You are a pediatric neurologist in a busy outpatient clinic. Your next patient is Abigail Adams, a 10-year-old girl, accompanied by her parents. They seem anxious and tired.

“We’re very concerned about Abigail’s movements,” her mother says. “It started with just some blinking a few years ago, but lately, she’s been jerking her head and making these squeaking noises. It’s disrupting her class, and she’s getting teased.”