Tutorial 47: distinguishing white and gray rami communicantes in dissection

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White rami are usually thicker than gray rami, and sometimes they are visibly different in color, but they are always the more lateral connections between the sympathetic chain and the intercostal nerves, and the ones you’ll see first when you peel off the parietal pleura. You may even see the white rami through the parietal pleura if it’s thin enough. Even if both rami have been exposed, just trace the one that’s more ventral and lateral (“in front” from your view peering into someone’s chest) and that’s the white ramus.

I’ve seen the white rami lie superior to the intercostal nerves in some cases and inferior to the intercostal nerves in others. Since that seems to be variable, I don’t rely on superio-inferior position at all in making my identifications. The mediolateral position of the rami will always steer you correctly, everything else is potentially subject to variation.

One thing to watch out for: the intercostal veins are often wrapping around the vertebrae to get to the azygous/hemiazygous/accessory hemiazygous veins, and those veins may pass behind the sympathetic chain and either obscure or mimic the appearance of the gray rami.

Remember that gray rami exist at every level of the sympathetic chain, including cervical, lumbar, and sacral, but the white rami are only present between T1 and L2, where sympathetic fibers are entering the chain from the spinal cord.

doi:10.59350/svpow.23725