A review of central nervous system effects of G-induced loss of consciousness on volunteer subjects.

A review of the literature on the central nervous system (CNS) effects of repeated centrifuge acceleration studies involving G-induced loss of consciousness (G-LOC) reveals that remarkably few adverse effects have been reported, aside from the G-LOC itself, even in subjects with numerous exposures. However, most of the followup studies were performed before the availability of sophisticated neuropsychological tests and non-invasive means of imaging the CNS, such as computerized tomography (CT), magnetic resonance imaging (MRI), brain electrical activity measurement (BEAM), and positron emission tomography (PET). Further, only a handful of long-term followup studies have been done. Thus, although repeated G-LOC may have induced some long-term adverse CNS effects, either organic or functional, little has been done to detect them. Even granted that some damage may be done, this risk must be weighed against the risk of aviators of similar damage from high +Gz exposures in flight, and even more against the risk of fatal G-LOC aircraft accidents. Volunteers for centrifuge acceleration studies should be fully informed about what is known and not known in this regard. As an ancillary measure, head restraints may be useful in avoiding postural trauma to the cervical spine, or impact injury to the head when G-LOC occurs and the head snaps forward and down.