Morphology of the Dural Venous Complex of Skull Base in Human Ontogenesis

Research Article

Austin J Anat. 2019; 6(1): 1091.

Morphology of the Dural Venous Complex of Skull Base in Human Ontogenesis

Kornieieva M*

Department of Anatomy, Histology, and Embryology, AUC School of Medicine, Sint Maarten

*Corresponding author: Maryna Kornieieva, Department of Anatomy, Histology, and Embryology, Lowlands, AUC School of Medicine, Sint Maarten

Received: September 09, 2019; Accepted: December 05, 2019; Published: December 12, 2019

Abstract

The development of the dural venous complex of the skull base formed by the cavernous, intercavernous, and petrous dural sinuses and their connections with the intra- and extracranial veins and venous plexuses, was investigated on 112 premature stillborn human fetuses from 16 to 36 weeks of gestation by methods of vascular corrosion casting.

It was established that the main intracranial dural canals approach similar to the mature arrangement at the very beginning of the early fetal period. In fetuses 16 weeks of gestation, the parasellar dural venous complex appeared as a plexiform venous ring draining the venous plexus of the orbits into the petrous sinuses. The average diameter of dural canals progressively enlarged and reached its maximum value 2.2 ± 0.53 mm approaching the 24th week of gestation. This developmental stage is characterized by the intensive formation of the emissary veins connecting the cavernous sinus with the extracranial venous plexuses. Due to the particular fusion of the intraluminal canals, the average diameter of the lumen gradually declined to reach 1.9 ± 0.54 mm in 36-week-old fetuses. By the end of the fetal development, 21.3% of fetuses featured a considerable reduction of the primary venous system with the formation of the one-canal shaped dural venous sinuses, obliteration of several tributaries, and decreased density of the extracranial venous plexuses. In the other third of fetuses, the enhanced venous basal complex with the multicanal shape of dural sinuses, and abundance of tributaries and anastomoses persisted thought the whole antenatal period.

Thus, the genetically determined pace of reduction of the primary venous plexuses determines the final shape of the dural venous system and its compensatory abilities.

Keywords: Cavernous sinus; Intercavernous sinuses; Superior petrous sinus; Inferior petrous sinus; Human fetal development

Abbreviations

SPS: Superior Petrous Sinus; IPS: Inferior Petrous Sinus, a Mean (μ) ± SD (ση-1), mm, Significance levels: *** p ‹ 0.001; ** p ‹ 0.01; * p ‹ 0.5; NS, no statistical significance

Introduction

At the beginning of the early fetal period, the dural venous complex of the skull base is represented by two cavernous sinuses connected via the anterior and posterior intercavernous sinuses, the superior and inferior petrosal sinuses, and the marginal sinus located around the foramen magnum. During the early fetal period, the basilar dural complex dominates over the sinuses of calvaria draining the intensively developing structures of the orbit. The progressive enlargement of the cerebral hemispheres on the following stages of fetal development triggers significant reconstruction of venous outflow canals with the establishment of numerous intra- and extracranial anastomoses [1,2]. Although the early embryogenesis of the cranial venous system is relatively well described in the previously mentioned works, the clinically relevant reorganization of the dural sinuses of the skull base at the early and late fetal trimesters have not got proper attention yet.

The reconstruction and maturation of the fetal dural system is an important concept critical for analysis and successful treatment of benign dural malformations in neonates, referred to as the dural arteriovenous shunts. The dural arteriovenous shunts in neonates are rare but potentially fatal entities [3]. The symptoms of the dural arteriovenous shunts largely depend on the type of variability of the basilar dural complex, the drainage patterns of the shunt, and the coexistence with venous thrombosis [3-6]. Analysis of 30 clinical cases with this pathology in neonates and infants shows that only half of them had received transvascular embolization treatment, preferably via the arterial tree. All untreated babies died, whereas 75% of treated ones had good neurological outcomes [3]. Comparison of outcomes for 27 adult patients treated by transvenous and transarterial embolization methods allowed the author to advocate the first approach, as it gave 87% of positive results [7]. Presumably, the intravenous approach would improve the outcomes in infants, too. Detailed morphologic analysis of the development and maturation of the fetal dural venous system could open up new possibilities for the treatment of such neonates.

Present morphologic research is designed to evaluate the developmental reconstructions of the dural venous system of the skull base in human fetuses from 16 to 36 weeks of gestation and to describe the range of variability of the cavernous, intercavernous and petrous dural sinuses established in preborn fetuses.

Materials and Methods

This study was carried out on 112 premature stillborn human fetuses (64 males and 48 females) aged between 16-36 weeks of gestation. The gestational age was estimated by the last menstrual period of the mother and by measuring of weight and length of the fetus. All specimens with congenital malformations of the head and central nervous system were excluded from the study. The research had been conducted at the Lugansk State Medical University (Ukraine) following International Norms of Biological Research and was approved by the Institutional Ethics Committee (Protocol number 10.978.03 from 23.01.2007).

In the selected specimens, the extended thoraco- and pericardiotomy were performed, exposing the surface of the heart. A fine catheter introduced into the superior vena cava via the right atrium of the heart was used to inject 1:3 mixture of acrylate monomer with dichloromethane into the venous system until complete filling of the superficial veins of the scalp. The oil-based blue paint was added to the plastic to color the vessels. After the injection, a fetus was immersed into 10% formaldehyde for 5-7 days. Then, the head of the specimen was placed into the concentrated hydrochloric acid for 10- 14 days for corrosion of the soft tissues. An obtained plastic cast of the venous system of the head was carefully rinsed under running water.

The components of the dural venous complex of the skull base were studied through a monocular biological microscope with tenfold magnification (Levenhuk 5S NG). The diameter and length of the cavernous, anterior and posterior intercavernous, and superior and inferior petrous sinuses were measured under a microscope eyepiece micrometer with calibration measuring scale ruler reticle 0.1 mm. The intracranial tributaries and emissary veins attached to the sinuses were enumerated. The mean and standard deviation of the resultant data were calculated for the early (16-20-24 weeks) and late (28-32-36 weeks) trimesters of the fetal development separately. The difference of results was evaluated with paired t-test (2-tailed). A p-value 0.05 and less was considered as statistically significant.

Results

It was established that the main intracranial dural canals approximate the mature arrangement at the very beginning of the early fetal period (Figure 1). In fetuses 16 weeks of gestation, the parasellar dural venous complex appeared as a plexiform venous ring formed by paired cavernous sinuses connected via anterior and posterior intercavernous sinuses.