Carpal tunnel syndrome (CTS) is the complex of symptoms and signs caused by dysfunction of the median nerve due to trauma or compression as it travels through the carpal tunnel.
Median nerve compression results from either a decrease in the size of the carpal tunnel, an increase in the size of its contents, or increased susceptibility of the nerve to pressure.
Epidemiology including risk factors and primary prevention
- Estimated prevalence of 3 to 5% in the general population 1
- In patients with nerve conduction study (NCS) evidence of CTS in one hand, the contralateral asymptomatic hand will show NCS abnormalities about 50% of the time.2
- Most frequent compressive focal mononeuropathy seen in clinical practice1
- Known risk factors include:
- Female sex
- Decreased cross-sectional area of carpal tunnel
- Hormonal factors may play a role
- Pregnancy, oral contraceptives, hormone replacement therapy increase risk
- Oophorectomy appears to reduce incidence3
- Inflammatory/connective tissue diseases
- Rheumatoid arthritis
- Diabetes mellitus and the metabolic syndrome
- Familial and congenital CTS
- Anatomic “square wrist”
- Ratio of AP to mediolateral diameter at wrist crease >0.7
- Wrist/hand fractures
- Mass lesions
- Wheelchair use
- Prolonged or repeated wrist flexion/extension
- High levels of hand force
- Prolonged use of hand-held vibratory tools
- No clear association has been established between computer work and CTS
- The carpal tunnel is formed by the flexor retinaculum on the volar surface and carpal bones dorsally.
- Traversing through this tunnel are the median nerve and 9 flexor tendons of the forearm (flexor pollicis longus and the four flexor digitorum superficialis and four flexor digitorum profundus tendons).
- Increased median nerve pressure or sensitivity leads to myelin injury secondary to ischemia and mechanical disruption.
- Pressures are greater in wrist extension than flexion4
- Sensory fibers appear to be more sensitive to compression and are routinely affected prior to motor fibers.
Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)
- New onset/acute
- Intermittent numbness, tingling, pain and/or burning in the radial 3-1/2 digits
- Nocturnal paresthesias
- Persistence or worsening of acute symptoms/signs
- Sensory symptoms may progress from intermittent to persistent as CTS worsens.
- Progression leads to weakness of the hand and coordination deficits.
- Fixed sensory loss is often a late finding.
- CTS may progress without worsening of symptoms.
- Late-stage CTS can become difficult to treat and may not respond to even surgical decompression.
- About one in five patients will show improvement with no intervention other than modifying their hand activities.1
- Not applicable
ESSENTIALS OF ASSESSMENT
- Presentation most commonly includes paresthesias affecting the median innervated first 3½ digits, with symptoms worsening at night.5
- Although sensory symptoms are usually limited to median-innervated fingers, there exists a wide range of variability in presentation which can include the entire hand and proximal extremity.6
- May complain of deep aching pain in the hand and wrist
- Symptoms may be worsened by activities such as driving or reading.5
- Report relief by shaking their hands (flick sign) or by placing them under warm water
- (+) flick sign predicted electrodiagnostic abnormality in 93% of cases7
- Evaluation should include the cervical spine, shoulder, and elbow.
- Findings may be normal in mild cases.
- Sensory findings
- Objective sensory deficits may be detected involving the median-innervated fingers, but sparing the thenar eminence as the palmar cutaneous sensory branch arises proximal to the carpal tunnel.
- 2-point discrimination is generally affected before pain and temperature.
- Motor findings
- Objective weakness can occur in advanced CTS, manifesting as weakness of thumb abduction and opposition.
- Atrophy of the thenar eminence may be observed.
- Provocative tests may reproduce patient’s paresthesias into the hand in those with CTS and include:
- Tinel’s sign 67% sensitive and 68% specific 8
- Phalen’s test 85% sensitivity and 89% specificity 8
- Carpal compression test (87-89% sensitive9)
- A reasonable approach is to screen with the Tinel’s sign and if negative, check the more sensitive carpal compression test.
- A detailed occupational history includes the type of work performed, tools used and workstation design.
- The history should also include an assessment of all activities outside of work which may predispose to CTS.
