Approximately one in 500 children develop hydrocephalus, excessive cerebrospinal fluid accumulation in the ventricles of the brain, the National Institute of Neurological Disorders and Stroke states. Obstruction of cerebrospinal fluid drainage or decreased absorption of fluid causes hydrocephalus, the most common cause of an abnormally large head in an infant. Spina bifida, an abnormal spinal opening, and Dandy-Walker malformation, a syndrome that causes progressive ventricle enlargement, result in obstructive problems. Additionally, infection and brain hemorrhage can cause decreased fluid absorption, the Merck Manuals Online Medical Library explains. Placing a shunt in a newborn's head to drain fluid treats hydrocephalus, but can have side effects.
Blockages
Blockages within the shunt generally develop slowly over time. Gradual reappearance of learning difficulties, motor dysfunction, headache, lethargy, irritability or a bulging fontanel can indicate a blockage in the shunt which allows fluid to build up in the ventricles. Scalp veins may appear more visible than normal in infants and head size may gradually enlarge. Personality changes, loss of previous abilities and extreme tiredness may develop, warns the SANDI Project, a collaborative of the University of Houston, the Hospital for Sick Children in Toronto, and several other Houston hospitals. Blockage that develops suddenly may cause severe headaches, vision disturbances and vomiting. Seizures may also occur. The blocked shunt may require removal and surgical replacement or adjustment.
Infection
Infection can occur around the shunt. Symptoms of infection depend on the type of shunt used. Most shunts drain into the abdominal cavity, while others drain into the right atrium of the heart. An infection in a shunt that drains into the abdominal cavity, called a ventriculoperitoneal shunt, can cause abdominal pain and fever, along with the symptoms of blockage. An infection in a shunt that drains into the atrium, called a ventriculoatrial shunt, can cause intermittent fever, anemia and rashes. Back and neck soreness and redness along the shunt may also occur with shunt infection, NINDS states. Ventriculoatrial shunt infection may take months to become evident, the SANDI Project reports. An infected shunt requires removal and often a course of antibiotic therapy before placing a new shunt.
Mechanical Failure
A valve in the shunt keeps fluid flowing in only one direction and also regulates the amount of flow. Mechanical problems with the valve can cause too much or too little fluid to drain from the ventricles. Over-draining can cause collapse and tearing of the ventricles, causing headache, hemorrhage into the brain or development of slit ventricle syndrome, NINDS warns. Under-draining can lead to recurrence of the symptoms of hydrocephalus. Mechanical problems require surgical repair or replacement of the shunt.
