Low-pressure headache

[Dorothey Allen]

Low-pressure headaches result when cerebrospinal fluid is removed during a spinal tap (lumbar puncture) or leaks out because of a cyst or tear in one of the layers of tissues that cover the spinal cord (meninges). Loss of this fluid, which flows around and cushions the brain, reduces pressure around the brain.
(See also Overview of Headache.)
Most commonly, low-pressure headaches occur after the following:

A spinal tap (lumbar puncture)

A low-pressure headache occurs in up to a third of people who have had a spinal tap, usually hours to a day or two afterward.
In a spinal tap, doctors insert a needle between two vertebrae in the lower back, and withdraw a sample of cerebrospinal fluid from the spinal canal. The cerebrospinal fluid, which flows through a channel between the layers of tissues (meninges) that cover the brain and spinal cord, helps cushion and support the brain. After a spinal tap, cerebrospinal fluid sometimes continues to leak out of the tiny hole made by the needle. If fluid leaks out faster than the body can replace it, the amount of fluid around the brain decreases, and the brain may sag downward, stretching the surrounding blood vessels and supporting tissues. This stretching results in a headache.
Low-pressure headaches may also occur when other problems cause cerebrospinal fluid to leak out:

A cyst in or near the meninges where a nerve comes out of the spinal cord bursts. Cysts sometimes burst when people cough or sneeze because coughing and sneezing cause the pressure within the cerebrospinal fluid to suddenly increase. Cerebrospinal fluid sometimes leaks spontaneously—for no apparent reason.
The meninges are torn during an injury, particularly when the head or face is injured.

Low-pressure headaches are intense. They occur when people sit or stand and may be relieved by lying flat. People usually also have a stiff, painful neck and nausea and may vomit.