Meninges vascularization CSF · Meninges Duramater (==pachymeninx )-tough, fibrous structure...

MeningesMeninges

Coverings of the brain and spinal cordCoverings of the brain and spinal cord

Coverings of the brain and spinal cordCoverings of the brain and spinal cord

�� The CNS is enclosed in the bony The CNS is enclosed in the bony structures structures

((craniumcranium && vertebral columnvertebral column))

�� Separating the brain and spinalSeparating the brain and spinal cord from the cord from the

calcified tissue are calcified tissue are 33 approx.approx. cconcentriconcentric

membranesmembranes →→ meningesmeninges

Meninges

�� DDuraura mater (mater (== pachymeninxpachymeninx)) -- tough, fibrous tough, fibrous

structure structure

�� LeptomeninxLeptomeninx

�� Arachnoid materArachnoid mater

�� Pia materPia mater

Dura mater (Lat. “tough mother”)

�� Surrounds brain, closely adherent to skull (no epidural Surrounds brain, closely adherent to skull (no epidural space)space)

�� Two fused layers (periosteal and meningeal) which split Two fused layers (periosteal and meningeal) which split to form venous sinusesto form venous sinuses

�� Very thick and leatherVery thick and leather--like, contains many pain like, contains many pain receptors (unlike arachnoid, pia, or brain)receptors (unlike arachnoid, pia, or brain)

DDuraura matermater

�� TTough, fibrous structure ough, fibrous structure

�� OOuter (uter (periostealperiosteal) layer) layer -- attached to the internal table of the attached to the internal table of the diplodiploëë and acts as a true periosteumand acts as a true periosteum�� composed of inelastic connective tissuecomposed of inelastic connective tissue

�� at the rim of the foramen magnum becomes continuous with the at the rim of the foramen magnum becomes continuous with the periosteum of the vertebral canalperiosteum of the vertebral canal

�� rich vascular supplyrich vascular supply

�� IInner (nner (meningealmeningeal) layer ) layer -- in intimate contact with the arachnoidin intimate contact with the arachnoid�� dense connective tissue layerdense connective tissue layer

�� inner layer of fibroblasts (separates arachnoidea from the collainner layer of fibroblasts (separates arachnoidea from the collagenous genous layer)layer)

�� at the rim of the foramen magnum becomes continuous with at the rim of the foramen magnum becomes continuous with the dura the dura mater of the spinal cord mater of the spinal cord

�� no vascular supplyno vascular supply

�� The The 22 layerslayers of dura are tightly attached to each other; however, of dura are tightly attached to each other; however, in certain regions thein certain regions theyy are separated from each other to form are separated from each other to form venous channelsvenous channels →→ sinusessinuses

Structures formed by tStructures formed by the meningeal layer of durahe meningeal layer of dura

�� RReflecteflections of the meningeal layerions of the meningeal layer upon itself to form upon itself to form duraldural foldsfolds →→ separate parts of the brain from one separate parts of the brain from one anotheranother�� falx falx (L., sickle) (L., sickle) cerebricerebri

�� tentorium cerebellitentorium cerebelli

�� falx cerebellifalx cerebelli

�� Other structuresOther structures�� diaphragma selladiaphragma sellaee -- a diaphragm over the hypophyseal a diaphragm over the hypophyseal fossafossa

�� cavum trigeminale (Meckelcavum trigeminale (Meckel’’s cave)s cave) -- a roof over the a roof over the trigeminaltrigeminal ganglion, thus forming a shallow ganglion, thus forming a shallow cavity harboring cavity harboring the ganglion of CN V)the ganglion of CN V)

