Letter to the Editor. The use of a shuntogram in the diagnosis of shunt failure

Paula AlcazarHospital Universitario Miguel Servet, Saragossa, Spain

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Juan Casado PellejeroHospital Universitario Miguel Servet, Saragossa, Spain

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TO THE EDITOR: We read with great interest the article by Adamski et al.1 (Adamski A, O’Brien MW, Adamo MA. Shuntogram utility in predicting future shunt failures. J Neurosurg Pediatr. 2021;28[3]:315-319).

Adamski et al. provided an excellent description of the contrast-based shuntogram technique and presented their experience with 95 cases, reporting a positive predictive value (PPV) of 100% and a negative predictive value (NPV) of 61.2% for valve failure within 1 year from the performance of the test. Of the patients with a negative result (with a normal flow of contrast), 38.8% were later diagnosed with valve malfunction, requiring revision surgery. Of the patients who had a false-negative result, 38.5% required valve replacement (without specifying whether the shunt system was replaced or if the pressure level was changed), and 30.8% of the cases required a combination revision.

CSF shunts have a failure rate of 30%–40% at 1 year in children,2 yet it is estimated that 45.7% of valve revisions could have been avoided.3 Especially dramatic are the cases of shunt complications in pediatric patients, where a misinterpretation of the clinical situation may lead to chain surgeries with little success.

Despite correct anamnesis, physical examination, and imaging tests (radiography, abdominal ultrasound, CT, and MRI), sometimes we cannot reach a concluding diagnosis. As neurosurgeons, we have several tools that complement each other, such as valve infusion tests,4 shuntograms,5 intracranial pressure (ICP) monitoring,6 and intraabdominal pressure (IAP) measurements.7

The shuntogram is a rapid, nonaggressive, and useful test for diagnosing shunt failure due to obstruction, as shown by a PPV of 100%. However, there are many other causes of shunt failure, including functional failure due to underdrainage and overdrainage, that cannot be diagnosed by a shuntogram. Hence, in our opinion, the NPV of this test should be considered based on the ability to diagnose valve obstruction, with results that are likely to differ from those stated in the article.

In our clinical practice, we use a protocol for suspected valve failure in high-pressure hydrocephalus, mainly to try to avoid diagnostic errors and unnecessary surgeries.

In cases with the typical symptoms of shunt failure but nonpathological tests, in which no clear valve failure or infection of the system is found, we attempt a valve removal protocol after endoscopic third ventriculostomy (ETV). If the patient is not considered suitable for ETV, we perform an urgent valve revision. Yet if the symptoms are mild and the patient does not improve after a change in the valve pressure level, we perform a shuntogram.

If the test is positive, the probability of obstruction is higher, so revision surgery is carried out, focused on solving the problem. In the case of a negative test, we consider continuous ICP monitoring with serial IAP measurements in the supine and standing positions very useful to define the type of failure, saving valve infusion tests for doubtful cases.

Acknowledgments

This work is supported by the Servicio Aragonés de Salud.

Disclosures

The authors report no conflict of interest.

References

  • 1

    Adamski A, O’Brien MW, Adamo MA. Shuntogram utility in predicting future shunt failures. J Neurosurg Pediatr. 2021;28(3):315319.

  • 2

    Hanak BW, Bonow RH, Harris CA, Browd SR. Cerebrospinal fluid shunting complications in children. Pediatr Neurosurg. 2017;52(6):381400.

  • 3

    Kaestner S, Poetschke M, Kehler U, Antes S, Krause M, Deinsberger W. Revision surgery following CSF shunt insertion: how often could it be avoided?. Acta Neurochir (Wien).2020;162(1):914.

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  • 4

    Dias SF, Lalou A, Spang R, et al. Value of computerized shunt infusion study in assessment of pediatric hydrocephalus shunt function—a two center cross-sectional study. Childs Nerv Syst. 2019;36(1):5971.

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  • 5

    Broggi M, Zattra CM, Schiariti M, et al. Diagnosis of ventriculoperitoneal shunt malfunction: a practical algorithm. World Neurosurg. 2020;137:e478e486.

