Cerebrospinal fluid (CSF) shunt systems are used to treat hydrocephalus by draining excess CSF to an alternative location in the body. A shunt has three segments: a proximal catheter, a valve and reservoir or reservoirs, and a distal catheter. The proximal catheter is commonly placed in a ventricle of the brain, but it may also be placed in a cyst. The valve of the shunt system controls the drainage of CSF. Some examples of valve mechanisms include regulation by differential pressure, siphon resistance (which prevents overdrainage in the upright position), flow regulation (in which different flow rates change the regulation mechanism), and external adjustment. Shunt systems often have one or two reservoirs (sometimes referred to as bubbles) that can be either part of or separate from the valve. CSF can be accessed from the reservoir to help diagnose shunt infection or malfunction. The distal catheter is commonly inserted into the peritoneal cavity, but it can also be placed in the right atrium, pleural cavity, and rarely, the gallbladder or ureters.

Evaluation of a CSF shunt is indicated when the clinical history and physical examination suggest the diagnosis of shunt malfunction or shunt infection, or both. Because the symptoms of shunt malfunction may be subtle or nonspecific, the clinician should always keep malfunction in the differential when evaluating a child with a CSF shunt. In infants and preverbal children, the symptoms (Table 188-1) may be difficult to differentiate from those of other diseases. The parental history is valuable for giving the practitioner an understanding of the patient’s baseline as well as perspective on how shunt malfunction normally manifests in the child.

Shunt infection is most common in the first few months after placement or revision of a shunt. CSF shunts that end in the peritoneal cavity can also become infected from a primary abdominal infection. Symptoms of shunt infection include those of shunt malfunction as well as fever and erythema or edema of the skin along the shunt site. Please see Chapter 107 for further discussion of device-related infections.

There are no contraindications to evaluation of a CSF shunt.

The majority of CSF shunt assessment is done through the history, physical examination, and radiologic studies. The history should include an assessment of the type and location of the shunt and its reservoir or reservoirs. Common signs on physical examination that suggest shunt malfunction are listed in Table 188-2. The shunt can also be evaluated by pumping the reservoir (Table 188-3). This procedure should be interpreted cautiously because it is not a sensitive method of detecting shunt malfunction. Pumping the shunt may also be associated with entrapment of tissue in the proximal catheter so should only be done after consulting a pediatric neurosurgeon.