The amount of cerebrospinal fluid (CSF) removed by the spinal tap will be replaced by the body in about an hour. Some patients – especially adults – are prone to developing a headache after a spinal tap. To help prevent this, the physician may tell patients to lie flat in bed or with their head slightly raised at no more than a 30-degree elevation for several hours. However, this does not always prevent the headache and not all physicians make this recommendation. Drinking caffeinated beverages such as tea or coffee after the spinal tap may also help relieve the headache.  

The physician will check the puncture site for redness, drainage or swelling every hour for the first four hours, and then once every four hours until the patient is discharged from the hospital. The physician will also perform a neurological assessment every hour, or more frequently if the patient’s CSF pressure is elevated. This elevation in pressure could indicate an increase in intracranial pressure due to a cerebral hemorrhage, tumor or swelling (edema) caused by the physical trauma of the spinal tap itself.

Children who have a spinal tap while under general anesthesia will remain groggy for a short period of time following the test. In most cases, children who undergo this type of procedure do not remember it later.

Once discharged, children may gradually resume regular activities. During this time, they should increase fluid intake and be cautious when performing any activity that requires moving the head or neck to avoid the most common side effect of this procedure – a post-spinal-tap headache.

Children may feel mild discomfort or pain for a few days following the procedure, for which the physician may prescribe pain-relieving medications. Parents should contact their physician immediately if their child:

• Has any increased pain, swelling, redness, drainage or bleeding in the puncture area.
  
  
• Develops signs of infection, including headache, muscle aches, dizziness, fever and/or neck rigidity and unusual irritability.
  
  
• Experiences any nausea or vomiting.

The fluid sample is sent to a laboratory for analysis. The various analytical tests:

• Assess the chemical composition of the fluid
  
  
• Identify cells floating in the fluid, including any potentially cancerous cells
  
  
• Detect signs that the fluid is infected

In some cases, results can be available in as little as 30 minutes. In other cases, a physician may request a bacterial culture to look for organisms growing in the sample. It usually takes 48 to 72 hours to get these test results back.

Technicians who examine the fluid will note the following:

• General appearance. Normal CSF is clear. Cloudy spinal fluid can indicate increased cells and proteins suspended in the fluid, which is a sign of infection.
  
  
• Cell count. The number of red blood cells and number and type of white blood cells will be noted, as normal spinal fluid does not contain significant numbers of these types of cells. Large numbers of white blood cells usually indicate an infection, whereas the presence of red blood cells may indicate cerebral hemorrhage.
  
  
• CSF gram stain and culture.  The spinal fluid is stained and examined under the microscope to look for bacteria. To check for infection, the fluid is also cultured to see if any organisms grow from the fluid.
  
  
• Presence of substances such as:
  
  
• • Protein. High levels suggest hemorrhage, trauma, tumor, diabetes or polyneuritis (inflammation of several nerves).
    
    
  • Glucose (blood sugar). Bacterial infections and hemorrhage often cause low glucose levels in the fluid.

High protein levels, low glucose levels, the presence of red blood cells and/or the appearance of blood in the CSF are indications of a hemorrhagic stroke caused by bleeding in the brain.