Fissure ventricular syndrome is a common complication after ventriculoperitoneal shunts for hydrocephalus, especially in children. Many babies who have hydrocephalus need a ventriculoperitoneal shunt to carry some of the excess water inside the brain to the stomach. The water shunted into the tummy is then absorbed through the peritoneum. For many possible reasons, the water in the shunt flows too much and too fast, and most of the water inside the brain is retained in the stomach. The ventricles that were originally dilated like a lake because of water accumulation gradually become as small as a stream, and we call such a ventricle a lacunar ventricle. When the baby’s ventricle is so small that it is only as thick as a shunt, the wall of the ventricle will wrap around the shunt and cause a temporary failure of the shunt, and then the baby will have headache, vomiting, poor appetite, stomach pain, sleepiness, and other manifestations, and in severe cases, even visual impairment, coma, and convulsions. When the water in the ventricle reaches a certain level, the ventricle will be “held” large again. The shunt reopens, and the baby’s symptoms improve. The recurrence of this condition is called lacunar ventricular syndrome.