- While laboratory studies are not used to diagnose CTS, they may be utilized to screen for conditions that may predispose to the development of CTS.
- Ultrasound (US) is becoming increasingly used for the evaluation of CTS, with mounting data on its utility for both the diagnosis of CTS and identification of its underlying causes.10,11,12 Advantages include:
- Ability to perform dynamic assessment
- Ability to detect an underlying abnormality (i.e., a mass)
- Capacity to identify a systemic disease process such as rheumatoid arthritis or dialysis-related amyloidosis
- US can confirm median nerve compression in individuals with signs/symptoms of CTS and normal NCS.11
- US demonstrates enlargement of the median nerve at the carpal tunnel inlet in individuals with CTS. Diagnosis may be based on absolute measurement of median nerve cross-sectional area (e.g. ≥ 10 mm2)12 or relative enlargement compared to a forearm measurement (e.g. wrist-to-forearm ratio ≥ 1.5).11
- Recent studies have demonstrated similar specificity and sensitivity to NCS for diagnosing CTS.12
- MRI is reserved for unusual cases (i.e. to evaluate for a mass).
Supplemental assessment tools
- Electromyography (EMG)
- NCS are the current reference standard for the diagnosis of CTS.
- EMG/NCS also screen for cervical radiculopathy, ulnar neuropathy, brachial plexopathy and proximal median neuropathy.
- The combined sensory index (CSI) has been shown to have the greatest sensitivity and specificity among NCS techniques.13
- Prolonged median sensory distal latency is usually the first abnormal finding on electrodiagnostic testing, secondary to damage to the myelin sheath.
- As CTS progresses, prolongation of the median distal motor latency will be noted on NCS.
- In more severe cases, axon loss may occur, resulting in a reduction of the median sensory nerve action potential amplitude or compound muscle action potential amplitude in association with abnormal findings on EMG of the abductor pollicis brevis (APB).
- In mild cases there may be an absence of abnormalities with an estimated 15% false negative rate.14
Early predictions of outcomes
- Symptoms of untreated patients with minimal or mild compression tended to worsen over the first year, while those with initially moderate or severe involvement tended to improve.
- Factors that have been associated with a failure of conservative therapy include long duration of symptoms (>10 months), age >50, constant paresthesias, and impaired 2-point discrimination.
- In approximately 50% of cases where CTS occurs in one wrist, the other will eventually become involved.
- Controversy remains regarding the role of workplace factors in the development of CTS.
- Food processing, construction, and manufacturing are occupations that have a higher incidence of CTS.
- Multiple studies have shown that keyboard use has no association with CTS 3,15,16,17
REHABILITATION MANAGEMENT AND TREATMENTS
Available or current treatment guidelines
The American Academy of Orthopaedic Surgeons (AAOS) provides guidelines for the treatment of CTS.
At different disease stages
- Conservative therapy for mild-moderate symptoms.
- Activity modification
- A nocturnal wrist splint or brace which maintains the wrist in neutral to 30° extension often provides significant symptom improvement. Splinted group had improved symptoms regardless of degree of median nerve impairment compared to control group18
- Tendon and nerve gliding exercises of the wrist and upper extremity are employed to maintain function and ROM.
- NSAIDs, vitamin B6, and oral steroids have been shown not to be of benefit.19
- Corticosteroid injectionINSTINCTS trial demonstrated superior clinical efficacy at 6 weeks compared to night splinting as a first-line treatment for mild-moderate CTS. Outcomes were similar to night splinting at 6 months.20
- Consider carpal tunnel release in severe CTS
- Constant symptoms
- Sensory loss
- APB weakness/thenar atrophy
- Corticosteroid injection
- Agarwal et al. (2005) reported marked symptom improvement in 93.7% of patients at 3 months21 and statistically significant benefit of symptoms at 6 months, as well as improvement in nerve conduction studies and decrease in cross-sectional area (i.e., swelling) of the nerve in the carpal tunnel.
