Aspirating subdural effusions, so called brain stem shock.

A shift of blood into the head during negative pressure aspiration of subdural haematomas in an infant has been demonstrated, and also that aspiration may restart bleeding. An estimate of the elasticity of a 47 cm circumference skull has been obtained. It is suggested that the observed changes in distribution of blood are sufficient to explain the occasional deaths of infants after aspiration of subdural haematomas and that so-called "brain stem shock" need not be invoked.