**1. Introduction**

Skull as a complicated mechanical construction, consists from 28 different bones, connected by sutures of different structural kinds - from smooth (face cranium) to teeth-like hardness (brain cranium). Basically, skull can be selected as face skull and brain skull. The last is composed from 8 bones with complicated connections between them, and namely brain skull will be described in the chapter presented.

Structure of "brain skull" (or simply – skull) is the most complicated, it is changeable and individual depending on age, sex and race. The most pronounced mechanical changes of skull properties are observed in babies and juniors which are connected with brain growing. Later, structural changes of the skull are concerned with structure of bone sutures, which tissues loss their elasticity with age. Volume of internal cavity of the skull of adult persons is balanced closely with volume of intracranial media so precisely, that the internal relief of skull bones reflects the structure of the brain and its vascular system. This confirms the idea, that skull plays protector function for brain, and it is well known.

However, this precisely high balance of internal skull volume and intracranial media volumes, due to natural variations of brain skull configuration, might be a reason of some diminishing of the skull internal volume to compare with intracranial media. Variations of the skull configuration, which actually diminish intracranial cavity, may be the most pronounced at middle ageing, when capabilities of the skull internal volume for adaptation also diminish due to decrease of the possibility of change of suture structure. Result of this may be some compressing of tissues, filled cranial cavity, first of all, liquid media blood and cerebrospinal fluid (CSF), which are responsible for circulatory-metabolic supply of brain functioning. As a consequence, some neurological symptoms may appear indicating that volume of intracranial cavity is really smaller, than optimal volume of intracranial media.

© 2012 Moskalenko et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### 64 Injury and Skeletal Biomechanics

The most reasonable way to treat of such neurological disturbances is to increase of internal skull volume. That is why the first method to treat such neurological disorders was neurosurgical skull trepanation which was practiced for numerous Centuries. It is confirmed by archeological findings of human skulls with trepanation performed on living persons. The long history of skull trepanation since 2000 B.C. reviewed in many publications [1, 2, 3].

The Role of Skull Mechanics in Mechanism of Cerebral Circulation 65

moveable system. This skull feature found practical application in osteopathic medicine and is used for diagnostic purposes and evaluation of results of osteopathic treatment up to the present time [8, 9]. These observations have shown, that for the skull bones the slow

The next important finding have been made during observation of neurosurgical patients, which have been shown, that skull as structural unity is characterized by the special property – Cranial Compliance, which was studied by injection into the skull of neurosurgical patients of artificial (mock) CSF and dependence "Pressure/Volume" for skull

The next step in the evaluation of the role of skull in mechanism of cerebral circulation was made not physiologists or physicians, but mathematicians, who in process of mathematical modeling of the cerebra-circulatory system inside closed skull, have established, that only if skull will accept some additional volume of blood during systolic increase of central arterial pressure, cerebrovascular system in coupling with CSF system could function [11]. This study permits to predict, that brain circulatory support system include as active element

Thus, this chapter will to describe the role of peculiarities of skull biomechanics as an active component of complicate physiological mechanisms, responsible for brain physiological

**2. The role of skull pulse expanding in mechanism of circulatory supply** 

The system of cerebral metabolic supply is dependent on the interaction of a number of elements some of them are determined by the skull properties. One of the most significant in this direction is clarifying the role of CSF movement to this system inside cranium and significance at this process of the bio-mechanical properties of the skull. Critical position in the role of the skull in support of circulatory-metabolic supply of brain functioning determined by the ability of the skull to accept an additional volume of blood during the

Indeed, arterial blood pressure consists of two components. One is the steady state of flow through the brain, determined by the basal tone of the brain blood vessels. The second occurs with each heart- beat, which initiated by arterial pressure increases and so drives the pulse volume into the cranium. It is this component that is influenced by the level of cranial

This increase in arterial pressure is short – about 0.1s. This means that the cranium needs to accommodate the increase in systolic blood volume very quickly in order to use it to drive cerebral circulation. This possibility, predicted by mathematical simulation of the cerebrovascular system [12], should be follow from biomechanical properties of the skull as

compliance, which in turn depends on the volume flexibility of the skull.

mechanism, responsible for circulatory-metabolic supply of brain functioning.

phase of systolic increase in central arterial pressure.

periodics are of special.

has been established [10].

skull bio-mechanics.

**of brain function** 

united bio-mechanical system.

This method have been used also at middle centuries, which is confirmed by one of art master pieces, named "Treatment of foolishness" - painting of Bosch (1475), presented process of trepanation to remove "the stone of foolishness" from the skull. All these examples show, that the role of trepanation, as method of treatment of some neurological pathology, was reasoned to increase of intracranial volume, and this had been understood Centuries ago.

It is well known, that one the most important physiological function of the skull is protecting brain from external mechanical disturbances. However, some negative role of close correspondences of brain and cranial cavity volumes may be the change of balance between these volumes in different living situation, and it becomes significant, when comparative increase of intracranial volume of media is taking place. Result of this, first of all, may be decrease of activity of Cerebro-Spinal Fluid (CSF) which compresses brain blood vessels and, in some cases, brain tissue, too. All these could evoke functional insufficiencies, as headache and some neurological symptoms. The high significance of balance between intracranial cavity volume and the media filled it, is critically important in connecting with fact, that brain at all situations needs intensive and stabile blood supply, because brain metabolism is founded on aerobic principle. For aging population, the limitation of intracranial volume becomes more important and could be reason of pronounced decrease of cerebral blood flow (CBF) resulted in dementia.

