Hydrocephalus

Question 1

What is hydrocephalus?

Answer 1

CSF building up abnormally within the brain and spinal cord. This is a result of either over production of CSF or a problem with draining or absorbing CSF.

Question 2

What is the normal CSF physiology?

Answer 2

There are 4 ventricles in the brain: two lateral ventricles, the third and the fourth ventricles. The ventricles contain CSF, which provides a cushion for the brain tissue. CSF is created in the four choroid plexuses (one in each ventricle) and by the walls of the ventricles. CSF is absorbed into the venous system by the arachnoid granulations.

Question 3

What is the most common cause of hydrocephalus?

Answer 3

Aqueductal stenosis, leading to insufficiency drainage of CSF. The cerebral aqueduct that connects the 3rd and 4th ventricle is stenosed, blocking the normal flow of CSF out of the ventricle, causing CSF to build up in the lateral and third ventricles.

Question 4

What are some other causes of hydrocephalus?

Answer 4

• Arachnoid cysts can block the outflow of CSF if they are large enough
• Arnold-Chiari malformation is where the cerebellum herniates downwards through the foramen magnum, blocking the outflow of CSF. - Chromosomal abnormalities and congenital malformations can cause obstruction to CSF drainage.

Question 5

What is the presentation of hydrocephalus in babies?

Answer 5

• the cranial bones in babies aren’t fused at the sutures until around 2 years of age → so the skull is able to expand to fit the cranial contents
• when a baby has hydrocephalus it causes outward pressure on the cranial bones
• therefore babies with hydrocephalus will have an enlarged and rapidly increasing head circumference (occipito-frontal circumference)
• bulging anterior fontanelle
• poor feeding and vomiting
• poor tone
• sleepiness

Question 6

What is the treatment of hydrocephalus?

Answer 6

• placing a VP shunt that drains CSF from the ventricles into another body cavity
• usually the peritoneal cavity is **used to drain CSF, as there’s plenty of space and it’s easily reabsorbed
• the surgeon places a catheter through a small hole in the skull at the back of the head and into one of the ventricles → the valve on the end of this tube is placed subcutaneously and a catheter on the other side of the valve runs under the skin into the peritoneal cavity
• the valve helps to regulate the amount of CSF that drains from the ventricles

Question 7

What are the VP shunt complications?

Answer 7

• infection
• blockage
• excessive drainage
• intraventricular haemorrhage during shunt related surgery
• outgrowing them (they typically need replacing around ever 2 years as the child outgrows)