Amid Bruce Willis' nearly three-year battle with dementia, the actor's brain is "failing him," and his ability to communicate is fading, according to his wife Emma Heming Willis.
"Bruce is still very mobile. Bruce is in really great health overall, you know," Heming Willis told ABC News' Diane Sawyer in the ABC special "Emma & Bruce Willis: The Unexpected Journey," a preview of which aired Tuesday on "Good Morning America." "It's just his brain that is failing him."
Willis' family shared publicly in 2023 that he had been diagnosed with frontotemporal dementia, a type of dementia that impacts one's personality and may cause behavioral changes, according to the Centers for Disease Control and Prevention.
For the 70-year-old actor, famous for delivering one-liners in movies, the primary symptom is the loss of language, according to Heming Willis, who has written a new book about her family's experience, "The Unexpected Journey: Finding Strength, Hope, and Yourself on the Caregiving Path."
"The language is going, and, you know, we've learned to adapt," she said. "And we have a way of communicating with him, which is just a ... different way."
In the first few months after Willis' diagnosis, Heming Willis said she, like so many caregivers, thought she had to do it alone, which meant lying awake at night to make sure Willis was safe and isolating the family away from social gatherings and playdates in order to make life more comfortable for Willis.
The experience spurred Heming Willis -- a model and entrepreneur who prefers to work out of the spotlight -- to move front and center to advocate for caregivers and for more support for loved ones of people living with conditions like dementia. She said she hopes her new book on caregiving, available on Sept. 9, can be a road map and guide for other caregivers.
Through it all, Heming Willis, 47, said she and her family, including the couple's 11-year-old and 13-year-old daughters, still see glimmers of Willis' personality and the "twinkle in his eye."
"Not days, but we get moments," Heming Willis told Sawyer. "It's his laugh, right? Like, he has such, like, a hearty laugh. And, you know, sometimes you'll see that twinkle in his eye, or that smirk, and, you know, I just get, like, transported."
She continued, "And it’s just hard to see, because as quickly as those moments appear, then it goes. It’s hard. But I’m grateful. I’m grateful that my husband is still very much here."
Willis was still working as an actor and enjoying life with his friends and family when FTD began to show up as a "whisper" in different ways, according to Heming Willis, including seeming to drift away from family members and skipping out on activities he usually loved. She said she is sharing Willis' symptoms to highlight the subtle signs of this little-known disease.
"It felt a little removed, very cold, not like Bruce, who was very warm and affectionate," she said. "To [go] the complete opposite of that was alarming and scary."
When the "Die Hard" actor was finally diagnosed with FTD, Heming Willis said she was given a pamphlet on the condition and was told there was nothing that could be done, because there are currently no treatments available for FTD. She described her reaction to hearing the diagnosis as feeling like she was "free falling."
Dementia -- an umbrella term for a decline in mental abilities such as thinking, memory, and decision-making -- impacts millions of Americans and their families. According to the CDC, nearly 7 million older adults in the U.S. have Alzheimer's, the most common type of dementia.
Heming Willis said she is not sure that Willis "ever really connected the dots" to be able to understand his diagnosis, a common reaction in FTD patients, according to Dr. Bruce Miller, a California-based neurologist and leading researcher on FTD who does not treat the actor.
"The patient is incredibly unaware of what is happening," said Miller, also the director of the UCSF Dementia Center in San Francisco. "I think the parts of the brain that allow us to suffer and self-reflect are lost very early in frontotemporal dementia."