Epidemiology of Concussions: A Deep Dive Into Brain Injuries from Car Accidents in Kansas City

Meta Description: Over 3.8 million Americans suffer concussions annually—often undiagnosed, especially after car accidents. Learn the science behind concussions, axonal shearing, BBB disruption, and how mild TBIs cause serious, lasting damage. Dr. Lance Stevenson, DC is Kansas City’s trusted concussion specialist.

Concussions Are a Silent Epidemic—And They're Everywhere

An estimated 3.8 million concussions occur annually in the United States, affecting roughly 1.15% of the population. Of these, over 240,000 result from motor vehicle accidents (MVAs). But many more go unreported because the injury is invisible—especially after low-speed car crashes, which are often dismissed as “minor.”

In Kansas City, we see patients from Liberty, Overland Park, Blue Springs, and The Plaza who walk away from collisions seemingly “fine,” only to experience memory issues, fatigue, anxiety, and sleep disruption days or weeks later. These symptoms are signs of a neurological injury, even if no impact to the head occurred.

What Is a Concussion—And What’s Really Happening in the Brain?

A concussion is a mild traumatic brain injury (mTBI). Despite the “mild” label, it represents a serious physiological injury to brain tissue, not a bruise, bump, or momentary daze.

The mechanism of a concussion involves:

• Rapid acceleration-deceleration of the skull

• Internal movement of the brain inside the cranium

• Axonal stretching and shearing

• Microscopic disruption of brain tissue and vasculature

• Altered chemical signaling and metabolic dysfunction

It’s no longer accurate to describe concussions as “coup-contrecoup” injuries (where the brain hits one side of the skull and then the opposite). The real problem is diffuse axonal injury (DAI)—a more subtle but widespread mechanism involving:

Axonal Stretching and Shearing

Axons are the long, thin projections of neurons responsible for sending signals across brain regions. These structures are delicate and susceptible to forces generated by:

• Rotational acceleration, not just direct impact

• Torsion that twists different parts of the brain at different speeds

• Shearing that causes axons to tear or become dysfunctional

In mTBI, axons may not snap completely, but instead become microscopically damaged, interfering with normal neurotransmission. This is often referred to as “axonal dysfunction without disconnection.”

Functional MRI and DTI (diffusion tensor imaging) studies confirm that this diffuse injury, especially in white matter tracts, underlies much of the cognitive and emotional impairment seen in post-concussion syndrome.

The Glasgow Coma Scale: Where Concussions Fall

Clinically, concussions fall under mild TBI based on the Glasgow Coma Scale (GCS):

• 13–15 = Mild

• 9–12 = Moderate

• 3–8 = Severe

The GCS assesses eye opening, verbal response, and motor response. However, this scale does not reflect the extent of microscopic damage, and nearly all concussion patients score 15 upon arrival at the ER.

This is why concussions are often missed or dismissed, even though the brain has sustained meaningful physiological disruption.

Why Car Accidents—Even Minor Ones—Cause mTBI

Most concussions we treat in Kansas City don’t come from a helmeted football tackle or a fall. They come from rear-end, front-end, and side-impact car crashes, many at under 25 mph.

Key forces at play:

• Linear acceleration (front-back motion)

• Rotational acceleration (twisting forces)

• Angular acceleration (diagonal shearing)

Because the brain has different densities in different areas, these forces create uneven movement—causing stretching, torsion, and shearing of axons, especially at the junction between gray and white matter.

Even if you don't hit your head, your brain can move at a different speed than your skull, and this relative motion is what causes most of the damage.

Concussion Physiology: Beyond Bruises and Bumps

A concussion disrupts brain function through a neurometabolic cascade, not through gross structural damage (like bleeding or bruising). This means most standard imaging (CT, MRI) will appear normal.

Key Physiological Events Include:

1. Axonal Stretching → Disrupts normal firing of neurons

2. Calcium Influx into Cells → Triggers mitochondrial dysfunction

3. ATP Depletion → Brain enters an energy crisis, up to 20–50% ATP loss

4. Glutamate Surge → Leads to excitotoxicity and cellular stress

5. Reduced Cerebral Blood Flow → Just when energy demands are highest

6. Leaky Blood-Brain Barrier (BBB) → Immune cells and toxins flood in

These changes can occur within minutes and may last weeks or longer, depending on the severity and whether proper rest and rehabilitation are pursued.

The Blood-Brain Barrier and Neuroinflammation

After a concussion, the blood-brain barrier (BBB)—which normally protects your brain from harmful substances—becomes compromised.

This allows:

• Inflammatory cytokines

• Immune cells

• Toxins

• Abnormal proteins

to enter the brain environment. The result is neuroinflammation, which can cause:

• Headaches

• Cognitive fog

• Mood changes

• Sleep disruption

• Hormonal imbalance

This inflammatory environment is what leads to persistent post-concussion symptoms, even if the patient "feels fine" for the first few days after the injury.

Cumulative Brain Injury: Why the Second Concussion Is Worse

One concussion causes metabolic and structural stress—but a second concussion during the recovery window can be devastating.

• ATP levels may not have normalized

• BBB may still be leaky

• Axons may be vulnerable to further stretching

• Neuroinflammation may already be primed

A second hit—even a mild one—can lead to a stacked depletion of brain energy and worsening symptoms. Studies show that back-to-back concussions increase the risk for:

• Post-concussion syndrome (PCS)

• Cognitive dysfunction

• Mood disorders

• Degenerative diseases like CTE

This is why return-to-play and return-to-life decisions must be made with professional oversight—not just based on how a person "feels."

You Deserve Expert Concussion Care in Kansas City

If you've been in a car accident—even if it was “just a fender bender”—you may have sustained a brain injury. Symptoms might not appear immediately, but undiagnosed concussions can have long-term consequences.

Dr. Lance Stevenson, DC is Kansas City’s expert in post-trauma brain injuries. Our clinic specializes in:

• Accurate mTBI evaluations

• Targeted therapies for neuroinflammation and vestibular dysfunction

• Medical liens so you pay nothing upfront

• Collaborations with top Kansas City personal injury attorneys

Call Today: 816-226-7476

Don't leave a brain injury untreated. Let us help you recover fully and safely.