Two young New Yorkers who overcame traumatic brain injuries — including one who had to relearn how to walk — are using their new lease on life to run in Sunday’s city marathon.

Alexa Casciano, 24, and Christian Longo, 26, are both joining the beastly race to benefit the Brain Injury Association of New York State in honor of other TBI victims who aren’t able to make the 26.2-mile trek.

Christian Longo and Alexa Casciano are traumatic-brain-injury survivors who are running this year’s New York City Marathon. Robert Miller

“The ability to walk, I find that people take for granted. But we have legs, and we complain about how many flights of stairs and all that stuff,” Longo said.

“Why are you complaining about things like that? You should be caring that your legs can handle climbing up those many stairs. Those are things that I always remind myself of because they really can always be worse.”

Completing the New York City Marathon is especially groundbreaking for Longo, who needed to relearn how to walk, talk and “all the basics” after he took a terrifying spill from a broken New Orleans balcony in April 2021.

The then-Tulane University senior said he barely remembers anything about his three-story fall.

His skull was the only bone he broke in his body — but his brain’s subsequent epidural hematoma left him with a life-altering TBI.

“I was like a baby,” said Longo, a Gramercy resident.

The marathon is the first for Longo, but the second for Casciano. Robert Miller

“The injury was on the right side of my head, which is in control of a lot of your cognitive abilities, like writing checks, what time it is, what year it is … even remembering, ‘What’s the word for this, what’s the word for that?’ “

Longo’s TBI even prevented him from fully understanding the trauma he had gone through: In his mind, he was still functioning at 100%, even as he was struggling to communicate with his loved ones who were rallying alongside his hospital bed.

“Looking back, I know I was dealing with so much and was not even a fraction of the person I’ve been able to become today,” he said.

Longo sustained a TBI when he fell from a third-story balcony in 2021. Robert Miller

Running the marathon wasn’t something Longo had considered before his accident, but he decided to put his mind and body to the test this year at the urging of his sister and biggest supporter, a woman named Julia.

The duo has collectively raised nearly $7,000 to benefit BIANYS, a nonprofit dedicated to supporting, educating and advocating for people and families impacted by brain injury and minimizing brain injury through prevention.

“Even though I’m doing it, it’s not for me,” Longo said of his upcoming run. “It’s for everybody who really can’t run a marathon, maybe somebody who’s had a brain injury that’s left them bound to a wheelchair.

“God decided to give me a chance to do this. I’m not going to squander it.”

Casciano suffered a TBI after she was diagnosed with Lumiere syndrome, an extremely rare bacterial infection. Robert Miller

The sentiment is something Casciano, 24, can get behind.

The TriBeCa resident has been living by the motto, “Do it for those who can’t” while training for the athletic endeavor.

Casciano’s TBI stemmed from her 2018 diagnosis of Lumiere syndrome, an extremely rare bacterial infection that can typically be treated with antibiotics but nearly became a death sentence for the then-16-year-old.

For unknown reasons, the infection rapidly spread to Casciano’s lungs and brain. Within a 28-day span, she underwent double lung reconstruction surgery and emergency brain surgery.

The pair are running to benefit the Brain Injury Association of New York State in honor of other TBI victims who aren’t able to make the 26.2-mile trek. Robert Miller

The disease left her with a titanium plating system in her brain that caused chronic, often debilitating headaches.

But she also found new strength from her ordeal.

“I went through this experience, and I was really lucky to come out of it alive and healthy, but others were not. Keeping them in my mind and running on behalf of them is something incredibly important to me,” Casciano said.

“That was a pretty transformational experience for me. … You only have one life, so make sure that you’re doing everything that you want to do and taking every day as if it could be your last and really living life to the fullest,” she said.

The race will be the second for the pharmaceutical consultant, who completed the Los Angeles Marathon in March purely to train for the treacherous bridges scattered across the New York City race.

Casciano continued training through the summer — even pushing through a 20-mile run just four days before she went back under the knife to finally alleviate those migraines she spent seven years suffering through.

As with Longo, Casciano is running to benefit BIANYS and has already raised over $4,000.

“I had gone through this experience of having brain surgery and recovering from it, but understanding that people are oftentimes not as lucky as I was to be able to really make a full recovery and have that experience, to be able to move forward and inspire others,” she said.