Microsurgical anatomy of Liliequist's membrane demonstrating three-dimensional configuration.

OBJECT: Liliequist's membrane (LM) is an important arachnoid structure in the basal cisterns. The relevant anatomic descriptions of this membrane and how many leaves it has are still controversial. The existing anatomical theories do not satisfy the needs of minimally invasive neurosurgery. We aimed to establish the three-dimensional configuration of LM. METHODS: Fifteen adult formalin-fixed cadaver heads were dissected under a surgical microscope to carefully observe the arachnoid mater in the suprasellar and post-sellar areas and to investigate the arachnoid structure and its surrounding attachments. RESULTS: It was found that the LM actually consists of three types of membranes. The diencephalic membrane (DM) was usually attached by the mesencephalic membrane (MM) from underneath, and above DM it was usually a pair of hypothalamic membranes (HMs) extending superomedially. The pair of HMs was stretched between the DM (or MM) and the hypothalamus and were seldom attached to the carotid-chiasmatic walls between the carotid cistern and the chiasmatic cistern. These three types of membranes (DM, MM, and HM) comprised the main arachnoid structure in the anterior incisural space and often presented as four connected leaves. However, only two thirds of the specimens had all three types of membranes, and there was considerable variation in the characteristics and shapes of the membranes among the specimens. CONCLUSION: All three types of membranes comprising LM serve as important anatomical landmarks and interfaces for surgical procedures in this area.

Landmark-based analysis of the morphological relationship between endocranial shape and traces of the middle meningeal vessels.

The morphogenesis and evolution of the cranium are the result of structural interactions among its components, leading to covariance between traits. Soft and hard tissues exert a reciprocal physical and physiological influence, leading to the final phenotype in terms of both ontogeny and evolution. The middle meningeal vessels, interfacing the brain and the braincase, provide an opportunity to study this network, even in extinct human species. Between and within-species variations of the vascular patterns may be mechanically influenced by the cranial morphology (structural hypothesis) or else by actual physiological responses and adaptations, mostly related to oxygen supply and/or thermoregulation (functional hypothesis). In this analysis, we tested the relationship between neurocranial shape and the general morphology of the traces of the middle meningeal vessels in a modern human population, by using landmark-based geometrical models. Although there are some neurocranial differences between groups with different vascular patterns, they are very small or not statistically significant. Only the depth of the imprints may be more influenced by the endocranial morphology. Even if the neurocranial differences among extinct hominids are definitely larger than those within the modern species, the present analysis suggests that it is unlikely that the differences in vascular patterns among the human species are related only to the effects of different neurocranial geometry. This is rather relevant when the marked development of the meningeal network in Homo sapiens is taken into account, compared with the patterns described for nonmodern human species.

Clinical anatomy of the human anterior cranial fossa during the prenatal period.

We examined the prenatal development of the human anterior cranial fossa and considered its clinical aspects. Our purpose was an evaluation of anterior cranial fossa geometry, its measurements and connections with the nasal cavity and middle cranial fossa. The study was performed on 29 foetuses from the first and second trimester of pregnancy. New methods of computer image analysis, Scion for Windows 98 and ELFv 4.2, were applied to examine this anatomical region. Different options used were binarisation, equalisation, filters, linear and non-linear transformations and mathematical operations of images. This enabled the dynamics of prenatal development to be accurately evaluated for parts of the base of the human skull. Measurements were taken of angles of the cranial base. The anterior cranial base angle (the apex in the middle of the sella turcica and the arms running through the zygomatic ossification points) decreased gradually between C-R 6 to 23.5 cm from 170 to 120 degrees and afterwards became constant. The contrary-medial cranial base angle (adjacent to the anterior cranial base angle and with a second arm running through the auricular cartilage) increased from 50 to 70 degrees. The anterior cranial fossa was first located on the same level as the middle and posterior fossae. The process of descent of the middle and posterior cranial fossa begins in the 4th gestational month. The geometry of the anterior cranial fossa changes rapidly, especially in the first trimester of pregnancy. The first trimester of pregnancy is crucial for the development of its defects. Preconception prophylaxis of inborn defects of the anterior cranial fossa is therefore extremely important.