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  • 6

    Sæhle T, Eide PK. Intracranial pressure monitoring in pediatric and adult patients with hydrocephalus and tentative shunt failure: a single-center experience over 10 years in 146 patients. J Neurosurg. 2015;122(5):10761086.

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  • 7

    Depauw PRAM, Groen RJM, VanLoon J, Peul WC, Malbrain MLNG, De Waele JJ. The significance of intra-abdominal pressure in neurosurgery and neurological diseases: a narrative review and conceptual proposal. Acta Neurochir (Wien).2019;161(5):855864.

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Ariana AdamskiAlbany Medical Center, Albany, NY

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Michael W. O’BrienAlbany Medical Center, Albany, NY

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Matthew A. AdamoAlbany Medical Center, Albany, NY

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Response

We greatly appreciate the authors’ interest in our article and their description of their protocol for dealing with ventriculoperitoneal shunt valve malfunction.

It has been our experience that children with valve malfunction are the most difficult to diagnose. At our institution, we have found the information gained from shuntograms helpful in determining the site of shunt malfunction, especially when the obstruction is within the ventricular or peritoneal catheters. Cases in which the entire system, including the valve, appears to be patent are the most challenging, especially when children appear to be symptomatic from hydrocephalus despite little to no enlargement of the ventricular system. In some of those cases, the contrast agent may flow slower than expected through the valve or not flow initially but then flow normally after a firmer bolus of contrast is pushed through the system.

Our data indicated that of patients with a normal shuntogram, 38.8% were later diagnosed with valve malfunction requiring revision surgery. When these shunts were explored, the valve was most often found to be at least partially patent but either with very slow flow or with flow measured through a manometer that stopped well short of the expected pressure based on the valve profile or pressure setting. Once it is determined that the valve is malfunctioning, we tend to replace the valve with the same hardware/same manufacturer. We do not change fixed pressure valves to programmable valves unless there is concern for slit ventricle syndrome or overdrainage contributing to the shunt failure, and we replace programmable valves with the same valve unless the patient has a non–MRI-compatible valve, in which case we will change to one that is MRI compatible.

The authors’ protocol for valve removal and ETV when anatomically appropriate versus urgent valve revision seems to be a well-thought-out process for dealing with this oftentimes difficult problem. Ultimately, the decision to replace the valve depends on multiple factors, and the use of shuntograms has proven to be beneficial to our patients.

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  • 1

    Adamski A, O’Brien MW, Adamo MA. Shuntogram utility in predicting future shunt failures. J Neurosurg Pediatr. 2021;28(3):315319.

  • 2

    Hanak BW, Bonow RH, Harris CA, Browd SR. Cerebrospinal fluid shunting complications in children. Pediatr Neurosurg. 2017;52(6):381400.

  • 3

    Kaestner S, Poetschke M, Kehler U, Antes S, Krause M, Deinsberger W. Revision surgery following CSF shunt insertion: how often could it be avoided?. Acta Neurochir (Wien).2020;162(1):914.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4

    Dias SF, Lalou A, Spang R, et al. Value of computerized shunt infusion study in assessment of pediatric hydrocephalus shunt function—a two center cross-sectional study. Childs Nerv Syst. 2019;36(1):5971.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    Broggi M, Zattra CM, Schiariti M, et al. Diagnosis of ventriculoperitoneal shunt malfunction: a practical algorithm. World Neurosurg. 2020;137:e478e486.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6

    Sæhle T, Eide PK. Intracranial pressure monitoring in pediatric and adult patients with hydrocephalus and tentative shunt failure: a single-center experience over 10 years in 146 patients. J Neurosurg. 2015;122(5):10761086.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    Depauw PRAM, Groen RJM, VanLoon J, Peul WC, Malbrain MLNG, De Waele JJ. The significance of intra-abdominal pressure in neurosurgery and neurological diseases: a narrative review and conceptual proposal. Acta Neurochir (Wien).2019;161(5):855864.

    • Crossref
    • Search Google Scholar
    • Export Citation

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