Subarachnoid SpaceSubarachnoid HemorrhageCerebrospinal FluidArachnoidMeningesCerebrospinal Fluid PressureCisterna MagnaCerebrospinal Fluid ProteinsVasospasm, IntracranialHydrocephalusCerebrospinal Fluid ShuntsPneumoencephalographyMeningitisCerebral VentriclesArnold-Chiari MalformationInjections, SpinalArachnoid CystsSpinal PunctureCerebral VentriculographyIntracranial PressureCerebrospinal Fluid RhinorrheaSubdural SpaceSyringomyeliaArachnoiditisAnesthesia, SpinalCerebral AqueductDura MaterMagnetic Resonance ImagingIntracranial AneurysmMyelographyMicroscopy, Electron, Scanning TransmissionMeningitis, PneumococcalCerebral AngiographyTomography, X-Ray ComputedVentriculostomyBrainBattered Child SyndromeForamen MagnumAneurysm, RupturedMeningeal NeoplasmsEpidural SpaceMeningitis, BacterialSpinal CanalSpinal CordChloral HydrateBrain DiseasesOptic NerveCerebral ArteriesBasilar ArteryCranial Fossa, PosteriorBlood-Brain BarrierLaminectomyCerebrovascular CirculationAnesthesia, EpiduralBupivacaineTime FactorsInjections, IntraventricularSubarachnoid Hemorrhage, TraumaticDogs