What is it ? (Definition)
The carpal tunnel syndrome is a compression of the median nerve at the wrist. It is the most common nerve compression in the upper extremity.
The carpal tunnel is a normal anatomical space whose floor is constituted by the carpal bones (small bones of the wrist), and roof by a thick ligament, called transverse carpal ligament (or flexor retinaculum).
Through the carpal tunnel goes the median nerve, which controls smalls but importants muscles of hand (thenarian muscles and lumbrical muscles) and also provides the sensitivity of thumb, index and middle finger.
Inside the carpal tunnel, the median nerve is surrounded by flexor tendons, themselves surrounded by a sheath facilitating their gliding : the synovial sheath.
If the synovial sheath becomes thicker, or if the transverse carpal ligament becomes tighter, the pression on the median nerve increases, leading to its disfunction.
On early stages, sensations of tickeling (paresthesias) and/or numbness appears in the fingers, especially at night and in the morning.
Later on, a lack of strength may develop (motor deficiency), eventually associated with an diminished volume of the thenarian muscles (muscular atrophy or amyotrophy).
Usually, no specific ethiology is found, and the carpal tunnel syndrome is then called « idiopathic ». Nevertheless, some co-factors are sometimes associated, such as diabetis, pregnancy, hypothyroïdia, rheumatoïd arthritis, etc.
How to diagnose it ? (Presentation)
The diagnosis is usually easy, based on history and physical examination.
A nerve conduction study or Electromyogram (EMG) is generally realized prior to treatment, in order to confirm the diagnosis and define the lesions precisely.
If the nerve fibers are intacts but transmit the electric signal slower, we talk about a « conduction block ». Those lesions are usually reversible.
If some nerve fibers are structurally damaged and do not conduct properly the electric signal anymore, we talk about « axonal lesions ». This is a factor of gravity.
Carpal tunnel syndrome can be associated with trigger finger or CMC1 arthritis.
What will happen if you do nothing ? (Natural evolution)
Spontaneous resolution is rather uncommon.
The functional situation can remain globally unchanged for several months, with punctual episodes of acute crisis.
Nevertheless, the situation may progressively deteriorate, until reaching a point where conservative or restorative options would not be possible anymore.
Then, only palliative procedure would be relevant.
The deterioration of the situation is not necessarily correlated with the pain and fuctionnal limitation, and often requires additional exams to be thoroughly assessed.
For this reason, follow-up is usually recommended even for patient who are reluctant to a surgical treatment in first line.
What are the therapeutical options ? (Treatment)
Conservative treatment can be attempted for carpal tunnel syndrome. It usually associates a splint at night, NSAID, physiotherapy and occupational therapy.
Cortisone injection is also suggested by some authors.
Those treatments can ease the symptoms although they do not solve the cause of the problem.
Ultimately, in severe forms or in case of failure of conservative options, the treatment is surgical.
The surgery, called Carpal Tunnel Release (CTR), is usually performed in ambulatory condition, under local anesthesia.
The goal of the surgery is to release pressure on the median nerve by opening the Transverse Carpal Ligament, which is the roof of the carpal tunnel. This can be done through an open approach with a small incision in the palm of the hand, or endoscopically, with a more proximal incision at the wrist.
To date, there is no clear evidence for superiority of one technique over the other, and this topic is still subject to passionate debates in the Hand Surgeon’s Community.
What is the postoperative care ?
A protective dressing is applied for two weeks, then the stitches are removed and massages of the scar are encouraged.
Depending on the type of surgery performed, the postoperative care may require early physiotherapy with early range of motion, and/or the use of a splint that can be static (immobilisation) or dynamic.
Patient’s involvement during this phase is of paramount importance for an optimal final result.
What are the reasonable expectations ? (Goals)
– If all goes well :
Return to almost normal activities is allowed in immediate post operative period, but discomfort and functional limitation are often related up to 2 months after surgery.
It usually takes up to several months before recovering a normal feeling of the hand, but there is no danger in using it once the healing is complete.
It is very important to understand that if the nerve has been definitively damaged by the disease, or if there is associated cause for nerve injury (diabetic neuropathy, cervical spine nerve compression, etc), complete resolution of symptoms will not occur, and the goal of surgery is then mostly to prevent deterioration.
– In case of problem :
Occasionally, the surrounding tendons sticks into their sheath and lead to post operative stiffness. This is usually solved by physiotherapy.
Some cases of persistant and unexplained postoperative pain has been described.
As in any operation, the theoretical risk of infection exists but this complication remains rare, thanks to the rigor of prevention protocols.
Other complications may occur but appears to rare to be mentioned here.
Dr Franck ATLAN