Called “lumbar puncture” (“LP”) in medical jargon, a spinal tap extracts cerebrospinal fluid (CSF) which flows around the brain and spinal cord to cushion them. It’s obtained from the lower level of the spine, where the spinal cord has already ended, but the fluid canal remains. Analyzing the CSF is critical to diagnosing meningitis and other brain infections, bleeding from ruptured aneurysms, and sometimes for determining if there are Cancer cells up there.
Unfortunately, many people get irrationally afraid of spinal taps. They hear that you can become paralyzed (extremely rare, see below), or cause meningitis (spinal taps diagnose the meningitis that was already present). However, there are some side effects and possible complications:
- Headache, may occur in less than a third of people, is treatable & goes away on its own
- Back pain, occurs in 25% of people, lasts 1-2 days, goes away on its own
- Semi-paralysis of the legs — only happens in <10% of people taking anticoagulants (blood thinners) like warfarin and its newer competitors, not aspirin. Must use caution for patients with low platelets, or taking clopidogrel (Plavix®) (especially if aspirin too).
Another danger of spinal taps occurs if there’s too much pressure in the brain from a tumor; by removing fluid, the pressure can push the brain downward, fatally. Therefore, many ERs routinely order CT scans of the brain to be sure. However, if you have meningitis, the delay in obtaining the CT can be fatal. For patients with likely meningitis (fever, severe headache, stiff neck), clinicians should be able to tell from physical exam if there’s any danger of a tumor. If so, they should have a blood culture drawn & then receive a dose of antibiotics before heading for the CT (people with very weakened immune systems also).
Summary — Spinal Taps are very safe. compared to the risk of not diagnosing a lethal illness.