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CC BY-NC-ND 4.0 · Asian J Neurosurg 2025; 20(03): 651-655
DOI: 10.1055/s-0045-1809052
Case Report

Endoscopic Third Ventriculostomy in a Child with Tectal Glioma and Extremely Diminished Prepontine Interval

Mohammad Elbaroody
1   Department of Neurosurgery, Cairo University, Cairo, Egypt
,
Mahmoud Talaat Shafiey
1   Department of Neurosurgery, Cairo University, Cairo, Egypt
,
Wally Hesham Moemen
1   Department of Neurosurgery, Cairo University, Cairo, Egypt
,
Ehab El Refaee
1   Department of Neurosurgery, Cairo University, Cairo, Egypt
2   Department of Neurosurgery, University Medicine Greifswald, Greifswald, Germany
› Author Affiliations

Funding None.
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Abstract

Diminished prepontine interval is a challenging intraoperative finding that creates an additional risk while doing an endoscopic third ventriculostomy (ETV) due to the proximity of the basilar artery to the ventriculostomy site. It is not a contraindication for the procedure especially in patients with thinned floors through which the vascular structures can be easily visualized and it was not proven to be a risk factor for failure of the procedure. Old children with hydrocephalus secondary to tectal glioma have a high chance of successful ETV, thus avoiding shunt dependency. A 12-year-old male patient presented with headache and grade III papilledema, magnetic resonance imaging brain revealed tectal glioma and triventricular hydrocephalus. He underwent a successful ETV despite a challenging intraoperative, extremely diminished prepontine interval. At 1-year follow-up, brain imaging showed a complete resolution of hydrocephalus and stationary course for the tectal glioma. The present case highlights that diminished prepontine interval is not a contraindication for doing ETV unless safety cannot be guaranteed, and it was not proven to be a risk factor for ETV failure. Creating a stoma on the dorsum sellae after palpating the bone or just behind it using blunt fenestration is a safe way especially in the presence of a thinned third ventricle floor with clearly visualized vascular structures.


 

Keywords

dorsum sellae - endoscopic third ventriculostomy - ETV - hydrocephalus - prepontine interval - tectal glioma

Introduction

Tectal gliomas (TGs) are rare pediatric brain tumors that originate from the tectal plate with most of these tumors being low-grade astrocytomas.[1] [2] [3] TG commonly presents with hydrocephalus due to obstruction of the aqueduct of Sylvius, and this typically occurs over a long duration of time due to the slowly growing nature of low-grade glioma.[1] [2] [4] In a systematic review including 355 patients with TG, 89.3% required at least one cerebrospinal fluid (CSF) diversion procedure during their lifetime.[1] Children with TG who are ≥ 10 years and without a history of shunt insertion have a 90% success rate of their endoscopic third ventriculostomy (ETV),[5] this makes ETV superior to ventriculoperitoneal shunt (VPS) insertion and the first choice in children with TG who develop hydrocephalus.[3] [6] [7] Some anatomical variations in the floor of the third ventricle could make performing ETV challenging in some patients and this includes diminished prepontine interval (PPI),[8] [9] [10] [11] despite this puts a risk of inadvertent injury to the basilar artery, this is not a contraindication for the procedure and there was no arterial injury mentioned in studies at which ETV was done with narrow PPI.[8] [9] [10]

We herein present a case of a child with TG who underwent ETV with an extremely diminished PPI found intraoperatively, 1-year follow-up magnetic resonance imaging (MRI) brain showed complete resolution of the hydrocephalus and stationary course for the TG.


 

Case Report

A 12-year-old male patient presented with intermittent headache and dizziness for 1 year, which became progressive 3 weeks before admission; he sought medical advice for whom an MRI brain with contrast was done and showed massive triventricular hydrocephalus, a diminished PPI < 1 mm, and nonenhancing tectal mass of 17 × 18 mm, mostly low-grade glioma ([Figs. 1] and [2A]). The extraocular muscles were not affected, and fundus examination revealed grade III papilledema. He underwent ETV ([Video 1]), intraoperatively, and we found a narrow anterior third ventricle floor with extremely diminished PPI ([Fig. 3]). The floor was thin through which the basilar artery was visualized clearly. Using the LOTTA rigid endoscope STORZ (GmbH & Co. Tuttlingen, Germany), we made a small stoma using the Decq forceps through a narrow window immediately behind the dorsum sellae (DS). The child was discharged in good condition, the headache was completely relieved 1 week later, and 2.5 months later the fundus examination was normal. Seven months later, an MRI brain with contrast showed dramatic improvement of hydrocephalus, evident flow through the stoma, and stationary course of the tectal mass, which was confirmed in a 1-year follow-up after surgery ([Figs. 2B] and [4]); the patient is still under conservative serial follow-up imaging.