Falx cerebriFalx cerebri

TTentorium cerebelli entorium cerebelli

Falx cerebri and tentorium cerebelli Falx cerebri and tentorium cerebelli

Note the continuity between the meningeal layer of dura mater within

the skull and the dura mater of the spinal cord at the foramen magnum

Cranial nerve leaving skull

CCavum trigeminaleavum trigeminale

Layers of dura materLayers of dura mater

Dura - periosteal layerDura - meningeal layer

Venous sinuses of dura materVenous sinuses of dura mater

�� RReceive blood from the brain through the eceive blood from the brain through the

cerebral veins and cerebral veins and CSFCSF from the subarachnoid from the subarachnoid

space through the arachnoid villispace through the arachnoid villi

�� DDrain into the internal jugular veins in the neckrain into the internal jugular veins in the neck

�� EndotheliallyEndothelially lined, hlined, have no valvesave no valves

�� GGrouped into rouped into 22 major categories, themajor categories, the anterior anterior

inferiorinferior and and posterior superiorposterior superior groupsgroups

Venous sinuses of Venous sinuses of

dura materdura mater�� AAnterior inferior nterior inferior groupgroup

�� cavernous sinuscavernous sinus

�� anterior & posterior intercavernous sinusesanterior & posterior intercavernous sinuses

�� sphenoparietal sinussphenoparietal sinus

�� superior & inferior petrosal sinuses superior & inferior petrosal sinuses

�� basilar plexusbasilar plexus

�� PPosterior superior grouposterior superior group

�� superior superior && inferior saginferior sagggittalittal sinusessinuses

�� sstraighttraight sinussinus (sinus rectus)(sinus rectus)

�� ttransverseransverse sinussinus

�� ssigmoidigmoid sinussinus

�� ppetrosquamousetrosquamous sinussinus

�� occipital sinus occipital sinus

�� confluence of sinusesconfluence of sinuses

Venous sinuses

Venous sinuses Venous sinuses –– saggital viewsaggital view

Cavernous sinus Cavernous sinus (several structures are (several structures are

embedded in its lumen)embedded in its lumen)

Dural venous sinus are linked with external Dural venous sinus are linked with external

veins of the skull via emissary veinsveins of the skull via emissary veins

Dural venous sinus are linked with external Dural venous sinus are linked with external

veins of the skull via emissary veinsveins of the skull via emissary veins

External veinExternal vein Emissary veinEmissary vein Dural venous sinusDural venous sinus

Clinically important anastomosesClinically important anastomoses

Vascular supply of dura materVascular supply of dura mater

EEpidural pidural vsvs subdural hemorrhage subdural hemorrhage

Epidural Epidural →→ middle meningeal artery or veinmiddle meningeal artery or vein

Between periosteal & meningeal layers of duraBetween periosteal & meningeal layers of duraSubduralSubdural →→ superior cerebral veinssuperior cerebral veins

Between meningeal layer of duraBetween meningeal layer of dura & arachnoidea& arachnoidea

EEpidural pidural vsvs subdural hemorrhagesubdural hemorrhage

NNerve supply of dura matererve supply of dura mater

Anterior

cranial fossa

Posterior

cranial fossa

Middle

cranial fossa

ArachnoidArachnoid

•• Closely associated with Closely associated with brain and dura (no brain and dura (no subduralsubduralspace).space).•• Subarachnoid space where Subarachnoid space where CSF and blood vessels are CSF and blood vessels are locatedlocated•• Does not follow surface of Does not follow surface of brain into sulcibrain into sulci•• Forms arachnoid Forms arachnoid granulations on the dorsal granulations on the dorsal surfacesurface•• Small one way valves for Small one way valves for drainage of cerebral spinal drainage of cerebral spinal fluid into venous systemfluid into venous system

ArachnoidArachnoid

ArachnoidArachnoid

�� DDelicate, impermeable membrane elicate, impermeable membrane

�� SSeparated from the dura by a potential space, the eparated from the dura by a potential space, the subdural space, filled by a film of fluidsubdural space, filled by a film of fluid

�� SSeparated from the pia by the eparated from the pia by the subarachnoid spacesubarachnoid space, , which is filled with cerebrospinal fluid which is filled with cerebrospinal fluid

