A 57-year-old woman comes to the office due to discomfort in her right hand. She reports that periodically her fingers "feel numb, with some tingling, sort of like they fell asleep." When the patient shakes her hands, normal sensation is partially restored. The symptoms are more often present at night but are occasionally experienced during the daytime as well. She has not had abnormalities of sensation on the dorsal surfaces of her hands, and she reports no shoulder or neck pain. There is no history of injury to the upper extremities. Medical history is notable for irritable bowel syndrome, mitral valve prolapse, degenerative knee arthritis, and hypertension controlled with lisinopril. She also takes an over-the-counter fiber supplement. The patient works as a bookkeeper. She does not use tobacco, alcohol, or illicit drugs. Vital signs are normal. BMI is 32 kg/m². Neurologic examination shows no sensory loss, muscle weakness, or muscle atrophy in the right upper extremity. The patient comes for follow-up 6 weeks after the initial visit. She has had no noticeable benefit from initial treatment measures and reports that she has had to reduce her work hours due to increasingly severe symptoms. Which of the following tests should be offered to this patient?

Question

Quizplus · Accepted Answer

Explanation: Compression of the median nerve in carpal tunnel syndrome (CTS) results in loss of myelination. Axonal loss may also occur if the compression is severe. Nerve conduction studies (NCS) can confirm the diagnosis and assess the severity of CTS by demonstrating slowed conduction along the nerve at the level of the carpal tunnel. Reduced amplitudes indicate axonal loss. Electromyography (EMG) is frequently combined with NCS and may show denervation of muscles innervated by the median nerve with relative sparing of those that are not. NCS and EMG are indicated for patients with chronic or refractory CTS who are being considered for surgery. They are not usually needed in the initial diagnosis (which is typically based on clinical features) but can be considered if the diagnosis is uncertain. (Choice A) CTS occurs more frequently in certain connective tissue diseases (eg, rheumatoid arthritis), but serologic testing is not necessary unless there are other findings (eg, pain, swelling in the metacarpophalangeal joints). (Choice B) Neck MRI is useful to evaluate a cervical radiculopathy. Clinical features that warrant neck MRI include symptoms that are worse with neck movement, symptoms involving the dorsal hand, radicular pain in the neck and upper arm, and proximal arm weakness or diminished reflexes. (Choice C) Wrist MRI can demonstrate changes in the median nerve and carpal tunnel to support a diagnosis of CTS, but this is typically reserved for excluding a local mass lesion in atypical cases. (Choice E) X-rays of the hand do not show the median nerve, flexor tendons, or carpal ligament. X-rays are used in acute traumatic CTS to exclude a fracture. Educational objective: Nerve conduction studies can confirm the diagnosis and assess the severity of carpal tunnel syndrome. They are used in preparation for surgery or when the diagnosis is uncertain.

A 57-Year-Old Woman Comes to the Office Due to Discomfort