History and exam

Key diagnostic factors

common

presence of risk factors

Key risk factors include age between 40 and 60 years, female sex, high BMI, pregnancy, and diabetes.

numbness of hand(s)

Dominant hand is usually the first and worst affected. Extreme caution should be exercised in diagnosing CTS if there are no sensory complaints in hand(s).

night-time worsening

Waking up at night-time with paraesthesias/pain in hand/wrist, and shaking the hand to relieve symptoms, is classic for CTS.

numbness in median nerve distribution

Should be sparing of thenar eminence (supplied by palmar branch) and other peripheral nerve territories (ulnar and radial in particular).

uncommon

numbness confined to palmar aspect of the first 4 fingers

Associated with the median nerve distribution. However, many patients with CTS complain of numbness of the whole hand.

Other diagnostic factors

common

symptoms are intermittent

This is typical of CTS, whereas most differential diagnoses are associated with constant symptoms.

onset is gradual

Helps to rule out other major differential diagnoses, such as radiculopathy, that are acute.

weakness of hand

Decreased strength, particularly for rotational movements (e.g., opening jars or turning a wrench).

clumsiness

In particular, dropping things or difficulty doing fine-motor tasks.

aching and pain in arm

Typically, radiating from ventral aspect of wrist proximally to forearm and upper arm.

weakness of thenar muscles (abductor pollicis brevis, or APB, in particular)

Test for thumb abduction at 90° to plane of palm. Abductor pollicis longus will compensate for weak APB.

normal reflexes

Biceps, brachioradialis, triceps, and long finger flexor reflexes should be normal in pure CTS and help in ruling out radiculopathy in particular.

uncommon

finger stiffness

Difficulty flexing and extending fingers, worse on first awakening.

cold sensitivity

Some patients complain of vasomotor symptoms similar to Raynaud's phenomenon, presumably due to involvement of sympathetic fibres travelling with the median nerve.

atrophy of thenar eminence

If present can indicate severe CTS. The thenar eminence can also appear flattened due to underlying joint deformity (e.g., osteoarthritis of carpometacarpal joint).

Risk factors

strong

age 40-60 years

The peak onset of carpal tunnel syndrome (CTS) is usually between 40 and 60 years.[1][2][4][5]​​ 

high BMI

There is a positive correlation between increasing BMI and increasing risk of CTS. Being obese (BMI >29.9) may carry over twice the risk of having CTS versus being non-obese. The reason for this association is not clear.[1]​​​[3][15]​​[16]​​​​​

female sex

CTS is more common in women than in men, for reasons that are not clear.[1][2]​​​[3][4]​​

fractured wrist/carpal bones

Previous wrist fracture more than doubles the risk of CTS.

CTS can present acutely at the same time as the fracture, probably from direct trauma to the nerve or from haemorrhage and oedema causing an acute rise in carpal tunnel pressure. Subacute presentation may be at least in part due to external compression from casts or splints, or from increased force through the wrist during rehabilitation. Chronic CTS may be due to a decrease in space in the carpal tunnel from callus or deformity.[17][16]

diabetes

People with both type 1 and type 2 diabetes have an increased risk of CTS.[3]​ Potential underlying mechanisms include an increased susceptibility to compression in nerves affected by polyneuropathy, and musculoskeletal abnormalities that cause tenosynovitis and limited joint motion.​[16][19][20]​​​​​[21]

pregnancy

The prevalence of CTS may range from 7% to 62% during pregnancy, with symptoms often persisting into the postnatal period. Possible mechanisms include oedema and hormonal changes.[3]

congenital carpal tunnel stenosis

Variations in the anatomy of the carpal tunnel might be inherited. Most notably, congenital carpal tunnel stenosis may predispose an individual (or family) to the development of CTS.[7][8]

weak

square wrist

Squarer-shaped wrists may be associated with the development of CTS, particularly if the ratio of wrist depth to wrist width is greater than 0.7.[18]​ 

rheumatoid arthritis

Some studies have shown a weak association between arthritis and increased risk of CTS, but this remains under debate. Presumably the main mechanism is due to a narrowing of the carpal tunnel from thickening of the wrist joint synovium and tendon sheaths.[3]​​[16]​​

occupational exposure

Occupations involving repetitive bending or twisting of the hands or wrists, or the use of vibrating tools (e.g., construction, manufacturing), may cause damage to the median nerve over time and increase the likelihood of CTS.[1][22]​​ The usual clinical presentation in CTS, whereby the dominant hand is affected first and most severely, would suggest that activity is a potential cause. However, in general, the importance of work is likely overstated, particularly once other risk factors (e.g., BMI) are taken into consideration.[2]​​[23]​​[24][25]​​​​​

tobacco smoking

Some studies have reported an association between tobacco smoking and CTS; however, evidence remains conflicting.[3]

thyroid disorders

There is a possible link between hypothyroidism and CTS. In general, the strength of the association lessens once other risks factors are controlled for (e.g., BMI).[3]​​​[19]​​​[21]

significant computer use

The association between significant use of a computer keyboard and/or mouse, for example through a person's occupation, and CTS remains controversial.[1][3][23] The suggested mechanism is that computer overuse is a source of mechanical stress on the median nerve, but evidence from robust studies is lacking.[3]

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