The hydrocephalus represents a condition having set of etiological factors. It arises owing to disbalance between production and absorption of a liquor: it is absorbed less liquor, than it is produced. The reason of it can become obstructive process in ventricles or in a subarachnoid space. Less often the reason is the true hyperproduction of a liquor, as, for example, at a papilloma of a villiferous plexus.

The hydrocephalus is traditionally sectioned on informed and not informed.

Not informed hydrocephalus is caused by the process causing an occlusion of ventricular system.

The informed hydrocephalus arises at an obstacle of an output from the fourth ventricle to inflow of a liquor.

The functional hydrocephalus can develop as a result of a hypersecretion of a liquor at a papilloma of a villiferous plexus. This tumour and in itself can cork ventricular system, leading to development of not informed hydrocephalus. In other cases small hemorrhages from these tumours can cause obstruction of subarachnoid spaces. It cases of conservation of a hydrocephalus after an oncotomy speak.