Around his 31st birthday in April 2021, Brian Hertz scratched the side of his head and felt something strange.

“It’s hard to describe, but part of my head felt hollow,” recalls Brian, who mentioned it to his wife and later noticed a bump had formed in the same spot after a few days. “Three weeks later, the bump was clearly growing, and I knew this was not normal.” 

Brian’s wife, Jennifer, was pregnant with their first...