Spinal Tap

http://www.emedicinehealth.com/spinal_tap/article_em.htm



Spinal Tap Introduction

• A spinal tap is a procedure performed when a doctor needs to look at the cerebrospinal fluid (also known as spinal fluid). Spinal tap is also referred to as a lumbar puncture, or LP.
  
  
• Some of the reasons your doctor may want to do a spinal tap include the following:
  
  
  • To look for infection
    
    
  • To check to see if there is bleeding around the brain (subarachnoid hemorrhage)
    
    
  • To look for causes of unexplained seizures
    
    
  • To look for causes of headaches
  
  
• Cerebrospinal fluid is a liquid that bathes the brain and spinal cord. An adult has about 140 mL (just under 5 oz) of spinal fluid. Typically, an adult makes 30-100 mL of spinal fluid daily.
  
  
• A spinal tap can be performed in any person and at any age from newborn to age 100 years and older.

Risks

Although infrequent, several complications can occur as a result of a spinal tap.

• Headache
  
  
  • About 5-30% of people who have a spinal tap get what is commonly referred to as post –lumbar puncture headache.
    
    
  • Your headache may start up to 48 hours after the procedure and usually lasts for 2 days or less.
    
    
  • The headache typically worsens when you are in an upright position and lessens when you lie flat.
    
    
  • The cause of the headache is leakage of the spinal fluid from around the puncture site.
    
    
  • Younger people and males have an increased risk of headaches after lumbar puncture compared with older people and females.
    
    
  • You reduce your chance of getting one of these headaches by drinking plenty of fluids, especially caffeine products such as tea, coffee, and cola.
    
    
  • Occasionally, a blood patch is needed. An anesthesiologist or pain management specialist injects a small amount of your own blood at the site where the spinal tap was performed. You usually experience relief within 30 minutes after this procedure.
  
  
• Herniation
  
  
  • A herniation can occur if an abscess (pocket of infection) or increased intracranial pressure (ICP) is present during your spinal tap.
    
    
  • If the pressure in your brain is elevated when the spinal tap is performed, the flow of fluid from the brain down the cord may cause the brain to get squeezed down into the direction of the spinal cord. This is extremely rare and occurs only with elevated intracranial pressure.
    
    
  • If a person has signs and symptoms consistent with meningitis (fever, headache, and stiff neck), then the spinal tap may be performed immediately. In some people, a CT scan of the brain is performed first, however, to rule out the possibility of bleeding or other causes that may increase the pressure within the skull or around the brain.
    
    
  • If increased intracranial pressure is suspected, great caution is taken and your condition is carefully discussed before a spinal tap is performed, if it is performed at all.
  
  
• Bleeding
  
  
  • Injury to the blood vessels that surround the covering of the spinal canal may occur when the needle is being inserted. Frequently referred to as a traumatic tap, this may cause a small amount of localized bleeding.
    
    
  • Sometimes this can affect the results of the procedure, which would mean that the doctor would have to re-insert the needle into another area of the back, frequently an inch or so away from the first site. Proper numbing medicine, if needed, is injected to decrease any pain.
    
    
  • The spinal cord ends at the level of the first or second lumbar vertebrae, and the needle is usually inserted at a level between the third and fourth or the fourth and fifth lumbar vertebrae, keeping the spinal cord completely out of danger.
  
  
• Epidermoid cyst
  
  
  • Rarely, certain tissues (epidermoid) are accidentally implanted into the spinal canal when the spinal tap is performed.
    
    
  • The likelihood of an epidermoid cyst is much greater when a needle without a stylet is used, and this almost never occurs today. All spinal tap kits used today have needles with stylets.

Spinal Tap Preparation

• No special preparation is needed on your part before a spinal tap.

• Always ask your doctor to fully explain the process to you as she or he is doing it. This talking through helps to lessen any anxiety that you may experience.

During the Procedure

Most spinal taps can be completed within 5-10 minutes.

• You are asked to lie on your side with your legs and hips bent (flexed) up toward your chest and your neck slightly bent forward. This position is often called the fetal position. (Some doctors place you in a seated position, where you lean forward and rest your arms on a tray or back of a chair. This is an acceptable alternative position.)

• The doctor always wears sterile gloves and occasionally also wears a mask and gown.

• The spinal tap is performed using sterile technique, meaning that everything used is sterilized to minimize any risk of infection.

• The doctor next identifies landmarks on your body. Frequently, the doctor does this by feeling the top of the pelvis bone (on your side). This area corresponds with the fourth and fifth lumbar space where the needle is inserted.

• A numbing medication (lidocaine) is injected first into your skin and then into the deeper tissues of your lower back to numb the area completely. This injection causes some minor discomfort, which is usually brief and has been described as a burning sensation.

• You should inform the doctor at any time if you feel pain when the procedure is being performed.

• The needle is then inserted in your lower back, usually at the third and fourth lumbar or fourth and fifth lumbar level. The needle passes between the 2 vertebrae to enter the space where the fluid is contained. Placing you in the fetal position allows the vertebral spaces to open more widely to make needle passage easier.

