Brain CT Anatomy and Basic Interpretation Part II
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Transcript of Brain CT Anatomy and Basic Interpretation Part II
DR SAKHER AL-KHADERI CONSULTANT RADIOLOGIST
AMC
BRAIN CT ANATOMY AND BASIC INTERPRETATION PART II
VENTRICLES
OBJECTIVES
Illustrate and describe the ventricles.
Describe the structure of the ventricles.
Illustrate and describe the cerebrospinal fluid (CSF) formation, absorption and circulation.
VENTRICLES(Ventricular System) A ventricle is an
internal cavity of the brain. Within the brain, which is filled with cerebrospinal fluid(CSF).
The ventricular system is composed of two lateral ventricles and two midline ventricles( third and fourth ventricles).
VENTRICLES(Ventricular System) The chambers are
connected to allow the flow of cerebrospinal fluid via two interventricular foramen (referred to as the foramen of Monro) and the cerebral aqueduct (referred to as the aqueduct of Sylvius).
Lateral view to show the ventricular system of the CNS
Central canal of medulla oblongata & spinal cord
Fourth ventricle
Lateral ventricle
Third ventricle
Interventricular foramen (Monro)
Cerebral aqueduct
VENTRICLES(Ventricular System)
CONSISTS OF :1) Lateral ventricle2) Third ventricle3) Fourth ventricle 4) Central canal of
the medulla oblongata & spinal cord
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Lateral Ventricles
The lateral ventricles are two curved shaped cavities located within the cerebrum.
The lateral ventricles are separated by the septum pellucidum and do not communicate directly
Lateral ventricle
Frontal lobe
Parietal lobe
Temporal lobe
Occipital lobe
C-shaped cavity & may be divided into :
2. Anterior horn
1. Body
3. Posterior horn
4. Inferior horn
Third ventricle
Fourth ventricle
Lateral view of the ventricular cavities of the brain
Lateral ventricle
Anterior horn
Inferior horn
Posterior horn
Lateral view to show the ventricular system of the CNS
The third ventricle is a narrow cavity or a slitlike cleft between the 2 thalamus Communicates ;
• Anteriorly with lateral ventricles through interventricular foramina (of monro)
• Posteriorly with fourth ventricle through cerebral aqueduct (of sylvius)
Posterior view to show the ventricular system of the CNS
Third ventricle
Frontal lobe
Parietal lobe
Temporal lobe
Occipital lobe
Third ventricle
Third ventricle
Hypothalamus
Coronal section of the brain (posterior view)
Third ventricle
Thalamus
ROOF
FLOOR
Lateral wall
Body of fornix
Fourth ventricle The fourth ventricle Is
a rhomboid or diamond shaped cavity.
It is a wide and flattened space located just anterior to the cerebellum and posterior to the upper, or superior, half of the medulla oblongata and the pons.
Cerebellum
Pons
Medulla oblongata (superior half)
Sagittal section of the 4th ventricle
Cerebral aqueduct
Central canal (spinal cord)
Fourth ventricle
Fourth ventricle
ANTERIORPOSTERIOR
Frontal lobe
Parietal lobe
Temporal lobe
Occipital lobe
Fourth ventricle
Pons
Medulla oblongata (superior half)
Fig. : Sagittal section of the 4th ventricle
Cerebral aqueduct
ANTERIOR
POSTERIOR
Superior part of the roof ;Superior medullary
velum
Inferior part of the roof ;
Inferior medullary velum
Roof or posterior wall of fourth ventricle :
CENTRAL CANAL
Opens superiorly into the fourth ventricle
Fourth ventricle
Inferior ½ of medulla oblongata
Entire length of spinal cord
Central canal(Lined with
ependyma but no choroid plexus in the central canal)
Extends ;
Frontal lobe
Parietal lobe
Temporal lobe
Occipital lobe
CENTRAL CANAL
Conus medullaris-Terminal ventricle
CEREBROSPINAL FLUID
CHOROID PLEXUS
It is formed by invaginating of vascular pia mater into the ventricular cavity
It becomes highly convoluted & produce a spongy-like appearance
It enters the 3rd and 4th ventricles through their roofs, and the lateral ventricles through the choroid fissure
produces cerebrospinal fluid (CSF)
Lateral ventricle
Third ventricle
Fourthventricle
What is cerebrospinal fluid (CSF) ?• Clear, colorless fluid• Produced by the choroid plexus • Found in the :
Ventricles of the brain Subarachnoid space (between Arachnoid + Pia mater) around the
brain & spinal cord
The pressure of the CSF is kept remarkably constant.
