What Causes Fluid on the Brain?

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  • Written By: Marlene Garcia
  • Edited By: Jenn Walker
  • Last Modified Date: 13 September 2019
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Fluid on the brain, also called water on the brain and hydrocephalus, is caused by birth defects, tumors, head or spinal injuries or bleeding in the brain during the birthing process. It can also develop after a stroke or bout of meningitis, which is an infection of the membrane that covers the spinal cord and brain. In rare cases, some people acquire water on the brain for no known reason.

Genetics might play a role in birth defects that result in excess fluid on the brain. The most common disorder is aqueductal stenosis, wherein the passages between ventricles in the brain become narrow and do not allow sufficient cerebral-spinal fluid to leave the head. Pressure builds up and the head may become enlarged.

Spina bifida is another birth defect that results in fluid on the brain in a high percentage of babies born with the condition. During fetal development in the womb, an opening occurs in the spinal column that permits nerves to poke through and develop outside the skin. If this happens near the brain, hydrocephalus may develop. There is no known cause for spina bifida but studies show that taking folic acid during pregnancy might prevent the disorder.


A tumor that develops in the brain or brain stem can also block the flow of fluid from the brain, causing it to accumulate. Tumors can be detected through scans of the head or blood tests. Medication may be used to shrink the tumor, or surgery may be performed to remove it, allowing cerebral fluid to flow naturally. Chemotherapy, with or without radiation, is common if the tumor tests positive for cancer.

Cerebral-spinal fluid is produced continually in the brain and spinal cord of healthy individuals. It cushions the brain and provides nutrients as it circulates through the head. The fluid is reabsorbed by the blood vessels in a continual process so it doesn’t build up. When this process is disrupted by disease or trauma, fluid on the brain is not dispersed, leading to hydrocephalus.

Fluid on the brain is commonly treated by using a shunt to divert fluid from the blocked area in the head into the chest or stomach where it can be reabsorbed by the body. This procedure does not work for all patients with fluid on the brain, and complications can arise if the shunt becomes blocked or infection sets in. Surgery to insert the shunt also can damage blood vessels and cause memory problems.

In children with hydrocephalus, the head usually grows too large for the body. They may be unable to control the weight of the head, which might affect balance. In babies, the soft spot at the top of the head could appear swollen instead of depressed. Older children and adults with fluid on the brain may complain of headaches, sleepiness and nausea.



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