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Wednesday, April 4, 2007

Know Your Dermatomes For The USMLE

I won't attempt to cover them all, but I can give you a few pearls here.
It's something random that over the years have gotten me a bunch questions right without trying much.

  • C6 includes your thumb and index finger (medial half)
    • to remember this, make the number 6 with your left hand by touching your index finger to your thumb now look at your hand and say to yourself "C6"
    • knowing this I can deduce C7 and C8 which I give C8 the lateral digit and half of the 4th while C7 just gets whats inbetween C6 and C8
  • L5 vs S1 = very HY
    • intervetebral discs commonly herniate at this level
    • L5 affects the big toe
      • I remember it by saying "L5 = Largest of the 5"
      • L5 root is compressed by a herniated disc at the L4-L5 level
    • S1 affects the smallest toe
      • "S1 = the smallest one"
      • S1 root is compressed at the L5-S1 level
      • (If your toes don't follow this order you may need a different memory tool, sorry buddy.)
    • L1 = Skin overlying the inguinal ligament
      • L for ligament, 1 for 1nguinal
    • S5 = Anus
      • "S5 is the doodie hive"
  • Other ones everyone probably knows but listed here just in case
    • T10 = Umbilicus
      • BellybuT-TEN
    • L4 = Knee
      • "L4 hits the floor" (when standing on your knees)

Remember that the above list isn't meant to be complete, and some dermatomes include more, but I hope this helps you to think of it in a way where you won't forget it! For exams knowing this usually gets me the point and when it comes to the USMLE, that is all I care about.


VampRN said...

I think my favorite is the Doodie Hive. I laughed about that for days and will NEVER forget it!!! Thanks man.

Reynold said...

Nice post on USMLE!
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Ved said...

Here's a much easier way to remember the entire dermatomal distribution. Check it out.