Idiopathic intracranial hypertension and idiopathic normal pressure hydrocephalus: diseases with opposite pathogenesis?

Idiopathic intracranial hypertension (IDICH) and idiopathic normal pressure hydrocephalus (IDNPH) are disorders of the circulation of the cerebrospinal fluid (CSF) with opposite diagnostic features, obscure etiology but the same treatment: CSF drainage. In both diseases a large quantity of CSF exists: equilibrated by the brain edema in IdICH with high ICP and not equilibrated by brain pressure, and the ventricles are enlarged in IdNPH. The same anatomical structure involved in both diseases is the ventricular wall and this represents a true barrier, a glial-ependymal barrier and it acts as a barrier only in connection with the difference between the pressures. The spontaneous course of both diseases suggests that an open glial-ependymal barrier protects the brain parenchyma.