Carpal tunnel syndrome is characterized by compression of the median nerve as it passes under the flexor retinaculum in the wrist. The most common cause is idiopathic, but other potential causes include obesity, hypothyroidism, diabetes, arthritis, and trauma. Clinical features include tingling and numbness in the thumb and first two fingers, especially at night, and difficulty with fine motor tasks. Nerve conduction studies can confirm delayed conduction in the median nerve. Treatment involves surgically decompressing the nerve by dividing the flexor retinaculum.