Page 104 - AN-3-4

Advanced Neurology Shuntogram technique in programmable valves

sufficiently sensitive to confirm patency nor specific limitations in accurately delineating shunt function after
enough to justify diagnostic intervention. 28 40 years.
Vernet et al. analyzed 56 radionuclide scans, observing In 2024, Nandoliya et al. reported on 211 nuclide
24
18
a trend in flow with clearance half-time for the reservoir procedures performed from 2003 to 2022. They injected
ranging from 1 – 7.5 min. They concluded that a negative 0.5 ml or less of nuclide followed by a small saline flush.
scan was characterized by contrast distal to the tip within Patients were encouraged to ambulate, if possible, during
10 min, extending up to 30 min after injection. However, the 30-min imaging period. No valve setting adjustments
even with these new time guidelines, subsequent studies were made. The study reported a sensitivity of 92.3% and
reported false-negative rates of 14 – 25% and near-zero false a specificity of 96.2%, with no mention of programmable
positives over the following decade, with a recommended valve adjustments.
flow detection window of 10 – 15 min. 2,17
These studies do not specifically address the current
Due to the significant variability in findings, Ouellette widespread use of programmable shunt valves. It is possible
et al. conducted a retrospective study on 69 patients that limited or absent flow may occur simply because the
7
presenting to the emergency department who underwent patient’s intracranial pressure is below the valve setting at
99m Tc-DTPA shuntograms. Three blinded investigators any specific moment. Therefore, shunt obstruction cannot
interpreted the results: patients who did not return within be accurately diagnosed unless the valve pressure has been
4 weeks were classified as negative, while those with sufficiently reduced to allow flow, even if the intracranial
intraoperative confirmation of shunt issues were classified pressure is extremely low. In addition, variability in
as positive. The study reported a sensitivity of 92.6% and radiocontrast usage persists within the same study, with
a specificity of 59.5% in patients who had a shuntogram. 99m Tc-DTPA remaining the most commonly administered

Six years later, Thompson et al. highlighted the contrast agent in shuntograms.
3
challenges in determining shunt failure through a large- Research into biodegradable nanoshells (e.g., hyaluronic
scale study reviewing 259 shuntograms. The inclusion acid) encapsulating radiotracers is growing. Ganau et al.
29
criteria were discordant symptoms with stable ventricle highlighted the diagnostic potential of nanoshell technology
size. Imaging was performed every 15 min over 1 h. in inflammatory and oncologic pathologies, noting its
A “normal” shuntogram was defined in four different ways optimization of contrast media for neuroradiology and
based on contrast movement into the distal site. Despite nuclear medicine, including applications with 99m Tc-
“normal” times ranging from 15 to 45 min, they found low DTPA. Further studies may benefit from this technology,
sensitivity and high specificity. Ultimately, they determined potentially establishing a standardized radiotracer for
that a true negative result occurred when a patient with shuntograms.
a normal shuntogram did not return to the emergency
department within 30 days. This finding underscored the 4. Conclusion
need for clinical judgment and ongoing observation in
interpreting shuntogram studies. The burden of shunt-dependent hydrocephalus underscores
the need for reliable methods to accurately detect shunt failure.
In 2020, Quezada and Gordon conducted 146 This article presents evidence highlighting the heterogeneous
11
radiopharmaceutical flow studies in patients presenting techniques and outcomes associated with shuntograms,
with headache, nausea, vomiting, irritability, and altered alongside an example of successful implementation
neurologic function despite normal computed tomography following our institutional protocol. With proper techniques
or magnetic resonance imaging. Patients were placed in and protocols, shuntograms have the potential to serve as a
a recumbent position and prepared with chlorhexidine valuable tool for diagnosing shunt patency.
and isopropyl alcohol before a 25-gauge butterfly needle
was used to inject 99m Tc-DTPA. Fluoroscopy images were Acknowledgments
taken every 15 min over 1 h. Rapid flow through the We thank the Department of Neurosurgery at Oregon
distal catheter into the peritoneum or vascular system Health and Science University for their support.
was considered negative. They reported a true negative
rate of 91% and a true positive rate of 70%. Around the Funding
same time, a retrospective study of 95 patients found that
predicting shunt revision within 30 days had a negative None.
predictive value of 68.3%. Both studies highlight that, Conflict of interest
5
despite advancements in procedural techniques and
imaging, shuntogram interpretation continues to have The authors declare that they have no competing interests.

Volume 3 Issue 4 (2024) 6 doi: 10.36922/an.4180