volar wrist or by sustained activities involving repetitive motion such as keyboarding.
• Prolonged exposure to vibration, such as while using power tools, can also provoke symptoms.
EASING ACTIVITIES
Avoiding aggravating factors relieves symptoms;splinting to prevent end-range wrist positions and frequent rest breaks during sustained activities are the primary methods.
24-HOUR SYMPTOM PATTERN
Carpal tunnel syndrome symptoms can occur at any time; however, it is common for the initial symptoms to appear at night, often waking the patient.
PAST HISTORY FOR THE REGION
There is no consistent prior local history; however, injuries to the wrist area, such as a distal radius fracture, may be noted.
PHYSICAL EXAMINATION
• Initial complaints are of pain and decreased sensation.
• Little objective evidence will be found in most patients; in more advanced cases, thenar weakness or atrophy or hypohidrosis in the involved area may be noted.
IMPORTANT OBJECTIVE TESTS
• Clinical tests
Carpal tunnel compression test
Phalen’s test
Tinel’s test at the wrist
• Nerve conduction studies are the gold standard for carpal tunnel syndrome. They are highly specific but not very sensitive when the condition is mild (complaints primarily of intermittent pain).Concurrent compression of proximal nervous structures (double or multicrush syndrome) may be overlooked.
DIFFERENTIAL
DIAGNOSIS
• The primary pathology to rule out is nerve compression proximal to the carpal tunnel; cervical nerve roots, brachial plexus, and areas around the elbow should all be considered and examined.
• One helpful finding is the presence or absence of sensory changes and hypohidrosis in the palm.
• Since this area is supplied by a branch of the median nerve that does not pass through the carpal tunnel, symptoms in the palm suggest more proximal compression.
CONTRIBUTING FACTORS
• Factors that may decrease the volume of the tunnel include the following:
Arthritic spurs in the radiocarpal or intercarpal joints.
Synovitis caused by RA.
Tumor formation such as a ganglion cyst.
Chronic positioning in mid- to end ranges of wrist flexion or extension.
• Factors that may increase the volume of the contents include the following:
Systemic conditions that increase fluid retention such as hypothyroidism and pregnancy.
Irritation of the tendon sheath because of overuse.
Congenital anomalies such as unusually proximal lumbrical origin on the flexor digitorum profundus tendon.
• Other risk factors include diabetes,smoking, obesity, and alcoholism.
Carpal-Tunnel-Syndrome
TREATMENT
SURGICAL OPTIONS
• Surgery involves release of the transverse carpal ligament. There are two primary types of surgery: open and endoscopic. There is little difference in long-term outcomes for the two groups other than a 5% recurrence problem with endoscopic surgery caused by incomplete release.
• Estimates of effectiveness of carpal tunnel release vary from 46% to 87%.
• Surgery is indicated in the presence of constant measurable sensory loss or weakness/atrophy of the thenar muscles.
Carpal tunnel syndrome cles. Surgery may also be indicated for patients with intermittent pain or sensory changes who fail to improve with conservative treatment.
REHABILITATION
• Patients with carpal tunnel syndrome should be fitted with a prefabricated or custom splint designed to hold the wrist in neutral position.The splint should be worn when sleeping and whenever the patient performs activities that provoke symptoms.
• Patients should be instructed in activity modification to decrease the effects of the aggravating factors.
• Pulsed ultrasound, nerves gliding exercises,carpal bone mobilization,magnetic theray, and yoga have also been shown to be helpful with some patients.
• A home program of nerve gliding exercises may be useful.
Carpal-Tunnel-Syndrome
PROGNOSIS
• The long-term outlook for patients with mild carpal tunnel syndrome treated conservatively is good for symptom control, although long-term splint wear and/or activity modification may be necessary.
• If the patient returns to the same activities without modification and discontinues splint wear, the symptoms may return.
• Long-term outcomes after surgery are generally good, but weakness/atrophy may not be reversible and advanced sensory loss may not recover fully.
• Some patients experience pain (“pillar pain”) in the thenar and hypothenar areas after surgery that generally resolves in about 3 months. A small number of patients do not fully regain ROM.
SIGNS AND SYMPTOMS
INDICATING REFERRAL
TO PHYSICIAN
_Worsening sensory symptoms or the development of atrophy/weakness in the thenar muscles may indicate the need for surgery.
SUGGESTED READINGS
_ Ashworth NL. Carpal Tunnel Syndrome. Retrieved November 23, 2007, from http://www.emedicine.com/pmr/topic21.htm;2006.
_ Muller M,Tsui D, Schnurr R, Biddulph-Deisroth iL,Hard J,MacDermid JC.Effectiveness of hand therapy interventions in primary management of carpal tunnel syndrome:a systematic review.J Hand Ther. 2004;17(2):2188.
