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An 83-year-old male patient with ventriculoperitoneal shunt underwent radionuclide shunt study using single-photon emission computed tomography/computed tomography (SPECT/CT) to evaluate the shunt patency. The planar images showed activity at the cranial region and spinal canal but no significant activity at the peritoneal cavity. However, SPECT/CT images clearly demonstrated accumulation of activity at the superior part of bifurcation level with no activity at the distal end of shunt as well as no spilling of radiotracer into the peritoneal cavity indicating shunt obstruction. SPECT/CT makes the interpretation of radionuclide shunt study more accurate and easier as compared with traditional planar images.
An 83-year-old male patient with ventriculoperitoneal shunt implanted for normal pressure hydrocephalus underwent radionuclide shunt study by direct administration of 6 mCi of technetium-99m diethylene triamine pentaacetic acid into the shunt reservoir. The anterior-posterior (AP) static imaging of the vertex-thoracic region at 30 min after injection [Figure 1a] showed very intense radiotracer uptake at the cranial region and transit of activity through the proximal part of shunt. However, subsequent AP static images of thoracoabdominal region [Figure 1b] demonstrated linear extension of activity through the distal part of shunt without significant spread to the remainder of the peritoneal cavity.
Upon this, single-photon emission computed tomography/computed tomography (SPECT/CT) images were acquired from the vertex to pelvis. Cranial sections revealed the passage of activity to the proximal part of spinal canal indicating proximal patency of the shunt [Figure 2a]. However, abdominal slices showed accumulation of activity at the superior part of bifurcation level with no activity at the distal end of shunt as well as no spilling of radiotracer into the peritoneal cavity indicating shunt obstruction [Figure [Figure2b2b and andcc].
The primary treatment for hydrocephalus is ventricular shunt placement, and the most commonly used type is ventriculoperitoneal shunt.[1,2] The leading cause of shunt malfunction is mechanical failure and less commonly infection. In patients with suspected shunt malfunction, initial examination is plain radiography for disconnections, kinks, breaks, or migration of the shunt tubing that may be confirmed with other imaging techniques including CT of the head, radionuclide shunt study to evaluate the patency of shunt, ultrasonography to assess distal end of the shunt, magnetic resonance imaging to evaluate central nervous system infection, hemorrhage, and injection of iodinated contrast media to confirm the cerebrospinal fluid (CSF) leaks or site of shunt obstruction. Radionuclide CSF study is a simple, effective, and low-radiation-dose procedure for the assessment of shunt patency with sensitivity, specificity, and accuracy of 97%, 90%, and 93%, respectively. If a block is present, then localization of the blockage site is needed to plan the suitable surgical technique. In a normal study, activity must be diffusely visualized in the abdomen. However, to confirm this, imaging should be performed again at the 3 and 24 h marks in patients with no activity in peritoneal cavity, demonstrating an obstructed shunt at the distal level.[6,7] With the help of CT image of SPECT/CT, the interpretation becomes more accurate and easier. In our case, although SPECT/CT images were not necessary for diagnosis, fused SPECT/CT images clearly demonstrating the obstruction site and provide increased diagnostic confidence as compared with the conventional planar images.
There are no conflicts of interest.