The Added Value of Magnetic Resonance Imaging Cisternography and Ventriculography as a Diagnostic Aid in Pediatric Hydrocephalus

The prepontine block and its relevance for the development and treatment of hydrocephalus

OBJECTIVE

Pulsatile CSF flow patterns include flow through the ventricles to the subarachnoid space and cisterns and from the infra- to the supratentorial subarachnoid space. In this study, we demonstrate how an obstruction at the level of the prepontine space may lead to obstructive hydrocephalus with specific radiological characteristics, as well as the implications for treatment options.

METHODS

We retrospectively collected data of patients who underwent surgery between February 2010 and December 2022 for hydrocephalus secondary to a suspected prepontine block. One additional patient diagnosed with prepontine block who did not undergo surgery was also included. We excluded patients with a background of previous unrelated neurosurgical procedures or CNS infections.

RESULTS

Six children and two adults were included. Three presented with hydrocephalus on imaging, without any other underlying pathology. Five had a suprasellar arachnoid cyst, with its lower border abating the pons and occluding the spinal subarachnoid space (SAS). All cases had an open aqueduct on T2 sagittal sequences, as well as an infracerebellar or retrocerebellar CSF collection. In most cases, a horizontal web was identified in the prepontine region. Seven cases were treated with an endoscopic fenestration. One patient subsequently underwent a shunt surgery. All the operated children reached normal developmental milestones after surgery.

CONCLUSIONS

This paper describes a rather small series of cases where clear obstruction was observed at the level of the prepontine subarachnoid space. We believe this anatomical subtlety adds to a better understanding of CSF pathways and the role of ETV in treating hydrocephalus, focusing on a small subgroup of patients without a clear obstruction.

Surgical treatment and outcome of posterior fossa arachnoid cysts in infants

OBJECTIVE

The aim of this cohort study was to describe and analyze the surgical treatment and outcome of posterior fossa arachnoid cysts (PFACs) in infants.

METHODS

Patients presenting with a PFAC at infancy or prenatally, between the years 2000 and 2019, and who were surgically treated before the age of 2 years, were included in this study. Patient data were retrospectively collected including baseline characteristics and surgical variables. Factors related to revision surgery were analyzed through uni- and multivariate analysis.

RESULTS

Thirty-five patients, of whom 54.3% were male, were included. The cyst was diagnosed prenatally in 23 patients (65.7%). Surgery was typically recommended after a mean cyst follow-up of 3.4 ± 3.9 months, with a mean age at surgery of 6.1 ± 5.1 months. In 54.3% of patients (n = 19), surgery was performed before the age of 6 months. The PFAC was treated purely neuroendoscopically in 57.1% of patients (n = 20), while 28.6% of patients underwent open cyst procedures (n = 10), 5.7% (n = 2) were treated with a shunt, and 8.6% (n = 3) underwent a combined procedure. Additional surgery was required in 31.4% of patients (n = 11; mean 2.36 ± 2.11 surgeries per patient). At the last follow-up (61.40 ± 55.33 months), no mortality or permanent morbidity was seen; radiological improvement was apparent in 83.9% of the patients. Those patients treated before the age of 6 months (p = 0.09) and who presented before surgery with a stable cyst size that was maintained throughout preoperative monitoring (p = 0.08) showed a trend toward higher revision rates after surgical treatment.

CONCLUSIONS

PFACs in infancy may require surgical treatment before the age of 6 months. Navigated endoscopy was a valid surgical option. Overall mortality or permanent morbidity was rare. Additional surgery was required in up to 30% of the patients; younger age and a preoperatively stable cyst might be risk factors for revision surgery.

Usefulness of postoperative ventriculography and intracranial pressure monitoring following endoscopic third ventriculostomy

PURPOSE

The authors sought to determine whether the insertion of an external ventricular drain (EVD) at the time of surgery to monitor intracranial pressure (ICP) and ventriculography done within the first day following an endoscopic third ventriculostomy (ETV) is of benefit in postoperative patient management.

METHODS

Following IRB approval, ETV procedures done by the senior author between January 1, 2007, and December 31, 2016, were reviewed. Included in a consecutive fashion were all patients who underwent an ETV with placement of an external ventricular drain (EVD) that was preceded preoperatively by an MRI or CT study and followed by a contrast CT ventriculogram within the first postoperative day.

RESULTS

Identified were 72 patients who met the above criteria; however, technical ventriculography failure occurred in 4 (6%) and were eliminated from the analysis. Of the remaining 68 patients, contrasted CSF was seen in the basal cisterns/subarachnoid spaces (SAS) in 66 (97%) indicating a patent ETV and absent in 2 (3%) indicating a non-patent ETV. Of the 66 patients with a patent ETV, 34 (52%) patients were discharged on postoperative days 1 (8), 2 (13), and 3 (13) as their ICPs were not elevated and their clinical symptoms normal. EVDs placed at the time of the ETV recorded raised ICP > 20 cm H₂O in 17/68 (25%) patients for 1 or more days, all of whom had a patent ETV. Because of persistently elevated ICP requiring CSF drainage for control, 4 of these patients were shunted on postoperative days 5, 6, 6, and 10 and 3 with prolonged elevated ICP for 5, 6, and 11 days postoperatively were not shunted as their ICP and symptoms progressively normalized. The remaining 17/68 (25%) patients did not have a postoperative ICP > 20 cm H₂O; 14 were discharged after resolution of symptoms and other clinical factors, 1 was shunted on postoperative day 3 due to persistent symptoms and a consistently large volume of CSF drainage, and 2 had a non-patent ETV with 1 undergoing shunt placement and the other discharged because of the absence of symptoms. The sensitivity of ventriculography was only 13%; however, the specificity was 98% and the accuracy 88%.

CONCLUSION

After reviewing this series, the continued use of a postoperative EVD appears appropriate as the risk is low and it provides ventricular access to control ICP, thereby, improving patients' safety and reducing the need for CSF shunting on an urgent/emergent basis should the ETV prove to be unsuccessful. From our limited series, the usefulness of a 1-day postoperative ETV ventriculogram is less clear and would need confirmation with additional studies.