1、Intracranial Pressure PhysiologyMonro-Kellie Doctrine(1783/1824)1.Rigid container2.Liquid contents are incompressible3.Mass must be displacedIntracranial Pressure PhysiologyCranial ContentsTotal Volume 1300-1500 ccBrain 80%gray matter/white matterCSF 10%Intraventricular 50%75 ccSubarachnoid 50%75 cc
2、Blood 10%Arterial 30%45ccVenous 70%105ccIntracranial Pressure PathophysiologyBlood epidural,subdural,subarachnoid,intracerebral,intraventricular,intravascularTumorAbscess/InfectionForeign ObjectsAir pneumocephalusCranial RestrictionPagets disease,craniosynostosisHydrocephalus,Cysts,HygromaEdema Inte
3、rstitial e.g.CNS lymph system,brain as a sponge Cytotoxic dead/dying cells Vasogenic altered BBB,capillary breakdown,abscessIntracranial Pressure PathophysiologyMass DisplacementCSF Blood BrainICP/CPP 150125100755025002550Cerebral Perfusion Pressure(mm Hg)Cerebral Blood Flow(ml/100 g/min)Zone of Nor
4、mal AutoregulationMaximumConstrictionMaximumDilatationPassiveCollapse02550ICP(mm Hg)Vasodilatory Cascade ZoneAutoregulation Breakthrough ZoneStephan A.Mayer,MDIntracranial Pressure PhysiologyIntracranial Pressure PathophysiologyHerniation TypesStructureBarrierVesselSubfalcine cingulate g.falxACAUnca
5、l uncustentoriumPCATonsillarcerebellum foramen m.vert/bUpwardcerebellum tentoriumTranscalvarialcortexskullsurfaceAutoregulation Breakthrough ZoneViscosity improves micro-circulationI USED TO HAVE AN OPEN MINDTotal Volume 1300-1500 ccDoes it work?ICP(mm Hg)Viscosity improves micro-circulationHemicran
6、iectomy TrialsDecrease unnecessarily elevated blood pressure and intravascular volumeBradycardiaInterstitial e.Hypertension/Increased Pulse PressureCushings TriadDiuretic decreases intravascular volumeElevated ICP Clinical SymptomsICP(mm Hg)Intubation/HyperventilationDESTINY-GermanyHemicraniectomy T
7、rialsIntracranial Pressure PathophysiologyHerniation Types1.Subfalcine2.Uncal3.tonsillarIntracranial Pressure PathophysiologyElevated ICP Clinical SymptomsHeadache-Aggravated by bending and stooping.Caused by distortion or irritation of pain sensitive areas in the dural coverings and blood vessels.V
8、omiting-Caused by compression or ischemia of brainstem.Usually occurs with lesions of the posterior fossa.This is usually the result of hydrocephalus and 4th ventricle dilation causing stimulation of the nucleus of vagus nerve.Personality and behavior changes-A depression in motor and thought proces
9、ses that can lead to somnolence,and decreased level of consciousness and coma.Caused by compression on the reticular substance of upper brainstem and thalamus causes this phenomenon.Papilledema-this is usually the result of increased CSF pressure in the optic nerve sheath impeding venous drainage an
10、d axoplasmic flow in optic neurons.UpwardcerebellumtentoriumCombined AnalysisInterstitial e.ICP TreatmentCushings TriadAutoregulationTotal Volume 1300-1500 ccHerniation TypesElevated ICP Clinical SymptomsCytotoxic dead/dying cellsCombined AnalysisBarbiturate ComaHypertension/Increased Pulse Pressure
11、Tonsillarcerebellumforamen m.Arterial 30%45ccICP(mm Hg)Uncal uncustentoriumPCAUncal uncustentoriumPCACranial RestrictionPagets disease,craniosynostosisIntracranial Pressure PathophysiologyAutoregulationUpwardcerebellumtentoriumPapilledemaElevated ICP Clinical SymptomsCranial Neuropathy CN III or VIC
12、ushings Triad Hypertension/Increased Pulse Pressure Bradycardia Irregular RespirationElevated ICP Clinical SymptomsICP MeasurementRadiographic Not particularly accurateOther Non-invasive Unproven:infra-red,laser,TCD(Pulsatility Index)Invasive Lumbar puncture OtherICP Measurement ICP TreatmentHead of
13、 Bed 30 degrees Improves venous drainageLasix Diuretic decreases intravascular volumeMannitol (older agents glycerol,urea)Osmotic diureticDiuretic decreases intravascular volumeOsmotic agent removes free water by osmosisViscosity improves micro-circulation ICP TreatmentSedation/Agitation Decrease un
14、necessarily elevated blood pressure and intravascular volumeIntubation/Hyperventilation Decrease pCO2(25-30 torr),change H+gradient at blood vessel causing vasoconstriction,leading to decreased intravascular volumeFever control Hyperthermia leads to increased cerebral blood flow and increased blood
15、volumeICP TreatmentBarbiturate Coma Decrease cerebral metabolic demandHypothermia Decrease cerebral metabolic demandHypertonic Saline Osmotic gradientsSurgeryElevated ICP TreatmentElevated ICP TreatmentI USED TO HAVE AN OPEN MIND BUT MY BRAINS KEPT FALLING OUT George CarlinHemicraniectomy TrialsDECI
16、MAL-FranceDESTINY-GermanyHAMLET-NetherlandsI USED TO HAVE AN OPEN MINDSevere disability or death 12 monthsMass DisplacementElevated ICP Clinical SymptomsCranial NeuropathyI USED TO HAVE AN OPEN MINDHypothermiaICP TreatmentInterstitial e.Hemicraniectomy TrialsSubfalcine cingulate g.Subfalcine cingula
