Which surgical procedure involves making an opening into the skull?

The surgical procedure that involves making an opening into the skull is a craniectomy. This procedure entails the removal of a portion of the skull to access the brain, often for necessary treatments such as relieving pressure due to swelling, hemorrhaging, or to remove brain tumors. By allowing direct access to the cranial cavity, a craniectomy is crucial in treating various conditions that affect brain function or structure.

The other procedures listed do not involve the skull: a laparotomy refers to an incision into the abdominal cavity typically for surgeries involving the organs within; a thoracotomy involves an incision into the chest cavity to access organs like the lungs or heart; and a cholecystectomy is the surgical removal of the gallbladder, which is situated in the upper right abdomen. Each of these procedures targets different body systems and parts, highlighting the distinct function of a craniectomy in neurosurgery.