Brain injuries are characterized based on initial presentation. Basically: How bad are symptoms right after the injury?

In some ways it’s like categorizing paintings as small, medium, large, and extra-large. It’s easy to apply. But doesn’t really tell you about the impact the painting is going to have on the world.

For example, The Lacemaker, by the Johannes Vermeer, is only 9.6″ × 8.3″. It’s smaller than a sheet of notebook paper.

A “severe” brain injury may start with "big" symptoms but ultimately not have a major effect on some particularly resilient people (like setting an intense fire during rainy seasons).

And a “mild” concussion may start with small symptoms but can initiate a series of events that has a profound effect on a more vulnerable/susceptible person (like setting a little fire when everything is really dry or it’s windy out).

The "size" of the symptoms right after a head injury does not predict the extent of the recovery or disability the injured person will experience.

Beyond initial triage, outcome seems like a much more important consideration than initial severity.