Anatomy

For most medical students, the brachial plexus is a nightmare. The nerves from the cervical and upper thoracic spine that give sensation to the arm seem to have no rhyme or reason. They branch, connect, intertwine, and split off seemingly randomly, and for most of us, it is an exercise in memorization and then prompt amnesia.

I had thought myself free of the brachial plexus. But unfortunately, understanding the sensory innervation of the arm is essential to the regional anesthesiologist. The anesthetic plan differs whether the surgeon is working on the index finger versus the pinky, the wrist versus the elbow versus the shoulder. Performing a successful nerve block requires an understanding of which nerves need to be anesthetized and how to get to those nerves. Sometimes we have to block the roots as they come out, sometimes we block the divisions. We also have to understand the nearby anatomic structures to avoid crucial vessels and guide our needle. Which muscle layers overlie the nerves? How is each division situated in relation to the artery?

We don't learn most of this in our general anesthesia rotations. Although we study it for our tests, our month on regional anesthesia is the opportunity to apply this theoretical knowledge of anatomy into practice. Over the month, I saw different anatomic variants of the normal. I recognized how other factors - trauma, obesity, swelling, positioning affect the difficulty of the block. This month has helped me place anatomy into a clinical context. Of course, relearning brachial plexus anatomy was just the beginning; I had to pull out my notes on innervation of the leg, the lumbar plexus, the abdominal nerves, and other factoids from the first year of medical school.

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