Michael Bolton’s Daughters Share the ‘Weird’ Symptom That Led to His Brain Cancer Diagnosis (Exclusive)

Michael Bolton was enjoying time with his family in the fall of 2023 when something unexpected happened.

While out for a night of bowling with his kids and grandkids, the Grammy-winning singer, 72, bowled out of turn. Then he did it again. And again.

The incident was “super weird,” his daughter Taryn recalls in this week’s PEOPLE cover story — and it turned out to be a major indicator that Bolton was dealing with a serious health issue that would later be diagnosed as glioblastoma, a rare and aggressive form of brain cancer.

“That was when we were like, ‘Something’s wrong with his brain,’” Taryn, 45, says. “Everything that happened was weird for him but not super alarming. When you look back at everything together … We missed so many things.”

At the time, Bolton’s career was thriving. He’d recently performed a number of concert dates, appeared on The Masked Singer, released an album in July 2023 and filmed a cameo in the movie The Fabulous Four that October.

But a performance in mid-November at a charity event on Richard Branson’s Necker Island was marred by an unusual bout of nausea and balance issues, which Taryn and her sisters Holly, 47, and Isa, 49, chalked up to stress and exhaustion.\

“Is this stress? Is this sleep?” Taryn remembers wondering. “He’d been working nonstop that whole time. Traveling, doing shows, doing all of these things. We were like, he’s getting older, he’s tired, he’s stressed out. All of these things we sort of explained in a way, one by one.”

The bowling outing happened just after Thanksgiving 2023, and earlier that same night, Bolton’s family noticed another red flag.

“He fell out of his chair to the left, which is very unusual. He’s super athletic, and he doesn’t drink,” says Taryn. “So he fell, and we were like, ‘What just happened?’”

Over the same weekend, Bolton had a “bad” headache — and on Monday, he went to the hospital, where an MRI confirmed he had a brain tumor. The tumor was removed in its entirety during surgery, and about a week later, doctors confirmed it was glioblastoma, which affects approximately 15,000 Americans each year, per the National Brain Tumor Society.

Bolton’s neuro-oncologist, Dr. Ingo Mellinghoff of Memorial Sloan Kettering Cancer Center in New York City, says symptoms of brain tumors often include sudden changes in personality, severe headaches, seizures, coordination issues and muscle weakness and paralysis.

“If all of a sudden you’re a completely different person, and people are like, ‘He never gets out of bed anymore. What’s going on? He doesn’t want to do anything’…,” Mellinghoff says. “If somebody can’t move one part of their body, that’s never normal. Or changes in sensation. When they say, ‘I can’t feel anything anymore on my right side.’”

Mellinghoff adds that changes in speech patterns can also be a red flag.

“Speech is pretty sensitive. We all have our speech patterns, and if all of a sudden your friend says, ‘It sounds so strange, and it doesn’t make sense,’ that is definitely something,” he says.

Still, Mellinghoff says that glioblastoma is very rare.

“It’s really hard to put out the message of, ‘If you have a headache, think about brain cancer,’ because that’s so rare,” he says. “Many of these symptoms are very nonspecific, so we have to be careful not scaring everyone.”

For Bolton, treatment has included radiation and chemotherapy, which he finished in October. Because glioblastoma has an extremely high recurrence rate, Bolton undergoes MRIs every two months to ensure his tumor has not returned. His most recent scan, in early April, was clear.

For more on Michael Bolton, pick up the latest issue of PEOPLE, on newsstands Friday, or subscribe here.