SSubarachnoid cisterns ubarachnoid cisterns

�� Pia follows surface of the brain, while arachnoidea Pia follows surface of the brain, while arachnoidea does not does not →→ spaces form of variable sizespaces form of variable size

cerebellomedullary cistern

(cisterna magna)

interpeduncular cistern

SSubarachnoid ubarachnoid

cisternscisterns

Arachnoid villi & granulationsArachnoid villi & granulations

�� AArachnoid villi rachnoid villi –– projections of projections of arachnoid into arachnoid into

the the duraldural sinuses sinuses →→ aaggregations of arachnoid ggregations of arachnoid

villi villi == arachnoid granulationsarachnoid granulations

�� MMost numerous along the superior sagittal sinus ost numerous along the superior sagittal sinus

�� SSites where the cerebrospinal fluid diffuses into ites where the cerebrospinal fluid diffuses into

the bloodstream the bloodstream

Arachnoid villi & granulationsArachnoid villi & granulations

Meningioma Meningioma –– tumor arising from arachnoidtumor arising from arachnoid

Pia Pia mmaterater

•• Closely adherent to Closely adherent to

surface of the brainsurface of the brain

•• Cannot be separated Cannot be separated

without destroying without destroying

cortical surfacecortical surface

•• Follows vessels as they Follows vessels as they

pierce the cortexpierce the cortex

•• Follows brain contour Follows brain contour

into into sulcisulci

•• FFormed from a layer of ormed from a layer of

leptomeningeal cells, leptomeningeal cells,

which is often only 1 to which is often only 1 to

2 cells thick 2 cells thick

The subarachnoid space is divided by trabeculaeThe subarachnoid space is divided by trabeculae

�� As an As an artery enters the cortex, a layer of pia accompanies the artery enters the cortex, a layer of pia accompanies the vessel into the brainvessel into the brain

�� Not in the case of veinsNot in the case of veins

Between pia and Between pia and

neural elements is a neural elements is a

thin layer of thin layer of

astrocyticastrocytic processes processes

Spinal meningesSpinal meninges

The periosteal layer of spinal dura is the

true periosteum of the vertebral canal and

is separated from the meningeal layer by a

loose connective tissue and fat-filled

epidural space

Comparison of the layers of meninges around

the brain and spinal cord

Vascular supply of the Vascular supply of the

brainbrain

BloodBlood--brain barrierbrain barrier

Blood flow & brainBlood flow & brain

�� AAbout 15 percent of cardiac output reaches the bout 15 percent of cardiac output reaches the

brain brain

�� AAbout 20 percent of oxygen utilization of the bout 20 percent of oxygen utilization of the

body is consumed by the adult brain and body is consumed by the adult brain and ((50 50

percent by thpercent by the e infant braininfant brain))

�� The blood flow through the human brain is The blood flow through the human brain is

estimated to be 800 ml/min, or approximately estimated to be 800 ml/min, or approximately

50 ml/100 g of brain tissue per minute 50 ml/100 g of brain tissue per minute

Brain is supplied by 4 arteriesBrain is supplied by 4 arteries

�� 2 internal carotid arteries 2 internal carotid arteries (ICA)(ICA)

�� 2 vertebral arteries2 vertebral arteries

�� Types of circulationTypes of circulation�� anterior anterior →→ ICAICA

�� posterior posterior →→ vertebral a.vertebral a.

Anterior

Posterior

External carotid artery

Vertebral artery

Internal carotid artery

Basilar artery

Vascular territories of main arteriesVascular territories of main arteries

Arteries of the brainArteries of the brain

�� Anterior circulationAnterior circulation

�� Internal carotid artery (ICA)Internal carotid artery (ICA)

�� Anterior cerebral artery (ACA)Anterior cerebral artery (ACA)

�� Middle cerebral artery (MCA)Middle cerebral artery (MCA)

�� Posterior circulationPosterior circulation

�� Vertebral arteryVertebral artery

�� Basilar arteryBasilar artery

�� Posterior cerebral artery (PCA)Posterior cerebral artery (PCA)

Course of internal carotid arteryCourse of internal carotid artery

Carotid

syphon

Cavernous segmentCavernous segmentACA

ICA bifurcation

MCA

Cavernous segment

CN III

CN IV

CN VI

V1

V2


Internal carotid arteryInternal carotid artery

�� CN III, IV, V1, V2, VICN III, IV, V1, V2, VI

�� CN VI only TRUE CN VI only TRUE intracavernousintracavernous

�� Important relationship: ICA, CN VIImportant relationship: ICA, CN VI

Cerebral aneurysms

�� 62 year old, Caucasian, female62 year old, Caucasian, female

�� Sudden onset:Sudden onset:

-- eye paineye pain

-- left diplopia, ptosis, dilated pupilleft diplopia, ptosis, dilated pupil

�� Symptoms due to locationSymptoms due to location

-- mass effect in cavernous sinusmass effect in cavernous sinus

Cavernous segment

CN III

CN IVCN VI

V1

V2


Internal carotid artery: cavernous aneurysms

Clinoid process

Supraclinoid

Infraclinoid

Parts of internal carotid arteryParts of internal carotid artery

�� Infraclinoid branchesInfraclinoid branches

-- meningohypoph.meningohypoph.

�� Supraclinoid branchesSupraclinoid branches

-- ophthalmicophthalmic

-- sup hypophysealsup hypophyseal

-- post communicat. arterypost communicat. artery

-- ant choroidal arteryant choroidal artery

Branches of ICABranches of ICA

Anterior cerebral artery (ACA)

Middle cerebral artery (MCA)

Middle cerebral artery (MCA)

�� Terminal branch ICATerminal branch ICA

�� Majority of ICA blood flowMajority of ICA blood flow

�� Courses within the Sylvian fissureCourses within the Sylvian fissure

Middle cerebral artery (MCA) – lateral view

Middle cerebral artery (MCA) - segments

�� MCA bifurcates 78%, trifurcates 12%, multiple 10%MCA bifurcates 78%, trifurcates 12%, multiple 10%

Sylvian Fissure

M1 (pre-bifurcation)

M1 (post-bifurcation)

M2 segments

M3 segments

M4 segments (cortical branches)

Genu

Top of circular

sulcus

A2HA

ICA

M4

M4

M1

M2

M3

MCAMCA

�� PerforatorsPerforators

-- basal gangliabasal ganglia

-- internal capsuleinternal capsule

-- corona corona radiataradiata

�� Cortical branches Cortical branches

-- motor cortexmotor cortex

-- sensory cortexsensory cortex

-- speechspeech

-- vision (temporal loop)vision (temporal loop)

Regions supplied by MCA & its branches

Cerebral arteries – medial view

Anterior cerebral

Posterior cerebral

Anterior & posterior cerebral arteriesAnterior & posterior cerebral arteries

�� Terminal branch of ICATerminal branch of ICA

�� Passes above optic nervePasses above optic nerve

�� Linked by communicating arteryLinked by communicating artery

�� Enters interhemispheric fissureEnters interhemispheric fissure

ICA ON

Frontal lobe

ACA

MCA

A1

A2

Anterior cerebral artery

�� Passes above corpus callosumPasses above corpus callosum

�� Courses along medial hemispheric Courses along medial hemispheric

surfacesurface

PC

CM

A2

CM

Frontal lobe

PC

A2

CC



-- optic chiasm, tractoptic chiasm, tract

-- hypothalamushypothalamus

-- ant limb internal capsule ant limb internal capsule

�� Branches Branches

-- corpus callosumcorpus callosum

-- gyrus rectusgyrus rectus

-- motor cortex (leg)motor cortex (leg)

-- sensory cortex (leg)sensory cortex (leg)


Regions supplied by ACA & its branches

Basilar A.

PICA

Ant. Spinal A

C1

C6

Vert A.

Subcl A.

Extraossous

V1

Foraminal

V2

Extraspinal

V3

Intradural

V4

V1

V2

V3

V4

Posterior circulation – vertebral arteries

P.Com. A.

PCA (P2) PCA (P1)

SCA

Basilar A.

AICA

PICA

Vertebral A.

SCA

PCA (P2)

Basilar A.

PICA

AICA

Vertebral A.

Posterior circulation

Posterior circulation – brainstem supply

�� PICA PICA –– medulla, inferior cerebellar peduncle, inferior cerebellar surfmedulla, inferior cerebellar peduncle, inferior cerebellar surfaceace

�� AICA AICA –– pons, middle cerebellar peduncle, lateral cerebellar surfacepons, middle cerebellar peduncle, lateral cerebellar surface

�� SCA SCA –– midbrain, sup. cerebellar peduncle, sup. cerebellar surface midbrain, sup. cerebellar peduncle, sup. cerebellar surface

Posterior circulation – cerebellar arteries

SCA

PCA

Tentorial notch

Basilar artery

Clivus

�� passes around cerebral pedunclepasses around cerebral peduncle

�� courses above tentoriumcourses above tentorium

�� travels on medial surface of:travels on medial surface of:

-- temporal lobetemporal lobe

-- occipital lobe occipital lobe

Posterior cerebral arteryPosterior cerebral artery

PCA

Calcarine a.

Splenial a.



-- mesencephalicmesencephalic

-- post. thalamoperforatorspost. thalamoperforators

-- thalmogeniculatethalmogeniculate

�� Distal branchesDistal branches

-- medial post choroidalmedial post choroidal

-- lateral post choroidal lateral post choroidal

-- post. temporal branchespost. temporal branches

-- calcarinecalcarine

-- splenialsplenial


Regions supplied by basilar artery & its branches

AArterial circulation of deep cerebral structures rterial circulation of deep cerebral structures

Hemorrhage in the right posterior thalamus Hemorrhage in the right posterior thalamus

and internal capsule in a 64and internal capsule in a 64--yearyear--old woman old woman

�� Medial striate artery (Heubner)Medial striate artery (Heubner)

from ACA supplies:from ACA supplies:

-- RostroventralRostroventral part of the head of part of the head of

caudate, putamen, internal caudate, putamen, internal

capsulecapsule

�� Lateral striate arteriesLateral striate arteries from MCA from MCA

supply:supply:

-- Remainder of caudate nucleus, Remainder of caudate nucleus,

putamenputamen

-- Lateral part of globus pallidusLateral part of globus pallidus

-- Anterior limb of internal capsuleAnterior limb of internal capsule

-- Dorsal portion of posterior limb Dorsal portion of posterior limb

internal capsuleinternal capsule

�� Thalamoperforators Thalamoperforators (Basilar and (Basilar and

PCA) supply:PCA) supply:

-- geniculate bodiesgeniculate bodies

-- thalamusthalamus

AArterial circulation of deep cerebral structures rterial circulation of deep cerebral structures

Arterial supply of the primary motor and Arterial supply of the primary motor and

sensory cortex sensory cortex

IInfarct caused by occlusion of the internal nfarct caused by occlusion of the internal

carotid artery carotid artery

IInfarct caused by nfarct caused by MCAMCA occlusion occlusion

Arteries at skull baseArteries at skull base

Arteries at skull base Arteries at skull base –– anastomotic sitesanastomotic sites

AnastomosesAnastomoses

�� Intracranial Intracranial –– circle of Willis (main) & otherscircle of Willis (main) & others

�� Extracranial to intracranialExtracranial to intracranial

Circle of WillisCircle of Willis

Circle of Willis Circle of Willis -- aneurysmsaneurysms

Aneurysms are local dilation or ballooning

of a vessel due to the weakening of its wall.

The most common location for an

aneurysm in the brain is the posterior

communicating artery as it originates from

the internal carotid artery.

