The nervous system of the human body is a very complex structure. It comprises an extensive network of interdependent nerves that work endlessly to keep the entire body functional. Due to their interdependence, medical conditions affecting a particular region could sometimes be traced to a completely different part of the body.
Sometimes, these conditions could also be related to other diseases, and treatment cannot be administered until the actual underlying causes have been ascertained. For example, if you experience pain radiating from your lumbar region to your buttocks, and all the way down to the back of your leg, you could be suffering from sciatica—but then again, it may be another disease. How do you tell them apart?