[Sonographic characteristics of the Arnold-Chiari syndrome and hydrocephalus in children with meningomyelocele].

22 children with myelomeningocele had serial examination by gray scale ultrasonography through the open fontanelle as an acoustic window. 18 children (82%) developed a progressive hydrocephalus and were eventually shunted. In 18 children the hydrocephalus was caused by an Arnold-Chiari-II-malformation with the sonografic signs of a caudal displacement of the dysplastic cerebellum, brainstem, 4th ventricle and cisterna magna. The forth ventricle was elongated and flattened in all babies with Arnold-Chiari-syndrome. The cisterna magna was not visible in any child. The Arnold-Chiari-II-malformation caused an occlusive hydrocephalus which was characterized by the dilatation of the occipital horns (91%) and frontal horns (86%) of the side ventricles, whereas the temporal horns were normal in size (86%). The dysplastic 3. ventricle was displaced caudally and ventrally and showed a prominent suprapineal recess in 41%. Associated malformations of the brain were a large massa intermedia (55%), a prominent plexus choriodeus (50%) and agenesia (36%) or fenestration (9%) of the septum pellucidum. Gray scale ultrasonography is the best method not only for early diagnosis of Arnold-Chiari-malformation and resulting hydrocephalus in infants but also for further controls after shunt implantation, especially for early detection of shunt complications and shunt insufficiency.