Top 5 Symptoms and causes of hydrocephalus

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Definition

Hydrocephalus means abnormal or excessive accumulation of CSF in the intracranial cavity.

To understand Hydrocephalus , we have to take an idea about the cerebrospinal fluid (CSF) circulation.

CSF Circulation CSF is a dynamic fluid, its main function is to

keep the internal environment of Central Nervous System (C.N.S) constant. It also play a role in mechanical protection of the brain and spinal cord.

Because CSF is dynamic fluid it is secreted and reabsorbed continuously. CSF is secreted by choroid plexus, the main bulk of choroid plexus is present in the Lateral Ventricles, but there is choroid plexus also in the Third Ventricle and Fourth Ventricle.

CSF Circulation (Cont.) The rate of formation of CSF is about 0.3-

0.35 ml/min i.e. it is about 500 cc/day although the constant amount of CSF present in the ventricles and subarachnoid space is about 150 cc. This means that most of the amount secreted is reabsorbed again.

CSF pass from lateral ventricles through Foramina of Monro to the third ventricle, then through Aqueduct of Sylvius to the fourth ventricle ( Fig. 1).

Figure 1: CSF Circulation

CSF Circulation (Cont.) The fourth ventricle have three apertures

or foramina, One mid-line (Foramen of Magendi) and two lateral foramina (Foramena of Luschka) (Fig. 2). Through these Foramina CSF passes from the ventricular system to the subarachnoid space .

It accumulate first in Cisterna Magna, part of CSF descends downwards around the spinal cord, but the majority passes upwards through the Tentorial Hiatus over the surface of both cerebral hemispheres to be absorbed by the Arachnoid villi in the Superior sagittal sinus (SSS).

Figure 2: CSF Circulation

CSF Circulation (Cont.)

So, CSF is secreted from the blood by choroid plexus and reabsorbed in the blood by Arachnoid villi, this explains the physiological dynamic function of CSF that keeps the internal environment of CNS constant. ( Fig. 3).

Figure 3: CSF Circulation

Pathogenesis of Hydrocephalus Any disturbance in CSF secretion,

circulation and absorption will results in abnormal accumulation, so the pathogenesis may be : Obstruction of CSF pathway (main

factor). Excessive formation of CSF as in case of

choroid plexus papilloma ( rare ). Decreased absorption as in SSS

thrombosis around arachnoid villi.

Etiology of CSF pathway Obstruction

Congenital anomalies: this is Commonly seen in the area of Aqueduct, such as forking of Aqueduct, gliosis or obstruction. N.B. CNS is the commonest system in the body liable to congenital anomalies.

Post–traumatic or Post–Hemorrhagic: Subarachnoid hemorrhage, whether spontaneously (as in Ruptured Intracranial aneurysm or AVM) or after head trauma may result in inflammatory reactions, adhesions, and obstruction of subarachnoid space and so Hydrocephalus

Etiology of CSF pathway Obstruction (Cont.)

Post–Inflammatory or Post-meningitic: Inflammation of Meninges usually heals by Fibrosis and adhesions within the subarachnoid Spaces, so obstruction of CSF pathway.

Neoplasm: Any abnormal mass such as tumor or abscess along the pathway of CSF may result in obstruction.N.B: In some cases of Hydrocephalus, we can not diagnose the underlying etiological cause, this is what is called Hydrocephalus of undetected cause. These cases are mostly due to mild unnoticed Head trauma or sub clinical Meningitis.

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