Carpal Tunnel Syndrome: A Review

By Chris Faubel, MD —

Background

• Carpal tunnel syndrome is a peripheral entrapment mononeuropathy of the median nerve as it courses through the carpal tunnel.
• Local compressive entrapment causes demyelination leading to nerve block (neuropraxia).  If the compression persists, local nerve blood flow decreases (vasa nervorum)  leading to a cascade of events eventually causing axon damage (axonotmesis).
• The pain is thought to result from inflammatory mediators (TNFα) causing abnormal Na+ influx into these damaged nociceptive fibers.

Epidemiology

• Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy.
• A Swedish general population survey in 1999 [1] showed 14.4% of responders reported numbness and/or tingling in the median nerve distribution, although only 1 in 5 (20%) symptomatic subjects were found to have clinically AND electrodiagnostically confirmed CTS.
  • The overall prevalence was said to be 2.7% — of CTS confirmed by clinical exam and nerve conduction studies
• A US survey conducted in 1988 [2] showed an estimated 1.88% of the general population had self-reported carpal tunnel syndrome, with females and whites having the highest prevalence
• Certain occupations have been shown to have a much higher prevalence of CTS than the general population
  • Female supermarket checkers:  prevalence = 62.5% (self-reported symptoms only) [3]
  • Mail service, health care, construction, and assembly and fabrication. [4]
• Risk factors (most strongly associated with CTS) [4]
  • Repetitive bending/twisting of the hands/wrists at work (OR = 5.2)    [OR = odds ratio]
  • Race (OR = 4.2; WHITES higher than nonwhites)
  • Gender (OR = 2.2; FEMALES higher than males)
  • Use of vibrating hand tools (OR = 1.8)
  • Age (OR = 1.03; risk increasing per year)
  • Wrist ratio (A-P:med-lat) – If the anterior to posterior distance is ≥70% of the medial to lateral distance, there is a significant association with idiopathic CTS. [30]
  • High body mass index (BMI) – obesity [38]
• Keyboard Use and CTS
  • Some studies have shown no association between computer use and carpal tunnel syndrome. [31] [32]
  • Another study found that workers who identified themselves as “intensive keyboard users” had less CTS than the control group. [34]
    • A big problem with this study was that the control group had a significantly greater number of manual laborers with jobs that required repetitive twisting/bending of the wrists (the number one risk factor above).
  • The question of whether intense keyboard use (i.e., >4 or >6 hours per day) is associated with an increased or decreased risk of CTS is still unanswered. [33]
• Bilateral CTS [29]
  
  • 87% of patients with CTS, have electrodiagnostic (EDX) abnormalities bilaterally.
  • 50% of asymptomatic hands have EDX findings of CTS.
  • Most cases of unilateral CTS developed symptoms in the contralateral hand over time.
  • Duration of symptoms, not severity of symptoms, positively correlated with developing bilateral CTS.
• Pregnancy
  • Carpal tunnel syndrome is common during pregnancy.
  • Wearing a night-time wrist splint helps reduce the pain for a week, but then it stays the same until delivery. [35]
  • Pain cuts in half during the first week after delivery, then half again the next week. [35]
    • Pain reduction strongly correlated with weight loss after delivery.
  • Symptoms frequently persist after delivery
    • More than 50% of the patients after 1 year and in about 30% after 3 years [36]
  • Corticosteroid injections provide significant relief [37]
    • 4 mg of dexamethasone acetate was used in the third trimester.
    • A month after delivery, both the injected and non-injected hands had symptom improvement.

