Significance of relative movements of scalp, skull, and intracranial contents during impact injury of the head.

High speed cinephotography provides an ideal method for the study of rapid movements occurring at the time of impact. We have used this technique to analyze blows to the head by linear and rotating impactors in the dog, Rhesus monkey, in human cadavers, and skull models. Movements of the skull in its soft tissue environment may be seen at the time of impact in spite of restraints. 5 This is seen in exaggerated form in Fig. 1 when the head is free to move; after impact the stiffer skull tends to move more rapidly than the scalp, which appears to lag behind. Such movements may result in tear of connecting blood vessels between scalp and skull. Subaponeurotic hematoma may develop by this mechanism with no apparent bruise or laceration of the scalp. Relative movements of the intracranial contents have been deduced on clinical grounds; for instance, anosmia due to torn olfactory nerve filaments may result from a deceleration impact of the occipital area. Movements of the brain within the dural sac due to angular acceleration may produce