CSF shunt placement is the most common neurosurgical procedure performed in children More than 4,400 CSF shunts were placed in 2003; CSF shunt–related problems accounted for almost 15,000 hospital admissions and almost $300 million in charges for shunt malfunctions CSF shunts are placed to divert CSF from the brain to another area of the body, most commonly the peritoneal cavity The clinician evaluating a child with a CSF shunt should be aware of associated complications such as infection, obstruction, and overdrainage, because certain complications can be disastrous if unrecognized and untreated However, children with CSF shunts may often exhibit symptoms of their chronic illnesses that are unrelated to shunt malfunction Pathophysiology CSF is an ultrafiltrate of plasma produced at a rate of 500 mL/day in a 70-kg adult and proportionally less in children and infants The fluid is mainly produced by the choroid plexus and various extrachoroidal sites within the brain CSF travels from the lateral ventricles into the third ventricle through the foramen of Monro and then again through the aqueduct of Sylvius to the fourth ventricle The CSF then enters the subarachnoid space via the foramina of Luschka and Magendie and travels through the brain and spinal canal CSF is reabsorbed and enters the venous system through the “one-way valves” of arachnoid villi that penetrate the dura Hydrocephalus can result from oversecretion, impaired absorption, or blockage of CSF pathways Oversecretion can occur in some choroid plexus tumors Impaired absorption can occur as a result of increased CSF protein, often a result of perinatal hemorrhage or meningitis or less commonly etiologies such as subarachnoid hemorrhage, or Guillain–Barré syndrome Severe congestive heart failure or any other condition that raises venous pressure may impair CSF absorption as well Impaired absorption is the cause of communicating hydrocephalus, in which flow from the lateral ventricles to the foramina of Luschka and Magendie is not obstructed Blockage of CSF pathways , or obstructive hydrocephalus, is the most common cause of hydrocephalus in children This is often located at the narrow aqueduct of Sylvius proximal to the fourth ventricle and is referred to commonly as aqueductal stenosis Conditions that can cause obstruction are intraventricular bleeding or scarring, tumors, or congenital malformations Dandy–Walker cysts cause obstruction of the foramina of Luschka and Magendie and therefore may result in enlargement of all four ventricles Equipment