Pierluigi Longatti, Andrea Porzionato, Luca Basaldella, Alessandro Fiorindi, Pietro De Caro and Alberto Feletti
The human area postrema (AP) is a circumventricular organ that has only been described in cadaveric specimens and animals. Because of its position in the calamus scriptorius and the absence of surface markers on the floor of the fourth ventricle, the AP cannot be clearly localized during surgical procedures.
The authors intravenously administered 500 mg fluorescein sodium to 25 patients during neuroendoscopic procedures; in 12 of these patients they explored the fourth ventricle. A flexible endoscope equipped with dual observation modes for both white light and fluorescence was used. The intraoperative fluorescent images were reviewed and compared with anatomical specimens and 3D reconstructions.
Because the blood-brain barrier does not cover the AP, it was visualized in all cases after fluorescein sodium injection. The AP is seen as 2 coupled leaves on the floor of the fourth ventricle, diverging from the canalis centralis medullaris upward. Although the leaves normally appear short and thick, there can be different morphological patterns. Exploration using the endoscope's fluorescent mode allowed precise localization of the AP in all cases.
Fluorescence-enhanced inspection of the fourth ventricle accurately identifies the position of the AP, which is an important landmark during surgical procedures on the brainstem. A better understanding of the AP can also be valuable for neurologists, considering its functional role in the regulation of homeostasis, emesis, and cardiovascular and electrolyte balance. Despite the limited number of cases in this report, evidence indicates that the normal anatomical appearance of the AP is that of 2 short and thick leaves that are joined at the midline. However, there can be great variability in terms of the structure's shape and size.
Alberto Feletti, Alessandro Fiorindi, Vincenzo Lavecchia, Rafael Boscolo-Berto, Elisabetta Marton, Veronica Macchi, Raffaele De Caro, Pierluigi Longatti, Andrea Porzionato and Giacomo Pavesi
Despite the technological advancements of neurosurgery, the posterior part of the third ventricle has always been the “dark side” of the ventricle. However, flexible endoscopy offers the opportunity for a direct, in vivo inspection and detailed description of the posterior third ventricle in physiological and pathological conditions. The purposes of this study were to describe the posterior wall of the third ventricle, detailing its normal anatomy and surgical landmarks, and to assess the effect of chronic hydrocephalus on the anatomy of this hidden region.
The authors reviewed the video recordings of 59 in vivo endoscopic explorations of the posterior third ventricle to describe every identifiable anatomical landmark. Patients were divided into 2 groups based on the absence or presence of a chronic dilation of the third ventricle. The first group provided the basis for the description of normal anatomy.
The following anatomical structures were identified in all cases: adytum of the cerebral aqueduct, posterior commissure, pineal recess, habenular commissure, and suprapineal recess. Comparing the 2 groups of patients, the authors were able to detect significant variations in the shape of the adytum of the cerebral aqueduct and in the thickness of the habenular and posterior commissures. Exploration with sodium fluorescein excluded the presence of any fluorescent area in the posterior third ventricle, other than the subependymal vascular network.
The use of a flexible scope allows the complete inspection of the posterior third ventricle. The anatomical variations caused by chronic hydrocephalus might be clinically relevant, in light of the commissure functions.