A probability of occurrence of a shunt malfunction of 81% at 12 years of follow-up has been reported in multicentric studies (75). A complication in a patient with a shunt may have clinical, psychological, and economic consequences.
Shunt occlusion represents about half of shunt complications in pediatric series (75). Occlusion can occur at three different levels: proximal catheter, valve system, or distal catheter.
Shunt disconnection or fracture constitutes the second most frequent cause of mechanical shunt malfunction. Disconnection is defined as a loss of continuity of the shunt at connecting points between catheters, valves, and/or connectors, whereas fracture is an actual breakage of the catheter with separation between the segments.
To migrate, a shunt needs to be pulled and be able to move into the subcutaneous tissue. Loose or improper connection will allow catheters to get disconnected from a valve or other segment of the shunt and migrate. Overdissection of the subcutaneous tissue also predisposes to migration.
The shunt can be improperly placed at the level of the ventricles or at the level of the drainage cavity.
Overdrainage is caused by an increase of the differential pressure applied to the shunt system that exceeds the sum of the opening pressure of the valve plus the pressure of the drainage cavity (1). This can happen normally with postural changes, REM sleep, straining, etc. Overdrainage can cause symptomatic orthostatic hypotension, subdural CSF collections, slit ventricle syndrome, craniosynostosis, and loculation of the ventricles. The risk of overdrainage can be minimized by increasing the opening pressure of the valve (programmable valves), adding a siphon-resistive device to the system, or using a flow-regulating device (Orbis-Sigma valves).
The risk of subdural collection (hematoma, hygroma), caused by disruption of the arachnoid or the stretched subarachnoid vessels, is related to the drainage capacity of the shunt, the size of the ventricles, and the compliance of the brain.
Slit ventricle syndrome is a complex complication of shunts defined as severe, life-modifying headaches in patients with shunts and normal or smaller-than-normal ventricles. Five different pathophysiological processes have been involved (79): 1) severe intracranial hypotension analogous to spinal headaches, 2) intermittent obstruction of the ventricular catheter, 3) intracranial hypertension with small ventricles and a failed shunt (normal volume hydrocephalus), 4) intracranial hypertension with a working shunt (cephalocranial hypertension), and 5) shunt-related migraine.
Acquired post-shunt craniosynostosis is a relatively common complication, but in most cases, is mild.
Although they are most commonly seen in inflammatory or infectious processes, loculated ventricles can be caused by overdrainage.
Follow linkage to chapter dedicated to the long-term outcome of patients with shunts.