Zoom
Fig. 1 Preoperative magnetic resonance imaging (MRI) brain axial T2 cuts. Triventricular hydrocephalus with obstructed flow at the 4th ventricle, tectal mass closing the aqueduct of Sylvius (green arrows), extremely diminished prepontine interval between the basilar artery and the clivus (red arrows), massive dilatation of the 3rd ventricle splitting the interpeduncular cistern, permeation through the ventricular wall (orange arrows), and absence of differentiation of cortical sulci and gyri.
Zoom
Fig. 2 (A) Preoperative magnetic resonance imaging (MRI) brain sagittal T1 cut, compressed midbrain from massive chronic hydrocephalus (blue arrow), tectal mass closing the aqueduct of Sylvius (green arrow). (B) Postoperative MRI brain sagittal T2 cut after a 1-year follow-up, resolved hydrocephalus with normal appearance of the midbrain (blue arrow), tectal mass closing the aqueduct of Sylvius (green arrow), evidence of signal voids of cerebrospinal fluid (CSF) flow across the stoma on the floor of the 3rd ventricle up to the lateral ventricle (yellow arrows), the extremely diminished prepontine interval between the basilar artery and the clivus (red arrow) still evident in the postoperative MRI.
Zoom
Fig. 3 Intraoperative endoscopic views during performing the endoscopic third ventriculostomy (ETV). (A) The 3rd ventricle floor before performing the ETV, the extremely diminished prepontine interval between the basilar artery (orange arrows) and dorsum sellae (purple arrows), black asterisks point to the mammillary bodies. (B) Using the Decq forceps and creating the stoma just behind the dorsum sellae. (C) Widening of the stoma with Decq forceps while doing mild elevation of the thinned floor to be safe and away from the basilar complex. (D) Endoscopic view showing patent stoma under irrigation. (E) Visual inspection through the edges of the stoma for confirmation of the naked basilar artery in the subarachnoid space (orange arrows). (F) A view from the posterior 3rd ventricle floor shows obstruction of the aqueduct of Sylvius with no bulge inside the 3rd ventricle (black arrows).
Zoom
Fig. 4 Postoperative magnetic resonance imaging (MRI) brain axial T2 cuts after a 1-year follow-up. A decrease in the ventricular size after endoscopic third ventriculostomy (ETV), tectal mass closing the aqueduct of Sylvius (green arrows), still evident extremely diminished prepontine interval (red arrow), resolution of the preoperative permeation through the lateral ventricle wall, and restoration of normal cerebrospinal fluid (CSF) at the cortical level with differentiation between sulci and gyri.

Video 1


 

Discussion

A diminished PPI has been defined as the distance between the upper portion of the basilar artery and the DS of ≤ 1 mm.[8] [9] [10] This anatomical variant is not a contraindication to perform an ETV, studies which reported ETV with diminished PPI did not mention vascular injuries in those patients,[8] [9] [10] the use of stereotactic guidance, intraoperative Doppler, and making a blunt fenestration at the DS after palpation of the bone or immediately behind the DS are important tips to decrease vascular injury.[8] [9] [10] [11] The presence of a thinned floor with clear visualization of the basilar and posterior cerebral arteries should encourage the neurosurgeon to make a blunt penetration under vision on the DS or immediately behind it in front of the basilar artery,[8] and even a small stoma would be enough after visual confirmation of the basilar artery through the stoma.

Obstructive hydrocephalus is a typical presentation of TG due to the interruption of CSF flow across the aqueduct of Sylvius.[1] [2] [3] [4] Management of TG consists of radiological surveillance with close clinical and radiological follow-up owing to their indolent course, and CSF diversion for the associated hydrocephalus either through ETV or placement of VPS.[1] [2] [6] According to the ETV success score, children with TG older than 10 years without a history of VPS insertion have a 90% success rate of the ETV.[5] ETV has been reported with high success rates managing the hydrocephalus-associated TG with 82,[4] 85,[12] 89,[13] and 100%[3] of patients being shunt free at the last follow-up.