Based on the Monro-Kellie doctrine : “Volume of BLOOD, CSF & BRAIN at any time
must be relatively constant”
Physical characteristics and composition of the CSF
Appearance Clear and colourlessVolume 130 mlRate of production 0.5 ml/minPressure 60-150 mm of waterComposition protein 15-45 mg/100 ml glucose 50-85 mg/ 100 ml chloride 720-750 mg/100 mlNo. of cells 0-3 lymphocytes/cu mm
Function of the CSF :
1. Cushions & protects the CNS from trauma2. Provides mechanical buoyancy & support for
the brain3. Serves as a reservoir & assists in the
regulation of the contents of the skull4. Nourishes the CNS5. Removes metabolites from the CNS6. Serves as a pathway for pineal secretions to
reach the pituitary gland
Sites of formation :1. Choroid plexus of the ventricle cavities,
mostly is formed in the LATERAL VENTRICLES 2. Some originate from the ependymal cells
lining the ventricles3. Some from the brain substances through
perivascular spaces
Movement of CSF inside the ventricle is controlled by the:1. Pulsation of the artery in the choroid plexus2. By the aid of the cilia & microvilli of the
ependymal cells
cerebrospinal fluid (CSF) The CSF is formed in the
lateral ventricles escapes by the foramen of monro into the third ventricle
From the third ventricle by the aqueduct into the fourth ventricle.
Then from the fourth ventricle the fluid is poured into the subarachnoid spaces through the medial foramen of majendie and the two lateral foramina of luschka.
There is no evidence that functional communications between the cerebral ventricles and the subarachnoid spaces exist in any region except from the fourth ventricle.
Choroid plexus of the lateral ventricle
Site of formation
1. Lateral ventricle
2. Third ventricle
Interventricular foramina
3. Fourth ventricle
Cerebral aqueduct
3.2 Lateral foramina (Luschka)3.1 Median
foramen (Magendie)
3.2 Lateral foramina (Luschka)
4. Subarachnoid space
Inferiorly
Superiorly
Absorbed
Superiorly
Absorbed
Median sagittal section to show the subarachnoid cisterns & circulation of CSF
Superior cistern
Interpeduncular cistern
Cerebellomedullary cistern
Chiasmatic cistern
Pontine cistern
Circulation of CSF in subarachnoid space :
Median foramen of 4th ventricle
Factors that facilitate the flow of CSF in subarachnoid space ;
1. Pulsation of the cerebral & spinal arteries2. Movements of the vertebral column3. Respiration & coughing4. Changing of the positions
Absorption of CSF into dural venous sinuses Main sites - arachnoid villi
(project into dural venous sinuses, especially, superior sagittal sinus)
Arachnoid villi are covered by endothelium of the venous sinus
Arachnoid villi tend to be grouped together & form elevations known as arachnoid granulations
CSF pressure >> the pressure in the sinus
The rate of absorption of CSF through the arachnoid villi controls the CSF pressure
BLOOD SUPPLY OF THE BRAIN
OBJECTIVES
Illustrate and describe the formation of the circle of willis
Describe the blood supply of the brain
Arterial supply Venous drainage
Blood Supply of The Brain The brain receives
it arterial supply from two pairs of vessels, the vertebral and internal carotid arteries which are interconnected in the cranial cavity to produce an arterial circle (of Willis).
