Until she was 26 years old, Cole Cohen had no idea why she couldn’t tell time, learn how to drive, cross a street on her own, or know how long to hug someone.

Finally, an occupational therapist in her native Portland, Oregon, suggested Cohen get an MRI, and on the morning of June 17, 2007, she and her parents met with her neurologist, Dr. Volt, for the results.

In her new memoir, “Head Case: My Brain and Other Wonders,” she describes receiving her diagnosis.

“Dr. Volt is behind his desk; his computer monitor is turned toward us. I don’t understand the image in front of me. It’s a black-and-white splice of a brain, I assume mine, with an inky black spot on it in the shape of a lopsided heart.

“I tell myself that this is a spot on the film, which it’s way too large to actually be. It’s something not to worry about, something I don’t understand that the doctor will explain away.

“We are all staring dumbly at the image on the screen until Dr. Volt begins to speak. ‘So, this is your brain . . . and this’ — he points with a pencil to the black spot — ‘is a hole.’ The image comes into focus. It is not debatable.

“A hole.”

“Yes.”

“There is a hole in my brain.”

“Yes.”

Cohen asked the next obvious question: How big is it?

Volt took his pencil and pointed to the image of her eyeballs on the scan. He tapped from one eyeball to the hole, back and forth, until he filled the void.

“About 20 eyeballs,” he said. “About the size of a lemon. Or, say, a small fist? Like the fist of a 10-year-old?”

As far as Cohen knows, there has never been another recorded case like hers. After her appointment with Volt, she and her parents went to lunch at a Chinese restaurant, where they largely sat in silence.

“We were stunned,” Cohen tells The Post. “We were all just trying to digest it.”

Cohen’s mother worried it was genetic. Her own brother had died of a brain aneurysm, at 17. Volt assured her Cohen’s case was unrelated — in fact, they had no idea what caused it.

Cohen couldn’t believe that she had spent 26 years walking around with a hole in her head — that she wasn’t dead, or severely impaired. She worried the hole would keep growing. Volt ­assured her it would not.

Still, after that lunch, she raced home to see what she could find online. There was almost nothing.

“It pretty quickly started to feel kind of absurd,” Cohen says. “I mean, what a weird syndrome to have. It feels like it doesn’t exist.”

We learned subtraction with Cheerios, but I didn’t understand that I was supposed to take away the Cheerios. I ate them. - Cohen

Cohen was lucky. Her hole, filled with brain and spinal fluid, was where the parietal lobe would have been. Had she been missing her frontal lobe, she indeed would have been developmentally disabled, or dead. But the parietal controls spatial sense, number comprehension, sensory information and navigation.

Suddenly, here was an explanation for her entire life: Why she could never tell how far away an oncoming car was while crossing the street. Why every time she walked into her local grocery store, it was as though everything had been rearranged, and she couldn’t figure her way around. Why an analog clock made no sense. Why, as a child, she couldn’t understand basic math.

“We learned subtraction with Cheerios,” she says, “but I didn’t understand that I was supposed to take away the Cheerios. I ate them.”

Yet Cole excelled in English and reading, so her parents had her evaluated in the school system. Psychiatrists and educators diagnosed Cohen as learning-disabled and suffering from ADD/ADHD.

She spent her life on and off medications, and her extreme neediness caused a lot of tension with her two younger sisters.

“It was especially hard for them because we didn’t have something concrete we could point to,” Cohen says. “Instead it was, ‘She takes up a lot of attention because she’s bad at math and can’t drive.’ I’m the oldest, but my sisters say they feel like I’m the youngest.”

Cohen also suffered from behavioral issues but isn’t sure how much the meds were to blame. By the time she saw Volt, she was taking 100 milligrams of the antipsychotic Seroquel (commonly used to treat bipolar disorder and schizophrenia), 100 milligrams of Lamictal (also an antipsychotic), 8 milligrams of Rozerem (for sleep) and Ativan tabs (for anxiety).

“When I was in my 20s, I used to have tantrums and act out,” Cohen says. She went to college at the Johnston Center for Integrative Studies in California, where she burned through a series of roommates and embarked on a chaotic romance with a friend’s brother.

Cohen couldn’t keep a job, no matter how menial. She couldn’t count change, and all she could tell her employers was that she had a learning disability.

The anger that I feel toward myself for not being able to do what comes easily to others is slick dark fuel pooling with each passing year. - Cohen

“The anger that I feel toward myself for not being able to do what comes easily to others is slick dark fuel pooling with each passing year,” she writes. “I start jumping out of cars while my parents are driving and just start running.”

Out of frustration and self-loathing, Cohen began slapping herself in the face whenever she felt overwhelmed. She had no coping mechanisms and became suicidal.

“What I have isn’t just about counting change and telling time,” Cohen says. “It’s perception and mapping and how I see the world, which doesn’t line up with how everybody else sees the world. And no one can validate you. So: Am I going crazy? What’s wrong with me?”

As soon as she received her diagnosis, Volt took Cohen off all her meds. She began seeing Dr. Z, a neurological chiropractor. Not even Cohen can describe exactly what kind of doctor he is, but he seems to help.

She describes her elation at her first appointment with him.

“Do you shave your legs?” he asks.

“Yes,” Cohen says. “But sometimes I forget to . . . shave one leg.”

He tells her it’s her left. Why would that be, when we know the right side of the brain controls the left side of the body and vice versa?

As it turns out, Cohen’s parietal lobe has been smushed out by all that fluid, so the brain matter is technically there, but on the right especially it’s atrophied — hence the confused signaling.

“I need to strengthen my brain, not coddle it,” Cohen writes. “That means moving all of the folders on my computer to my left side, sitting to the right of my professor, anything to force my right brain to process information coming from my left side.”

Then there is socialization. For Cohen, knowing when and how to give a hug, or introduce herself, will never come naturally.

“I’ve actually looked at my watch to see how long to say hi to my roommate,” she says. “Hugs — applying pressure — that’s a motor-skill issue. You don’t assume it’s a neurological issue if you meet me, but it does cause social anxiety.”

For that, Cohen has had group and individual therapy and continues to see a psychotherapist once a week. She earned an MFA at the California Institute of the Arts, and now lives alone in Santa Barbara, Calif., where she works as a coordinator at the University of California, Santa Barbara.

“There was all kinds of worry and anxiety as to whether living alone would work out for me,” Cohen says. “So far, it works out pretty well.”

Getting to and from work isn’t a problem. Cohen takes the same bus every day. But if she goes out after work, things get complicated. Technology has made some things easier — she occasionally uses Uber and is thinking of ordering her groceries online — but other advances can’t help.

If Cohen gets lost, for example, Google Maps only goes so far. “I can’t translate what I see on my phone,” she says. “I understand that the little dot represents a human being, but I still get lost.”

Written directions aren’t any better. “If it says ‘go left’ or ‘go right,’ I know I have a 50/50 shot of going the right way,” she says.

Still, Cohen is living a far more independent life than expected, and this alone is a testament to the brain’s adaptability. That she can be missing a part of her brain and not sitting in a home somewhere, a lobotomy by birth, is astonishing. She wants very much to be studied.

“It was infectious excitement to be a medical discovery,” she says.

Now that the book is out, she feels far less self-conscious. “Transparency has made a big difference,” Cohen says. “I’m not asked to do things I can’t do.”

She wants to find another boyfriend and maybe, someday, have kids. She’s no longer afraid of how potential dates might react.

“My story is unusual,” she says, “but there’s lots of people who have things from their past that are difficult. So I don’t think I’m a special case.”