Carpal tunnel syndrome: a Q & A with Reid Abrams, chief of hand and microvascular surgery
Carpal tunnel syndrome (CTS) is not a modern affliction. It has plagued workers since at least the Industrial Revolution and the dramatic rise in jobs requiring repetitive, physically stressing movements, from assembly-line workers to meat-cutters and machine operators.
There may be fewer of those jobs these days, but plenty of other ways to develop CTS, from dental hygienists and supermarket cashiers to bank tellers and baseball pitchers.
Women are three times more likely to develop CTS than men, according to the National Institutes of Health, though the reasons are unclear. Evidence suggests 3 percent of women and 2 percent of men will be diagnosed with CTS during their lifetime. Age is major risk factor. Peak prevalence for CTS occurs in women older than 55.
Researchers have been studying CTS and other repetitive stress injuries for years, with clinical trials focusing on preventative measures and behaviors. We asked Reid Abrams, MD, professor of clinical orthopedic surgery at UC San Diego and chief of hand and microvascular surgery at the UC San Diego Medical Center, to talk about what’s known about CTS and how best to treat it.
Q: What is carpel tunnel?
A: The carpal tunnel is an oval-shaped canal at the base of the palm, about 1 ½ inches long and an inch wide. The tunnel is surrounded on three sides by bone and on the palm side by a thick ligament. All of the flexor tendons that control the fingers and thumb run through the tunnel, plus the median nerve. This is the nerve responsible for sensation in the thumb, index, middle and half of the ring finger, plus motor function for most of the muscles at the base of the thumb. CTS is what happens when the median nerve becomes compressed.
Q: How do you know you have CTS?
A: The condition produces a constellation of symptoms, including intermittent or constant numbness or tingling in the thumb, index, long and ring fingers. There can be hand numbness, tingling or burning at night, which awakens patients; swelling or stiffness in the hand; grip weakness; a tendency to drop things.
Not all hand pain is caused by CTS. If the pain is not associated with hand tingling or numbness, it’s not CTS. Also, not all hand tingling or numbness is CTS. Other nerve problems originating in the hand, forearm, elbow, shoulder or neck can also cause these symptoms.
Q: What causes it?
A: CTS occurs when there is abnormally high pressure on the median nerve, so high that the nerve can’t function. That pressure can be the result of an injury that produces sudden swelling, like a wrist fracture, or something else in the canal crowding the nerve, like an engorged blood vessel or intruding muscle.
Most often, the cause is idiopathic or unknown. It’s often activity-related because the dimensions of the carpel tunnel change with different positions of the wrist and fingers. Activities such as driving, tightly holding a book or newspaper while reading, jobs that entail sustained periods of wrist flexion or extension while gripping or pinching, such as maneuvers performed by a dental hygienist, mechanic or construction worker, can bring on symptoms. Some summer activities can set off CTS, such as carrying a surfboard for long distances, cycling or racket sports.
It’s a myth that keyboard use causes CTS. It’s been shown that intense keyboard users have the same incidence of CTS as the general population. This is not to say that symptoms of CTS can’t be brought on by keyboard use. If keyboarding is performed in a non-ergonomic fashion, with the wrists in hyper-flexion or extension, CTS symptoms could arise. Keyboarding can also be responsible for painful problems other than CTS.
Q: How is CTS treated?
A: In the mildest forms, keeping the wrist straight or wearing a splint at night may completely relieve symptoms. Avoiding extreme wrist positioning and repetitive or sustained heavy pinching and gripping can help. Cortisone injections into the carpal canal can also provide temporary relief, though severe CTS usually requires surgery.
Carpal tunnel release surgery enlarges the carpal canal by cutting the transverse carpal ligament. We know the ligament heals with the canal 25 percent bigger. It’s highly successful with rare complications, failures or recurrences.
There are two basic techniques; both work. Endoscopic is done through one or two small incisions using a visualizing camera and a specialized small blade. It produces a modestly faster return to work, but has a three-fold higher incidence of transient median nerve injury. Open surgery through an incision in the palm has a slightly higher incidence of wound healing problems.