A 48-year-old woman presents to her primary care physician with complaints of pain and numbness of her right hand for the past month. The patient describes the pain as a burning sensation that wakes her up from sleep at night. She also experiences pain and numbness along the first three fingers of her right hand while unscrewing tight bottles. She used to work as a banker, spending several hours working on her computer. She quit her job a year ago to spend more time with her family. She has no complains of recent trauma, fever, or other joint pains. She does not drink alcohol, smoke cigarettes, or use illicit drugs. She does not take any medications currently. Vital signs are normal. On physical examination, pain is reproduced by asking her to flex her wrist at 90 degrees.
B) Nerve conduction studies
This patient’s presentation is consistent with carpal tunnel syndrome (CTS). CTS is caused by the compression of the median nerve as it passes below the flexor retinaculum in the wrist. This causes paraesthesia and numbness along the median nerve distribution in the hand. Pain is aggravated at night due to incorrect posturing of the wrist while sleeping. CTS can be caused by repetitive motions of the wrist such as typing and wringing. It can also be seen in patients with diabetes, rheumatoid arthritis, thyroid disorders, and acromegaly. Although the diagnosis is clinical via provocative tests such as the Phalen test (flexing the wrist at 90 degrees reproduces the pain) and a positive Tinel sign (median nerve percussion causes pain in the area of median nerve supply in the hand), nerve conduction studies can be used to demonstrate decreased conduction velocities.
Answer choice A: CT angiography of the upper limb vessels, is incorrect. This can be used to assess the vascular status in patients with concerning features like decreased pulses and pale skin. Usually a history of fracture mandates this investigation.
Answer choice C: Serum uric acid, is incorrect. Serum uric acid is typically elevated in gout. Gouty arthritis presents as an inflamed joint (most commonly the first metatarsophalangeal joint) due to deposition of uric acid crystals in the joint.
Answer choice D: X-ray of the cervical spine, is incorrect. X-ray of the cervical spine can be used to diagnose cervical rib. A cervical rib can cause compression of the inferior trunk of the brachial plexus, leading to weakness in the motor strength of muscles of both the arm and the forearm along with clawing affecting the medial three fingers. It usually also causes compression of the subclavian artery which can lead to decreased pulsations distally and discoloration.
Answer choice E: X-ray of the wrist, is incorrect. The patient has no history of trauma, and carpal tunnel syndrome is a compression pathology that may not be evident on an X-ray.
Key Learning Point
Carpal tunnel syndrome is a disorder characterized by median nerve compression as it enters the wrist through the carpal tunnel. It causes numbness and pain along the distribution of the median nerve in the arm. Diagnosis can be done by provocative tests. Nerve conduction studies would reveal decreased conduction velocities.