Clinical Features

• CTS can be thought of as occurring in three stages
  • First stage
    • Nocturnal sensations of hand swelling, numbness/tingling (in the median nerve distribution), and pain that frequently is felt all the way up to the ipsilateral shoulder.
    • Patients may report that shaking their hands helps.
    • Hand stiffness in the morning
  • Second stage
    • Same symptoms, but now during the day; mostly when the patient’s wrist remains in the same position too long, or with repetitive wrist movements.
    • Dropping objects — patients may start reporting that they drop objects because of hand weakness.
  • Third stage
    • Noticeable thenar muscle atrophy.
    • Note: sensory complaint are now much less, or even completely absent.
• Paresthesia distribution in the hand [39]
  • 70.4% of patients with CTS present with whole hand distribution of paresthesias
  • 29.6% present with paresthesias strictly in the median nerve distribution
  • Patients suffering from severe CTS were more likely to have median nerve distribution symptoms.
• Severity of symptoms vs NCS findings
  • No statistically significant relationship between the severity of symptoms a patient has, and the severity of electrodiagnostic findings. [40]

Diagnosis

• Important history (to get from the patient)
  • Symptom onset (night vs day)
  • Provocative factors (certain positions; repeated movements)
  • Occupation (wrists movements; vibratory tools)
  • Pain localization (median distribution; ascending to shoulder; descending from shoulder)
  • Alleviating maneuvers (shaking out hands; position changes)
  • Predisposing factors (diabetes, obesity, acromegaly, pregnancy, polyarthritis)
  • Sports/activites (baseball; body-building)
• Physical examination
  • Katz hand diagram (click here for image)
    
    • A patient is given a sheet of paper with outlined palmar and dorsal hands, and is asked to fill in the areas where they experience symptoms (pain; numbness; tingling).
    • The physician then looks at the filled out diagram and classifies it as “classic“, “probable“, and “unlikely“.
    • It was originally thought to correlate well with whether the patient will have electrodiagnostically-confirmed CTS. [5]
    • A recent study in 2010 [6] had two hand surgeons evaluate 75 diagrams (filled out by patients with CTS and other pathologies) at two occasions 4-weeks apart.
      • Inter-rater agreement was poor and intra-rater agreement was fair, making this test unreliable and inconsistent.
  • Tinel’s test (at the wrist)
    • Tapping over the median nerve directly over the carpal tunnel, or just proximal
    • Sensitivity = 67%, Specificity = 68% [8]
    • Very little diagnostic value in CTS
    • More likely to be positive in the later stages of nerve compression [7]
  • Phalen’s test
    • Static wrist flexion for 60 seconds (or until symptoms)
    • Sensitivity = 85%, Specificity = 89% [8]
    • Positive mostly in moderate to severe CTS [41]
  • Hypalgesia in the median nerve distribution
    • Sensitivity = 51%;  specificity = 85% [9]
• Electrodiagnostics
  • **For a more detailed electrodiagnostic review of carpal tunnel syndrome, click here.
  • Nerve conduction studies (median sensory and motor) – setup description and photos here
    • Median sensory and motor NCS:  Sensitivity = 85%;  Specificity = 95%
    • If the median sensory is abnormal, test the ulnar sensory to make sure this isn’t a polyneuropathy
    • If the median sensory is normal, perform the combined sensory index (CSI)  – numb thumb, split ring, P8 (details here)
  • Needle electromyography (EMG)
    • Used to evaluate for axonal degeneration of the motor fibers in the median nerve (will see positive sharp waves and fibrillations)
    • Also used in the rest of the ipsilateral upper extremity to rule out other possible diagnoses.
      • Not performed unless the patient has signs/symptoms that could be from another pathology.
  • Grading the severity of electrodiagnostically-confirmed CTS
    • Negative CTS = Normal findings on all tests
    • Borderline mild CTS = Abnormal findings only on comparative or CSI tests (side-to-side comparison with ulnar sensory, or CSI tests)
    • Mild CTS = Slow median sensory with normal distal motor latency
    • Moderate CTS = Slow median sensory AND distal motor latency
    • Severe CTS = Absent sensory and increased motor latency
    • Profoundly severe CTS = Absent sensory and motor response
• MRI resonance imaging
  • Median nerve signal intensity, transverse carpal ligament bowing, and other measurements of the carpal tunnel has a very high sensitivity [10]
  • Also useful if a space-occupying lesion is the suspected cause of the CTS
• Ultrasound (image of carpal tunnel here – excellent!)
  • A study in 2009 showed that sonographic measurement of the median nerve cross-sectional area (CSA) at the tunnel inlet is a good alternative to NCS as the initial diagnostic test for CTS, but it cannot grade the severity of CTS as well as NCS. [11]

