BROOKE SHIELDS is ter­rified she’ll be stricken with Alzheimer’s disease and spend her final days in the same kind of senile haze that her beloved mother suffered through.

Still reeling from the Oct. 31 death of her hard-drinking stage mom Teri Shields, 79, Brooke is said to still be badly shaken by the way the disease ravaged someone she loved dearly.

“Brooke saw firsthand how it devastated her mother,” a source close to the 47-year-old actress told The ENQUIRER.

“She had to care for her mom, as well as her children, and it was difficult. She eventually had to put Teri in a skilled nursing facility.”

Now the former “Suddenly Su­san” star’s “greatest fear” is being robbed of her mind just like the woman who steered her to stardom, added the source.

Even her daughter Rowan, 9, has wondered if Brooke will lose her mind like Grandma “Toots” did!

Brooke once told a reporter: “My oldest is uncomfortable be­cause she knows more. One day she said, ‘Mom, are you gonna be crazy like Toots when you grow up?’ I was like, Oh, God.”

Experts agree that the ac­tress has good reason to worry because the life-shattering dis­ease has a genetic link.

“If someone has a sibling or parent with Alzheimer’s, that person’s own risk is double,” said renowned expert Dr. Gary Small, direc­tor of the UCLA Longevity Center.

“At age 65 or older, the risk is about 10 percent for the general popu­lation. So if you have a parent with the disease, it would be a 20 percent risk in that age group.”

Fortunately, regular exercise can help fight off the disease, noted Dr. Small, co-author of “The Al­zheimer’s Prevention Program.”

But Brooke may be at added risk because a new study suggests that

 people who have symptoms of depression in middle age are much more likely to suffer de­mentia decades later.

And mother-of-two Brooke bravely fought postpartum de­pression following the birth of her first child Rowan in 2003. She even wrote a book about her struggle.

“Brooke is really shaken up and grieving over her mom,” said the source. “And she’s praying the same fate doesn’t befall her.”