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 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.

Routes of the thalamus through the history of neuroanatomy

The most distant roots of neuroanatomy trace back to antiquity, with the first human dissections, but no document which would identify the thalamus as a brain structure has reached us. Claudius Galenus (Galen) gave to the thalamus the name 'thalamus nervorum opticorum', but later on, other names were used (e.g., anchae, or buttocks-like). In 1543, Andreas Vesalius provided the first quality illustrations of the thalamus. During the 19th century, tissue staining techniques and ablative studies contributed to the breakdown of the thalamus into subregions and nuclei. The next step was taken using radiomarkers to identify connections in the absence of lesions. Anterograde and retrograde tracing methods arose in the late 1960s, supporting extension, revision, or confirmation of previously established knowledge. The use of the first viral tracers introduced a new methodological breakthrough in the mid-1970s. Another important step was supported by advances in neuroimaging of the thalamus in the 21th century. The current review follows the history of the thalamus through these technical revolutions from Antiquity to the present day.

The terminal ventricle of Saguinus leucopus (Primate)

The terminal ventricle is a dilation of the ventricular system located within the spinal cord, which is enveloped in ependymal cells that are involved in the dynamic of the cerebrospinal liquid. In the present study, four Saguinus leucopus specimens were dissected, two males and two females, whose spinal cords were extracted and histologically processed via hematoxylin and eosin stains of cuts at the conus medullaris. The S. leucopus' terminal ventricle was observed at the conus medullaris, and had an average diameter of 241.38 μm. Thus, the presence of the terminal ventricle in the S. leucopus at the level of the conus medullaris was established.