In order to understand the pathophysiology of hydrocephalus, it is necessary to mention some brief anatomical notes.
The central nervous system (brain and spinal cord) is immersed in the Cerebrospinal fluid (CSF) (spinal fluid), which performs various functions, some of which are: mechanical protection and enabling the exchange of substances with the nervous system.
The CSF is continuously produced by structures called the choroid plexuses, which are located in cavities known as the ventricles of the brain. From there it flows to reach the surface of the brain and spinal cord where it is then reabsorbed by other structures defined as the Pacchionian granulations.
Hydrocephalus is defined as the dilation of one or more ventricles due to excess CSF accumulated in them.
Hydrocephalus may occur due to an excessive production of spinal fluid, a reduction in CSF reabsorption, or due to an obstruction of the circulation of the spinal fluid itself, with consequent accumulation of CSF upstream of the obstruction.
Hydrocephalus may occur in a short time (acute hydrocephalus) and endanger patient’s life if not promptly treated or it may develop very slowly (normal pressure hydrocephalus or chronic hydrocephalus).
Acute hydrocephalus usually develops following a cerebral hemorrhage and needs to be treated urgently by positioning a small catheter inside the right lateral ventricle in order to drain out the excess spinal fluid and normalise the intracranial pressure (EVD- external ventricular drain).
In this chapter, we will discuss the Normal Pressure Hydrocephalus (NPH) in detail.