Dr. Adam Ratner hovered over a gravely ill infant in a New York City intensive care unit on a grim day in 2022. The 3-month-old girl spiked a fever two days earlier and had become lethargic. Soon she was having seizures and struggling to breathe. She didn’t register Ratner’s towering frame or the bright hospital lights. Her eyes stared up and to the right, eerily frozen. He ran his hand over the soft spot on her head, which should have been flat. Instead, it bulged, a sign that too much fluid was building up inside her skull. The baby’s life...