Q. A 65 year-old man presents with a several month history of back pain and progressive gait impairment. He says that whereas over the summer, he was able to walk three miles a day, now, in the winter, he is barely able to get down the driveway without having to stop due to pain and imbalance. He is having trouble getting up out of bed and down stairs and stays in his living room for most of the day. At first, his family thought he was depressed due to the loss of his wife a few years ago, and assumed his lack of activity was secondary to motivational issues. Now, they are not sure. He does have a history of a foot injury at the start of the summer that created an open sore and took a long time to heal. It caused fevers and eventually, he started an antibiotic for it, but other than that, he has been a healthy person. His vital signs are notable for a low-grade fever but are otherwise unremarkable. Labwork demonstrates an elevated white blood cell count but his metabolic profile is normal. You get MRI imaging of this spine and find evidence of an abnormality tracking along the epidural space and into the paraspinal muscles in that region and there is evidence of spinal cord compression. His family is stunned about this finding and ask you how it is possible that all this happened. You explain: