Meninges Meninges Coverings of the brain and spinal cord Coverings of the brain and spinal cord
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 artery
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
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) – 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
Anterior cerebral artery
�� PerforatorsPerforators
-- 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)
Anterior cerebral artery
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.
Posterior cerebral arteryPosterior cerebral artery
�� PerforatorsPerforators
-- 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
Posterior cerebral arteryPosterior cerebral artery
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
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
The Ventricular System
The Ventricular System
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
The Ventricular System
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