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Background
Cerebral spinal fluid (CSF) shunts are used to provide an alternative route for CSF flow into the peritoneum, pleura, or vasculature to treat hydrocephalus. One of the main limiting factors affecting their use is the complications arising from them. This exhibit will explore the different types of CSF shunts and show how radionuclide scintigraphy can be used to differentiate the various complications that occur with their use.

Educational Goals / Teaching Points
The first goal of this exhibit is to discuss the different types of CSF shunts, their indications, and their normal radiographic and scintigraphic appearance. There will also be a description of the different radiotracers and protocols used in nuclear medicine shunt evaluations. Finally, the scintigraphic findings of shunt malfunctions and complications will be discussed along with the common pitfalls in interpretation and management. Throughout the exhibit, case-based presentations will be employed to provide real-world examples.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
CSF shunts are used to relieve both non-communicating and communicating hydrocephalus. They consist of a proximal and distal catheter in addition to a reservoir and/or valve. Common locations of CSF shunting are the peritoneum, pleural space, or right atrium. When complications arise, patients typically present with symptoms of recurrent hydrocephalus and the initial step in evaluating the shunt is a radiographic shunt series to check for discontinuity, externalization, or kinking. If that does not reveal the cause of the malfunction, the next step is a radionuclide shunt study to assess the function of the shunt. This will reveal whether there is partial or complete luminal obstruction and can often localize the site of mechanical failure. Signs of other complications such as pseudocyst formation or catheter migration can also be seen on scintigraphic studies, although CT may be required for definitive diagnosis.

Conclusion
Nuclear medicine scintigraphy is a useful tool for the evaluation of CSF shunt function and can be used in combination with other imaging modalities to guide management. The diagnosis of shunt malfunction can be suspected based on the history and physical exam findings, but imaging is necessary to confirm the diagnosis and can often reveal the underlying cause. As a result, radiologists must have knowledge not only of the different types of shunts and the complications that can arise, but also of the role that radionuclide scintigraphy plays in the evaluation of shunt patency.