- Regarding long-term outcomes, Evers et al. (2017) reported that 32% of patients did not require re-intervention. 63% ultimately went on to surgery.22
- A randomized trial by Roh et al. (2019) demonstrated similar symptomatic and functional outcomes between palpation-guided and ultrasound-guided carpal tunnel injection.23
- Carpal tunnel release for severe CTS
- Carpal tunnel release may be indicated when conservative treatment modalities have failed and in those with severe symptoms.
- The goal of carpal tunnel release is to expand the carpal tunnel via division of the transverse carpal ligament to relieve pressure on the median nerve.
- There is no definitive evidence supporting an open or endoscopic approach being more effective than the other.24There is limited evidence that the mini-open technique assisted by the Knifelight instrument is more effective than a standard open release at a follow-up of 19 months but not at 30.24
- Advantages: shorter recovery period, can be performed in office setting
- Rojo-Manaute et al. reported superior functional outcomes from the first week to the sixth month using an ultrasound-guided hook knife technique compared to a mini-open surgical technique, with functional scores (QuickDASH) approaching each other at 12 months.25,26
- The SX-One MicroKnife is a single-use device that employs a balloon catheter to establish a safe zone for transection of the transverse carpal ligament. Results comparable to mini-open and endoscopic release have been documented at 3 months.27
- Recurrence of CTS after successful treatment is rare, although some patients experience residual numbness, pain or weakness.
- If pain and symptoms return then surgery may be repeated.
- Consider ultrasound evaluation of median nerve at 3 months postop in patients with persistent symptoms.28
- No consensus exists regarding the optimal presurgical or postsurgical rehabilitation and treatment programs.
Pre-terminal or end of life care
Patient & family education
The AMA Guides to the Evaluation of Permanent Impairment
MEASUREMENT OF PATIENT OUTCOMES
- QuickDASH Outcome Measure
- The Carpal Tunnel Questionnaire (CTQ) has demonstrated a greater responsiveness to clinical change following release of the carpal tunnel than the Michigan Hand Outcomes Questionnaire (MHQ).
- The combined sensory index electrodiagnostic tool has been shown to effectively establish a correlation with clinical outcomes following surgical intervention for carpal tunnel syndrome.13
Translation into practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills
- Presentations of CTS will often include symptoms that do not fit a classical median nerve distribution.
- Anatomical variants may also contribute to symptoms outside of the typical median portion of the hand.
- A normal physical exam does not rule out CTS.
- Electrodiagnosis is the current reference standard. However, recent studies have demonstrated comparable diagnostic sensitivity and specificity with ultrasound.
- Diagnostic ultrasound should be considered in patients with signs/symptoms of CTS and normal NCS.
- Many non-surgical methods of treatment have proven benefit and warrant trials before carpal tunnel release in patients with mild-moderate CTS.
- Minimally-invasive ultrasound-guided techniques for carpal tunnel release can be performed in the office setting, have less morbidity compared to open or mini-open carpal tunnel release, and have been shown to have comparable short- to medium-term results.
CUTTING EDGE/EMERGING AND UNIQUE CONCEPTS AND PRACTICE
Cutting edge concepts and practice
- Diagnostic ultrasound has been demonstrated to have utility similar to NCS in diagnosing CTS.
- Outcomes appear to be similar between palpation-guided and ultrasound-guided carpal tunnel injections.
- Ultrasound guided carpal tunnel release has emerged as an alternative to open or endoscopic surgery for CTS.
GAPS IN THE EVIDENCE-BASED KNOWLEDGE
Gaps in the evidence-based knowledge
- Long-term follow-up data is lacking for outcomes of ultrasound-guided carpal tunnel release.
- Randomized prospective trials are needed to evaluate the effectiveness of ultrasound-guided versus standard surgical techniques.
- The optimal timing of surgery in the natural history of CTS has not been established.
- No evidence exists regarding the best technique for carpal tunnel injection, and ultrasound guidance has not been proven to improve outcomes.
- Outcomes of long-term serial carpal tunnel injections have not been studied.
- Stewart JD. Focal Peripheral Neuropathies. Philadelphia, PA: Lippincott, 2000.
- Padua L., et al. Incidence of bilateral symptoms in carpal tunnel syndrome. Journal of Hand Surgery (Br) 1998 Oct;23(5):603-6.
