A spinal tap is a procedure in which a long needle is inserted in the spinal canal in the lower back to collect cerebrospinal fluid (CSF) for laboratory analysis. This clear, watery fluid circulates around the brain and spinal cord and is tested for:

• Protein. High levels of protein may indicate an infection or another condition.
  
  
• White blood cells. High levels of white blood cells may indicate infection.
  
  
• Glucose (blood sugar). Low glucose levels may indicate the presence of an infection.

Also known as a lumbar puncture, a spinal tap is an outpatient procedure. However, the patient typically has to remain in the hospital for several hours afterward for monitoring. Although a spinal tap is not generally painful, it can cause discomfort. Children in particular may find the procedure to be uncomfortable, and may have to be gently restrained during the test.

Spinal taps are used to diagnose several conditions. Spinal taps in children are most often performed to diagnose meningitis, an infection and inflammation of the membrane covering the brain and spinal cord. In children, spinal taps may also be used to diagnose the cause of ongoing headaches (which can result from spinal fluid pressure that is too high or too low), multiple sclerosis (chronic autoimmune disorder that can result in disability and impaired function), bleeding around the brain (subarachnoid hemorrhage), Guillain-Barre syndrome (a rare inflammatory disorder of the peripheral nerves) and various cancers of the brain and spinal cord.