It's basically saying that your spine is fine structurally but you have a lesion at the 7th-8th thoracic vertebrae that is consistent with demylination. (D7-8 is the same place, just a different way of saying it.)
Focal hyperintensity means a white spot which basically means a lesion.
I think that enhanced study means a better MRI scan using thinner slices so they can see more detail. I don't believe that the radiologist would say that if he/she meant LP - I think in that case they would say something along the lines of "examination of CSF".
I'm guessing that you are wondering what this means with regard to a diagnosis. If your brain lesions are in a typical MS area (i.e. periventricular: touching the ventricles which are the large reservoirs of CSF in the middle of the brain, or juxtacortical: next to the gray matter) then this new lesion means that you now satisfy the 2010 McDonald criterion for dissemination in space. This is because a spinal lesion is an accepted substitute for an infratentorial lesion - the third MS typical area, which is the cerebellum and brainstem. (You need to have at least one lesion in at least two typical areas.) If this is a new lesion, then you also satisfy the dissemination in time criterion. If this is the case, then (sorry) you are likely to be told that it is MS.
If they have never scanned your spine before, then this lesion may have been there for a while. In that case, you need to have had at least two attacks to satisfy the dissemination in time criterion.
If your neuro tells you that you have probable MS but won't diagnose MS, then you need to be asking which version of the McDonald criteria they are using and why they think that you don't satisfy the latest, 2010 revised version (published in early 2011). If you've had the runaround for a while from this neuro, think about going armed with a list of your relapses to date (along with the standard list of symptoms and questions) and have a read of Polman et al (2011) Diagnostic Criteria for Multiple Sclerosis: 2010 Revisions to the McDonald Criteria. It's free to download.
If you do get a diagnosis, then please ask about whether or not your neuro can prescribe DMDs. If he/she can't, then ask about getting referred to an MS specialist. You may not be eligible yet, but it's better to be in the right place when you are.
It's just occurred to me that you may not be RRMS. If you aren't, please let me know and I will go through the diagnostic criteria for PPMS for you. These are in the Polman et al paper too of course.
I hope this helps!