Every month, I get dozens of messages on Instagram from parents, grandparents, and caregivers who’ve just heard the words “agenesis of the corpus callosum (ACC)” for the first time. Some are moms still pregnant, scared about what’s ahead. Others are grandparents wanting to know what life might look like for their grandchild.
This is our story—not because it’s the only story, but because it’s ours. My daughter, Lillie, is seven, and she was born with ACC. Around here, we call it her “race car brain”—because it works differently, but it’s powerful, fast, and uniquely hers.
Every Child With ACC Is Different
One of the hardest truths to grasp about ACC is that no two kids look the same. Some kids have severe motor delays. Some don’t talk until they’re four. Some breeze through academics but crumble socially. Some do the opposite.
Lillie’s story is her own. But many of the things she struggles with—and the places where she surprises us—line up with what’s considered “common” for kids with ACC. I want to share these because when you first hear this diagnosis, you might Google “symptoms” or “outcomes” and feel completely lost. My hope is that this gives a real picture of what these terms look like in everyday life.
Executive Functioning: What It Really Means
“Executive functioning” sounds like a big, clinical phrase, but it basically means the brain’s management system. It’s the set of skills that help us plan, organize, start tasks, finish tasks, and shift from one thing to another.
For Lillie, this is a big struggle. A simple instruction like “clean your room” is overwhelming because it’s too big, too open-ended. She shuts down. So instead, we break it down: “Pick up your baby doll,” or “Can you find four things to put away?” Sometimes we even turn it into a game, like “Let’s see if you can beat me to pick up five toys.”
Another example? Getting ready in the morning. Instead of telling her “go get dressed”, we hand her a checklist. Pajamas off, clothes on, brush teeth, comb hair. If we phrase it casually (“are you dressed yet?”), she’ll get defensive—because she’s not, and to her that feels like we’re pointing out failure. But with a list, she feels in control.
That’s executive functioning in her world: she can do the pieces, but she needs them broken down, structured, and predictable.
Processing Speed (and Why Games Are Hard)
Processing speed is another one of those terms that shows up in reports and evaluations. It basically means: how fast does the brain take in information, make sense of it, and respond?
For Lillie, slow processing speed makes activities like timed tests and games especially hard. We love family board games, but what should be a fun night often ends with frustration. Games like Spot It, War, or Mario Kart on the Nintendo Switch highlight the gap. By the time she’s seen the card, remembered the word for it, and decided how to respond, her brother has already shouted it out or won the round.
She hates losing—not just because nobody likes to lose, but because to her it confirms a fear: I’m less than. She stomps off, defeated, and what started as connection becomes conflict.
This is one of the hardest dynamics in our house, because her brother just wants to play a “normal” game night, and Lillie leaves the table angry and empty. It’s not about changing who she is—it’s about us learning how to adapt family time so everyone feels included.
Social Cognition: Friendships in Black and White
Social cognition is the ability to read people—tone of voice, facial expressions, sarcasm, inside jokes. It’s knowing when someone is teasing versus being mean.
This is tough for Lillie. She thinks very black and white. If someone says “I don’t like that shirt,” she hears “I don’t like you.” If someone says something sarcastic, she takes it literally. Jokes often fly over her head, and in groups she burns energy just trying to keep up.
That’s why outings with friends have to be intentional. She thrives in one-on-one playdates where she can focus on just one person. But in bigger groups—movie nights, group sleepovers, playground cliques—she often ends up on the fringe, pitcher drained, feeling like she doesn’t belong.
So we protect her energy. We plan shorter playdates. We choose friends who bring out her best. We give her one-on-one time where she can shine instead of constantly trying to “keep up.”
Motor Skills: Where She Surprises Us
Many ACC kids struggle with fine or gross motor skills, but this is an area where Lillie blows us away.
She’s athletic. She learned to ride a bike with ease, which often requires left brain/right brain communication that can be hard for kids with ACC. She loves softball, and she’s actually really good at it. Catching, throwing, running—these come naturally to her.
She also loves activities that use her fine motor skills: crafting, writing, cutting. Her handwriting is neat, her creativity pours out on paper, and she finds joy in showing what her hands can do.
This is one of the biggest surprises of her journey. Where doctors told us to expect delays, we’ve found strengths.
Anxiety: Hyperfixation and the Need for Certainty
Anxiety is one of the heaviest things she carries. For Lillie, it’s not just worry—it’s hyperfixation.
If she has a question, she needs an answer. “When is the makeup softball game?” “Can my friend come over this weekend?” “What time is dinner?” If you don’t know, or if the answer is “we’ll see,” it’s like someone tips her pitcher over. She cannot let it go. She will ask again and again, circling back like her brain is stuck on a track it can’t exit.
And in real life, we don’t always have answers. Sometimes we don’t know when a game will be rescheduled. Sometimes we can’t say if a friend can come over. But uncertainty is unbearable for her. It leaves her anxious, frustrated, and often melting down because her brain can’t rest without resolution.
This is where visual schedules, calendars, and planners help—but they don’t fix everything. Sometimes life is just uncertain. And that’s one of the hardest lessons for her, and for us.
Where She Fits—and Where She Shines
So yes, Lillie fits many of the “classic” ACC challenges: executive functioning, slow processing speed, social cognition, and anxiety. But she also shines in unexpected ways—athletic ability, fine motor skills, creativity, and humor.
Her race car brain makes her path different. It makes her need more pit stops, more structure, and more support. But it also makes her resilient, resourceful, and uniquely her.
If you’re new here because ACC has become part of your story, welcome. You’re not alone.
I’ve written more about our life with ACC—the joys, the struggles, and everything in between. You can find all of those posts here. If you are new to disorders of the corpus callosum, I also recommend checking out the NODCC's website or on Facebook. The NODCC is an amazing resource—they host webinars, have a large and supportive Facebook community, and hold conferences to learn more about the diagnosis, ongoing research, and to connect families together.
Because a race car brain doesn’t mean a broken brain—it means a different kind of magic. ✨
