Carpal Tunnel Syndrome is a common problem which
interferes with the normal use of the hand. Typical symptoms are
pain and a pinching or tingling feeling in the fingers, hand and
wrist. The pain may even radiate up to the shoulder. People affected
may feel weakness in the hand, drop things, and frequently wake up
in the middle of the night with numbness and tingling.
Findings: Plain radiographs are useful for
evaluating the wrist and carpal bones for trauma and fractures
(especially the hook of the hamate and the tubercle of the
trapezium), severe osteoarthritis, and other arthropathies.
Degree of Confidence: Plain films are of limited use in diagnosing
or evaluating carpal tunnel syndrome. Plain films are not useful for
evaluating the small soft tissue structures of the carpal tunnel,
many of which can cause the syndrome. Only a very rough idea of the
cross-sectional area of the carpal tunnel is provided using a carpal
tunnel view of the wrist.
CT is useful for its ability to display and evaluate the
cross-sectional volume of the carpal tunnel and for detecting subtle
calcification in the tendons within the canal. CT also provides an
excellent tool for evaluating the carpal bones through multiplanar
and 3-dimensional reconstructions.
False Positives/Negatives: CT is limited in its ability to visualize
the median nerve and tendons of the carpal tunnel well enough to
allow definitive differential diagnoses to be rendered. Therefore,
other methods of visualizing the soft tissues of the carpal tunnel
In patients with flexor tenosynovitis, axial MRI demonstrates bowing
of the flexor retinaculum.
Inflamed synovium and tendon sheaths demonstrate low signal
intensity on T1-weighted images and increased signal intensity on
T2-weighted, T2*-weighted, and short tau inversion recovery (STIR)
Regardless of the etiology of carpal tunnel syndrome, changes in the
median nerve are similar and include the following:
Diffuse swelling or segmental enlargement of the median nerve may be
demonstrated (usually seen best at the level of the pisiform).
The median nerve may flatten (usually demonstrated best at the level
of the hamate).
Palmar bowing of the flexor retinaculum may be noted (usually
demonstrated best at the level of the hamate).
MRI also is useful in detecting and characterizing space-occupying
lesions, such as neuromas, ganglion cysts, lipomas, and hemangiomas.
ULTRASOUND Section 6 of 8
Findings: The development of high-resolution ultrasound (US)
transducers (7-15 MHz) has allowed evaluation of normal and abnormal
US appearances of the median nerve and adjacent tendons.
High-resolution US allows noninvasive imaging of the carpal tunnel
and its contents. It has several advantages over MRI, including
being relatively fast and inexpensive and allowing additional
dynamic and blood flow imaging with relatively little additional
On transverse US scans, the normal median nerve is elliptical and
flattens progressively as it courses distally. On US, median nerve
compression reveals the classic triad of nerve flattening in the
distal tunnel, nerve swelling at the level of the distal radius
(less frequently in the proximal tunnel), and palmar bowing of the
Carpal Tunnel Syndrome is a condition
affecting the hand and wrist. The carpal tunnel is a space in the
wrist surrounded by wrist bones and by a rigid ligament that links
the bones together
Through this small tunnel pass the flexing tendons of the fingers
and thumb as well as the median nerve (see Figure 2). These tendons
attach muscles to bones in the hand and transfer the movement of the
fingers from muscles to bones. The median nerve carries signals
from the brain to control the actions of the fingers and hand.
It also carries information about temperature, pain and touch from
the hand to the brain, and controls the sweating of the hand.
The thumb, index, middle and ring fingers are under the control of
the median nerve
In the carpal tunnel, the tendons of the fingers surround the median
nerve. Swelling of the tendons reduces the space in the tunnel and
squeezes the median nerve which is softer than the tendons. Pressure
on this nerve can injure it.
Such injury results in sensations of numbness, tingling, pain, and
clumsiness of the hand. This combination of symptoms is called
carpal tunnel syndrome. People with carpal tunnel syndrome
experience difficulty in performing tasks such as unscrewing bottle
tops, fastening buttons, or turning keys.
Carpal tunnel syndrome is particularly associated with certain
- repetitive hand motions
- awkward hand positions
- strong gripping
- mechanical stress on the palm
Non-occupational factors of carpal tunnel syndrome
Carpal tunnel syndrome is associated with several diseases and
situations. They are:
- amyloidosis (infiltration of the liver, kidneys, spleen with a
- hypothyroidism (subnormal activity of the thyroid gland)
- tumours of tendon sheaths
- wrist fractures and dislocations
- wrist cysts
- use of oral contraceptives
- gynecological surgery
All these diseases and situations increase the volume of the
contents of the carpal tunnel, resulting in compression of the
median nerve. Also some individual factors, such as the size and
shape of the wrist and the shape of the median nerve, may contribute
to the development of carpal tunnel syndrome.
When symptoms of carpal tunnel syndrome are mild or likely to be
temporary, treatment includes rest, anti-inflammatory drugs, and a
metal splint. Even if a patient wears a splint that has been
prescribed, he or she should avoid the activities that caused or
aggravate the injury. Where this is not possible, patients should
wear the splint after work and particularly during sleeping hours.
Surgery may be necessary if the symptoms are severe and if the other
measures do not provide any relief. Surgery should not be the first
choice for treatment. Even after surgery, a number of patients may
still have some problems. Weakness of grip in the operated hand
persists in about 30 percent of cases.
Diagram and radiograph of the Carpal Tunnel
Image 2 Ultrasound image of the carpal
Image 2 MRI image of the carpal tunnel