spinal tap

A spinal tap is a procedure where a special needle is inserted between the vertebrae in the lower back and into the space that surrounds the spinal cord, usually to look for evidence of infection. The space surrounding the brain and spinal cord is filled with cerebrospinal fluid (CSF). The cerebrospinal fluid works like a shock absorber and filter.

 

When a person is thought to have a disease or injury that affects the brain, spinal cord, or their protective membranes, a spinal tap may help determine the cause. A spinal tap is a very useful procedure.

 

Healthcare professionals use a spinal tap to:

 

A spinal tap can be performed with a person bending over while sitting in a chair, or lying down on his or her side with the knees drawn up close to the chest. These positions help to separate the vertebrae of the lower back, giving the healthcare professional a larger space to insert the spinal needle. The area where the needle is to be inserted is cleaned and medication is injected into the skin to provide local anesthesia. A person may feel a burning sensation for a few seconds while the medication is administered.

 

After the area has been prepared, a special spinal needle is inserted. A person may feel the insertion of the spinal needle as a pushing or tugging sensation. Once the needle is in the proper place, the pressure can be measured and a sample of CSF can be collected or drugs injected. The procedure generally lasts 15 to 20 minutes. Once the procedure is completed, a dressing over the puncture site is applied and the person is instructed to lie flat.

 

Depending on the reason for the spinal tap, a person may be instructed to lie flat from 2 to 12 hours. This is done to avoid a post-procedure spinal headache. After the procedure is completed, the person is instructed to drink plenty of fluid. This will help the body replenish the cerebrospinal fluid which was removed for testing.

 

A person is also instructed to report any numbness and tingling to the legs, bleeding or oozing from the puncture site, or headaches that fail to improve. Normal activity can usually resume once a person has had enough rest. Sometimes the area where the spinal needle was inserted remains sore for a day or two. No other special home care is required.

 

The most common complication from a spinal tap is a post-procedure spinal headache. These headaches occur because of a drop in cerebrospinal fluid pressure as a result of removing some fluid for testing, and can usually be avoided if a person lies flat for several hours and drinks plenty of fluids. The spinal headache typically goes away in a few hours. Severe cases may require pain medication or another special procedure to repair the spinal tap site.

 

A person should request specific instructions from his or her health care professional.

Normally, spinal fluid will be clear and colorless and contain no blood and no organisms. Protein levels are usually 15 to 45 mg/dl of CSF, although in the elderly and children the level may be 70 mg/dl. Lactic dehydrogenase (LDH) levels are usually less than 2.0 to 7.2 U/ml.