Experimental head injury in monkeys --concussion and its tolerance level--.

Abstract

The authors obtained the following results in this experiment in which monkeys were subjected to frontal and occipital blows with their heads in an unrestrained condition. 1) With respect to the impact to the head and the occurrence of concussion, translational acceleration is more important than rotational acceleration. 2) The concussion threshold of monkeys was an equal speed curve of 16 m/s for occipital blows, while in the case of frontal blows, a hyperbolic curve which is somewhat higher than that for occipital blows was obtained. This concussion tolerance curve was converted into the concussion tolerance curve for humans by means of dimensional analysis. 3) A close correlation was suggested between changes in the EEG amplitude and the severity of the concussion. The more severe the concussion, the greater the decrease in the EEG amplitude. 4) The concussions could be classified into three types pathologically. The first type showed capillary dilatation and vascular permeability. The second type showed hemorrhages at sites far from the cerebral cortex and the third type showed hemorrhages in the cerebral cortex. The second and third types were in parallel with the severity of the concussion.