Transverse Myelitis is essentially demyelination across a portion of the spinal cord. In itself, it can be an episode unrelated to MS, or an instance of an MS condition. Tightness across the chest is not required. Multiple
Sclerosis (or scar, I think its Greek derivation) refers by definition to multiple instances or attacks of demyelination across the brain and / or spine. In some patients TM can represent an instance of MS.
The incidence of MS that brought me into hospital prior to my diagnosis was essentially TM. However an MRI showed additional plaques on the brain, sufficient along with a remembered instance of optic neurosis to make an MS diagnosis definite.
The McDonald criteria for MS basically specifies the sufficient presentation to make a diagnosis. You can quite easily research this.
Has an MRI been ordered for your case?
Good luck, hope you feel better soon