Natural History of CTS

• 1/3 of hands mid and moderate cases improve [27]
• In another study of 132 patients that received no treatment at all, 47.6% recovered, 28.8% remained stable, 23.4% worsened [28] — two-year followup
  • Nerve conduction study results mostly either stayed the same or improved
• Remission rates are highest in young females, and pregnant women.

Treatment (Non-Surgical)

• Always start with a conservative approach unless motor deficits and severe sensory or electrodiagnostic abnormalities are present.
• Corticosteroid injections (carpal tunnel injection image and technique)
  • More effective than placebo (saline) injections in the short-term, but not at a 12-month follow-up [12]
    • Note: they only used 10-mg of kenalog, not the 40mg typically used in clinical practice, so the results may have been even better.
  • Another study found that steroid injections and wrist splinting are effective for relief of mild-moderate carpal tunnel syndrome symptoms but have a long-term effect in only 10 percent of patients (those with symptom duration less than 3 months and no thenar atrophy). [15]
    • This study gave patients three injections of betamethasone throughout the year, not just a single injection.
  • Many other studies have demonstrated clinical efficacy for months, but not an entire year.
  • Keep in mind that corticosteroid injections can be repeated when symptoms return.
  • Dosing matter!
    • A study in 2006 looked at the efficacy of different doses of Depo-Medrol. [16]  In the 20, 40 and 60 mg treatment groups, 56%, 53% and 73% of the patients respectively were free of important symptoms at six months follow-up.  Also, fewer patients in the 60-mg group went on to get surgery within a 12-months.
• Oral Corticosteroids
  • Multiple studies have shown that oral steroids are less effective than injected steroids (into the carpal tunnel)
  • Better than placebo — with dose of 20-mg prednisolone daily for 2 weeks, followed by 10-mg daily for 2 weeks [17]
• Corticosteroid Iontophoresis
  
  • Six sessions of 0.4% dexamethasone was not effective in the treatment of mild to moderate CTS [13]

• Wrist splints (image of neutral wrist splint)
  • Use a neutral wrist splint, instead of a cock-up (extension) splint [20]
  • Advised to tell patients to use only at night, because daytime use interferes with normal activities and the patient is therefore more likely to discontinue use all together
  • Nighttime-only use of a neutral wrist splint was shown to be significantly more effective than doing nothing in patients with mild, recent onset CTS [14]
• NSAIDs
  • No better than placebo [17]
• Diuretics
  • No studies have shown any clinical benefit
• Yoga
  • In one trial involving 51 people yoga significantly reduced pain after eight weeks compared with wrist splinting. [18] [19]
• Carpal mobilization
  • In one trial involving 21 people carpal bone mobilisation significantly improved symptoms after three weeks compared to no treatment. [18]
• Pyroxidine (B6)
  • In two trials involving 50 people, vitamin B6 did NOT significantly improve overall symptoms. [18]
• Ergonomic keyboards
  • Two trials involving 105 people compared ergonomic keyboards versus control and demonstrated equivocal results for pain and function. [18]
• Ultrasound
  • Short to medium term benefits due to ultrasound treatment in patients with mild to moderate idiopathic carpal tunnel syndrome [21]
    • 20 sessions of ultrasound (active) treatment (1 MHz, 1.0 W/cm2, pulsed mode 1:4, 15 minutes per session).  Daily for two weeks, then twice a week for 5 weeks.
• Trials of magnet therapy, laser acupuncture, exercise or chiropractic care did NOT demonstrate symptom benefit when compared to placebo or control. [18]

