Have you ever stopped to wonder why babies are so cute? It’s their big heads! Think about the size of a baby’s head compared to his body… it’s disproportionately big. I personally think babies hit maximum cuteness around 6-8 months, and this is in part because of their giant noggins and chubbiness. Inside that bobble head is a brain that is bathed in a fluid called the cerebrospinal fluid (CSF), or spinal fluid. Unfortunately, leukemia cells like to get into that CSF and hide out. This is a problem because the body has a blood brain barrier, which is in place to protect the brain from things like infections and drugs. Most chemotherapy can’t cross the blood brain barrier and the CSF has to be treated by directly injecting chemotherapy into the spinal fluid through a lumbar puncture, which is also called a spinal tap. Generally, children receive a smaller dose of medication than adults. The dose is either based on weight or body surface area. This doesn’t work for medications that are injected into the spinal fluid, because children reach the adult volume of spinal fluid by three years of age because of their big heads! This was figured out in the 1980s through a series of studies and now we calculate the dosage of these types of medications based on the child’s age, rather than their size or weight. Fascinating isn’t it?!
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