A multicenter study including 761 children showed that the original ETV success score still has a good predictive ability to predict the success of ETV, and diminished PPI was not mentioned as a risk factor for ETV failure.[14] Children with the highest chance of ETV success[5] [14] should take their chance completely because this means avoiding lifelong shunt dependency, shunt infection, and the possibility of overdrainage.[1] [7] [12] Unless intraoperative safety is not guaranteed, diminished PPI is not a contraindication for doing ETV, especially in patients with thinned floors with clearly visualized underlying vascular structures.


 

Conclusion

Diminished PPI is not a contraindication for doing ETV unless safety cannot be guaranteed, and it was not proven to be a risk factor for ETV failure. Creating a stoma on the DS after palpating the bone or just behind it using blunt fenestration is a safe way especially in the presence of a thinned third ventricle floor with clearly visualized vascular structures.


 

 

Conflict of Interest

None declared.

Authors' Contributions

M.E. contributed to concepts, design, definition of intellectual content, literature search, manuscript preparation, manuscript editing, and manuscript review. M.T., W.M., and E.E. helped in the design, definition of intellectual content, literature search, manuscript preparation, manuscript editing, and manuscript review. M.T. and W.M. were involved in data collection and manuscript preparation. All the authors approved the manuscript before submission.


Ethical Approval

All procedures performed in the studies involving human participants were in accordance with the ethical standards of the institutional and national research committee and with the 1964 Declaration of Helsinki and its later amendments.


Patients' Consent

Informed consent to participate and for publication was obtained from all individual participants included in the study. Written informed consent was obtained from the parents as legal guardians.



Address for correspondence

Mohammad Elbaroody, MD
Department of Neurosurgery, Faculty of Medicine, Cairo University
Al-Saray Street, El Manial, Cairo
Egypt 11956   

Publication History

Article published online:
08 May 2025

© 2025. Asian Congress of Neurological Surgeons. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/)

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Zoom
Fig. 1 Preoperative magnetic resonance imaging (MRI) brain axial T2 cuts. Triventricular hydrocephalus with obstructed flow at the 4th ventricle, tectal mass closing the aqueduct of Sylvius (green arrows), extremely diminished prepontine interval between the basilar artery and the clivus (red arrows), massive dilatation of the 3rd ventricle splitting the interpeduncular cistern, permeation through the ventricular wall (orange arrows), and absence of differentiation of cortical sulci and gyri.
Zoom
Fig. 2 (A) Preoperative magnetic resonance imaging (MRI) brain sagittal T1 cut, compressed midbrain from massive chronic hydrocephalus (blue arrow), tectal mass closing the aqueduct of Sylvius (green arrow). (B) Postoperative MRI brain sagittal T2 cut after a 1-year follow-up, resolved hydrocephalus with normal appearance of the midbrain (blue arrow), tectal mass closing the aqueduct of Sylvius (green arrow), evidence of signal voids of cerebrospinal fluid (CSF) flow across the stoma on the floor of the 3rd ventricle up to the lateral ventricle (yellow arrows), the extremely diminished prepontine interval between the basilar artery and the clivus (red arrow) still evident in the postoperative MRI.
Zoom
Fig. 3 Intraoperative endoscopic views during performing the endoscopic third ventriculostomy (ETV). (A) The 3rd ventricle floor before performing the ETV, the extremely diminished prepontine interval between the basilar artery (orange arrows) and dorsum sellae (purple arrows), black asterisks point to the mammillary bodies. (B) Using the Decq forceps and creating the stoma just behind the dorsum sellae. (C) Widening of the stoma with Decq forceps while doing mild elevation of the thinned floor to be safe and away from the basilar complex. (D) Endoscopic view showing patent stoma under irrigation. (E) Visual inspection through the edges of the stoma for confirmation of the naked basilar artery in the subarachnoid space (orange arrows). (F) A view from the posterior 3rd ventricle floor shows obstruction of the aqueduct of Sylvius with no bulge inside the 3rd ventricle (black arrows).
Zoom
Fig. 4 Postoperative magnetic resonance imaging (MRI) brain axial T2 cuts after a 1-year follow-up. A decrease in the ventricular size after endoscopic third ventriculostomy (ETV), tectal mass closing the aqueduct of Sylvius (green arrows), still evident extremely diminished prepontine interval (red arrow), resolution of the preoperative permeation through the lateral ventricle wall, and restoration of normal cerebrospinal fluid (CSF) at the cortical level with differentiation between sulci and gyri.