[Characteristics and Treatment of Young Adult-Onset Hydrocephalus]

Certain congenital or developmental anomalies of adult-onset hydrocephalus often share clinical symptoms with idiopathic normal pressure hydrocephalus(iNPH). These anomalies include long-standing overt ventriculomegaly in adults(LOVA), persistent Break's pouch cyst(PBC)and panventriculomegaly(PaVM). Certain patients with adult-onset hydrocephalus might have congenital or secondary etiologies, such as late-onset idiopathic aqueductal stenosis(LIAS), and syndrome of hydrocephalus in young and middle-aged adults(SHYMA). Some of these conditions have unknown etiologies, and the definitions of LOVA differ between Japan and overseas. Adult-onset hydrocephalus usually presents with chronic onset, with younger patients tending to have headaches and older patients tending to have iNPH symptoms. In cases where the third ventricle floor bulging, endoscopic third ventriculostomy(ETV)is often performed. However, the arachnoid membrane of the pontine cistern might be strong, and the brain stem might be shifted to the clivus due to the enlarged fourth ventricle. For treating such patients, experienced hands might be needed. At present, it is necessary to carefully examine the cerebrospinal fluid dynamics in each patient and select the best test and treatment.