The force of the head movement can tear blood vessels that bridge the brain and skull, because these are fragile and immature. When shaking occurs, the brain bounces within the skull cavity, bruising the brain tissue. The brain swells, creating pressure and leading to bleeding at the back of the eye. This can cause blindness. Some blood vessels that feed the brain are torn, which leads to additional brain damage or abnormalities.
Blood collects inside the skull, creating more pressure.
Immediate effects include seizures, lethargy, vomiting, and irritability, or in extreme cases, coma or even death. Infants can also sustain eye injuries, such as detached retinas or retinal bleeding, from the violent shaking. Long-term effects include learning disabilities, physical disabilities, seizures and, in extreme cases, death. The injuries are usually caused by parents or carers who have become frustrated by their inability to stop a baby who is crying constantly. Adults who were victims of abuse themselves and have low frustration levels may be more likely to shake a baby to hush its crying.