On a ride to high school one morning, Shelley Marshall asked her daughter how things were going with her field hockey team.

At least, that’s what she intended to say. The words came out so garbled that her daughter said, “Mom, what is going on? Are you having a stroke or something? Look at me.”

Marshall looked fine. Although slurred speech is a classic stroke symptom, she didn’t have a droopy face or arm weakness. In a clear voice, she told her daughter not to worry.

Marshall, though, was concerned.

Two days earlier, she noticed that she’d slurred her own name. Her blood pressure had recently been slightly elevated. And she was still recovering from a serious bout of COVID-19, her third. All of this was unusual for Marshall, then 47 and in excellent health, thanks in part to running nearly every day.