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Cerebrovascular Supply , CSF , Ventricles and Meninges Yatharth Verma Intercalating Medical Student University of ManchesterContents Dura Meninges: Arachnoid CSF Production Pia CSF Flow and Ventricles Anterior Circulation Posterior Circulation Circle of Willis Venous SinusesMeninges • Brain and spinal cord entirely enveloped by 3 concentric membranes; the dura mater, arachnoid mater and the pia mater • Provide support and protectionDura Mater • Consists of 2 layers of mambranes which are thick, dense and fibrous; the outer endosteal layer and the inner meningeal layer • Layers are united except where they separate to enclose the venous sinuses • Adherent to the bone via fibrous bands; especially firm at sites of cranial sutures, skull base and the foramen magnum: • Extradural space is a potential space, not an ‘actual’ space!!!Dural Partitions • Meningeal layer reflected inward to form 4 septa: 1. Falx Cerebri 2. Tentorium Cerebelli 3. Falx Cerebelli 4. Diaphragma Sellae • Divide cranial cavity partially into compartmentsVascular Supply of the Dura • Anterior cranial fossa – anterior meningial branches of the anterior and posterior ethmoidal and internal carotids (ICAs) and a branch of the middle meningeal artery • Middle cranial fossa– middle and accesory meningeal artery, branches from the ICAs, ascending pharyngeal and a recurrent branch of the lacrimal artery • Posterior cranial fos– meningeal branches from the occipital artery, vertebral artery and also from the ascending pharyngeal arteryInnervation of the Dura • V1: • Anterior Cranial Fossa • Falx Cerebri • Tentorium Cerebelli • V and V : 2 3 • Middle Cranial Fossa • X and C1-3: • Posterior Cranial FossaArachnoid Mater • Middle Meningeal Layer • Looks like spider webs, hence arachnoid • Seperated from the Dura by Subdural space • Subarachnoid space; this space contains the CSF which bathes the CNS structures and blood vessels • but does not enter sulci or fissuresSubarachnoid Cisterns • Subarachnoid spaces in certain parts of the cranium can be large and these spaces are termed cisterns • There are many but the main ones are: • Cisterna magna/Cerebellomedullary cistern (foramen of Magendie) • Pontine Cistern • Interpeduncular CisternArachnoid Villi and Granulations • Extensions of the arachnoid mater and subarachnoid space through the wall of the dural venoud sinuses • Major pathway involved in CSF reabsorption into the blood • Most prominent in the great longitudinal fissure where they project into the SSSPia Mater • Delicate membrane that closely invests the surface of the brain, follows the contours of the brain into the concavities and depths of the sulci and fissures • Acts as a form of regulatory interface between the subarachnoid space and the brainSensation to the dura in the anterior cranial fossa is received by which nerve? • Anterior dural nerve • Opthalmic nerve • Sciatic nerve • Maxillary nerve • Sensory branches from C1-3What is the largest cistern found in the subarachnoid space? • Interpeduncular cistern • Pontine cistern • Cerebellomedullary cistern • Quadrigeminal cistern • Cistern of the lamina terminalisRupture of the middle meningeal artery leads to what type of intracranial hemorrhage? • Subarachnoid hemorrhage • Subdural hemorrhage • Intracerebral hemorrhage • Intraventricular hemorrhage • Extradural hemorrhageCSF Production • Secreted by choroid plexuses • Choroid plexuses located in the medial wall of the lateral ventricles and the roof of the 3rd and 4th ventricles • CSF in a colourless liquid in normal individuals • Total volume is approximately 150 ml of which 125 ml is intracranial • Functions to protect the brain, removes waste products and provides comfortable environment for neurons to workLateral Ventricles • Roughly C-shaped with an occipital tail • Divided into a body, anterior (frontal) horn, posterior (occipital) horn and inferior (temporal) horn • Seperated by septum pellucidum • CSF flows from the lateral ventricles into the 3rd ventricle via the