A light on the dark side: in vivo endoscopic anatomy of the posterior third ventricle and its variations in hydrocephalus

The Cerebral Aqueduct Compliance: A Simple Morphometric Model

BACKGROUND AND OBJECTIVES

This work aimed to identify different configurations of the adytum of the cerebral aqueduct suggesting its safe neuroendoscopic navigation. This concept is intimately connected to the physiological aqueductal dilatability or compliance, which is relatively ignored in the literature. A better knowledge of the extent of physiological aqueductal dilatability might better define the ideal diameter and safer features of dedicated flexible endoscopes.

METHODS

The study includes 45 patients operated on using a flexible scope with a 3.9-mm diameter, where the structural elements of the adytum of the cerebral aqueduct are clearly visible. Patients were grouped according to the pathology (colloid cyst/normal anatomy, intraventricular hemorrhage, tetraventricular obstructive hydrocephalus, normal pressure hydrocephalus, and distal membranous aqueductal stenosis). A simple geometrical scheme was applied to the endoscopic anatomy of the aqueductal adytum in relation to the posterior commissure to measure its pathologic deformations. Eventual damages to the aqueduct walls caused by the endoscope were also reported.

RESULTS

Proceeding from normal anatomy to hydrocephalic condition, the ratio between the commissure and the aqueductal access area progressively decreases, while the vertex angle increases. Interestingly, the entity of the ependymal damages due to the passage of the endoscope correlates with such measures.

CONCLUSION

The cerebral aqueduct, excluding atrophic processes, is provided with a certain degree of dilatability, which we estimate to be around a diameter of 4 mm. This represents the maximum size for a flexible neuroendoscope for a safe aqueductal neuronavigation. The schematic model of the aqueductal adytum as a triangle defines 3 different aqueductal patterns and can be helpful when an intraoperative decision on whether to navigate the aqueduct must be taken.

How I do it: endoscopic evacuation of intraventricular lesions using a flexible endoscope in combination with an angiographic catheter

BACKGROUND

In intraventricular surgery using a flexible endoscope, the lesion is usually aspirated via the working channel. However, the surgical view during aspiration is extremely poor because the objective lens is located adjacent to the working channel.

METHOD

To address this issue, we developed a novel surgical procedure using an angiographic catheter. In this procedure, the catheter is inserted into the working channel, and the lesion is aspirated through the catheter. Besides, continuous intraventricular irrigation is performed via the gap between the catheter and the working channel.

CONCLUSION

This procedure maintains a clear view during surgery and reduces complications.

The Roof of the 4th Ventricle Seen From Inside: Endoscopic Anatomic Illustration-A Case Series

BACKGROUND

The anatomy of the roof of the fourth ventricle has been illustrated in many laboratory investigations, but in vivo reports of the roof anatomy and its variants are still lacking.

OBJECTIVE

To describe the topographical anatomy of the roof of the fourth ventricle explored through a transaqueductal approach that overcomes cerebrospinal fluid depletion, displaying in vivo anatomic images possibly quite close to normal physiological conditions.

METHODS

We critically reviewed the intraoperative video recordings of our 838 neuroendoscopic procedures, selecting 27 cases of transaqueductal navigation that provided good quality image details of the anatomy of the roof of the fourth ventricle. Twenty-six patients affected by different forms of hydrocephalus were therefore categorized into three groups: Group A: blockage of the aqueduct-aqueductoplasty, Group B: communicating hydrocephalus, and Group C: tetraventricular obstructive hydrocephalus.

RESULTS

Group A has shown what the roof of a normal fourth ventricle really looks like albeit the structures seemed overcrowded because of the narrow space. Images from groups B and C paradoxically allowed a more distinct identification of the roof structures flattened by ventricular dilation, making them more comparable with the topography traced on the laboratory microsurgical studies.

CONCLUSION

Endoscopic in vivo videos and images provided a novel anatomic view and an in vivo redefinition of the real topography of the roof of the fourth ventricle. The relevant role of cerebrospinal fluid was defined and outlined, as well as the effects of hydrocephalic dilation on some structures on the roof of the fourth ventricle.

Morphological evaluation of the normal and hydrocephalic third ventricle on cranial magnetic resonance imaging in children: a retrospective study

BACKGROUND

Third ventricle morphological changes reflect changes in the ventricular system in pediatric hydrocephalus, so visual inspection of the third ventricle shape is standard practice. However, normal pediatric reference data are not available.

OBJECTIVE

To investigate both the normal development of the third ventricle in the 0-18-year age group and changes in its biometry due to hydrocephalus.

MATERIALS AND METHODS

For this retrospective study, we selected individuals ages 0-18 years who had magnetic resonance imaging (MRI) from 2012 to 2020. We included 700 children (331 girls) who had three-dimensional (3-D) T1-weighted sequences without and 25 with hydrocephalus (11 girls). We measured the distances between the anatomical structures limiting the third ventricle by dividing the third ventricle into anterior and posterior regions. We made seven linear measurements and three index calculations using 3DSlicer and MRICloud pipeline, and we analyzed the results of 23 age groups in normal and hydrocephalic patients using SPSS (v. 23).

RESULTS

Salient findings are: (1) The posterior part of the third ventricle is more affected by both developmental and hydrocephalus-related changes. (2) For third ventricle measurements, gender was insignificant while age was significant. (3) Normal third ventricular volumetric development showed a segmental increase in the 0-18 age range. The hydrocephalic third ventricle volume cut-off value in this age group was 3 cm³.

CONCLUSION

This study describes third ventricle morphometry using a linear measurement method. The ratios defined in the midsagittal plane were clinically useful for diagnosing the hydrocephalic third ventricle. The linear and volumetric reference data and ratios are expected to help increase diagnostic accuracy in distinguishing normal and hydrocephalic third ventricles.

How I do it: flexible endoscopic aspiration of intraventricular hemorrhage

Background

As intraventricular blood is a strong negative prognostic factor, intraventricular hemorrhage requires prompt and aggressive management to reduce intracranial hypertension.

Method

A flexible scope can be used to navigate and to aspirate blood clots from all four ventricles. Complete restoration of CSF pathways from the lateral ventricle to the foramen of Magendie can be obtained.

Conclusion

Flexible neuroendoscopic aspiration of IVH offers the opportunity to immediately reduce intracranial hypertension, reduce EVD obstruction and replacement rates, and decrease infections and shunt dependency.

Electronic supplementary material

The online version of this article (10.1007/s00701-020-04499-z) contains supplementary material, which is available to authorized users.

Use of flexible endoscopic aspiration for an intraventricular small floating clot with hemorrhage: a technical note

BACKGROUND

Although flexible endoscopy is effective for intraventricular lesions, it is less frequently used for hemorrhagic cases. In some hemorrhagic strokes, blood clots may plunge into the cerebral aqueduct and cause acute obstructive hydrocephalus. A flexible endoscope can aspirate clots and prevent acute hydrocephalus.

METHODS

Here, we report four cases of hemorrhage: one of intracerebral hemorrhage and three of subarachnoid hemorrhages.

RESULTS

In all cases, acute hydrocephalus was not apparent upon admission. Sudden comatose occurred; computed tomography revealed acute obstructive hydrocephalus with a strangulated clot in the cerebral aqueduct. We performed aspiration of the strangulated clot using a flexible endoscope. Consciousness improved in all cases, and acute hydrocephalus was prevented in all cases.

CONCLUSION

The use of simple flexible endoscopic aspiration for clots might be a beneficial and less-invasive procedure for acute obstructive hydrocephalus caused by a small clot with hemorrhagic stroke.