An endoscopic, cadaveric analysis of the roof of the fourth ventricle

The debated neuroanatomy of the fourth ventricle

The fourth ventricle is a small, fluid-filled cavity located within the brain that plays a vital role in the body's physiological functions. Therefore, the anatomical elements forming it bear significant clinical relevance. However, the exact relations between the elements that form its roof are still debated in the neuroanatomical literature; the inferior medullary velum, and the ventricle's median aperture in particular. In some atlases, the inferior medullary velum is placed in the midline, while in others, it is placed in the transverse plane. The median aperture is also displayed in different ways in midsagittal drawings: as a round perforation of a midline velum, as a foramen in an uncharacterized part of the ventricle, and as a gap between the nodule and the brainstem. This work aims to provide a comprehensive review of the different descriptions of the fourth ventricle, in order to gain a clearer understanding of the ventricular system's structure.

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.

The functional anatomy of the foramina of Luschka revisited

Background:

The German Anatomist Hubert Von Luschka first described the foramina of Luschka (FOL) in 1855 as lateral holes in the fourth ventricle. By his discovery, he refuted previous beliefs about the lateral recess as blind ends of the fourth ventricle, proving the continuity of the ventricular system with the central canal of the spinal cord. In this paper, we question the outline variations of the patent parts of FOL and their consistency, drawing attention to the apparent query of the valvular mechanism of FOL.

Methods:

We conducted a literature review in PubMed and Google Scholar databases to review the existing literature describing the history, pertinent anatomy, and function of FOL. In addition, we reviewed the original German book written by Luschka.

Results:

While reading the available articles and original works regarding FOL, we noticed the developmental phases through which FOL was discovered, tracking the process from Aristotle till Luschka’s discovery. We also discussed controversies and opinions about FOL’s existence and function.

Conclusion:

FOL is halved into two compartments: choroidal and patent. The function of FOL resembles a oneway valve mechanism, and it depends on the patent slit-like part. Luschka had discovered over 20 anatomical structures, including several foramina, confusion in a debate may result from eponyms.

Anatomy of the Ventricles, Subarachnoid Spaces, and Meninges

The ventricular system, subarachnoid spaces, and meninges are structures that lend structure, support, and protection to the brain and spinal cord. This article provides a detailed look at the anatomy of the intracranial portions of these structures with a particular focus on neuroimaging methods.

Dorsal extensions of the fastigium cerebelli: an anatomical study using magnetic resonance imaging

BACKGROUND AND PURPOSE

The fastigium cerebelli is an important topographical landmark for neurosurgeons and radiologists. However, few studies have characterized the morphology of the fastigium cerebelli. We aimed to investigate the fastigium cerebelli using postmortem specimens and magnetic resonance imaging (MRI) in vivo.

MATERIALS AND METHODS

Three cadaveric brains were midsagittally sectioned for observing the fastigium cerebelli. Additionally, 66 outpatients underwent MRI, including sagittal T1-weighted imaging, axial T2-weighted imaging, and coronal constructive interference in steady-state (CISS) sequence.

RESULTS

In the cadaveric specimens, the fastigium cerebelli was observed as a beak-like dorsal protrusion of the fourth ventricle. Its inner surface was observed as a small fovea. On serial CISS images, the fastigium cerebelli consistently possessed a pair of triangular-shaped, dorsal extensions lying parasagittally along the nodule. These extensions were classified as symmetrical, right-side dominant, or left-side dominant. The symmetrical type was the most predominant and comprised 60.6% of the extensions, while the right-side dominant and left-side dominant types comprised 13.6 and 25.8%, respectively. In 91% of the 66 patients, the number of slices covering the entirety of the dorsal extensions were the same on both sides. The fastigial angle (θ) formed by lines tangent to the superior and inferior medullary velums varied widely.

CONCLUSIONS

The fastigium cerebelli has a pair of dorsal extensions lying parasagittally along the nodule. Coronal CISS sequence is useful in delineating the fastigium cerebelli in vivo.

Delayed Diagnosis of Enhancing Posterior Fossa Tumors Mimicking the Tela Choroidea of the Fourth Ventricle

BACKGROUND

Posterior fossa brain tumors are common in children. Symptoms typically develop when the tumors have reached sufficient size to cause compression of adjacent neural structures or cause obstructive hydrocephalus. Many tumors in this region originate from the tela choroidea and choroid plexus of the fourth ventricle. Enhancement of the fourth ventricular tela choroidea and choroid plexus is uncommon in children, and when such enhancement is present, it may represent early tumor growth.

METHODS

A 5-year-old girl with a history of congenital nystagmus, for whom initial work-up was reported as negative, presented again several years later with headache, nausea, and vomiting. She was found to have a large posterior fossa lesion on repeat neuroimaging that was retrospectively seen on the first neuroimaging scan as prominent enhancement in the region of the fourth ventricular choroid plexus. The second patient presented with congenital nystagmus and a lingual tremor and was found to have a slowly growing lesion situated in the fourth ventricle. Initial imaging was read as nodularly enhancing tela choroidea, but subsequent scans revealed enlargement of the lesion.

RESULTS

The first patient underwent gross total resection, and neuropathology was consistent with an atypical teratoid rhabdoid tumor. The patient has done well with postoperative adjuvant therapies. In the second patient, resection of the lesion revealed ependymoma; the patient has done well after adjuvant radiation therapy.

CONCLUSIONS

Pediatric patients who have enhancing tela choroidea or choroid plexus without an obvious mass lesion of the fourth ventricle may harbor early tumors. Surveillance imaging in these patients may be warranted given the aggressive nature of certain posterior fossa tumors in children. Failure to recognize abnormal enhancement patterns in this region may lead to delayed diagnosis.