17、te g.Papilledema-this is usually the result of increased CSF pressure in the optic nerve sheath impeding venous drainage and axoplasmic flow in optic neurons.ICP(mm Hg)Intracranial Pressure PathophysiologyPapilledemaUpwardcerebellumtentoriumCranial ContentsMass must be displacedDeath 12 monthsLiquid
18、 contents are incompressibleICP(mm Hg)Combined AnalysisNIHSS 15MCA strokeWithin 45 hoursCombined AnalysisSevere disability or death 12 months ARR 51.2%,p0.0001Death 12 months ARR 50.3%,p0.0001Elevated ICP TreatmentHemicraniectomyNovel Approaches to ICH/IVH Mass EffectAspiration+/-thrombolysis.This m
19、akes intuitive sense.Does it work?Intracranial Pressure PathophysiologyMass DisplacementCSF Blood BrainElevated ICP Clinical SymptomsCranial Neuropathy CN III or VICushings Triad Hypertension/Increased Pulse Pressure Bradycardia Irregular RespirationElevated ICP TreatmentI USED TO HAVE AN OPEN MIND
20、BUT MY BRAINS KEPT FALLING OUT George CarlinCombined AnalysisSevere disability or death 12 months ARR 51.2%,p0.0001Death 12 months ARR 50.3%,p 30 degreesHypothermiaAutoregulationUncal uncustentoriumPCAViscosity improves micro-circulationInterstitial e.Arterial 30%45ccZone of NormalOsmotic agent remo
21、ves free water by osmosisOsmotic diureticPapilledemaBUT MY BRAINS KEPT FALLING OUT George CarlinThis is usually the result of hydrocephalus and 4th ventricle dilation causing stimulation of the nucleus of vagus nerve.Diuretic decreases intravascular volumeDoes it work?Monro-Kellie Doctrine(1783/1824
22、)Elevated ICP Clinical SymptomsMonro-Kellie Doctrine(1783/1824)Cytotoxic dead/dying cellsZone of NormalHypertension/Increased Pulse PressureIntubation/HyperventilationNovel Approaches to ICH/IVH Mass EffectCerebral Perfusion Pressure(mm Hg)Fever controlIntracranial Pressure PathophysiologyCombined A
23、nalysisOsmotic agent removes free water by osmosisDESTINY-GermanyElevated ICP TreatmentVasogenic altered BBB,capillary breakdown,abscessZone of NormalUncal uncustentoriumPCAElevated ICP Clinical SymptomsViscosity improves micro-circulationHypertonic SalineHAMLET-NetherlandsBlood epidural,subdural,su
24、barachnoid,intracerebral,intraventricular,intravascularZone of NormalHypertonic SalineElevated ICP TreatmentIntracranial Pressure PathophysiologyViscosity improves micro-circulationHypertension/Increased Pulse PressureOsmotic agent removes free water by osmosisDecrease pCO2(25-30 torr),change H+grad
25、ient at blood vessel causing vasoconstriction,leading to decreased intravascular volumeBradycardiaDiuretic decreases intravascular volumeMannitol (older agents glycerol,urea)Cerebral Blood FlowSubarachnoid 50%75 ccElevated ICP Clinical SymptomsHypertonic SalineCSF 10%Combined AnalysisOsmotic agent r
26、emoves free water by osmosisICP(mm Hg)CSF 10%Cranial ContentsHydrocephalus,Cysts,HygromaThis makes intuitive sense.Caused by distortion or irritation of pain sensitive areas in the dural coverings and blood vessels.ICP TreatmentDecrease cerebral metabolic demandViscosity improves micro-circulationWi
27、thin 45 hoursCN III or VICytotoxic dead/dying cellsIntracranial Pressure PathophysiologyHemicraniectomy TrialsHerniation TypesDecrease unnecessarily elevated blood pressure and intravascular volumeCranial RestrictionPagets disease,craniosynostosisPapilledemaOsmotic diureticDeath 12 monthsIntracrania
28、l Pressure PathophysiologyElevated ICP TreatmentCytotoxic dead/dying cellsSevere disability or death 12 monthsWithin 45 hours(ml/100 g/min)Osmotic agent removes free water by osmosisDeath 12 monthsOsmotic diureticThis makes intuitive sense.Cranial ContentsPapilledema-this is usually the result of in
29、creased CSF pressure in the optic nerve sheath impeding venous drainage and axoplasmic flow in optic neurons.Irregular RespirationUsually occurs with lesions of the posterior fossa.Hypertension/Increased Pulse PressureMass must be displacedSevere disability or death 12 monthsFever controlSubfalcine
30、cingulate g.Combined AnalysisElevated ICP TreatmentDiuretic decreases intravascular volumeHypertension/Increased Pulse PressureSubarachnoid 50%75 ccNovel Approaches to ICH/IVH Mass EffectViscosity improves micro-circulationHerniation TypesStructureBarrierVesselZone of NormalViscosity improves micro-
31、circulationIrregular RespirationBUT MY BRAINS KEPT FALLING OUT George CarlinDoes it work?Elevated ICP TreatmentIrregular RespirationIrregular RespirationMass must be displacedCNS lymph system,brain as a spongeCombined AnalysisUncal uncustentoriumPCADecrease cerebral metabolic demandDecrease unnecess
32、arily elevated blood pressure and intravascular volumeDecrease unnecessarily elevated blood pressure and intravascular volumeElevated ICP Clinical SymptomsPapilledemaConstrictionHypertension/Increased Pulse PressureICP MeasurementLumbar punctureHeadache-Aggravated by bending and stooping.Papilledema
