(B) Vein of Gallen malformation[?]Communicating Hydrocephalus:There is free flow throughout the ventricular system.Impaired CSF resorption by the arachnoid granulation accounts for majority of casesSAHInfectious meningitisMalignant meningitisGranulomatous meningitis: TB, sarcoidosisAltered venous Dynamics: Vein of Galen malformation, venous obstructionVein of Galen Aneurysmal Malformation:Direct AV fistula b/w deep choroidal arteries & persistent embryonic precursor of VOGLarge midline venous pouch behind the 3rd ventricle.Aetiology:Obstructive - Congenital or Acquired:Congenital Causes:-Aqueductal stenosis or forking-Dandy Walker syndrome (Atresia of foramina of Magendie & Luschka)-Arnold Chiari malformation (Type 2-progressive hydrocephalus + myelomeningocele)-Vein of Galen aneurysm Clinical Features:>30% of symptomatic VM in childrenRare in adultsNeonates - high output CCF with cranial bruitOld infants - Macrocrania + hydrocephalus +/-CCFOlder Children - Developmental delay and seizuresYoung adults - HeadacheLarge VGAMS - Cerebral ischemia and dystrophic changes.Left untreated - Die of progressive brain damage and in- tracatable CCF.Dandy-Walker Malformation: Triad of Abnormalities:1. Incomplete development of vermis; Retro-vermian cyst continuous to 4th ventricle; 3. Hydrocephalus Crouzon syndrome:Crouzon syndrome is a genetic disorder characterized by the premature fusion of certain skull bones (craniosynostosis). This early fusion prevents the skull from growing normally and affects the shape of the head and face. Many features of Crouzon syndrome result from the premature fusion of the skull bones.