Sunday, April 23, 2017

Nerve Root(s)

In season 3, episode 18 of Star Trek: Deep Space Nine Dr. Bashir has to deal with some deep-seated personal issues. One of these is the fact that he graduated second in his medical school class because he mistook a "pre-ganglionic fiber for a post-ganglionic nerve." Spoiler alert: He did it on purpose because he didn't want to deal with the pressure of being first.

Dr. Bashir is not alone. I see this lead to 2 errors every day in our trainees. The clinical implication is zero, because the referring physicians also don't make this distinction (two wrongs do make a right, apparently).

First, take a look at the image below:

Note that there are 2 nerve roots (dorsal and ventral) on each side (left and right). When you say a lumbar disc compresses a nerve root in the central spinal canal, you need to add an "s," because these dorsal and ventral nerve roots travels down together in the cauda equina. Next time you look at an axial T2-WI of the lumbar spine, see if you can see two distinct nerve roots on either side.

Second, note that once we're post-ganglionic, we're dealing with a nerve, not a root. So, if you're talking about a nerve root outside the foramen, you're about as anatomically correct as a Ken doll.

The same goes for the "nerve roots" of the brachial plexus and the famous Randy Travis Drinks Cold Beer mnemonic for the brachial plexus anatomy (sorry, Randy). All is not lost. Just replace Randy Travis with Nikola Tesla.


  • Basic anatomy that everyone ignores.

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