A 40-year-old female office worker presents with a 3-month history of numbness and tingling in her right thumb, index, and middle fingers. The symptoms are worse at night and often awaken her from sleep. She finds relief by shaking her hand. On examination, there is weakness of thumb abduction and a positive Tinel sign at the wrist. Tapping over the carpal tunnel elicits paresthesias in the median nerve distribution.
Which of the following is the most accurate test to confirm the diagnosis?
- Wrist X-ray
- Nerve conduction studies (correct answer)
- MRI of the cervical spine
- Measurement of serum TSH
Explanation: The patient's symptoms are classic for carpal tunnel syndrome, which is caused by compression of the median nerve at the wrist. While the diagnosis is often made clinically, nerve conduction studies (NCS) are the most accurate diagnostic test. NCS can confirm the diagnosis, determine the severity of nerve compression, and rule out other neuropathies. Wrist X-rays are not useful unless a fracture is suspected. MRI of the cervical spine would evaluate for cervical radiculopathy, which can present similarly but typically involves neck pain and different sensory distribution. TSH is checked to rule out hypothyroidism as a secondary cause but does not confirm the diagnosis of carpal tunnel syndrome itself.