Okay I am not a doctor and don’t play one on TV but here is how I understand it. Transverse Myelitis is a condition where something has created a lesion in the myelin (the layer of fatty tissue that insulates the spinal chord). With that exposed it is much like a power chord, the conductor of the nerve strands are damaged or simply exposed causing disruption and false stimulus. It is very similar to MS, however as the MS acronym would indicate by its name, implies multiple lesions as where TM is generally a singular lesion. Depending on the size and location of the lesion(s) is the determining factor of what symptoms you will have.
The methods of detection are as I found out are very difficult. Lots of MRI’s, and the ones with contrast really mess me up. There was the other procedure that seemed like a form of medieval torture with this tilting table and of course lumbar punctures also known as spinal taps.