How It Is Done continued...
When the needle is in the spinal canal, a device called a manometer is hooked to the needle to measure the pressure of the CSF. You may be asked to straighten your legs while you are lying down. Your doctor takes the pressure reading, called the opening pressure, and checks whether the fluid is clear, cloudy, or bloody. Several small samples of fluid are collected and sent to the lab for study.
A final pressure reading, called the closing pressure, may be taken after the fluid samples are done. The needle is taken out and the puncture site is cleaned and bandaged.
The doctor also may look into your eyes using a special lighted scope (ophthalmoscope) to see if the pressure is high.
The entire procedure takes about 30 minutes.
To lower your chance of getting a headache following a lumbar puncture, you may be told to lie flat in bed or with your head slightly raised for 1 to 4 hours. Since your brain makes new CSF all the time and replaces it 2 or 3 times a day, the small amount of fluid that is removed will be quickly replaced. You may be told to drink extra fluids after the procedure to help prevent or to reduce the severity of a headache.
How It Feels
Some people find it uncomfortable to lie curled up on their side. The soap may feel cold on your back. You will probably feel a brief pinch or sting when the numbing medicine is given. You may feel a brief pain when the spinal needle is inserted or repositioned.
During the procedure, the needle may touch one of your spinal nerves and cause a tingling feeling, like a light electrical shock, running down one of your legs. The needle will not touch or damage the spinal cord.
You may feel tired and have a mild backache the day after the procedure. Some people have trouble sleeping for 1 to 2 days.
A lumbar puncture is generally a safe procedure. In some cases, a leak of cerebrospinal fluid (CSF) may develop after a lumbar puncture. Symptoms of this problem are a headache that does not go away after 1 to 2 days. A CSF leak can be treated with a blood "patch," in which the person's own blood is injected into the area where the leak is occurring in order to seal the leak.