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Old 07-13-2006, 09:11 PM
gabriela gabriela is offline
Join Date: Mar 2006
Posts: 1,158

This doesn't work for the scar that you feel in two places - for that, you need Shagnasty's explanation. Which was lucid and helpful.

Dermatomes are pieces of skin that got a nerve to grow to them while you were a fetus; the same nerve also grew to other tissues. For instance, a classic sign of blood accumulating beneath the diaphragm is pain over the top of the shoulder. This is because the same nerve runs to the diaphragm as to that spot on the skin of the shoulder. I missed this once when I was an intern. Guy who was in hospital after getting beaten up told me it was weird, but his shoulder was starting to hurt. I told him maybe he got hit there during the fight and didn't notice it. He gave me a look and told me he didn't think he could get hit without noticing it.

He was quite right. When I told my second-year resident about it, he immediately recognized phrenic pain and got the guy a CT scan. And I've never forgotten it.

Pain from the fifth sacral vertebra is often alleviated by scritching in a circle just around the anus. Pain from the fifth lumbar vertebra can often by temporarily alleviated by scritching a broad band over the top of the hip and down the outer side of the top of the leg. Pain from the first sacral vertebra is a broad band that is slightly lower across the hip and buttock and then runs along the inside of the back of the leg. I can often tell which nerves my husband's compressed vertebral fractures are affecting most today by scritching his ass and leg, and seeing what relieves the pain.

Not all odd skin/other place combinations are explained by dermatomes, but quite a number of them are.