A 58-year-old right-handed man comes to primary care complaining of hand pain for several weeks. One month ago, he noticed tingling and burning pain on the palmar side of his right thumb, index and middle fingers. He works in an office and does computer work every day. His symptoms occasionally feel worse when he is typing. They fluctuate during the day and gets worse again overnight. One week ago, he noticed similar symptoms beginning in his left hand, but not to the same degree. His hands feel puffy and swollen, although he hasn’t noticed any physical changes.
He has had no history of neck complaints and notices no arm or hand symptoms with changes in head position. He does not have similar symptoms elsewhere. He is married, does not smoke, has one to two drinks several nights per week, and takes no medications. He has no significant past medical history and has not traveled recently. He is sedentary and states that although he had been moderately overweight for many years, he is frustrated by further weight gain over the past several months. His wedding ring and shoes have felt tighter over the past year but he attributes this to his weight gain.
Exam – P – 86, BP – 160/86, T – afebrile, Pulse ox – 98%, BMI – 29; large, coarse facial features, with skin thickening; normal sensory and motor evaluation of the upper extremities, including normal thumb strength, and no thenar atrophy; Tinel’s test (percussion over volar wrist) – negative bilaterally; Phalen’s test (wrists flexed to 90⁰ for one minute) + tingling sensation over the front side of his right thumb, index, and middle fingers; negative on the left
Labs – normal CBC, chemistries, except blood glucose (random) – 168 mg/dL
Discussion
Carpal tunnel syndrome is the most common entrapment neuropathy, experienced by approximately five percent of the U.S. population. Although working on a computer is frequently cited as a common cause of carpal tunnel syndrome, a direct link has never been proven. Poor desk ergonomics may cause muscle strain associated with hand and wrist pain, however, these symptoms are not necessarily due to carpal tunnel syndrome. Most cases of carpal tunnel syndrome do not have an identifiable cause.
The carpal tunnel contains nine flexor tendons (two for each finger, one for the thumb) and the median nerve. It is formed by the carpals and the flexor retinaculum, a fibrous band located on the palmar side of the wrist, bound to the pisiform and hook of the hamate on the ulnar side, and the scaphoid and trapezium on the radial side. Increased pressure in the tunnel compresses the median nerve, causing injury. Additionally, inflammation of the flexor tendons in the carpal tunnel, either primarily, as in a repetitive motion injury, or secondarily, from the increased pressure itself, may cause further nerve damage.
Early symptoms include tingling and burning pain over the distribution of the median nerve in the hand, with sparing of the proximal palm and thenar eminence, as pictured.
The spared areas are innervated by the palmar cutaneous branch of the median nerve. This sensory branch arises proximal to the wrist and travels to the hand outside of the carpal tunnel. Thus, the sensory examination can help differentiate carpal tunnel syndrome from other causes.
Without treatment, median nerve injury can progress from sensory to motor symptoms, which may involve loss of hand coordination and overt weakness. Eventually, thenar atrophy may develop (except in those who have ulnar nerve contribution to the thenar area).
When the history and physical exam suggest carpal tunnel syndrome, nerve conduction studies (NCS) and electromyography (EMG) are often used as confirmatory tests. Positive findings on NCS include slowed median nerve velocities over the carpal tunnel, and EMG can detect denervation of hand muscles early, even prior to the patient noticing any motor symptoms. It can also help discriminate between muscle and nerve abnormalities.
Although the majority of cases have no known cause, carpal tunnel syndrome has been associated with several conditions. It is important to rule out a secondary cause, as many of these are life-threatening, and carpal tunnel syndrome may be the first sign of underlying disease. Some of the more common conditions include obesity, hypothyroidism, diabetes, arthritis, and pregnancy. Less common are hyperparathyroidism, renal failure and dialysis, sarcoidosis, amyloidosis, and leukemia.
This case provides an example of a rare condition causing carpal tunnel syndrome. The weight gain, tight-fitting shoes and wedding ring, coarsening of skin and facial features, increased blood pressure, and possibly the increased blood sugar (sample was not drawn while the patient was fasting) point to acromegaly, a condition of excess growth hormone in an adult. Acromegaly is most commonly caused by a pituitary adenoma (about 95% of cases) and further evaluation with additional laboratory studies and brain imaging are the next step in its evaluation. The appropriate treatment of acromegaly has been shown to reverse carpal tunnel syndrome (and many other associated signs and symptoms). The first physical changes associated with acromegaly can be very subtle, and the diagnosis is often delayed. When diagnosed and treated early, the life expectancy of those with acromegaly has been observed to be the same as that of the normal population.
If a cause of carpal tunnel syndrome is not discovered, treatment is determined by the severity of signs and symptoms. Early or mild carpal tunnel syndrome is usually treated with conservative measures: avoidance of repetitive motion, neutral wrist splinting, and nonsteroidal anti-inflammatories. A local steroid injection may also be used to reduce inflammation and swelling. If symptoms are severe or do not improve with conservative measures, a surgical referral may be required. In surgery, the flexor retinaculum is divided, by either an open or endoscopic method, providing an immediate reduction in pressure on the median nerve. Most patients will get significant relief after surgery. However, if the nerve was significantly damaged prior to surgery, recovery may take several months or longer. Physical therapy is usually advised to assist the patient with regaining full function.
References
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