Know your spinal cord – The tethered spinal cord

This has been a fun series of posts and today is day seventeen! As usual, you can check out all of our posts under the neuroanatomy category. I’ve got some good news and some bad news. The good news is we’re still going! The bad news is we’ve pretty much covered the anatomy. So for the next few posts, we will look at some issues the spinal cord may have. First up, let’s talk about a tethered spinal cord!

Fun fact, the spinal cord moves. No really, depending on if you are standing, sitting, lying prone (on your stomach) or lying supine (on your back) your spinal cord can shift by about 6mm (or for my US friends, about 0.25 inches)! For something so delicate, that feels like a lot. These numbers were found using an MRI machine fairy recently, in 2008, below is the chart showing the spinal cord range of motion and a link to the study if you’re interested!

Figure 3 of the study, here is the caption “Movement of the CM anteriorly and laterally towards dependent side when changing from the supine to the lateral position with knees and  hips flexed. Boxes show medians (Wilcoxon P,0.001) and 25th–75th percentiles, and whiskers show the range. Ranger et. al (2008)

This information is important because it tells us that the spinal cord in its natural state should be able to move somewhat. Considering how we as humans bend, twist, and move throughout the day, this is probably good news. However, what happens when your spinal cord doesn’t have the range of motion it should have?

We never formally covered the filum terminale, but we did touch on it when we covered the meninges. The filum terminale (terminal fiber) attaches the end of the spinal cord, the conus medullaris, which we also never formally covered, to the first segment of the coccyx. In one case of a tethered spinal cord, the filum terminale is too tight, literally tethering the spinal cord. This can be caused by the filum terminale being too thick as well, but in either case this can be very debilitating.

Notice the spinal cord on the right is pulled down when compared to the normal cord position on the left. The filum terminale is keeping the cord from moving up the spinal column like it should

Symptoms of a tethered spinal cord vary depending on severity, but can range from lipomas (fatty tumors that are usually benign) forming on the lower back, hairy patches on the lower back, lesions, weakness of the legs, lower back pain, abnormal gait (the way you walk), or urinary problems. Just to name a few things that can go wrong when you have a tethered spinal cord.

Other causes of a tethered spinal cord include things like a spinal tumor, spinal surgery, trauma to the spine, spina bifida, or something called a split spinal cord (Diastematomyelia) which I think we will end up covering tomorrow since it is very interesting and quite rare.

Thankfully depending on the cause surgical intervention is usually the way to treat it. Unfortunately this typically wont reverse any sort of neurological damage that was done. Therefore the key is early detection and intervention, BEFORE, neurological symptoms occur. However, this is an issue since most cases aren’t found until adulthood when symptoms start to show unless it is caused by a primary issue (such as a tumor or spina bifida). A tethered cord is rare, which makes catching it early particularly difficult since we don’t normally test for it.

Thus concludes our dive into the tethered spinal cord. Go ahead and stretch, you know you want to. So like I said earlier in the post, I think tomorrow we will dive into diastematomyelia (yeah it’s a mouthful). We will also look at more common issues such as spina bifida and of course, spinal cord injury. I hate to say we’re nearing the end of the series, but it really looks that way. Maybe we can cover some of the minor things we haven’t talked about, but overall I think if you’ve followed along you’ve gained a new appreciation for your spinal cord.

Until next time, don’t stop learning!