A blow to the head does not have to bleed to break something. The scan can come back clean and the person can still be gone.
The injury you cannot see
In a hard enough hit, the brain shifts inside the skull and the long fibers that carry its signals, the axons, are stretched and sheared at the moment of impact. This is diffuse axonal injury. It is not a bruise you can point to on a picture. It is a disruption spread thin across the wiring, thousands of small breaks in the connections that make a person feel like themselves.
Why the scan is clean
A CT looks for blood and broken bone. In a concussion it usually finds neither, and the report comes back normal. Standard MRI often does the same. The damage is microscopic and everywhere at once, which is exactly the kind of injury these scans were never built to see. Specialized imaging can pick up the white-matter damage, but it is rarely ordered. A normal scan is not a healthy brain. It is a scan that did not look for this.
What the fog is
The words that will not come. The appointment forgotten. The fatigue that sleep does not fix. The light and the noise that never used to bother them. The person who is half a step behind the person they were. This is post-concussive, and to the people who live with the client it is not subtle at all.
The lesson
When the defense holds up a clean CT like a verdict, that is the trap. The absence of blood on a scan is not the absence of injury. Prove the harm through the life it changed, honestly and within what the science supports, and the clean scan stops being a shield.
On the mechanics of brain injury and its aftermath, see Traumatic brain injury (Nature Reviews Disease Primers) and A Multidimensional Approach to Post-concussion Symptoms in Mild Traumatic Brain Injury (Frontiers in Neurology). This is general information, not medical or legal advice.
