Children with ventricular shunts can present to the emergency department (ED), office, or clinic with signs or symptoms of two major shunt complications—obstruction or infection. Shunt puncture, or “tapping” the shunt, refers to withdrawing cerebrospinal fluid (CSF) from the shunt apparatus percutaneously to aid in diagnosing a shunt malfunction or infection. In some cases, elevated intracranial pressure may be acutely relieved by removing some ventricular fluid. However, because shunt puncture carries an approximately 1% risk of introducing infection, and because improperly performed taps can damage certain types of shunt components, the physician should try to identify shunt problems without tapping the shunt when possible (1). Ideally, shunt punctures should be performed by a neurosurgeon who is familiar with the particular type of shunt in question and who has assessed the patient and can weigh the relative risks and benefits to be derived from a shunt tap. Because some shunt problems require immediate attention, however, the goal of this chapter is to review the basics of shunt anatomy and evaluation and to describe the indications and techniques for shunt puncture and burr hole puncture when a neurosurgeon is unavailable. Because of the potential for cardiorespiratory instability in the child with a shunt obstruction or infection, a physician should only perform this procedure in an area where monitoring, resuscitation equipment, and personnel are sufficient to handle sudden decompensation, such as in the ED, intensive care unit, or operating room.

The majority of shunts placed for hydrocephalus consist of the following four main components (Fig. 42.1):

There are many types of valves, ranging from simple designs to more complex programmable valves that can be adjusted to increase or decrease resistance to flow by the application of an external magnetic device (Fig. 42.2).

Shunts are described according to their proximal and distal drainage sites; therefore, a ventriculoperitoneal (VP) shunt drains from the ventricle to the peritoneal cavity, a ventriculojugular (VJ) or ventriculoatrial (VA) shunt drains the ventricle through the jugular vein into the right atrium, and a lumboperitoneal (LP) shunt drains the lumbar subarachnoid space into the peritoneum. In addition, shunts have “brand names,” which often identify the manufacturer and the model of the shunt. As the number of valves available has increased, the terminology can be quite confusing. Clinicians can often sort out which valve is present in the patient by asking the family, by checking the operative report, or by looking at the plain films (shunt survey). Most major manufacturers have websites on which specific valve types are pictured; by searching these sources and comparing them to the appearance on plain films, most valves can be identified when this becomes necessary during shunt “troubleshooting.”

“Pumping” the shunt to assess its function involves pressing on the reservoir or valve and assessing how it refills; this requires experience with the specific shunt type and can be interpreted only in the context of the ventricular size or volume of fluid in the space being drained. Tapping the shunt requires identifying the reservoir, which is specifically designed for this purpose. A shunt survey (plain radiographs of the shunt along its course) will usually show its location. The part of the shunt that is “pumped” usually, but not always, is the part that is tapped. For example, with a Holter-type valve, a separate (Rickham) reservoir is usually placed in the burr hole itself (Fig. 42.3); tapping the pumping chamber of the cylindrical Holter valve may cause it to be damaged.

As always, there are exceptions and variations in shunt components. Proximal catheters are sometimes multiple and may drain other cavities such as cysts, a trapped fourth ventricle, or the subdural space. Some shunts do not have reservoirs or valves, and some components may be radiolucent on radiograph. The consulting neurosurgeon can usually help sort out these less common situations.