CARPAL TUNNEL SYNDROME


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What is a Carpal Tunnel Syndrome?

Carpal tunnel syndrome is a neurologic condition in the wrist.  Its caused by compression of the median nerve, which gives sensation to the palm of the hand, and strength to some of the hand muscles.

carpal tunnel syndrome is edema causing compression on the median nerve

Think of the median nerve as a electrical wire that plugs into certain hand muscles to give them power (if the electrical wire isnt working, the muscles dont get power, and the fingers dont work).  

The median nerve begins in the arm pit (its a branch of a branch of the spinal cord) and travels through the arm, entering the hand through a space formed by the wrist bones called the "carpal tunnel".  Like most tunnels, the carpal tunnel has a long of things traveling through it, including 9 tendons that attach to our finger bones.  The roof (or top of the “tunnel”) is formed by a ligament called the "transverse carpal ligament", and this helps to keep everything in place as we move our wrist. In a healthy wrist, theres enough space for everyone (the nerve and the tendons).  But inflammation can cause swelling in this space.  An injury or arthritis can narrow this space.  In these situations the pressure increases within the tunnel and the nerve is compressed.  

A compressed nerve cannot send normal signals, and this leads to the symptoms seen in carpal tunnel syndrome.  

Inflammation of the carpal tunnel is typically caused slowly, overtime, by repetitive movements of the wrist, or holding the wrist in an awkward position for an extended time (like typing on a keyboard). Swelling of the tunnel is also seen commonly in pregnant women, who are generally swollen from the changes of being pregnant. Other common associated causes are obesity, hypothyroidism, rheumatoid arthritis.

How is a Carpal Tunnel Syndrome diagnosed?

There are common symptoms associated with carpal tunnel syndrome that give us clues to this diagnosis. Usually patients complain of numbness, or pins and needles in their thumb, index and middle finger, sometimes all three are symptomatic, but often just one or two. Pain is also a complaint, as is hand weakness or "clumsiness".  The symptoms can be constant (long time carpal tunnel) or intermittent, particularly at night.  Once carpal tunnel syndrome is suspected, there are a variety of tests that confirm the diagnosis.  

When examining the hand, your doctor looks at the thumb muscles to see if there are signs of weakness (atrophy) which shows these muscles are not getting the strong signals they need. We can also press on the carpal tunnel itself to increase the compression of the nerve and see if this can recreate the pain or numbness. We can also tap over the nerve to see if its acutely sensitive and painful.

Usually x-rays are not necessary, and sometimes we order tests to measure the nerve conduction and determine how impaired the median nerve is. There are two tests doctors use: the EMG (electromyography) and the NCV (nerve conduction velocity).  The EMG will look at the function of the muscle (looking for twitches), the NVC looks for a slowd conduction velocity of a nerve signal.  There is debate among doctors about whether its necessary, carpal tunnel can be diagnosed by experts without any of this "technical" information, based solely on the symptoms and examination findings.  However, in cases where the diagnosis is not clear, additional tests like an EMG, NCV or even MRI can be helpful.

How is a Carpal Tunnel Syndrome treated?

Once carpal tunnel syndrome is diagnosed, doctors treat the problem stepwise. Meaning, you should rarely jump right into to surgery unless its very advanced when its first diagnosed.  All treatments are aimed at decreasing the pressure within the carpal tunnel.  

Initial treatment is aimed at reducing the inflammation that causes nerve compression. Doctors first prescribe anti-inflammatory medication and splints to wear at night (which reduces the pressure within the wrist).  If this fails, than doctor may inject steroids (a type of potent anti-inflammatory) directly into the tunnel. About 80% of people will report improvement with this injection right away and about 20% report being symptom free after one year. If symptoms recur, some doctors may considering repeating the injection, while others will proceed to the next level of treatment: surgery.

Surgery involves releasing the transverse carpal ligament (the roof of the tunnel) to decrease the pressure causing nerve compression. An incision is made over the wrist and palm typically about 1-2 inches in length.  Care is taken during the release to avoid the two branches of the median nerve: the palmar cutaneous branch (which gives sensation to part of the thumb), and the recurrent motor branch (gives strength to the thumb).  