Other intracranial anastomosesOther intracranial anastomoses

Extracranial to intracranial anastomosesExtracranial to intracranial anastomoses

Cerebral arteries differ from arteries Cerebral arteries differ from arteries

elsewhere in the body elsewhere in the body

�� Thinner wallsThinner walls

�� Absent external elastic laminaeAbsent external elastic laminae

�� Presence of astrocytic processesPresence of astrocytic processes

�� Presence of a perivascular reticular sheath Presence of a perivascular reticular sheath

consisting of arachnoid trabeculae (the latter consisting of arachnoid trabeculae (the latter

acquire an outer pial membrane when the vessel acquire an outer pial membrane when the vessel

penetrates the brain substance)penetrates the brain substance)

CCerebral venous system erebral venous system

�� Superficial vein system Superficial vein system

��Deep vein systemDeep vein system

Superficial vein system (lateral view)Superficial vein system (lateral view)

Superficial vein system (medial view)Superficial vein system (medial view)

deep system

Deep vein systemDeep vein system

Deep vein systemDeep vein system

Straight sinus

Great vein of Galen Great vein of Galen →→ straight sinusstraight sinus

CCerebral venous system erebral venous system

Venous drainage of brainstemVenous drainage of brainstem

Features of cerebral veinsFeatures of cerebral veins

�� TThinner walls hinner walls

�� DDevoid of valves and muscle fibersevoid of valves and muscle fibers

�� The absence of valves allows reversal of blood The absence of valves allows reversal of blood

flow when occlusion of the lumen occurs in flow when occlusion of the lumen occurs in

disease disease

Blood-brain barrier (BBB) → astrocytes

BBB vs non-BBB capillaries

Kandel, Schwartz, Jessell; Principles of Neural Science, 4th ed.

Molecular composition of endothelial tight junctions

Abbott NJ, et al. Nat Rev Neurosci. 2006;7:41-53.

Pathways across BBB

Abbott NJ, et al. Nat Rev Neurosci. 2006;7:41-53

Abbott NJ, et al. Nat Rev Neurosci. 2006;7:41-53.

Agents modifying brain endothelial function

and BBB tightness

� Agents that impair BBB function� Bradykinin, histamine, serotonin, glutamate� Purine nucleotides: ATP, ADP, AMP� Adenosine, platelet-activating factor� Phospholipase A2, arachidonic acid, prostaglandins, leukotrienes� Interleukins: IL-1α, IL-1β, IL-6� Tumor necrosis factor-α (TNFα), macrophage-inhibitory proteins� Complement-derived polypeptide C3a� Free radicals, nitric oxide

� Agents that cause BBB tightening and improved function� Steroids� elevated intracellular cyclic AMP � Adrenomedullin� noradrenergic agents

Circumventricular organs Circumventricular organs –– no BBBno BBB

At each of these structures, either neurosecretory products are secreted

into the blood or local neurons detect blood-borne compounds as part of a

mechanism for regulating the body's internal environment.

Cerebrospinal fluidCerebrospinal fluid

BloodBlood--CSF barrierCSF barrier

Cerebral ventricular systemCerebral ventricular system

The brain contains 4 ependyma-lined cavities known as cerebral ventricles

The Ventricular System

Four Parts:

•Lateral

Ventricle (2)

•Third Ventricle

•Fourth

Ventricle

Ventricular systemVentricular system

Atrium of the

Lateral Ventricle

Occipital

(Posterior) Horn

of the Lateral

Ventricle

Fourth Ventricle

Temporal

(Inferior) Horn

of the Lateral

Ventricle

Third

Ventricle

Frontal

(Anterior) Horn

of the Lateral

Ventricle

Body of the

Lateral Ventricle

Foramen

of Monro

Cerebral

Aqueduct

Body of lateral ventricleBody of lateral ventricle

IInferior horn of the lateral ventricle nferior horn of the lateral ventricle

Four Parts:

•Lateral

Ventricle (2)