Internal carotid artery
Internal Carotid Artery Begins – bifurcation of Com Carotid A Perforates base of skull – carotid canal Enters middle cranial fossa beside dorsum sellae In the cavernous sinus
Horizontal Emerge out – medial side of Ant clinoid process –
perforates dura & arachnoid mater – enters subarachnoid space
Turns posteriorly – below optic nerve Turns upward – lateral to optic chiasma Now is under anterior perforated susbtance Divides – into ANTERIOR & MIDDLE cerebral
arteries
Vertebral Artery Branch of first part of subclavian A Passes – foramen transvesarium C6 –
C1 Enters through foramen magnum –
perforates dura & arachnoid mater – enters subarachnoid space
Turns upward, forward, medially – medulla oblongata
Lower border of pons – joins opposite side BASILAR artery
Blood Supply of The Brain
VERTEBRAL Basilar Posterior cerebral
artery
INTERNAL CAROTID Middle cerebral Anterior cerebral Anterior
communicating artery
Posterior communicating artery
CIRCLE OF WILLIS
Branches of :-
VERTEBRAL Basilar PCA Pontine Labyrinthine Ant Inf CA Sup cerebellar Choroidal
INTERNAL CAROTID ACA MCA Ophthalmic Ant ComA Post Com A Choroidal
Circle of Willis
Interpeduncular fossa – base of brain
Anastomosis 2 internal carotid
arteries 2 vertebral arteries
In the subarachnoid space
Vertebral arteries
Basilar APosterior cerebral artery
Posterior communicating artery
Internal carotidartery
Middle cerebral artery
Anterior cerebral artery
Anterior communicating artery
Post Inf cerebellar A
Sup cerebellar A
Ant Inf cerebellar A
Middle cerebral artery
Anterior cerebral artery
Posterior cerebral artery
MIDDLE CEREBRAL ARTERYLOBE AREA
FRONTAL Motor – except for paracentral lobuleMotor speech – esp left side
PARIETAL Sensory – except for paracentral lobuleSensory speech
TEMPORAL Auditory
POSTERIOR CEREBRAL ARTERYLOBE AREA
OCCIPITAL Visual
TEMPORAL Olfactory
ARTERIES to specific brain areas
Corpus striatum Middle & lateral striate
Anterior & Middle cerebral arteryInternal capsule
Thalamus PComA, basilar, PCAMidbrain PCA, supCerebellarA, basilarPons Basilar, Ant, inf, supCerebellarA,Medulla oblongata
Vertebral, ASA,PSA,PICA, basilar
Cerebellum supCerebellar, AICA,PICA
VEIN of specific areasMidbrain Basal, great cerebral
Pons Basal, cerebellar
Medulla oblongata Anterior & posterior spinal
Cerebellum Great cerebral
Superior sagittal sinus
Inferior sagittal sinus
Straight sinus
Superior cerebral vein
Medial aspect of hemisphere
Great cerebral vein
Transverse sinus (R & L)
Sigmoid sinus (R & L)
Confluence of sinus
IntJugular vein
IntJugular vein
Cavernous sinus
Middle cerebral vein
Inferior petrosal sinus
Superior petrosal sinus
The subarachnoid cisterns are areas within the subarachnoid space where the pia mater and arachnoid membrane are not in close approximation. The subarachnoid tissue is not as abundant here as in the normal subarachnoid space and cerebrospinal fluid (CSF) gathers to form pools or cisterns (Latin: "box").Some major subarachnoid cisterns:cisterna magna (cerebellomedullary cistern): the largest of the subarachnoid cisternspontine cisternsuprasellar cisterninterpeduncular cisternquadrigeminal cistern (superior cistern or cistern of the great cerebral vein)ambient cistern
Sulcus : A sulcus is depression or fissure in the surface of the brain. ( valleys )
Gyrus : A gyrus is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci ( hills )
Typical continous fissure
Interhemispheric fissureSylvian fissure ( lateral sulcus )Parieto-occipital fissure Collateral sulcusCentral sulcusCalcarine Sulcus
Interhemispheric fissureDeep sulcus
upto corpus collosum
Divides brain into two hemisphere
Sylvian fissure
deep, mostly horizontal
insula is buried within it
separates temporal lobe from parietal and frontal lobes
Parieto - occipital fissure
very deepoften Y-shaped
from sagittal view
X-shaped in horizontal and coronal views
Collateral sulcus
Divides lingual and parahippocampal gyri from fusiform gyrus.
Central sulcus
usually freestanding (no intersections)
Seperates frontal and parietal lobe.
Calcarine sulcus
Lobes of brain
Frontal lobe.Parietal lobe.Temporal lobe.Occipital lobe.
Limbic lobe.Insular lobe.
• Frontal lobe:Anterior region of hemisphere; anterior to central sulcus, superior to sylvian fissure• Parietal lobe: Posterior region of hemisphere; posterior to central sulcus, anterior to parietooccipital sulcus• Occipital lobe: Posterior to parietooccipital sulcus• Temporal lobe: Inferior to sylvian fissure, anterior to angular gyrus
Lateral surface of brain
Medial surface of brain
Basal surface of brain
THE END