AS A toddler, Edward was overactive. He would frantically empty cupboards, throw pillows, and move chairs from one room to another. He was​—in his mother’s words—​“a holy terror.”

But when Edward started school, his behavior became even more startling. First, he began to make strange siren noises. Later, he developed twitches in his face and neck. He would grunt, bark, and make other odd sounds. He even had outbursts of vulgarity.

To an observer it might have seemed that Edward was a spoiled child who just needed discipline. In reality, however, he suffered from Tourette syndrome, a neurological disorder characterized by spasmodic muscular and vocal tics.

Vocal tics can be even more disturbing. Some of these are involuntary throat-​clearing, sniffing, barking, whistling, cursing, and repeating words or phrases. “By the time my daughter was seven,” says Holly, “she repeated everything. If she was watching TV, she would repeat what she heard, or if you talked to her, she would echo what you said. You might think she was being a smart aleck!”