Cerebrospinal fluid

The brain is bathed in a clear liquid called the cerebrospinal fluid (CSF). This provides nutrients, takes away waste materials, and helps cushion the brain from impact. If the flow of CSF is affected by a blockage or leak, this raises or lowers the CSF pressure, both of which can cause headache.

Sometimes doctors can cause a small leak when taking a sample of CSF to help investigate other problems. This can cause a headache from low CSF pressure, which is much worse on sitting or standing as the brain sags within the skull. It usually self-resolves but an ongoing leak is sometimes treated with a ‘blood patch’ where a patient’s own blood is injected at the site of the leak to form a ‘patch’.

Blocked CSF flow can be caused by mass effect such as a tumour, or may be a problem from birth resulting in hydrocephalus. A ‘shunt’ is a small tube which can treat the latter by diverting CSF to another location e.g. from a brain ventricle to the abdomen where it is absorbed.



Intracranial neoplasm/tumour

The brain itself doesn’t have pain receptors, but tumours cause problems by their ‘mass effect’ as they squish nearby structures such as nerves and blood vessels, and may block CSF flow.



After a seizure

Headache is common following a seizure in what is called the ‘post-ictal’ period. These usually last less than six hours if they occur.