Once surgery is complete, the nerve function will start returning to normal.  You can expect pinch strength to return in 6 weeks, grip strength to return in 12 weeks, but normal sensation takes longer to return, sometimes 6 months to a year, depending on how long the numbness occurred before surgery.  But these are only estimates, the return of nerve function can be highly variable.  The best way to think of it is the longer you had numbness before surgery, the longer it will take to go away after surgery.  If the symptoms fail to go away, its because the surgeon did not full release the ligament and there is still a band causing increased pressure or the numbness is caused by something else all together (a pinched nerve in the neck), or the nerve had been compressed for too long, and the damage done to the nerve is unfortunately permanent. 

treatment of carpal tunnel syndrome release of transverse carpal ligament

What is the long term outcome?  

Overall, people do great with this surgery. Recovery is quick and the effects usually last if the surgery is done correctly. Surgery is great at preventing further worsening of symptoms.  

Yet the return of normal function (undo-ing the damage that occurred already) is less predictable.  Many people regain full function, but some people, especially people with symptoms that lasted for many months, will not fully retain normal function.  The nerve conduction studies are the best predictors of long term return of a normal feeling hand.  People with muscle weakness are less likely to obtain normal function compared to people with numbness only.  

There is some debate about the best approach to surgery.  Some surgeons will make an incision directly over the carpal ligament (this is called an "open" approach).  Some surgeons will use an endoscopic approach, which uses a slightly smaller incision and a small camera to look at the carpal ligament.  This approach has a slightly faster recovery time, however, because the carpal tunnel is not see directly with the surgeons own eyes, some people claim there is a slightly higher risk for complications, like cutting one of the nerve branches.  Overall both approaches are very good, and have good outcomes.  

 

Related articles: nerve damage

 

References

Reviews

1. Keith MW et al. Treatment of carpal tunnel syndrome. JAAOS 2009; 17(6): 397-405. see article. review.

2. Sabin Cranford C et al. Carpal tunnel synd. JAAOS 2007; 15: 537-48. see article. review.

Diagnosis

3.  American Academy of Orthopaedic Surgeons: Clinical Guideline on Diagnosis of Carpal Tunnel Syndrome. Rosemont, IL: American Academy of Orthopaedic Surgeons, May 2007. Available at:http://www.aaos.org/Research/guidelines/CTS_guideline.pdf

Treatment

4. Gelberman RHAronson DWeisman MHCarpal tunnel syndrome: Results of a prospective trial of steroid injection and splinting. JBJS 1980;62:1181-1184. see article. splinting is effective treatment mainly for early CTS, less effective when signs of atrophy, weakness, sx >1 yr, EMG latency >6 miliseconds.

5. Marshall STardif GAshworth NLocal corticosteroid injection for carpal tunnel syndrome. Cochrane Database Syst Rev 2002. see article. 5 randomized control trials: steroid injection effective treatment for at least a few months. long term efficacy not studied. 

6. Thoma AVeltri KHaines TDuku EA meta-analysis of randomized controlled trials comparing endoscopic and open carpal tunnel decompression. Plast Reconstr Surg 2004114:1137-1146. see article. eval 13 randomized control trials.  better grip strength, less scar tenderness/residual pain at 3 mo with endoscopic.  earlier return to work. higher risk (3x) reversible nerve injury with endoscopic. both effective rx.

7. Rab MGrunbeck MBeck Het al.Intra-individual comparison between open and 2-portal endoscopic release in clinically matched bilateral carpal syndrome. J Plast Reconstr Aesthet Surg 200659:730-736. see article. 10 pt. with bilateral CTS, endoscopic vs. open showed no differences at any time.  

8. Bury TFAkelman EWeiss APProspective, randomized trial of splinting after carpal tunnel release. Ann Plast Surg 199535:19-22. see article. splinting postop has no effect on patient satisfaction, grip strength, bowstringing.

Outcome

1. Kronlage SC. The benefit of carpal tunnel release in people with mild or moderate electrophysiologically disease. JoH 2015. 

 

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