You may have more to worry about than just waking up from brain surgery if an egotistical doctor probes too deeply.
This Harvey Comics story was first published in 1952. It was printed in Chamber of Chills # 5 and John Giunta is listed as the penciller, with Manny Stallman credited for the inks at Grand Comic-Book Database.
I don't think it was good storytelling to show the monster in the opening splash panel. There isn't much suspense when the patient later transforms into a monster, but maybe the editors wanted to set you up for the true surprise ending later.