Why the overpressure on the anterior fontanelle by neonatal brain ultrasound cause bradycardia of the neonate?

Cushing reflex : Increased intracranial pressure from any cause at any age & decreased blood flow to certain parts of the brain can cause Cushing's triad: increased blood pressure, irregular breathing, & bradycardia. Since a neonate's skull bones aren't fused, increased pressure causes the fontanelle to bulge. Doctors will determine the cause - hydrocephalus, bleeding, infection, etc. & reduce the pressure ASAP.