Skull trepanation up to the present time is actively using when volume of intracranial media is increased by some reasons (closed brain injury, brain tumor), indicator of which is the increase of intracranial pressure.

It is necessary to mention, that so strong restrictions of intracranial cavity volume limit also possibilities for ranges of adaptation to different living situations and, diminish living capabilities. Therefore, it is reasonable to predict, that in process of evolution of mammals some protecting accommodations of intracranial volume, which are not diminish its protector function have been developed. The basis of these mechanisms should be founded on the possibility of some increase of intracranial volume compensation of change of volume media, filled the skull. Investigations at this direction become appear from the beginning of XX Century.

Primary, it was have shown, that some volume reserves is follows from the possibility of free replacements of CSF between cranial and spinal cavities and spinal cavity could accept some volume of cranial CSF due to elasticity of vertebral lumbal sack [4, 5, 6, 7]. In the middle of XX Century one more possibility, based on feature of the skull, have been discovered. It has been shown by palpation, that skull represents a complicated mechanical moveable system. This skull feature found practical application in osteopathic medicine and is used for diagnostic purposes and evaluation of results of osteopathic treatment up to the present time [8, 9]. These observations have shown, that for the skull bones the slow periodics are of special.

64 Injury and Skeletal Biomechanics

[1, 2, 3].

Centuries ago.

of cerebral blood flow (CBF) resulted in dementia.

increase of intracranial pressure.

beginning of XX Century.

The most reasonable way to treat of such neurological disturbances is to increase of internal skull volume. That is why the first method to treat such neurological disorders was neurosurgical skull trepanation which was practiced for numerous Centuries. It is confirmed by archeological findings of human skulls with trepanation performed on living persons. The long history of skull trepanation since 2000 B.C. reviewed in many publications

This method have been used also at middle centuries, which is confirmed by one of art master pieces, named "Treatment of foolishness" - painting of Bosch (1475), presented process of trepanation to remove "the stone of foolishness" from the skull. All these examples show, that the role of trepanation, as method of treatment of some neurological pathology, was reasoned to increase of intracranial volume, and this had been understood

It is well known, that one the most important physiological function of the skull is protecting brain from external mechanical disturbances. However, some negative role of close correspondences of brain and cranial cavity volumes may be the change of balance between these volumes in different living situation, and it becomes significant, when comparative increase of intracranial volume of media is taking place. Result of this, first of all, may be decrease of activity of Cerebro-Spinal Fluid (CSF) which compresses brain blood vessels and, in some cases, brain tissue, too. All these could evoke functional insufficiencies, as headache and some neurological symptoms. The high significance of balance between intracranial cavity volume and the media filled it, is critically important in connecting with fact, that brain at all situations needs intensive and stabile blood supply, because brain metabolism is founded on aerobic principle. For aging population, the limitation of intracranial volume becomes more important and could be reason of pronounced decrease

Skull trepanation up to the present time is actively using when volume of intracranial media is increased by some reasons (closed brain injury, brain tumor), indicator of which is the

It is necessary to mention, that so strong restrictions of intracranial cavity volume limit also possibilities for ranges of adaptation to different living situations and, diminish living capabilities. Therefore, it is reasonable to predict, that in process of evolution of mammals some protecting accommodations of intracranial volume, which are not diminish its protector function have been developed. The basis of these mechanisms should be founded on the possibility of some increase of intracranial volume compensation of change of volume media, filled the skull. Investigations at this direction become appear from the

Primary, it was have shown, that some volume reserves is follows from the possibility of free replacements of CSF between cranial and spinal cavities and spinal cavity could accept some volume of cranial CSF due to elasticity of vertebral lumbal sack [4, 5, 6, 7]. In the middle of XX Century one more possibility, based on feature of the skull, have been discovered. It has been shown by palpation, that skull represents a complicated mechanical The next important finding have been made during observation of neurosurgical patients, which have been shown, that skull as structural unity is characterized by the special property – Cranial Compliance, which was studied by injection into the skull of neurosurgical patients of artificial (mock) CSF and dependence "Pressure/Volume" for skull has been established [10].

The next step in the evaluation of the role of skull in mechanism of cerebral circulation was made not physiologists or physicians, but mathematicians, who in process of mathematical modeling of the cerebra-circulatory system inside closed skull, have established, that only if skull will accept some additional volume of blood during systolic increase of central arterial pressure, cerebrovascular system in coupling with CSF system could function [11]. This study permits to predict, that brain circulatory support system include as active element skull bio-mechanics.

Thus, this chapter will to describe the role of peculiarities of skull biomechanics as an active component of complicate physiological mechanisms, responsible for brain physiological mechanism, responsible for circulatory-metabolic supply of brain functioning.
