Carpal tunnel syndrome (CTS) is an entrapment neuropathy caused by compression of the median nerve as it travels through the wrist's carpal tunnel. It is the most common nerve entrapment neuropathy, accounting for 90% of all neuropathies. Early symptoms of carpal tunnel syndrome include pain, numbness, and paresthesias. These symptoms typically present, with some variability, in the thumb, index finger, middle finger, and the radial half (thumb side) of the ring finger. Pain also can radiate up the affected arm. With further progression, hand weakness, decreased fine motor coordination, clumsiness, and thenar atrophy can occur.
In the early presentation of the disease, symptoms most often present at night when lying down and are relieved during the day. With further progression of the disease, symptoms will also be present during the day, especially with certain repetitive activities, such as when drawing, typing, or playing video games. In more advanced disease, symptoms can be constant.
Typical occupations of patients with carpal tunnel syndrome include those who use computers for extended periods of time, those who use equipment that has vibration such as construction workers, and any other occupation requiring frequent, repetitive movement.   
Carpal tunnel syndrome results from increased pressure carpal tunnel pressure and subsequent compression of the median nerve. The most common causes of carpal tunnel syndrome include genetic predisposition, history of repetitive wrist movements such as typing, or machine work as well as obesity, autoimmune disorders such as rheumatoid arthritis, and pregnancy. 
In the United States, carpal tunnel syndrome has an incidence of 1 to 3 persons per 1000 per year, with a prevalence of 50 per 1000, with similar incidence and prevalence in most developed countries. It most commonly affects whites, has up to a 10 to 1 predominance in females, and has a peak age of 46 to 60. 
Carpal tunnel syndrome (CTS) is multifactorial, and often results from multiple patient-specific, occupational, social, and environmental risk factors. A single, specific cause is not always determined unless there is, for example, a space-occupying lesion that can be attributable to patient-reported symptoms. While this can be appreciated in select medical conditions (e.g., gout), these relatively straightforward clinical presentations are relatively uncommon in comparison to most presentations of CTS.
In general, the pathophysiology of CTS results from a combination of compression and traction mechanisms. The compressive element of the pathophysiology includes a detrimental cycle of increased pressure, obstruction of overall venous outflow, increasing local edema, and compromise to the median nerve's intraneural microcirculation. Nerve dysfunction becomes compromised, and the structural integrity of the nerve itself further propagates the dysfunctional environment-- the myelin sheath and axon develop lesions, and the surrounding connective tissues become inflamed and lose normal physiologic protective and supportive function. Repetitive traction and wrist motion exacerbates the negative environment, further injuring the nerve. In addition, any of the nine flexor tendons traveling through the carpal tunnel can become inflamed and compress the median nerve. 
Patients often report numbness, tingling, and pain that increase at night. Weakness, clumsiness, and temperature changes also are common complaints. The thumb, digits 2 and 3, and the radial half of digit 4 are typically affected. Patients with carpal tunnel syndrome often will have a positive "flick sign," meaning that symptoms improve when they flick their hand and wrist. Patients often find some relief with ice, rest if provoked by repetitive activity, and night splints.
Electromyography and nerve conduction studies are the basis for carpal tunnel syndrome diagnosis. Other clinical or special exams do not confirm carpal tunnel syndrome but do assist in ruling out other diagnoses. These findings can prompt electromyography and nerve conduction studies.
The clinical physical exam may include testing for sensory and motor deficits and evidence of thenar wasting. There are several special tests with varying degrees of sensitivities and specificities.
If carpal tunnel syndrome is identified early, conservative treatment is recommended. Initially, the patient should be instructed in modifying symptom provoking wrist movement. This can be through proper hand ergonomics such as placing the keyboard at a proper height and minimizing flexion, extension, abduction, and adduction of the hand when typing. It should be recommended to decrease repetitive activities if possible. Counseling on weight loss and increasing aerobic activity also can be beneficial. A properly fitted nighttime wrist splint can be offered. An occupational therapist trained in hand therapy also may be a beneficial referral. Combined therapy may be more beneficial than any single treatment. A short course of nonsteroidal anti-inflammatory medication can relieve symptoms but some do not feel it of adequate benefit.
If conservative treatments are not successful, an oral or local glucocorticoid could be offered. The definitive treatment for persistent carpal tunnel syndrome is surgical intervention with carpal tunnel release after nerve conduction studies showing significant axonal degeneration. Carpal tunnel release typically is performed by an orthopedic surgeon or hand surgeon. This procedure can be performed either open or endoscopically. Carpal tunnel release is considered a minor surgery in which the transverse carpal ligament or flexor retinaculum is cut, opening more space in the carpal tunnel and decreasing pressure on the median nerve. It does not typically require overnight hospitalization.   
The carpal tunnel includes the median nerve and nine flexor tendons. The flexor tendons include the four tendons from the flexor digitorum profundus, four tendons from the flexor digitorum superficialis, and one tendon from the flexor pollicis longus. The transverse carpal ligament (flexor retinaculum) makes up the superior boundary, and the carpal bones form the inferior border.
|||Why do local corticosteroid injections work in carpal tunnel syndrome, but not in ulnar neuropathy at the elbow?, Mezian K,Bruthans J,, Muscle & nerve, 2016 May 3 [PubMed PMID: 27144462]|
|||Neurological assessment., Maher AB,, International journal of orthopaedic and trauma nursing, 2016 Feb 26 [PubMed PMID: 27118633]|
|||Akhondi H,Varacallo M, Anterior Interosseous Syndrome null. 2018 Jan [PubMed PMID: 30247831]|
|||Sevy JO,Varacallo M, Carpal Tunnel Syndrome null. 2018 Jan [PubMed PMID: 28846321]|
|||Hegmann KT,Merryweather A,Thiese MS,Kendall R,Garg A,Kapellusch J,Foster J,Drury D,Wood EM,Melhorn JM, Median Nerve Symptoms, Signs, and Electrodiagnostic Abnormalities Among Working Adults. The Journal of the American Academy of Orthopaedic Surgeons. 2018 Aug 15 [PubMed PMID: 30028751]|
|||Pester JM,Varacallo M, Nerve Block, Median null. 2018 Jan [PubMed PMID: 29083641]|
|||Utilization of Preoperative Electrodiagnostic Studies for Carpal Tunnel Syndrome: An Analysis of National Practice Patterns., Sears ED,Swiatek PR,Hou H,Chung KC,, The Journal of hand surgery, 2016 Apr 8 [PubMed PMID: 27068003]|
|||Mooar PA,Doherty WJ,Murray JN,Pezold R,Sevarino KS, Management of Carpal Tunnel Syndrome. The Journal of the American Academy of Orthopaedic Surgeons. 2018 Mar 15 [PubMed PMID: 29420323]|
|||Raizman NM,Blazar PE, AAOS Appropriate Use Criteria: Management of Carpal Tunnel Syndrome. The Journal of the American Academy of Orthopaedic Surgeons. 2018 Mar 15 [PubMed PMID: 29432365]|
|||Benson DC,Varacallo M, Anatomy, Shoulder and Upper Limb, Hand Flexor Pollicis Longus Muscle 2019 Jan; [PubMed PMID: 30860725]|