Brain Subarachnoid Space Architecture: Histological Approach

Human brain is suspended in the skull through three fibrous tissue layers, dura mater, arachnoid and pia mater, known as the meninges layer. The space between the arachnoid and pia mater is known as subarachnoid space (SAS). SAS consists of arachnoid trabeculae and cerebrospinal fluid (CSF), which stabilizes the shape and the position of the brain during head movements. Through solid-fluid interaction, it has been shown that subarachnoid space (SAS) trabeculae plays an important role in damping and reducing the relative movement of the brain with respect to the skull, thereby reducing traumatic brain injuries (TBI), (Zoghi and Sadegh 2010). While the functionality of the SAS is understood, the architecture, the histology and biomechanics of this important region has not been fully investigated. In their modeling of the head, previous investigators have over simplified this important region. This is due to the trabeculae’s complex geometry, abundance of trabeculae and lack of the material properties. These simplifications could lead to inaccurate results of finite element head studies. Killer HE, et al, (2003) investigated the trabecular histology of optical nerves and Alcoldo, et al (1986) used Scanning Electron Microscopy (SEM) to study the arachnid mater of the SAS. The result of these studies reveal that the arachnoid is a thin vascular layer composed of fibroblast cells interspersed with bundles of collagen and the trabecula is also a collagen based structure. However, the brain SAS trabecular architecture and histology has not been fully investigated. The goal of this study is to investigate the mechanotransduction of the head impacts to the brain with the emphasis on the role of material modeling and architecture of the subarachnoid space as it relates to Traumatic Brain Injuries (TBI). This goal was accomplished through three aims including experimental studies, material modeling and a 3D finite element model. In this paper, to present a global view of this investigation, brief descriptions of each aim are presented. It was concluded that the trabeculae contain collagen Type I with tree-shaped architecture and the validated material properties of SAS is approximately E = 1000 Pa.