Chapter 4
Brain Tissue Mechanical Properties
Lynne E. Bilston
4.1 Introduction
The human brain is a soft highly metabolically active tissue, floating in cerebrospinal fluid (CSF) within the rigid cranium. This environment acts to isolate the
brain from the majority of external mechanical loads experienced by the head during
normal daily life. The brain does experience a range of mechanical loads directly,
as a result of blood and CSF flow and to some extent, body posture. The dynamic
balance of pulsatile hydrodynamic forces in the skull is maintained by blood and
CSF flow into and out of the skull throughout the cardiac cycle (the Monro-Kellie
hypothesis), since the internal volume of the skull is constant. Reflex responses
maintain blood flow during changes in posture and activity, so as to stabilise the
mechanical and biochemical environment of the brain.
Brain tissue consists of white and grey matter, and different regions of the brain
are made up of different proportions of white and grey matter. White matter is
largely composed of myelinated axons of nerve fibres, while the grey matter is
dominated by unmyelinated axons and cell bodies.
Since the brain is so well insulated from mechanical perturbations under normal
circumstances, one might ask why it is important to understand the mechanical
properties of brain tissue. While mechanical factors are thought to play a role
in a range of conditions, including brain development [1], brain mechanics have
been most commonly studied in an attempt to understand conditions where loads
are applied either directly or indirectly to the brain. Much of the early work on
brain mechanics was focused on understanding the biomechanics of traumatic
brain injury, where high loading rate motion of, or impacts to, the skull results
L. E. Bilston ()
Neuroscience Research Australia and University of New South Wales, Sydney, NSW, Australia
e-mail: L.Bilston@neura.edu.au
© Springer Nature Switzerland AG 2019
K. Miller (ed.), Biomechanics of the Brain, Biological and Medical Physics,
Biomedical Engineering, https://doi.org/10.1007/978-3-030-04996-6_4
71
Brain Tissue Mechanical Properties
Lynne E. Bilston
4.1 Introduction
The human brain is a soft highly metabolically active tissue, floating in cerebrospinal fluid (CSF) within the rigid cranium. This environment acts to isolate the
brain from the majority of external mechanical loads experienced by the head during
normal daily life. The brain does experience a range of mechanical loads directly,
as a result of blood and CSF flow and to some extent, body posture. The dynamic
balance of pulsatile hydrodynamic forces in the skull is maintained by blood and
CSF flow into and out of the skull throughout the cardiac cycle (the Monro-Kellie
hypothesis), since the internal volume of the skull is constant. Reflex responses
maintain blood flow during changes in posture and activity, so as to stabilise the
mechanical and biochemical environment of the brain.
Brain tissue consists of white and grey matter, and different regions of the brain
are made up of different proportions of white and grey matter. White matter is
largely composed of myelinated axons of nerve fibres, while the grey matter is
dominated by unmyelinated axons and cell bodies.
Since the brain is so well insulated from mechanical perturbations under normal
circumstances, one might ask why it is important to understand the mechanical
properties of brain tissue. While mechanical factors are thought to play a role
in a range of conditions, including brain development [1], brain mechanics have
been most commonly studied in an attempt to understand conditions where loads
are applied either directly or indirectly to the brain. Much of the early work on
brain mechanics was focused on understanding the biomechanics of traumatic
brain injury, where high loading rate motion of, or impacts to, the skull results
L. E. Bilston ()
Neuroscience Research Australia and University of New South Wales, Sydney, NSW, Australia
e-mail: L.Bilston@neura.edu.au
© Springer Nature Switzerland AG 2019
K. Miller (ed.), Biomechanics of the Brain, Biological and Medical Physics,
Biomedical Engineering, https://doi.org/10.1007/978-3-030-04996-6_4
71