Carpal Tunnel Syndrome: A Review


By Chris Faubel, MD —



  • 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.


  • 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]


  • 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.



1 – Atrosh et al.  “Prevalence of carpal tunnel syndrome in a general population.“  JAMA. 1999 Jul 14;282(2):153-8.

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.

3 – Margolis W, Kraus JF. “The prevalence of carpal tunnel syndrome symptoms in female supermarket checkers.”  J Occup Med. 1987 Dec;29(12):953-6

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

7 – Novak et al. “Provocative sensory testing in carpal tunnel syndrome.”  The Journal of Hand Surgery. Volume 17, Issue 2, April 1992, Pages 204-208

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

9 – D’Arcy CA, McGee S.  “The rational clinical examination. Does this patient have carpal tunnel syndrome?”  JAMA. 2000 Jun 21;283(23):3110-7.

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

13 – Amirjani et al. “Corticosteroid iontophoresis to treat carpal tunnel syndrome: a double-blind randomized controlled trial.”  Muscle Nerve. 2009 May;39(5):627-33

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

15 – Graham et al. “A prospective study to assess the outcome of steroid injections and wrist splinting for the treatment of carpal tunnel syndrome.”  Plast Reconstr Surg. 2004 Feb;113(2):550-6

16 – Dammers et al. “Injection with methylprednisolone in patients with the carpal tunnel syndrome: a randomised double blind trial testing three different doses.”  J Neurol. 2006 May;253(5):574-7

17 – Chang et al. “Oral drug of choice in carpal tunnel syndrome.”  Neurology. 1998 Aug;51(2):390-3

18 – O’Connor et al. “Non-surgical treatment (other than steroid injection) for carpal tunnel syndrome.”  Cochrane Database Syst Rev. 2003;(1):CD003219

19 – Garfinkel et al. “Yoga-based intervention for carpal tunnel syndrome: a randomized trial.”  JAMA. 1998 Nov 11;280(18):1601-3

20 – Burke et al. “Splinting for carpal tunnel syndrome: in search of the optimal angle.”  Arch Phys Med Rehabil. 1994 Nov;75(11):1241-4

21 – Ebenbichler et al. “Ultrasound treatment for treating the carpal tunnel syndrome: randomised “sham” controlled trial.”  BMJ. 1998 Mar 7;316(7133):731-5

22 – Brown et al. “Carpal tunnel release. A prospective, randomized assessment of open and endoscopic methods.”  J Bone Joint Surg Am. 1993 Sep;75(9):1265-75

23 – Verdugo et al. “Surgical versus non-surgical treatment for carpal tunnel syndrome.”  Cochrane Database Syst Rev. 2003;(3):CD001552

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

26 – Bland. “Treatment of carpal tunnel syndrome.”  Muscle Nerve. 2007 Aug;36(2):167-71

27 – Padua et al. “Natural history of carpal tunnel syndrome according to the neurophysiological classification.”  Ital J Neurol Sci. 1998 Dec;19(6):357-61

28 – Ortiz-Corredor et al. “Natural evolution of carpal tunnel syndrome in untreated patients.”  Clin Neurophysiol. 2008 Jun;119(6):1373-8

29 – Padua et al. “Incidence of bilateral symptoms in carpal tunnel syndrome.”  J Hand Surg Br. 1998 Oct;23(5):603-6

30 – Lim et al. “The role of wrist anthropometric measurement in idiopathic carpal tunnel syndrome.”  J Hand Surg Eur Vol. 2008 Oct;33(5):645-7

31 – Stevens et al. “The frequency of carpal tunnel syndrome in computer users at a medical facility.”  Neurology. 2001 Jun 12;56(11):1568-70.

32 – Andersen et al. “Computer use and carpal tunnel syndrome: a 1-year follow-up study.”  JAMA. 2003 Jun 11;289(22):2963-9

33 – Rempel et al. “Intensive keyboard use and carpal tunnel syndrome: Comment on the article by Atroshi et al.”  Arthritis Rheum. 2008 Jun;58(6):1882-3

34 – Atroshi et al. “Carpal tunnel syndrome and keyboard use at work: a population-based study.”  Arthritis Rheum. 2007 Nov;56(11):3620-5

35 – Finsen et al. “Carpal tunnel syndrome during pregnancy.”  Scand J of Plas and Reconst Surg and Hand Surg  2006, Vol. 40, No. 1 , Pages 41-45

36 – Padua et al. “Systematic review of pregnancy-related carpal tunnel syndrome.”  Muscle Nerve. 2010 Nov;42(5):697-702

37 – Niempoog et al. “Local injection of dexamethasone for the treatment of carpal tunnel syndrome in pregnancy.”  J Med Assoc Thai. 2007 Dec;90(12):2669-76

38 – Sharifi-Mollayousefi et al. “Assessment of body mass index and hand anthropometric measurements as independent risk factors for carpal tunnel syndrome.”  Folia Morphol (Warsz). 2008 Feb;67(1):36-42

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

40 – Chan et al. “The relationship between electrodiagnostic findings and patient symptoms and function in carpal tunnel syndrome.”  Arch Phys Med Rehabil. 2007 Jan;88(1):19-24

41 – Sawaya et al. “When is the Phalen’s test of diagnostic value: an electrophysiologic analysis?”  J Clin Neurophysiol. 2009 Apr;26(2):132-3

42 – Bland JD. “Do nerve conduction studies predict the outcome of carpal tunnel decompression?”  Muscle Nerve. 2001 Jul;24(7):935-40


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