• Occasionally, the doctor may measure the pressure within the fluid containing area. This does not change the procedure nor does it affect the results.

• The fluid is then allowed to collect into a series of 3 or 4 vials that are then sent to the lab for evaluation.

• The fluid collects passively, meaning it is allowed to drip out into each vial at its own pace. This step can take several minutes for a full specimen collection.
  
  
• After the fluid is collected, the needle is removed and a bandage or small dressing is placed over the area.

After the Procedure

• You may be asked to lie flat on your back for a time after the spinal tap. This is to reduce the possibility of headaches. Drinking fluids, especially caffeine products such as tea, coffee, and cola can also help to reduce headaches.

• Your puncture site may be sore for 1-2 days.

• As with any procedure where the skin is punctured, the area should be monitored for signs of infection. Redness, swelling, pus from the area, or tenderness to touch should prompt immediate attention from a doctor.

Next Steps

• Depending on the reason for the spinal tap, follow-up care may or may not be necessary.

• If the tap is performed in the emergency department, then you are frequently instructed to follow up in 24-48 hours, either with your doctor or in the emergency department.

• If the spinal tap is performed in a doctor’s office, then a follow-up telephone call may be suggested, or a follow-up appointment may be scheduled to discuss the results of the tests, especially if specialized testing is ordered.

When to Seek Medical Care

You should contact your doctor if any of the following occur:

• Infection

• Rarely, infection at the site where the needle was inserted may occur.
  
  
• Signs and symptoms include redness, swelling, tenderness, or pus from the site.

• Headache

• Headaches can occur after a spinal tap and occasionally may be severe.
  
  
• If this occurs, you should contact your doctor.

Any signs or symptoms of infection or severe headache should prompt immediate attention from your doctor. If you are unable to reach your doctor, then you should seek immediate attention from your local emergency department.

Multimedia

Media file 1: The lower portion of the back, or lumbar region. The doctor is pointing to the area where the needle will be inserted between the third and fourth vertebrae. Notice the other hand on the top of the pelvis bone serving to help locate this area. (For orientation purposes, the patient is on the right side with the head off to the right side of the screen.)

Media type: Photo

Media file 2: An example of the sterile technique used. A drape is placed around the area (the blue sheet), and then the needle is put in place. (The glass tube going up from the needle is the device used to measure the pressure of the fluid itself.)


Media type: Photo

Media file 3: The fluid is allowed to collect into each of the vials so that it can be sent to the lab for analysis.


Media type: Photo

Synonyms and Keywords

spinal tap, lumbar puncture, spinal puncture, cerebrospinal fluid analysis, LP

References

1. Cooper JR. Routine use of CT prior to lumbar puncture. Br J Radiol. Mar 1999;72(855):319. [Medline].

2. Gonzalez DP. Lumbar puncture headache exacerbated by recumbent position. Mil Med. Sep 2000;165(9):vi, 690. [Medline].

3. Greenhall R. Lumbar puncture. Br Med J. Mar 15 1980;280(6216):796. [Medline].

4. Kooiker JC, Roberts JR, Hedges JR. Spinal puncture and cerebrospinal fluid examination. In: Clinical Procedures in Emergency Medicine. 2^nd ed. 1991:969-84.

5. Linden CH, James WA, Hartigan CF. Cranial computed tomography before lumbar puncture. Arch Intern Med. Oct 9 2000;160(18):2868-70. [Medline].

6. Schull M, Tintinalli JE. Headache and facial pain. In: Emergency Medicine: A Comprehensive Study Guide. 5^th ed. 2000:1429.

7. Tattevin P, Bruneel F, Régnier B. Cranial CT before lumbar puncture in suspected meningitis. N Engl J Med. Apr 18 2002;346(16):1248-51; author reply 1248-51. [Medline].

8. Thomas SR, Jamieson DR, Muir KW. Randomised controlled trial of atraumatic versus standard needles for diagnostic lumbar puncture. BMJ. Oct 21 2000;321(7267):986-90. [Medline].

9. Vallejo MC, Mandell GL, Sabo DP, Ramanathan S. Postdural puncture headache: a randomized comparison of five spinal needles in obstetric patients. Anesth Analg. Oct 2000;91(4):916-20. [Medline].

Authors and Editors

Author: Scott D Fell, DO, FAAEM, Medical Director, Emergency Care Center, Bon Secours Venice Hospital.

Coauthor(s): Christina L Kukula, DO, Consulting Staff, Walk-in-Care Center, Bon Secours Venice Hospital.

Editors: Scott H Plantz, MD, FAAEM, Research Director, Assistant Professor, Department of Emergency Medicine, Mount Sinai School of Medicine; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Thomas Rebbecchi, MD, FAAEM, Program Director, Assistant Professor, Department of Emergency Medicine, University of Medicine and Dentistry of New Jersey.

Last Editorial Review: 10/20/2005