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Brain Meninges, Ventricles and CSF

Brain Meninges, Ventricles and CSF. Lecture Objectives. Describe the arrangement of the meninges and their relationship to brain and spinal cord. Explain the occurrence of epidural, subdural and subarachnoid spaces.

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Brain Meninges, Ventricles and CSF

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  1. Brain Meninges,Ventricles andCSF

  2. LectureObjectives • Describethearrangementofthemeningesandtheirrelationshipto brain and spinalcord. • Explaintheoccurrenceofepidural,subduralandsubarachnoid spaces. • Locate theprincipal subarachnoid cisterns, and arachnoid granulations. • Describetheventriclesofbrainandimportanceoftheirchoroids plexus. • Summarize the pathway of cerebrospinal fluid(CSF) circulation. • Locatethesafesitesforthelumbarpuncture. • Identify brain ventricles in CT scan, MRI andventriculograms.

  3. CerebralMeninges • Duramater • Endosteallayer • Meningeallayer • Arachnoidmater • Piamater

  4. DuraMater • Endosteal layer =periosteum • Venoussinuses • Meningeallayer • Continuous with spinaldura mater • Falxcerebri • Shape, Attachments &Sinuses • Tentoriumcerebelli • Shape, Attachments &Sinuses • Tentorialnotch • Falxcerebelli • Shape, Attachments &Sinuses • Diaphragmasellae • Shape, Attachments &Sinuses

  5. DuraMater • Nervesupply • Cranial nerves V &X • Referralpaintotheheadfromabove the tentoriumcerebelli • Spinal nervesC1-C3 • Referralpaintothebackofthehead and neck frombellow tentorium • Sympathetic • Bloodsupply • Internal carotid, maxillary,ascending pharyngeal, occipital & vertebralaa • Middle meningeala.

  6. Dural VenousSinuses • Location • Drains….. • Fate • Superior sagittalsinus • Venouslacunae • Inferior sagittalsinus • Straightsinus • Occipitalsinus • Transversesinus • Sigmoidsinus • Cavernoussinuses • Superior and inferior petrosalsinuses

  7. Dural VenousSinuses

  8. ArachnoidMater • Subduralspace • Subarachnoidspace • Cerebral BV & cranialnn. • CSF • Subarachnoidcisternae • Arachnoidvilli • Arachnoidgranulations • Fuse with epineuriumat foramina • Except for optic nerve - fusewith sclera

  9. PiaMater • Adheres closely to thebrain • Goes deep into thesulci • Fuse with nervesepineurium • Covers cerebral arteries entering brainsubstance • Specialized over theroofs of ventricles (tela choroidea) • Contributetoformationofchoroidplexuses

  10. VentricularSystem • Lateralventricles • Interventricularforamina • Thirdventricle • Cerebralaqueduct • Fourthventricle • Centralcanal • Terminalventricle

  11. LateralVentricles • Location • Shape • Parts • Body • Horns • Anterior, posterior,inferior • Choroidplexus

  12. LateralVentricles • Relations • Corpuscallosum • Septumpellucidum • Fornix • Thalamus • Caudatenucleus

  13. ThirdVentricles • Shape • Interventricular foramen(foramina ofMonro) • Cerebral aqueduct (aqueductof Sylvius) • Walls • Anteriorwall • Posteriorwall • Lateralwall • Roof • Floor • Choroidplexus

  14. FourthVentricle • Shape • Relations • Walls • Lateralwalls • Roof (posteriorwall) • Superior and inferior medullaryvelum • Median aperture (foramenof Magendie) • Lateral apertures(foramina of Luschka) • Choroidplexus • Floor (rhomboidfossa)

  15. SubarachnoidCisterns • Extended area ofthe subarachnoidspace • Subarachnoidcisterns • Cerebellomedullarycistern (cisternamagnum) • Medianaperture • Pontinecistern • Lateralapertures • Interpeduncularcistern

  16. SubarachnoidCisterns

  17. Cerebrospinal Fluid(CSF) • 80-150 ml(3-5oz) • Clear liquid containing glucose, proteins, &ions • Functions • mechanicalprotection • floats brain & softens impact with bonywalls • chemicalprotection • optimal ionic concentrations for actionpotentials • circulation • nutrientsandwasteproductstoandfrombloodstream

  18. Origin ofCSF • Choroid plexus =capillariescovered by ependymalcells • 2lateralventricles,onewithineachcerebralhemisphere • Roof of 3rdventricle • Roof of fourthventricle

  19. Drainage of CSF fromVentricles • One median aperture & two lateral apertures allowCSF to exitfromtheinteriorofthebrain

  20. Flow of Cerebrospinal Fluid

  21. Reabsorption ofCSF • Reabsorbed through arachnoidvilli • grapelikeclustersofarachnoidpenetrateduralvenoussinus • 0.5ml/minreabsorptionrate=sameasproductionrate

  22. Reabsorption ofCSF • Whenpressurein CSF > venous Reabsorptionoccur • When pressure in venous >CSF arachnoid villi work asvalve

  23. Hydrocephalus • Blockage of drainage of CSF (tumor,inflammation, developmental malformation, meningitis, hemorrhage orinjury) • Continuedproductioncauseanincreasein pressure ---hydrocephalus • In newborn or fetus, the fontanels allow this internalpressuretocauseexpansionofthe skull anddamagetothebraintissue • Neurosurgeon implants a drain shunting theCSF to theveinsoftheneckortheabdomen

  24. LeptomeningealDisease • Cancer metastasis throughCSF • Originatefrom • Primary CNStumors • Secondary distant tumors throughblood • Symptomsmayincludeheadache,spineorradicularlimbpainor sensory abnormalities, nausea andvomiting

  25. SubarachnoidHemorrhage • Nontraumatic(spontaneous) • Blood inCSF • Mainly fromaneurisms • Arise at arterial branchpoints • 85% anteriorcirculation • 15% posteriorcirculation • 30% anterior comm., 25% posterior comm.,20% MCA • Themainsymptomisasevereheadachethatstartssuddenly(oftencalled thunderclapheadache) • Traumatic • Morecommon • Duetocontusionsandothertraumaticinjuries • Severeheadache

  26. Extensions of the SubarachnoidSpace

  27. Blood BrainBarrier • protects cells from sometoxins andpathogens • proteins & antibiotics can notpass but alcohol & anestheticsdo • Structure • tight junctions sealtogether epithelialcells • continuous basementmembrane • astrocyte processescovering capillaries

  28. Blood BrainBarrier • Areas withoutBBB • Area postrema in thefloor of the fourthventricle • Areas in thehypothalamus • Structure • Endothelialfenestrations

  29. Blood Cerebrospinal FluidBarrier • Structure • Endothelialcells • BM of endothelialcells • Palecells • BM of choroidal epithelialcells • Tight junctions seal thechoroidal epithelialcells

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