•Third

Ventricle

•Fourth

Ventricle


Tela choroidea

A.horn

P.horn

CChoroid plexushoroid plexus

�� LocationLocation

�� body, atrium, body, atrium,

inferior horn of inferior horn of

lateral ventriclelateral ventricle

�� foramen of Monroforamen of Monro

�� roof of roof of 33rdrd ventricleventricle

�� posterior part of the posterior part of the

roof of roof of 44thth ventricle ventricle

�� VVascular pial foldascular pial foldss causing invagination of the causing invagination of the ependymal ependymal

lininglining

The absence of choroid plexus from the anterior horn makes it

an appropriate site for placement of shunt tubes for drainage

of CSF in hydrocephalus.

Choroid plexus → forms villi

Note the cuboidalNote the cuboidal cells of the choroid epithelium and cells of the choroid epithelium and

associated capillary networkassociated capillary network (fenestrated capillaries)(fenestrated capillaries)

Ependymal layer

CSF formCSF formationation

�� Ventricles Ventricles –– 60%60%

�� choroid plexus choroid plexus –– 30 % (30 % (500 ml/day500 ml/day))

�� ependyma ependyma –– 30% (much slower rate)30% (much slower rate)

�� EExtraventricular sites of production (cerebral xtraventricular sites of production (cerebral

pial surface, cerebral extracellular space, pial surface, cerebral extracellular space,

perineural spaceperineural space))

Mechanisms of CSF formationMechanisms of CSF formation

(CSF)

CSF composition CSF composition vsvs blood serumblood serum


Flow Patterns

Foramen of Monro

Cerebral

Aqueduct

3 CSF exit sites

(CSF circulates

around the brain

and spinal cord)

Exits:

Magendie

Luschka

lateral ventricle

↓

foramen of Monro

↓

3rd ventricle

↓

cerebral aqueduct

↓

4th ventricle

↓

foramen of Luschcka and

Magendie

↓

cerebellomedulary cistern

(cisterna magna)

↓

superior sagittal sinus

Circulation of Circulation of

CSFCSF

Neural and vascular elements

involved in the formation of the blood-

brain and blood-CSF barriers

Relationships between intracranial fluid compartments Relationships between intracranial fluid compartments

and the bloodand the blood--brain and bloodbrain and blood--CSF barriers CSF barriers

CSF functions CSF functions

�� SSupports the weight of the brain within the skull. This upports the weight of the brain within the skull. This buoyancy function is disturbed when CSF is withdrawn, buoyancy function is disturbed when CSF is withdrawn, resulting in headache because of more traction on resulting in headache because of more traction on vessels and nerves.vessels and nerves.

�� AActs as a buffer or cushion between the brain and cts as a buffer or cushion between the brain and adjacent dura and skull; it protects the brain from adjacent dura and skull; it protects the brain from physical trauma during injury to the skull by dampening physical trauma during injury to the skull by dampening the effects of trauma.the effects of trauma.

�� PProvides a stable chemical environment for the central rovides a stable chemical environment for the central nervous system. The chemical composition of CSF is nervous system. The chemical composition of CSF is rather stable even in the presence of major changes in rather stable even in the presence of major changes in the chemical composition of plasmathe chemical composition of plasma

HHydrocephalus ydrocephalus

�� Blocking the circulatory pathway of CSF Blocking the circulatory pathway of CSF →→dilatation of the ventricles upstreamdilatation of the ventricles upstream

�� PProduction of fluid usually continues despite the roduction of fluid usually continues despite the obstructionobstruction

�� TTypes of hydrocephalusypes of hydrocephalus

�� noncommunicating noncommunicating →→ dilatation of the ventricles dilatation of the ventricles upstreamupstream

�� communicating communicating →→ dilatation of dilatation of allall ventricleventricles and s and spinal central canalspinal central canal

Noncommunicating

hydrocephalus Communicating

hydrocephalus

HydrocephalusHydrocephalus

Meninges vascularization CSF · Meninges Duramater (==pachymeninx )-tough, fibrous structure...

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