Your physician usually can make a diagnosis of carpal tunnel syndrome based on your history and an examination. A history of numbness and tingling, nighttime symptoms progressing to daytime and activity-related symptoms, and an exam that shows loss of sensation or (in severe cases) muscle atrophy (muscle loss) in the muscles controlling the thumb are usually diagnostic. X-rays might be used to identify any bone-related causes for your symptoms.
If the diagnosis is not completely clear, your doctor might order a nerve conduction study (NCV) and/or electromyogram (EMG) to test check if there might be other areas in the neck or arm where nerves are compressed.