What Actually Happens to Your Brain During a Concussion?
If you’ve ever had a concussion, you’ve probably been given a generic explanation—or worse, no explanation at all. Most people think of a concussion as their brain “bouncing around” inside their skull, and while that’s part of the story, the reality is much more complex.
In fact, most of the concussion patients I see have been dealing with symptoms for over a year, have seen multiple providers, and yet no one has ever actually sat them down and explained what’s happening inside their brain.
So, let’s fix that. In this article, I’m going to break down what really happens when you sustain a concussion—starting with the big picture mechanics of injury, then zooming in to what happens at the cellular level, and finally, what that means for your recovery timeline.
What Is a Concussion? (And How It Actually Happens)
According to the 6th International Conference on Concussion in Sport, a concussion is defined as:
“A traumatic brain injury caused by a direct blow to the head, neck, or body resulting in an impulsive force being transmitted to the brain.”
Key takeaway? You don’t have to hit your head to get a concussion. Any force that shakes the brain inside the skull—whether from a fall, a car accident, a sports collision, or even a blast injury—can cause the same type of injury. But what actually happens inside the skull?
The Mechanics of Brain Injury: It’s More Than Just a Bounce
Most people think of a concussion as their brain slamming into the skull and bouncing back (coup-contrecoup injury). And while that does happen, there’s something even more important at play—rotation and shearing forces.
Why Rotation Matters
Your brain and skull are both round-ish, meaning that when your brain moves inside the skull, it doesn’t just go in one direction, stop, then bounce back. Instead, it rotates, and that rotation creates stretching and shearing forces that ripple through the brain tissue.
Think of it like wringing out a wet towel—the middle of the towel gets twisted and pulled the most. In your brain, the center takes the most strain—and what lives in the center?
The brainstem – Critical for eye movement, balance, heart rate, and breathing.
The vestibular nuclei – The system that tells your brain where you are in space.
These areas are highly sensitive to damage, which is why so many concussion symptoms involve dizziness, vision problems, and balance issues.
The Neuro-Metabolic Cascade: What Happens at the Cellular Level?
Now, let’s zoom in even further. At a cellular level, a concussion isn’t just about structural damage—it’s a chemical crisis. This is what’s called the neuro-metabolic cascade, and it’s why many people feel worse for days after a concussion, even if their initial symptoms seemed mild.
1. Molecules Swap Places
“When an mTBI is induced, the plasma membrane undergoes mechanoporation via sheering and stretching forces that cause an influx of sodium and calcium and an efflux of potassium.”
Your brain is made up of neurons, and these neurons communicate by passing electrical signals to each other. But to do that efficiently, they maintain a careful balance of charged molecules, mainly sodium and potassium.
Normally: There’s a high concentration of sodium outside the neuron and potassium inside the neuron. When a neuron wants to send a signal, a controlled exchange of these ions happens—sodium enters, potassium exits, and the message is passed down the line.
After a concussion: The force of impact disrupts this balance, causing sodium and potassium to rush across the neuron membrane uncontrollably—essentially tricking the neurons into thinking they’ve all been activated at once.
Imagine a massive group text message gone wrong—one person sends a message, but instead of it being delivered in an orderly fashion, everyone starts replying at the same time, flooding the chat with messages that don’t make sense. That’s what happens inside your brain.
2. Massive Energy Demand
Now that millions of neurons are firing all at once, your brain goes into crisis mode. It scrambles to restore order by pumping sodium out and potassium back in, trying to reset itself back to normal.
Here’s the problem: That process requires a TON of energy. And since the energy demand suddenly skyrockets, your brain burns through ATP (the cell’s energy currency) faster than it can produce it.
“It was reported that there was a 30–46% increase in neuronal glycolytic rate about 30 min after injury”
Think of it like your phone overheating because you have too many apps running at once—except instead of closing a few tabs, your brain is stuck in overdrive, desperately trying to fix the problem.