interventricular foramen (foramen of Monro)3rd Ventricle • Midline, slit-like cavity • Lies between the right and left halves of the thalamus and hypothalamus • Lateral walls are joined by the interthalamic adhesion (mass intermedia) • Communicates with the 4th ventricle through the Cerebral Aquaduct (Aquaduct of Sylvius)4th Ventricle • A wide, tent-shaped cavity lying between the brainstem and the cerebellum • At the pontomedullary junction, bilateral recesses extend to the lateral border of the brainstem at which point these open (foramen of Luschka) drain into the subarachnoid space at the cerebellopontine angle • At the roof of the ventricle, a large median aperture (foramen of Magendie) drains CSF into the cerebellomedullary cistern • Caudally, the 4th ventricle communicates with the central canal of the spinal cordHow many ventricles are present in the brain? • 2 • 5 • 3 • 4 • 1Which of these is not a part of the lateral ventricles? • Foramen of Magendie • Frontal Horn • Occipital Horn • Temporal Horn • BodyWhere does the foramen of Magendie drain CSF into? • Pontine cistern • Central Canal of the Spinal Cord • Cisterna Magna • Interpeduncular cistern • Quadrigeminal cisternCerebrovascular Supply The brain is a highly vascular organ It is a location with high metabolic activity and demands 15% of the total cardiac output and 25% of the total 2 consumed by the body The brain does not tolerate hypoxia (anoxia for only 3-6 minutes approximately) Brain supplied by 2 internal carotid and vertebral arteries that form a complex anatomotic network at the base of the brainAnterior Circulation • Provided by the Internal Carotid Arteries (ICAs) bilaterally • Travels up the neck and enters the skull through the carotid canal and enters the cranial cavity through foramen Lacerum • Supplies the forebrain except for th occipital lobe • Gives off multiple branches but the main ones include: • Opthalmic artery • Anterior choroidal artery • Posterior communicating artery • Middle cerebral artery • Anterior cerebral arteryPosterior Circulation • Provided by the Vertebral arteries • Ascend through the transverse foramen of C6- C1 and enter the cranial cavity through the foramen Magnum • Supplies the upper spinal cord, brainstem, cerebellum and the occipital lobe • Main branches include: • Anterior spinal artery • Posterior inferior cerebellar arteries (PICA) • Posterior spinal arteries (usually branch of PICAs)Circle of Willis • Aka circulus arteriosus • Anastomosis that unites the internal carotid and the vertebrobasilar systems at the base of the brain • Lies in the interpeduncular cistern and surrounds the optic chiasmVascular T erritoriesVenous Drainage of the Brain • Occurs via venous sinuses which drain deep and superficial veins • There are many but the main ones include: • Superior Sagittal Sinus • Inferior Sagittal Sinus • Straight Sinus • Transverse Sinus • Sigmoid Sinus • Occipital Sinus • Cavernous SinusCavernous Sinus • Lies on both sides of the body of the sphenoid bone • Extends from the superior orbital fissure to the apex of the petrous temporal bone (avg length 2cm and width 1cm) • The two cavernous sinuses are connecter anteriorly and posteriorly by 2 intercavernous sinuses and the basilar plexus • Many important structures pass through it: • ICA and associated sympathetic plexus • CN III, CN IV and CN VI • V and V divisions of CN V 1 2Which of the following is a branch of the ICA? • Basilar artery • Anterior spinal artery • Superficial temporal artery • Opthalmic artery • Posterior cerebral arteryThrough which foramen does the vertebral artery enter the cranial cavity? • Foramen magnum • Foramen of Luschka • Foramen ovale • Foramen lacerum • Foramen of MonroWhat structure does the circulus arteriosus encircle? • Midbrain • Cerebellum • Pineal gland • Thalamus • Optic chiasmWhich nerve lies just lateral to the ICA in the cavernous sinus? • Opthalmic nerve • Abducens nerve • Maxillary nerve • Occulomotor nerve • Trochlear nerveThank you for your attention! Email: yatharth.verma@postgrad.manchester .ac.uk