is usually obstructed by choroid plexus, but floating debris or hypercellular CSF can result in the same obstruction; the distal catheter can be obstructed by the surrounding omentum or can be kinked or coiled Both proximal and distal portions can be occluded by the products of infection or by migration of the catheter tip into the brain parenchyma or intra-abdominal structures Poor absorption of excess fluid in the peritoneum due to decreased surface area can create the appearance of luminal obstruction, particularly in neonates In addition, as the child grows, the tension on the shunt system can lead to disconnection of the distal tubing Up to 60% of patients with CSF shunts experience a shunt malfunction in their lifetime, most commonly within the first months of initial shunt placement Parental history is paramount in deciding whether a child is experiencing symptoms of shunt malfunction The parent often notices that the child “just isn’t acting right” or is less active or thinking less clearly than usual The statement, “This is exactly how he acted the last time his shunt was obstructed,” is suggestive of another malfunction, regardless of the presence or absence of the symptoms listed in the following section Common signs and symptoms of mechanical shunt failure include headache, visual disturbances, vomiting, lethargy, and irritability ( Table 135.2 ) The astute parent or clinician may note mild ataxia, increased head circumference or bulging fontanel in an infant, swelling at the reservoir site, poor cognition, or abnormal behaviors A classic sign is “sunsetting eyes,” which is really an upgaze paresis and eyelid retraction associated with Parinaud syndrome from pressure on the quadrigeminal plate by a dilated suprapineal recess in direct communication with the third ventricle Increased tone, hyperreflexia, or Babinski reflex represents stretching and disruption of the corticospinal fibers originating from the motor cortex and can suggest shunt malfunction in a patient with a previously normal examination, although these symptoms are rarely present in a child without a severe alteration of consciousness Patients with Cushing triad (hypertension, bradycardia, and abnormal respiratory pattern) require immediate maneuvers to decrease ICP and guide them quickly toward operative repair of the shunt Seizures are uncommon as the sole manifestation of CSF shunt malfunction However, seizures can occur in children who have predisposing brain lesions, and many patients with CSF shunts have epilepsy Shunt infection must be considered in the child with symptoms of shunt malfunction, especially if the child has a history of recent shunt revision Ronan et al reported that more than one-third of patients with shunt infection presented with symptoms of malfunction