Are you sure?. We have a thing called tomography with things like xrays, magnetic resonance that let's us look inside bodies.
Experiments were done in the past with animals that have a similar brain to us, specially aviation military, that were extremely interested on concussions.
At least they have x-rays photography of impacts. By the way all this research led to car's seatbelts.
Thousands of brain surgical procedures are done each year, there are experts in the anatomical features of the brain, and we have detailed maps of sliced brains and complete heads.
Tens of thousands of people die in car accidents and hundred of thousands are injured. Insurance companies have extensive documentation on those.
We know the physical properties of those things and we have things called computers that let us do very complex models about the brain with finite elements or just analog 3d printed models with gelatin and plastics.
To say that nobody can imagine a brain in motion, so everything is a hypothetical mechanism is quite unfortunate.
We know a lot about what happens more or less. Things have improved dramatically for people like motorbike racers because we actually know a lot and lots of lives had been saved because of that.