How Hydrocephalus may result from?

1. Blockage of cerebrospinal fluid (CSF) pathways:

- Aqueductal stenosis: Narrowing of the aqueduct of Sylvius, which connects the third and fourth ventricles.

- Stenosis of the foramina of Luschka and Magendie: These foramina allow CSF to flow out of the fourth ventricle into the subarachnoid space.

2. Impaired absorption of CSF:

- Arachnoid granulations: Small protrusions of the arachnoid membrane that facilitate the absorption of CSF into the venous system. When these granulations are dysfunctional or damaged, CSF can accumulate.

3. Overproduction of CSF:

- Choroid plexus papilloma: A benign tumor of the choroid plexus, which produces CSF.

4. Congenital malformations:

- Dandy-Walker malformation: A brain abnormality characterized by the absence or underdevelopment of the vermis of the cerebellum and enlargement of the fourth ventricle.

- Arnold-Chiari malformation: A condition in which the lower part of the cerebellum protrudes through the foramen magnum, putting pressure on the spinal cord and obstructing the flow of CSF.