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Advanced Neurology Shuntogram technique in programmable valves

“failed” shunts vary among institutions, one minimally undergoing a shuntogram are often positioned supine or
invasive method for objectively assessing shunt function is recumbent for variable durations before contrast injection
the shuntogram. In patients presenting with symptoms of and imaging. 3,9,11,12,16-18 Standard preparation includes
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shunt failure, the decision to perform surgery, regardless shaving the area and performing sterile skin preparation
of ventricular size, is often informed by shuntogram with either iodine-based or alcohol/chlorhexidine-based
findings. A shuntogram, most commonly a nuclear solutions, followed by sterile draping. 3,8,9,11,12,16-18
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medicine procedure, involves aseptic skin preparation over Access to the shunt reservoir or port is typically
a ventricular shunt valve and the injection of a radioactive achieved with a 23 – 25-gauge needle. 5,9,11-13,16,17,19 French
tracer into the device’s lumen. Scintigraphic images are and Swanson notably suggested making a small incision
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taken periodically to monitor flow and track tracer spread on the skin with a scalpel before penetration to reduce
within the cerebrospinal fluid (CSF) column, both distally the risk of introducing squamous cells or bacteria into the
and proximally. A diagnosis of shunt obstruction is made port. In some protocols, opening pressure measurements
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when the contrast fails to progress distally beyond the are taken, and/or CSF is aspirated to observe its
shunt’s distal tip, often necessitating surgical intervention.
characteristics. 13,16,19 The contrast medium is then injected,
Despite the longstanding use of the shuntogram, no with Tc-diethylene-triamine-pentaacetate (DTPA) being
99m
consensus exists on a standardized, stepwise procedure, the most commonly used tracer, followed by In-DTPA,
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which may contribute to the reported misinterpretation iohexol, iopamidol, metrizamide, meglumine diatrizoate,
rates. Furthermore, we propose that an understanding of and omnipaque. 2,3,5,7-9,11,12-14,16-23 The exact volume of the
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fluid dynamics and the design of shunts to accommodate injected tracer is seldom specified in the literature, and
variable intraventricular pressures has not been widely some protocols include flushing after injection. Imaging
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accounted for in the current shuntogram techniques. 8-10 As may commence immediately to ascertain tracer presence
a result, recent studies continue to report inconsistencies within the shunt lumen, potentially creating an immediate
in the reliability and predictive value of shuntograms. 5,11 ventriculogram depending on the amount of injectate
In this article, we aim to clarify the different techniques used. Delayed imaging protocols vary widely, lacking
documented in studies on shuntogram performance. We standardization across studies.
will further discuss the conflicting evidence regarding the Criteria for defining a failed shuntogram are also
shuntogram’s utility and present our institution’s protocol in inconsistent. Typically, a positive (failed) shuntogram
the context of programmable shunt valves. This discussion is indicated when the contrast remains within the shunt
will be supplemented by a case scenario that demonstrates lumen without progressing distally (stagnating in the
how our protocol accurately identified shunt patency after reservoir or ventricles) or failing to pass the distal tip within
an initial misdiagnosis of shunt obstruction. an accepted time frame. Time thresholds described include
2. Literature review: Shuntogram technique failure to pass the distal tip by 9, 12, 15, or 20 min post-
injection, with imaging sometimes continuing for up to an
and interpretation hour. Positional changes during observation are generally
The shuntogram remains one of the most common unreported. In some series, shunt patency was determined
procedures for assessing shunt function in the United through clinical follow-up, with a patent result indicated
States. However, the current body of literature on if the patient did not return to the emergency department
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shuntograms presents a heterogenous and poorly defined within 30-day post-shuntogram or if they were lost to
set of techniques, which obscures a comprehensive follow-up. 2,7,12,16,18,19 In addition, factors such as CSF reflux
understanding of the procedure’s accuracy in diagnosing into the ventricles and successful contrast administration
shunt failure. Despite numerous studies making influenced interpretations, while intraoperative findings
recommendations for specific procedural steps over the often served as the final determinant of failure or patency. 7
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years, no standard protocol has emerged. These protocols Shunt flow failure can typically be attributed to
vary widely in terms of technique, criteria for assessing discontinuities or obstructions at one of the three
shunt patency, and definitions of shunt failure. mechanical areas: the valve, the ventricular catheter, or
Patient selection criteria for shuntograms also vary the peritoneal catheter. An obstruction at any of these sites
significantly across institutions, often relying on non- may present similarly, with shuntogram imaging helpful in
specific symptoms of shunt malfunction, such as headache, identifying the precise site of obstruction. Shunt failure or
dysphoria, nausea, irritability, lethargy, behavioral changes, occlusion can result from protein deposits or other organic
pyrexia, disequilibrium, or other neurologic changes in cases materials, particularly within the ventricular catheter,
where imaging findings are inconclusive. 2,5,8,9,11-15 Patients causing a lack of passive or active reflux of contrast proximal

Volume 3 Issue 4 (2024) 2 doi: 10.36922/an.4180