What is the cause of Christina's condition? Do scientists think it is a plausible cause?

Christina's condition is caused by polyneuritis or a damage or inflammation of the sensory roots of spinal and cranial nerves throughout the neuroaxis. This causes her to be unable to coordinate her balance organs, eyes and proprioception. In fact she loses her proprioception entirely. It does not seem like a plausible cause because it isn't clear where her polyneuritis came from. It is hard to see how she could develop such a debilitating illness without something more severe.