Cranial SinusesSinus Thrombosis, IntracranialCerebral VeinsSagittal Sinus ThrombosisDura MaterSuperior Sagittal SinusArachnoidCentral Nervous System Vascular MalformationsIntracranial ThrombosisCerebral AngiographyCavernous SinusPhlebographyMaxillary SinusIntracranial HypertensionParanasal SinusesMagnetic Resonance AngiographyTomography, X-Ray ComputedSinus of ValsalvaCarotid SinusFrontal SinusMagnetic Resonance ImagingParanasal Sinus DiseasesSphenoid SinusCoronary SinusVenous ThrombosisCoronary OcclusionPregnancy Trimester, SecondBalloon OcclusionRetinal Vein OcclusionSick Sinus SyndromeArteriovenous FistulaEthmoid SinusRetinal Artery OcclusionEmbolization, TherapeuticFollow-Up StudiesParanasal Sinus NeoplasmsArterial Occlusive DiseasesContrast MediaMeningeal ArteriesTachycardia, SinusDental OcclusionTransverse SinusesRetrospective StudiesUltrasonography, PrenatalMaxillary Sinus NeoplasmsInfarction, Middle Cerebral ArteryPilonidal SinusTreatment OutcomeBrain IschemiaIntracranial Arteriovenous MalformationsCarotid Artery, InternalCollateral CirculationCraniotomyPolyvinylsHeadacheCerebral ArteriesDogs