The result?
You feel exhausted.
You experience brain fog.
Your symptoms might actually get worse in the first 24–48 hours.
That’s why rest is crucial early on—your brain is in survival mode, and it doesn’t have the energy to spare.
3. Oxygen & Blood Flow Drop
Here’s where things get even trickier. While your brain is scrambling for energy, it also loses access to one of its most important resources—oxygen. Normally, your brain receives steady blood flow, delivering oxygen and nutrients to fuel recovery.
“Cerebral blood supply has been demonstrated to be reduced by up to 50%.”
A 50% reduction in blood flow means your brain is now starved of oxygen and energy at the time when it needs it the most. It’s like trying to put out a massive fire with a garden hose—your brain needs as much fuel as possible, but it’s only getting half of what it should. This mismatch between high energy demand and low energy supply is what makes concussions so unpredictable—some people bounce back quickly, while others feel completely drained for weeks.
4. Your Brain Goes Into Energy Debt
Now, let’s talk about what happens after the initial injury. Because your brain just burned through an insane amount of energy and didn’t have enough blood flow to replenish it, you’re left in a state of energy debt—kind of like maxing out a credit card.
In the first few days, your body is scrambling to "pay off" that energy debt.
Your symptoms (fatigue, headaches, dizziness) reflect that recovery process.
Even when you start feeling better, your brain might not be fully back to normal yet.
This is why athletes who return to play too early are at the highest risk of a second concussion—their symptoms might be gone, but their energy reserves are still depleted. Imagine barely paying off the minimum balance on a credit card, then immediately maxing it out again. That’s exactly what happens if you push yourself too soon after a concussion.
Symptom Resolution vs. Brain Recovery: Why Timing Matters
A common mistake concussion patients make is assuming that if their symptoms go away, their brain is healed. Not necessarily. A study using magnetic resonance spectroscopy measured brain metabolism in concussed athletes over a 30-day period and found that:
“At 30 days post-injury, all athletes showed complete recovery, having metabolite ratios returned to values detected in controls. However athletes self-declared symptom clearance between 3 and 15 days after concussion.”
What This Means for You:
Just because you feel fine doesn’t mean your brain has fully recovered.
Returning to sports or normal activities too soon puts you at risk for prolonged recovery or even permanent damage.
On average, it takes 4-6 weeks for brain metabolism to return to baseline.
Think of it like paying off a credit card—even if you make a minimum payment, the debt (energy deficit) is still there, and interest is accumulating in the background. If you start spending again too soon, you dig yourself deeper into debt—which is exactly what happens when people return to play before full metabolic recovery.
Post-Concussion Syndrome: What If Symptoms Don’t Go Away?
For most people, concussion symptoms resolve within a few weeks. But for a minority, symptoms can persist for months or even years—this is known as post-concussion syndrome (PCS). Why does this happen?
There’s no single cause, but some common factors include:
Unresolved brainstem dysfunction (vestibular issues, dizziness, eye tracking problems).
Autonomic nervous system dysregulation (heart rate, blood pressure instability).
Neuroinflammation (lingering metabolic issues preventing full recovery).
Psychological factors (stress, anxiety, and past trauma can amplify symptoms).
If that sounds like you, that’s where someone like myself comes in. Through a comprehensive neurological exam, my job is to figure out which areas of your brain aren’t functioning optimally and create a treatment plan tailored to your specific needs.
For a more detailed breakdown of post-concussion syndrome check out our blog entitled: Why Some People Recover Quickly and Others Struggle for Months
Final Thoughts
If you’re struggling with a concussion that hasn’t fully resolved, you’re not alone—and there are answers.
Download my free Concussion Recovery Guide – A step-by-step breakdown of what to do and what to avoid to support healing.
Schedule a free consultation – If you’re still dealing with symptoms, let’s chat. I’ll listen to your story, assess your situation, and see if I can help—or point you in the direction of someone who can.
