Cerebrospinal fluid acts as a cushion for the soft tissue of the brain within the hard osseous chamber that is the skull. Because the CSF contains cells which kill bacteria and viruses such as macrophages it also provides immunological protection for the central nervous system. The human brain weighs approximately 1400 grams, however when suspended in the CSF its effective net weight is just 25 grams, this ensures that the brain does not put pressure on blood vessels and nerves which lie below it. The volume of CSF has an inverse relationship with intracranial pressure; therefore by regulating the volume of CSF intracranial pressure can be maintained.

Cerebrospinal fluid contains proteins known as biomarkers. The abundance of these specific proteins within the subarachnoid space can give an indication of the type of disorder a patient is suffering from. For example many types of meningitis can be distinguished through the study of CSF. In meningitis the CSF appears thick and yellow. Cerebrospinal fluid is used as a measure of Baricity (the density of a substance in comparison to CSF), this is used medically in anaesthesia to determine how quickly a drug will move through the CNS.

For tests to be carried out on the CSF it must firstly be removed from the subarachnoid space via a lumbar puncture procedure. A needle is inserted in-between the fourth and fifth vertebrae through the dura mater. The needle can be withdrawn giving a collection of fluid. This fluid can be tested via many techniques to give percentages of specific proteins which may indicate a disease/disorder/infection.

Cerebrospinal fluid has been linked to the diagnosis of many disorders such as:

• Meningitis
• Ischemic Stroke
• Alzheimer's
• Multiple sclerosis

Other illnesses such as bacterial infections are also diagnosable via CSF. For more information see the News section.

The regulation of cerebrospinal fluid is maintained via its production (by the choroid plexus) and absorption (by the arachnoid villi). This ensures that the volume of CSF within the subarachnoid space is kept constant. The volume of the CSF shares an inverse relationship with intracranial pressure (ICP). The maintenance of intracranial pressure is important because if it is too high blood flow to the brain is impaired eventually causing neuronal death. Therefore CSF volume regulation is essential for normal function of the CNS.

Before 3 years of age the bones of the skull are not fully fused. For enlargement of the head to occur hydrocephalus must occur before the child is three. Hydrocephalus is a lack of CSF drainage and reabsorption due to one or more factors. This causes an increase in the volume of CSF and therefore the intracranial pressure rises forcing the bones of the skull slowly apart. Bone then forms in the gaps thus increasing the size of the skull. Hydrocephalus can also cause convulsions and mental disability. For more information see Reabsorption.

The references & links page has links to journals which build upon the information discussed in this website. There is also a list of other similar websites which contain valid and comprehensive information about CSF.