PROCEDURES:

The Lumbar Puncture

Though once used frequently to help diagnose a variety of neurologic problems, this test, also known as an “LP,” a “spinal tap,” a just a “tap,” is now used infrequently.  Many years ago when there were only a few neurologic tests available, the lumbar puncture was used much more commonly than it is today.  Now there are many different types of nervous system tests in use and as a result the LP is used in only a handful of situations.  Today, the LP can help diagnose Multiple Sclerosis, meningitis, and a form of infectious neuritis called the Guillian-Barre Syndrome. Occasionally it is used to confirm one type of bleeding inside the head.  A “spinal tap” is also the means by which dye is introduced into the spine for two tests called myelography and  cisternography.

There is a prevalent belief that a mistake made during a lumbar puncture can injure the spinal cord and result in paralysis.  That is incorrect.  The spinal cord ends between the first and second vertebrae in the low back.  There are five vertebrae in the low back and the five vertebrae are counted from the top down.  An LP is done below the level of the spinal cord, usually no higher than between the 3rd and 4th vertebrae.

A lumbar puncture is usually done with the patient on his or her side with the knees elevated, the body in a curled position.  The small of the back is then cleaned and a quarter-sized spot on the skin and in muscles is then anesthetized with a local anesthetic.  After the tissues are numbed, the spinal needle is introduced.  If everything goes as planned, the patient experiences minor pain for only a split second as the needle first enters the spinal canal.

This test is usually simple and straightforward, especially in a young, relatively thin individual.  Obesity or previous back surgery can make an LP more difficult.  LPs are usually done in the “short stay” portion of the hospital, but if your neurologist thinks that your lumbar puncture might be difficult to perform, in order to minimize your discomfort he may ask that it be done in the Radiology Department, by a radiologist and under fluoroscopy.

The only problem that occurs with some frequency---between 10 and 20 percent of the time---after an LP is a “spinal headache.”  This is an annoying but harmless problem that can last for a few days and may require another minor procedure, called a “blood patch,” to correct.  Your neurologist will explain in detail how you can minimize the chance that you will get a “spinal headache,” or if you get it, how you can deal with it quickly and effectively.