- Newington L, Harris EC, Walker-Bone K. Carpal Tunnel Syndrome and Work. Best Pract Res Clin Rheumatol. 2015 June; 29(3):440-453.
- Gelberman RH, Hergenroeder PT, Hargens AR, Lundborg GN, Akeson WH. The carpal tunnel syndrome: a study of carpal canal pressures. Journal of Bone and Joint Surgery. 1981:63(2): 380-383.
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- Padua L et al. Carpal tunnel syndrome: clinical features, diagnosis and management. Lancet Neurol. 2016; 15: 1273-84.
- Pryse-Phillips W. Validation of a diagnostic sign in carpal tunnel syndrome. J Neurol Neurosurg Psychiatry 1984;47:870-872.
- Bruske J., et.al. The Usefulness of the Phalens Test and the Hoffmann-Tinel sign in the Diagnosis of Carpal Tunnel Syndrome. Acta Orthopaedica Belgica. 2002 Apr;68(2):141-5.
- Malanga GA, Nadler SF. Musculoskeletal Physical Examination: An Evidence Based Approach. Philadelphia, PA: Elsevier, 2006.
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- Aseem F, William JW, Walker FO, Cartwright MS. Neuromuscular Ultrasound In Patients With Carpal Tunnel Syndrome and Normal Nerve Conduction Studies. Muscle Nerve. 2017; 55:913-916.
- Fowler JR, Cipolli W, Hanson T. A Comparison of Three Diagnostic Tests for Carpal Tunnel Syndrome Using Latent Class Analysis. J Bone Joint Surg Am. 2015; 97:1958-61.
- Malladi N, Micklesen PJ, Hou J, Robinson LR. Correlation between the combined sensory index and clinical outcome after carpal tunnel decompression: a retrospective review. Muscle & Nerve. 2010 Apr;41(4):453-457.
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- Keith T et al. Carpal tunnel syndrome and its relation to occupation: a systematic literature review. Occupational Medicine (Oxford). 2007 Jan;57(1):57-66.
- Atroshi I et al. Carpal tunnel syndrome and keyboard use at work: a population based study. Arthritis & Rheumatism. 2007 Nov;56(11):3620-5.
- Stevens JC et al. The frequency of carpal tunnel syndrome in computer users at a medical facility. Neurology. 2001 Jun;56(11):1568-70.
- Werner R et al. Randomized controlled trial of nocturnal splinting for active workers with symptoms of carpal tunnel syndrome. Arch Phys Med Rehabil. 2005 Jan;86(1):1-7.
- Huisstede BM, Hoogvliet P, Randsdorp MS, Glerum S, van Middelkoop M, Koes BW. Carpal tunnel syndrome. Part I: Effectiveness of nonsurgical treatments â€“ a systemic review. Arch of Phys Med and Rehab. 2010;91(7):981-1004.
- Chesterton LS et al. The clinical and cost-effectiveness of corticosteroid injection versus night splints for carpal tunnel syndrome (INSTINCTS trial): an open-label, parallel group, randomized controlled trial. Lancet. 2018; 392:1423-33.
- Agarwal V et al. A prospective study of the long-term efficacy of local methyl prednisolone acetate injection in the management of mild carpal tunnel syndrome. Rheumatology (Oxford). 2005 May;44(5):647-50.
- Evers S, Bryan AJ, Sanders TL, Gunderson T, Gelfman R, Amadio PC. Corticosteroid injections for Carpal Tunnel Syndrome: long-term follow-up in a population-based cohort. Plast Reconstr Surg. 2017; 140(2):338-347.
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- Li M, Jiang J, Zhou Q, Zhang C. Sonographic follow-up after endoscopic carpal tunnel release for severe carpal tunnel syndrome: a one-year neuroanatomical prospective observational study. BMC Musculoskeletal Disorders. 2019; 20(1):157
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Original Version of the Topic:
Michael Mehnert, MD. Carpal Tunnel Syndrome. Publication Date: 2011/11/10.
Previous Revision(s) of the Topic
Stephen Kishner, MD, John Faciane, MD, Casey Murphy, MD. Carpal Tunnel Syndrome. Publication Date: 05/05/2016.
William A. Anderson, MD
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