Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery
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If the cerebrospinal fluid (CSF) is considered to be all the fluid (liquid), other than blood or the derivatives of its breakdown, that is normally contained within the brain, its cavities, and its spaces, this could be regarded as "brain fluid" in its most elemental form. "Pathological increases in intracranial CSF volume, independent of hydrostatic or barometric pressure", then, could be considered a definition of hydrocephalus. The observation of significant episodic variation in intracranial pressure (ICP) suggests the necessity of substituting the concept of "time-related pressure variations" for the older one of "level of pressure" in patients with defective ICP control mechanisms. It has been assumed that the subarachnoid channels are the first CSF compartment to dilate in response to the hydrocephalic process, reducing the CSF pressure and thereby establishing an equilibrium. ⋯ Thus, it becomes obvious that the term internal hydrocephalus is of little significance, since increases in intraparenchymal fluid--cerebral edema--cause the same volumetric changes as increases in intraventricular fluid volume. I suggest that hydrocephalus is a pathologic increase in intracranial CSF ("brain fluid") volume, whether intra- or extraparenchymal, independent of hydrostatic or barometric pressure. It may be classified as (1) intraparenchymal (cerebral edema) and (2) extraparenchymal, with the extraparenchymal types subclassified into subarachnoid, cisternal, and intraventricular forms.