I had a patient walk into the clinic today flicking their hand. While driving to the clinic she had started to experience numbness and tingling in the hand. She said this happens a lot, particularly when she wakes up in the morning. It is not often you can diagnose a patient as they walk in the front door (and as a doctor this always makes you feel a bit like Hugh Laurie’s Dr House), but this was highly likely to be a case of carpal tunnel syndrome.
Carpal Tunnel Symptoms
If you wake up at night with a numb hand and shake your hands to get the sensation to return, you have a 93% chance of having this Carpal Tunnel Syndrome. You may also get symptoms while driving or when holding a phone for long periods. Basically anything that causes excessive repetitive wrist movement or elevation can result in symptoms if you have the syndrome. If you leave this loss of sensation untreated for too long you may start to lose power in your hand and can then struggle with weakness of the muscles of your had. This would result in changes such as trouble opening jars, difficulty buttoning up a shirt or using keys in a lock. As the nerve is compressed the symptoms will become worse until the changes are permanent and no amount of releasing the nerve will fix it.
Carpal tunnel syndrome affects 3 out of every 100 people and results from pressure on the nerve as it travels from forearm to hand over the front of the wrist. Females are three times more likely to get Carpal Tunnel Syndrome than their male counterparts. It is thought that a job with a high degree of repetition or use of a vibrating tool may increase the risk of nerve impingement. Other risk factors for carpal tunnel syndrome include a previous medical history of diabetes, low thyroid hormone, rheumatoid arthritis or obesity. In addition increasing age and smoking also play a part. Men are usually affected later in life typically presenting between 75-84 years of age as compared to women who experience symptoms earlier at around 45-54 years old.
Anatomy of the Carpal Tunnel
What happens to cause this syndrome? The median nerve is one of three main nerves that provide sensation and power to the hand. It enters the hand on the palm side of the wrist through a tunnel – the carpal tunnel. This tunnel consists of bones making up the floor and walls of the tunnel and then a fibrous band (flexor retinaculum) stretches across the roof, as shown in the graphic below. The nerve travels through this tunnel with nine tendons around it making it somewhat tight on space. Compression of the nerve occurs when pressure rises within this tunnel as it has limited ability to expand given it is made up of bone and relatively inflexible fibrous tissue. When the pressure rises the ultimate result is compression of the nerve.
The most common cause of carpal tunnel is thickening of the fibrous band acting as the tunnel roof. As the thickening occurs the space available in the tunnel decreases resulting in increased pressure. It can however occur due to anything that increases the pressure in this area, obesity being a reasonably common cause. I did however read one paper which showed a carpal tunnel syndrome caused by a dog bite, with infection entering the tunnel causing an increase in pressure due to inflammation. Pregnancy is well known to cause carpal tunnel syndrome thought to be due to fluid shifts seen at this time, luckily these fluid shifts revert after giving birth and most times carpal tunnel in pregnancy will resolve after delivery. Whatever the cause, this compression of the nerve results in pain and numbness in a distinct pattern in the hand; specifically the palm side of thumb, index finger and middle finger and one half of the ring finger. The aching can often radiate to the elbow however presentation can vary greatly,
Diagnosis is usually based on you symptoms and can be done by your family GP. In addition to taking a thorough history your GP may do what’s called a “provocation test” to try and provoke the nerve into recreating your symptoms. This is done through applying pressure at the site of where the nerve passes through the tunnel and is achieved by getting you to put your wrist in various different positions for a period of time. No single test is indicative of carpal tunnel syndrome but a positive provocation test increases the probability that you have the syndrome. If the diagnosis is still uncertain, your Dr can request a an electrodiagnostic study on the affected hand. This is a specialist test usually completed by a neurologist and measures how your median nerve is functioning.
How do we treat this? Generally your doctor will try a non-operative treatment first. It is suggested that almost a quarter of cases will resolve if managed without surgical intervention. Use of splints or steroid injections can relieve symptoms and this may delay surgery for a period of time but for up to three quarters of cases an operative release of the tunnel is required. A GP should refer you for a surgical opinion if there are constant severe symptoms, if the hand is weak or numb, if symptoms are progressive and getting worse, or if there is no improvement in symptoms after conservative management for three months.
There are two forms of surgery available. One form is called open surgery where a cut is made length wise at the base of the palm This allows the surgeon to see the fibrous band (the “roof of the tunnel”) and then release it surgically. Endoscopic surgery is performed through a small incision with use of a camera, and with this approach there is a smaller incision on the skin and the surgeon can release the fibrous band from the inside.
Which should I go with Endoscopic or Open
While it is controversial, a series of analyses indicated that endoscopic surgery may be better short term due to factors such as earlier return to work, improved hand strength and less scar pain longer term. However by the sixth month after operation endoscopic patients had a greater risk of injury of the median nerve. Complications are usually rare in this surgery and patients usually do well. However, as with all medical procedures, it is important to discuss with your surgeon prior to surgery the pros and cons of surgery and the method planned and how these factors specifically apply to you.
So Carpal Tunnel Syndrome is a diagnosis usually made based on the patient’s presenting symtpoms but it can be confirmed on physical examination and in some cases specialist tests. More often than not treatment is surgical.
GPearls on the GC:
- carpal tunnel syndrome may resolve by itself
- left too long it can have serious consequence for hand function
- its concerning how many doctors wish they were Dr House