Shots - Health Blog
1:36 pm
Fri November 11, 2011

This Is A Spinal Tap

Today is special.

For devotees of the 1984 film This Is Spinal Tap, 11/11/11 is the day to honor the genius of Nigel Tufnel. The guitarist played by Christopher Guest rocked the world with amplifiers that "go to 11."

Heavy metal and "rockumentaries" go in and out in style. But what about real-life spinal taps, also known as lumbar punctures? The old procedure remains a staple of modern medicine.

In the popular imagination, spinal taps get top symbolic billing when it comes to medically induced pain and foreboding. But Paola Sandroni, a neurologist at the Mayo Clinic in Rochester, Minn., says that reputation is undeserved: "It's a benign procedure overall."

Doctors order spinal taps to check the pressure of fluid that surrounds the spinal cord and brain. And they also collect samples of the fluid to diagnose infections and other conditions. In some patients, the tap serves as a way to introduce drugs into spinal fluid as treatment.

How's it done? The best way is for the patient to lie on his side, curled up in the fetal position. That opens up spaces between the lower verterbrae, down in the lumbar spine. Put your hand on the top of your hip bone, then bring it around to your backbone. That's the sweet spot for a spinal tap.

"The ideal person is lean and mean, with a straight back and without much arthritis," Sandroni says.

After a little local anesthetic to numb the skin and the bones takes effect, the doctor or nurse inserts a needle between the bones. There's "a pop" when the needle goes through a ligament and into the sac where the spinal fluid is located. OK, that made me a little squeamish, I have to admit. But Sandroni assures me it's not as bad as it sounds, "Some patients hardly feel anything. You should only feel pressure."

The real problem to avoid is hitting nerve roots, the connections between the spinal cord and nerves like the ones that go down your legs. Hitting one of those hurts. If touched, the root usually "floats away" and after a pause the tap can continue, she says. Damaging a root is probably the biggest risk from the procedure.

On average, about 10 cubic centimeters, or about a teaspoon's worth, of spinal fluid is removed, Sandroni says. The fluid, in case you are wondering, is both a nutrient for the brain and a receptacle for waste products. "It's a sink for all the metabolic substances in the brain," she says. It's also provides a liquid cushion.

After the needle is slowly withdrawn, a bandage is placed over the hole. Then, she says, people are advised to rest for a half-hour or so and take it easy for the rest of the day. Plenty of fluid, including some drinks with caffeine, help reduce headaches, a common complaint after the procedure.

Your body makes a lot of cerebrospinal fluid, and within a few hours has replaced what's been removed.

The next day, a person might feel some pain and soreness, like a bruise from being punched. But, she says, if a puncture is "properly done it shouldn't be a big deal."

I have to ask if she's ever had a spinal tap herself. Nope. Ever seen Spinal Tap, the movie? Also, a no.

But Sandroni brightens and says she has her own movie coming out: a YouTube video for Mayo explaining spinal taps. In fact, the video got pushed out today, and you can watch it below.

Copyright 2011 National Public Radio. To see more, visit http://www.npr.org/.