Carpal tunnel syndrome

Medical warning

Carpal tunnel syndrome is a set of functional and physical signs linked to the suffering of the median nerve at the wrist by its compression (by elevation of the pressure within the carpal tunnel).
This syndrome results from many diseases, conditions and accidents.
The subject feels numbness (hypoesthesia), a tingling of the "middle" fingers, radiating arm pain and a motor deficit. Functional and physical table is amended by age or gender, or ethnicity or occupation and is caused by or associated with General diseases or local factors.

Anatomy of the carpal: reports of the median nerve

Carpal tunnel is the transition zone between the forearm and the hand. It is located in the joint of the hand.
This area represents an arch, bounded by the second row of the bones of the Carpus and closed to the ventral side by the anterior annular ligament of the Carpus (also called the flexor retinaculum).
Inside of this structure are the flexor tendons of the fingers and the median nerve.
When there is oedema or inflammatory damage to the sheath of flexor muscles, therefore an increase of pressure, causing a compression of the median nerve syndrome. This compression can lead to irreversible damage to the nerve.

Epidemiology

The annual incidence in the United States is around 400 cases per 100,000 inhabitants.
This is the most common occupational musculoskeletal disorder impairment in most western countries. Compression of the median nerve would increase to chronicity (stops working in series) with disabilities in 5-10% of cases.

Causes and contributing factors

Carpal tunnel syndrome is a compression of the median nerve in an inextensible channel formed by the bones of the Carpus backwards and the anterior annular ligament of the CARP ahead.
There are 2 different mechanisms of compression:
By increasing the volume of the tendons (suite a high loading, repetitive gestures combined to force, push-ups and friction of the too large tendons). When these structures will inflame, they swell (tendinitis or tenosynovites), they compress the median nerve. And more they rub against the other, more the inflammatory reflex is maintained.
By decrease of the diameter of the carpal tunnel, when the front of the wrist is resting on a surface (on the edge of a desk for example, or when regular strikes are applied with the Palm of the hand), or when the wrist is in hyper-extension: some carpal bones will slide forward as the hamatum coupled to the fact that the annular ligament tightens resembling the string of a bow thus decreasing the diameter of the channel, and compressing the median nerve and tendons on the bones of the Carpus.
There are in theory of multiple contributing factors known and described but relatively rare: bone abnormalities protruding into the canal, hormonal changes in women, kidney dialysis, obesity etc. There appears to also be a genetic  predisposition.
This syndrome occurs more often in women, or everything at least in subjects at thin wrist with regard to the length of the hand.
The syndrome is most common in the case of diabetes, hypothyroidism, myeloma or Sarcoidosis. Pregnancy can be a risk factor.
Part of the work environment may also explain the emergence of this syndrome: working in the cold, ergonomics of the work station...

Diagnosis

Symptoms

The symptoms are on the whole or a part, only in the anatomical territory of the median nerve. Carpal tunnel syndrome occurs bilaterally in over half of the cases.
Syndrome is expressed by tingling, numbness, tingling or electric shocks in the fingers. It requires the patient to raise their hand. The patients have said often that their hand was swollen, numb, sleeping, dead, its circulation seems stopped, it feels awkward. There is a weakness of the clamp thumb-index, decreased muscle mass (atrophy) of the thenar (under the thumb) eminence. The onset is usually gradual and the acute form remains quite rare.
Pain are typically nocturnal, waking the patient, forcing them to stand. Symptoms can appear only in the morning or be repeated several times during the night. In the day, the pain may be triggered by certain movements or the maintenance of position during activities such as call, read the newspaper, lead, knit... Crafts exceptional professional or leisure, or usual (such as computer video games), but intense, are sometimes the source of the outbreak of the syndrome.

Clinical examination

The clinical examination sometimes shows vasomotor disturbances (Acrocyanosis or finger blue, sometimes accompanied by pain in Raynaud's syndrome).
Alteration of the sensitivity of the hand can be detected by a Weber test.
Examination of the muscle shows that there may be a loss of the strength.

Complementary examinations

Electromyogram (EMG), used for the first time by Simpson in 1956 6 serves to examine the median nerve and would allow specialists to see if there is any nerve damage. It shows an increase in motor latency and decrease in nerve conduction. A normal EMG would, according to some, help to show a severe form of carpal tunnel syndrome from a normal form.
Except for very special cases, rheumatoid arthritis, hemodialysis, or anterior dislocation of the lunate, the expenditure for a routine radio is excessive. X-ray of the wrist, according to the incidence of carpal (hand glued to the plate, and perpendicular forearm), exceptionally would appreciate the mechanism. On the other hand, comparison of two shots face willingly the most affected side show (default user) demineralisation in substantiated cases...
Very good ultrasound of the nerve trunk could be interesting in the vast majority of common forms.
Other imaging (scanner, magnetic resonance imaging) are not systematically made, and that, even in cases, including failure of surgery (the release was generally insufficient: incision "sharp" or "low" and not "enough" long"), or atypical forms (forms to the effort or extrinsic compression).
The biological assessment shows nothing special. To systematically look for diabetes, non-exceptional association and promotes an extension of compression to the "high" part of the annular ligament, source of "bad outcome" If unknown.

 differential diagnosis

The most common are violations of C6 - C7, the syndrome of thoracic nerve root and peripheral neuropathy, the round pronator, damage of the anterior interosseous nerve syndrome.

Treatment

In moderate forms a medical treatment can be proposed. In more severe forms the surgery appears to preferable. Severe forms occur more often in the elderly.
Recurrences are not uncommon after medical treatment, but are exceptional after surgery.

Medical treatment

Derivatives cortisones into the canal (infiltration) injections can be effective for some weeks.
In  moderate forms, a wrist brace can often calm down the symptoms  It can be worn only at night. This improvement of symptoms is sometimes short-lived, forcing then to opt for surgery.
Drugs combining diuretics and anti-inflammatory have not demonstrated in a straightforward manner their effectiveness. It is the same for alternative techniques: laser, ultrasonic or yoga.

When possible, we recommend that you reduce repetitive strain, in particular exposure to vibration.

Surgical treatment

It is based on the neurolysis allowing the release of the median nerve of the structures which compress it. Surgery, regardless of the technique, open pit or by endoscopy, gives very good results.
Some very tight channels are not available to the endoscopy without major risk: these are the indisputable operative indications. It consists of the section of the anterior annular ligament of the carp. The endoscopic technique improves the result in the first three weeks but there is no significant difference in the medium and long term results. There is however a risk of injury to the median nerve by endoscopic that should not be overlooked.
A prolonged rest is necessary before the resumption of a demanding manual labour. A re-education is useful (a foam ball manipulation). Sham patients sometimes complain of some residual pain, a slight loss of grip force.
The post-operative are generally good: one person in six has, however, persistent pain but this can vary.  But there are complications: algodystrophy, infection (in about 1% of cases), recidivism.