WESTPORT — When Nathalie Jacob entered brain surgery to remove a benign tumor in 2015, she and her doctor thought everything would be fine, but instead Nathalie came out a different person.

After surgery, doctors walked Jacob’s, then 35, around the hospital hallways to test her functioning and when asked to read the door numbers, Jacob said each one was room eight.

“I saw everything as an eight. They asked me what year I was born, and I said 1800s, and they asked me what year it was and I said 1980,” Jacob said.

Jacob’s impaired brain functioning was a surprise to her neurosurgeon in Miami, where Jacob then lived, who said Jacob likely would not have any negative effects from the surgery and only a small chance of losing her peripheral eyesight.

“He was so relaxed when he explained it all and said don’t worry, this is a two-hour surgery, you can go back to work in three works,” Jacob said.

Jacob was first alerted to a bodily complication on a ski trip to Whistler with friends after she fell and her finger turned black. Upon return, Jacob contracted the flu and, after the sickness passed, still had headaches. A brain scan revealed Jacob did not have residual damage from the fall but did show an intraventricular meningioma, a rare breed that accounts for less than two percent of meningioma brain tumors.

To remove the tumor, surgeons would need to cut open Jacob’s skull, but despite the severity of the surgery, Jacob and her husband believed the doctor's optimistic predictions. In the lead-up to the surgery, Jacob’s parents visited from Columbia, where Jacob’s grew up, although her father is French and her mother Puerto Rican.

“My dad came over, we partied, we had Champagne. I was not stressed,” Jacob said.

After surgery, not only did Jacob’s interpret every number as an eight, but she had a speech impairment, lost her peripheral vision, and could not read, write, or add numbers. “I was so dumb. I couldn’t process it. I could not stop laughing. I was genuinely, innocently, having a lot of fun. I became a toddler in my mind,” Jacob said.

Despite the shock of her post-op condition, Jacob said she wasn’t concerned. “I found it fascinating. I was having an amazing time at the beginning,” Jacob said. Whenever she saw a bird, Jacob yelled out “birdy” excitedly. “I was like a newborn,” Jacob said.

At first, doctors said Jacob’s new behavior and loss of eyesight may be temporary, but as the weeks and months went on Jacob’s engaged in cognitive therapy and her speech and mental functioning improved, but it became clear she would never return her preoperative mental capacity.

“I couldn’t watch TV because it was too advanced, I wouldn’t understand what was happening. What I would do for two months is color like a two-year-old,” Jacob said.

Walking around the house, Jacob would hit herself and fall down stairs because she could, and still can, see only half of the picture in front of her. When looking at a computer, Jacob sees only half the screen, at the theater, she sees only half the movie, and during our interview, only half my face.

After the operation, Jacob only enjoyed natural foods and hated bread and anything processed or fried. “The brain just became very ancestral in a way,” Jacob said.

Jacob’s behaviors indicated she suffered from Gertsmann syndrome her doctor said. “If the brain tumor was rare, and the intraventricular tumor was rare, this was even more rare,” Jacob said, adding her doctors surprise shows how little we know about the brain.

“Brain surgery is a relatively new science. They know how to get you in and out alive, but they don’t really know the side-effects you’re going to have,” Jacob said.

While Jacob said she enjoyed the surgery’s immediate aftermath, she was devastated when the permanence of her condition and new reality set in. After a few months, Jacob’s lost her job as a high-level marketing executive in Miami and she and her husband struggled financially without two incomes.

“That was really hard because I’ve always been super smart. That was my thing, being smart and a workaholic and really good at my job,” Jacob’s said. In the years before her surgery, Jacob worked across the globe for Fortune 500 companies, such as Frito-Lay, Diageo, and Johnson & Johnson and always supported herself but now can no longer work and endures frequent brain fatigue.

Not long after her surgery, Jacob’s husband was relocated to Connecticut for his job and the couple moved to Norwalk, and then bought a house in Westport a year ago. Almost two years ago, in the midst of the darkness surrounding Jacob’s illness, the pair gave birth to a daughter.

Before her daughter’s birth, Jacob said she began writing her story as a way to practice her cognitive functioning and share her journey with other brain tumor survivors, but the ending for the book she wrote was full of sadness. “At that time, I was still not accepting this. I was grieving the death of my brain,” Jacob said.

Her daughter brought a light into her world, Jacob’s said, adding that she was encouraged to finish the book so her daughter would one day be able to read about who Jacob was before the surgery. Self-published through Amazon, Jacob’s book, “8: Rediscovering Life After a Brain Tumor,” is available online now.

Despite the ongoing challenges, Jacob said she’s in a better place now than she was before her daughter was born. “I am a very strong and happy, smiley person, so I have to accept it and move on. I’m not going to be depressed about this all my life. I have too much to do,” Jacob said.

svuaghan@hearstmediact.com; 203-842-2638; @SophieCVaughan1