Hydrocephalus-enlarged skull

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Hydrocephalus

Keywords:  Why the head is enlarged, Monro Kellin's doctrine, macrocephaly, Ex Vacuo, non-communicating, communicating, Internal hydrocephalus, External hydrocephalus.

What is hydrocephalus?

Excess accumulation of cerebrospinal fluid in and around the brain is hydrocephalus characterized by increased CSF volume and progressive dilatation of the ventricles.Its incidence is 0.1 to 0.2%

Hydrocephalus originates from the Greek word meaning water in the head or water in the brain. (Hydro=water,cephalus =head) It was described by Hippocrates 2000 yrs ago.

The average CSF volume is about 150 ml, out of which 40ml is present in the brain and 110ml  is outside the brain. The average capacity of the brain is about 1600-1800 ml.

The normal CSF pressure is 10 mm of Hg. or about 100 cm of water.

Types of  hydrocephalus :

1. Increased pressure hydrocephalus which may be

                   External-- communicating, and

                   Internal—non communicating maybe congenital and acquired

2. Normal pressure hydrocephalus.

3. Ex Vacuo

Sign and symptoms:

 In hydrocephalus, there is an increase in the volume and pressure of CSF. The skull can not expand, so brain tissue is compressed, and brain tissue damage will occur.

When hydrocephalus begins after fusion of the skull bones or in the elderly, symptoms are headache, diplopia, incoordination of the higher function of the brain.

          When hydrocephalus begins before the skull bones fuse, the size of the skull increases rapidly, leading to an increase in head size (macrocephaly).

Circulation of CSF 

   CSF is secreted mainly in the lateral ventricle, flows to the third ventricle through the foramen of the monoro. Some CSF is added in this ventricle as CSF is also secreted in the third ventricle. Then it passes through the aqueduct of Sylvius into the fourth ventricle. Some CSF is also added here. Finally, through the foramen of lushka and foramen of magendie. It enters into the cisterna magna and then subarachnoid spaces.

In the subarachnoid space, fluid moves upwards and downwards. In upward movement, it moves towards the cerebrum –superior sagittal sinus, arachnoid villi present there absorbs CSF and pass it to the cerebral venous sinuses.

In downward movement, it is absorbed in the subarachnoid space of the spinal cord.

 Communicating hydrocephalus: this is non-obstructive. CSF absorption decreases due to blockage or functional abnormality of the arachnoidal villi causing accumulation of the fluid outside the brain, and to some extent, inside the brain. The blockage may be due to an excess of cells, proteins, etc., in the cerebrospinal fluid.

Non-communicating hydrocephalus is an obstructive type in which there is an obstruction to the flow of CSF, causing an increase in volume inside the brain. The block usually occurs at the narrow part in the flow pathway, e.g., foramen and aqueduct of Sylvius. In the cerebrospinal fluid, An excess of cells, proteins, cell debris, etc. In the CSF will block the foramen and cerebellar aqueduct. In addition, congenital stenosis of the aqueduct may occur.

Normal-pressure hydrocephalus is due to the intermittent rise of CSF pressure, especially at night. The normal pressure hydrocephalus is seen after brain injury.

In the exvacuo hydrocephalus, there is a compensatory enlargement of the CSF spaces with the CSF  –the ventricles and subarachnoid spaces -caused by brain volume loss. Therefore, the total volume of the skull remains constant following Monro-Kellin's doctrine.

Diagnosis: Physical finding.CT Scan, MRI findings, and radionuclide scan will show impaired circulation

Treatment is available like ventriculoperitoneal shunting and other methods are present.

 Disclaimer: This information is provided as an educational service and public awareness. It is not medical advice.

Tag: Monro Kellin's doctrine, macrocephaly, Ex Vacuo, non-communicating, communicating, Internal hydrocephalus, External hydrocephalus.

Internal link:https:// blog.totalphysiology.com/2021/08/cerebrospinal fluid

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