Non Invasive Measurement With Trans Cranial Doppler Versus Invasive Measurement in Pediatric Age

This study is comparing a non-invasive brain monitoring method (transcranial Doppler ultrasound, which uses sound waves to measure blood flow in brain vessels) against invasive pressure monitors placed directly in the brain, in children who already require brain pressure monitoring as part of their care. **You may be eligible if...** - You are a child who already has an invasive brain pressure monitor placed as part of your medical treatment - Your parent or guardian has provided informed consent **You may NOT be eligible if...** - You have a fracture at the base of the skull - Informed consent has not been provided Talk to your doctor to see if this trial is right for you.