Treatment (Surgical)

• Indications
  • Patients who fail conservative methods, or have severe sensory deficits, or muscle atrophy.
• The major difference with the medical approach is that surgical transverse carpal ligament release (CTR) has very good long-term results, with very low recurrence rates. [25]
• Efficacy
  • A 2007 review of 209 studies showed: [26]
    • 75% – complete resolution of symptoms, or only mild residual symptoms
    • 17% – mild improvement or no change
    • 8% – worsening of symptoms
  • Best results are seen in patients with moderate NCS readings [42]
• Open vs Endoscopic release [22] (image of endoscopic carpal tunnel release)
  • Patient satisfaction was equal (84-89%)
  • Open method had longer return to work (median, 28 days, compared with 14 days )
  • Equal benefits (between the two techniques)
    
• Surgical vs splinting
  • A significant proportion of people treated with splinting-only will require surgery [23]
• Diabetics
  • Patients with diabetes have the same beneficial outcome after carpal tunnel release as nondiabetic patients. [24]
• Pregnant women should postpone surgery because symptoms frequently resolve completely soon after delivery.

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REFERENCES:

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2 – Tanaka et al. “The US prevalence of self-reported carpal tunnel syndrome: 1988 National Health Interview Survey data.”  Am J Public Health. 1994 Nov;84(11):1846-8.

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4 – Tanaka et al. “Prevalence and work-relatedness of self-reported carpal tunnel syndrome among U.S. workers: analysis of the Occupational Health Supplement data of 1988 National Health Interview Survey.”  Am J Ind Med. 1995 Apr;27(4):451-70.

5 – Katz JN, Stirrat C, Larson MG, et al. “A self-administered hand symptom diagram in the diagnosis and epidemiologic study of carpal tunnel syndrome.” J Rheumatol. 1990;17:1495-1498.

6 – Amirfeyz et al. “Katz and stirrat hand diagram revisited.”  Hand Surg. 2010;15(2):71-3

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8 – Bruske et al. “The usefulness of the Phalen test and the Hoffmann-Tinel sign in the diagnosis of carpal tunnel syndrome.”  Acta Orthopaedica Belgica 2002, N° 2 (Vol. 68/2) p.141

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10 – Britz et al. “Carpal tunnel syndrome: correlation of magnetic resonance imaging, clinical, electrodiagnostic, and intraoperative findings.”  Neurosurgery. 1995 Dec;37(6):1097-103

11 – Moran et al. “Sonographic measurement of cross-sectional area of the median nerve in the diagnosis of carpal tunnel syndrome: correlation with nerve conduction studies.”  J Clin Ultrasound. 2009 Mar-Apr;37(3):125-31

12 – Peters-Veluthamaninga et al. “Randomised controlled trial of local corticosteroid injections for carpal tunnel syndrome in general practice.”  BMC Fam Pract. 2010 Jul 29;11:54

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14 -Premoselli et al. “Neutral wrist splinting in carpal tunnel syndrome: a 3- and 6-months clinical and neurophysiologic follow-up evaluation of night-only splint therapy.”  Eura Medicophys. 2006 Jun;42(2):121-6

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24 – Thomsen et al. “Clinical outcomes of surgical release among diabetic patients with carpal tunnel syndrome: prospective follow-up with matched controls.”  J Hand Surg Am. 2009 Sep;34(7):1177-87

25 – Keiner et al. “Long-term follow-up of dual-portal endoscopic release of the transverse ligament in carpal tunnel syndrome: an analysis of 94 cases.”  Neurosurgery. 2009 Jan;64(1):131-7

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39 – Caliandro et al. “Distribution of paresthesias in Carpal Tunnel Syndrome reflects the degree of nerve damage at wrist.”  Clin Neurophysiol. 2006 Jan;117(1):228-31

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