98
K. H. Yang and H. Mao
and 60.7% of all TBI cases, respectively, for these two age groups. Other studies
suggested that transportation-associated incidents, construction- and sports-related
events, and violent assaults are other leading causes of TBIs [52, 91]. In recent
Middle East military conflicts, blast exposure became the leading cause of mild TBI
(mTBI) for active duty military personnel in war zones [66].
Summarised from these injury causation studies, TBI is most commonly induced
by mechanical forces that instigate a direct impact (e.g. head hitting windshield,
falling onto sidewalk, struck by an object, a direct blow to the head in a fist
fight) or an indirect impact (e.g. sudden motion of a well-restrained occupant in an
abruptly stopped car, exposure to blast waves) to the head. Both direct and indirect
impacts could cause immediate damage to the brain (primary injury mechanism)
or delayed impairment responses (secondary injury mechanism) due to biochemical
and pathophysiological reactions after the primary injury. Despite great progresses
have been made in a large number of animal studies, preclinical investigations, and
phase I clinical trials, it is unfortunate that nearly all phase II and III clinical trials
have failed to provide consistent treatment options for TBI patients [88, 102]. In the
USA, phase I clinical studies refer to the assessment of a drug/device safety, phase
II studies are related to testing the efficacy of a drug/device, and phase III studies
involve randomised and blind testing in a large number of patients.
5.1.2 Investigating the Mechanisms of TBI
As little can be done clinically to reverse the initial brain damage caused by trauma
at present, preventing TBI from happening and stabilising a TBI victim to prevent
further injury are two key areas of research for the biomechanical community.
To this end, a better understanding of the causations and mechanisms of TBI,
especially mTBI (e.g. concussion), can provide the scientific basis for designing
better protective devices (e.g. sports helmet), improving diagnosis and prognosis
tools, and devising new therapeutic methods for protecting the healthy ones and
stabilising the injured victims.
To study injury mechanisms or to create TBI in animals for drug testing,
impact equipment (such as sleds, pendulum, drop tower, fluid percussion devices,
or controlled cortical impact devices) are commonly used to generate sufficient
force or acceleration for the development of experimental models. During the
test, globally quantifiable variables (e.g. impact force, ambient pressure) and local
response variables (e.g. head acceleration, intracranial pressure) at a limited number
of locations are measured. Based on these measurements, a number of injury
mechanisms and associated thresholds (e.g. head injury criterion (HIC) less than
700, Brain Injury Criteria (BrIC) less than 1) have been hypothesised. As these
mechanisms do not always correlate with clinical or pathological observations,
considerable controversies still exist regarding the validity of these competing
hypotheses.
K. H. Yang and H. Mao
and 60.7% of all TBI cases, respectively, for these two age groups. Other studies
suggested that transportation-associated incidents, construction- and sports-related
events, and violent assaults are other leading causes of TBIs [52, 91]. In recent
Middle East military conflicts, blast exposure became the leading cause of mild TBI
(mTBI) for active duty military personnel in war zones [66].
Summarised from these injury causation studies, TBI is most commonly induced
by mechanical forces that instigate a direct impact (e.g. head hitting windshield,
falling onto sidewalk, struck by an object, a direct blow to the head in a fist
fight) or an indirect impact (e.g. sudden motion of a well-restrained occupant in an
abruptly stopped car, exposure to blast waves) to the head. Both direct and indirect
impacts could cause immediate damage to the brain (primary injury mechanism)
or delayed impairment responses (secondary injury mechanism) due to biochemical
and pathophysiological reactions after the primary injury. Despite great progresses
have been made in a large number of animal studies, preclinical investigations, and
phase I clinical trials, it is unfortunate that nearly all phase II and III clinical trials
have failed to provide consistent treatment options for TBI patients [88, 102]. In the
USA, phase I clinical studies refer to the assessment of a drug/device safety, phase
II studies are related to testing the efficacy of a drug/device, and phase III studies
involve randomised and blind testing in a large number of patients.
5.1.2 Investigating the Mechanisms of TBI
As little can be done clinically to reverse the initial brain damage caused by trauma
at present, preventing TBI from happening and stabilising a TBI victim to prevent
further injury are two key areas of research for the biomechanical community.
To this end, a better understanding of the causations and mechanisms of TBI,
especially mTBI (e.g. concussion), can provide the scientific basis for designing
better protective devices (e.g. sports helmet), improving diagnosis and prognosis
tools, and devising new therapeutic methods for protecting the healthy ones and
stabilising the injured victims.
To study injury mechanisms or to create TBI in animals for drug testing,
impact equipment (such as sleds, pendulum, drop tower, fluid percussion devices,
or controlled cortical impact devices) are commonly used to generate sufficient
force or acceleration for the development of experimental models. During the
test, globally quantifiable variables (e.g. impact force, ambient pressure) and local
response variables (e.g. head acceleration, intracranial pressure) at a limited number
of locations are measured. Based on these measurements, a number of injury
mechanisms and associated thresholds (e.g. head injury criterion (HIC) less than
700, Brain Injury Criteria (BrIC) less than 1) have been hypothesised. As these
mechanisms do not always correlate with clinical or pathological observations,
considerable controversies still exist regarding the validity of these competing
hypotheses.