An LP is an outpatient procedure where a small needle is inserted between the vertebrae (spinal bones) of the lower back at a level below the spinal cord to obtain a small amount of cerebral spinal fluid (CSF). It is sometimes referred to as a spinal tap.
What is the purpose of the LP in this study?
The purpose of obtaining spinal fluid is to learn as much as possible about the proteins and other chemical changes that may occur in individuals with neurological conditions, like Parkinson's disease (PD) and Lewy Body Dementia (LBD). Spinal fluid is useful because it bathes the brain and spinal cord, making it the best source of information about neurochemical changes that may be occurring in the brain. Because many proteins do not cross from the spinal fluid into the blood stream, spinal fluid is sometimes the only way to see that something is wrong with the brain. Scientists predict that proteins in the spinal fluid could be promising biomarkers of PD and related conditions. Being able to measure changes in specific proteins or neurochemicals in spinal fluid may provide a way to predict disease progression, evaluate why symptoms vary from person to person, and monitor if new treatments can slow progression of the disease.
What happens during the procedure?
The LP can be done in two positions: while you lie curled up on one side with knees close to the chest, or while you lean forward over a table while seated. The doctor will locate a puncture site in the lower back, between two vertebrae, then clean the area and inject a local anesthetic. You may feel a slight stinging sensation from this injection. Once the anesthetic has taken effect, the doctor will insert a special needle into the spinal sac and collect a small amount of fluid (usually about three teaspoons) for testing. This spinal fluid is normally replenished within one hour. Sometimes, a special x-ray or ultrasound may be used to help the doctor guide the needle into the right place. The entire procedure takes about 45 minutes.
Is the LP painful?
There are two parts in the beginning of the LP procedure that may cause some discomfort. First, during the administration of an anesthetic, you may feel a few seconds of stinging or burning when it is injected. Second, you may also feel a pressure sensation when the needle is inserted, and there is usually some brief pain when the needle goes through the tissue surrounding the spinal cord. Overall, discomfort throughout the entire procedure is minimal to moderate.
What are the risks of LP?
There is a small chance of developing a headache after the procedure. This usually gets better with rest and drinking plenty of fluids. Rarely, the headache may continue for more than 24 hours after the procedure and require additional treatment. There is no risk of paralysis. LPs are typically performed using a special needle designed for this procedure. LP needles have improved over time, and are now smaller, cause less pain at the site where the needle goes in, and are less likely to cause headache after the LP. When performed by an experienced doctor, an LP is safe and involves minimal discomfort.