A head-injured motorcyclist was defined
as a motorcycle driver or passenger
who, after having received direct or indirect
trauma to the head, exhibited obvious brain
concussion, contusion, skull fracture, or any
of their clinical manifestations, such as loss
of consciousness, amnesia, neurologic
deficits, and seizures. Clinical evidence of
skull fractures and intracranial hemorrhages
was also included to define the extent of head
injury. In general, a motorcyclist with 1 or
more of the aforementioned symptoms or diagnoses
was registered as a head-injured motorcyclist.4