A 45-yeаr-оld secretаry experienced "pins аnd needles" sensatiоns (paresthesia) and pain in her right hand during the night. These sensatiоns involved the palmar surface of her thumb and the lateral two and a half fingers. Her colleagues told her that she probably has carpal tunnel syndrome. Her family physician confirmed that this was the condition she was experiencing. She also told the physician that she was having some difficulty typing. On further examination, the physician detected some weakness of her right thenar muscles when compared with the left side. Otherwise motor functions were unimpaired currently. Which of the following statements best describes the most likely cause of the paresthesia experienced by the secretary?