I have no clue. The information stated is "Head injury is the general category and generally implies brain injury, but sometimes there is head injury without brain injury."
I see nothing about if "generally implies" means 5% or 95%. Do you? I assume it's "more than 50%", so I went to the referenced paper. That says:
> In Table 2 head injury is the most general injury category which may also include injury to the back of the head, face and brain (some studies consider facial injury as a head injury, other studies do not). Brain injury specifically refers to the brain, and facial injury specifically refers to injury to the face (chin, nose mouth, jaws, eyes, forehead, ears). Elvik compared the risk proportions of a specific injury occurring or not occurring
In Table 2, however, you'll see that brain injury appears to be less common than non-brain injuries involving the head.
However, Table 2 is a metadata analysis with insufficient few brain injury studies to "allow correction for publication bias", and not specific to the Netherlands. (A copy of the paper is at http://www.cycle-helmets.com/elvik.pdf .) Therefore it can't be used to conclude anything about the situation in the Netherlands.
You'll also notice that point 3 of the conclusion in Elvik reads "When the analysis is updated by adding four new studies, the protective effects attributed to bicycle helmets are further reduced. According to the new studies, no overall effect of bicycle helmets could be found when injuries to head, face or neck are considered as a whole."
So, no, I don't know. I ask how you know when that information isn't available in the papers you cited.
Where is the horror story?