A 38-year-old woman comes to the office for evaluation of pain and tingling in her hands. She works as a telemarketer for a local sales and marketing agency and has been having difficulty holding the phone. Review of systems is positive for frequent muscle aches in the arms and legs, constipation, lethargy, and difficulty concentrating at work. The patient has no other medical conditions and takes no medication. She does not use tobacco, alcohol, or recreational drugs. Blood pressure is 130/80 mm Hg, pulse is 62/min, and respirations are 14/min. BMI is 32 kg/m2. On examination, there is numbness in the thumb, index, and middle fingers of both hands. Deep tendon reflexes are 1+ in all 4 extremities. The skin appears doughy and dry at both elbows. Mild edema is present in both ankles. Which of the following is most likely responsible for this patient's hand symptoms?
Pathophysiology of carpal tunnel syndrome | |
Cause | Pathophysiologic features |
Idiopathic/overuse |
|
Hypothyroidism |
|
Diabetes mellitus |
|
Rheumatoid arthritis |
|
Pregnancy |
|
End-stage |
|
Acromegaly |
|
Gout |
|
HD = hemodialysis. | |
This patient has myalgia, constipation, impaired concentration, dry skin, mild edema, and hyporeflexia, suggesting hypothyroidism. She also has pain, paresthesia, and sensory loss in the distribution of the median nerve, findings consistent with carpal tunnel syndrome (CTS). CTS is an entrapment mononeuropathy caused by compression of the median nerve within the carpal tunnel in the wrist.
In addition to slowed metabolic activity, many symptoms of hypothyroidism (eg, myxedema, dry skin) are due to deposition of mucinous material composed of glycosaminoglycans, hyaluronans, and mucopolysaccharides within tissue. Direct infiltration of the median nerve and nerve sheath with mucinous material results in swelling and a localized ischemic neuropathy. Deposition on the tendons within the carpal tunnel results in swelling and compression on the nerve, leading to symptoms of CTS.
Patients with hypothyroidism are more likely to develop bilateral CTS, and their symptoms may be more severe. The risk does not appear to correlate with the severity of the underlying thyroid disease, although it is greater in patients with elevated BMI. Treatment of hypothyroidism with levothyroxine often leads to improved CTS symptoms.
(Choices A, B, and E) Patients with end-stage renal disease (ESRD) on hemodialysis frequently develop CTS due to accumulation of dialysis-related amyloid. When CTS occurs, it is more common in the arm used for vascular access (eg, access graft, arteriovenous fistula), suggesting a contribution of vascular steal or venous hypertension. ESRD can also lead to pathologic calcification with deposition of calcium phosphate, which can compress the nerve. However, these factors are unlikely in this patient.
(Choice D) Multiple sclerosis is characterized by demyelination in the periventricular white matter; common manifestations include weakness, sensory loss, incontinence, and optic neuropathy. However, symptoms are episodic and affect multiple, noncontiguous domains; symptoms involving the distribution of the median nerve in the hand are more consistent with CTS.
Educational objective:
Carpal tunnel syndrome is common in patients with hypothyroidism and is frequently bilateral. Hypothyroidism causes soft tissue thickening and mucinous infiltration, which can lead to compression of the median nerve within the carpal tunnel.