by Staff 7.10.2007
During a shaking episode, the infant's brain moves back and forth in a figure-eight motion. This movement creates acceleration-deceleration forces on the brain. This force causes blood vessels to break and blood to spill into the spaces between the brain and its protective covers. Subdural hemorrhages are seen in 90% - 98% of SBS cases (Duhaime et al 1987) and subarachnoid hemorrhages are seen in approximately 83%, and in almost all autopsy cases (Gilles & Nelson 1998). Epidural hemorrhages, bleeding between the outermost protective cover and skull, as well as subgaleal hemorrhages, bleeding between the scalp and skull, are occasionally seen when shaking is accompanied by impact.
Hemorrhages often increase pressure in the brain producing other injuries. The extra pressure squishes the brain inside the skull causing it to swell - cerebral edema. This in turn can cause other injuries such as hypoxia - lack of oxygen in the brain, ischemia - lack of oxygenated blood in the brain, infarction - tissue death, and encephalomalacia - brain softening. It is these secondary injuries that can cause the most devastating impact on infants such as cerebral palsy and death.
In addition to blood vessels breaking, a shaking episode can also create traumatic axonal injury. The axons are part of the neurons that are responsible for receiving and sending messages needed for breathing, thinking, heart functioning, etc. During the shaking episode, these axons can stretch and tear which damages the neurons to such an extent that the brain can stop functioning properly and these neurons can die.
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