I think anatomically it is cervical. Each disc is described in relation to the vertebrae it is under I believe. So I think the disc between C7-T1 is called C7's disc. Also, the injections are not into the disc but into the nerve roots, so in that case it would be the C7 nerve roots being injected.
Best of luck with this. I can't imagine how aggravating this is for you.
Gayle, age 46
Boston brace as a teen for AIS
Oct. 2010 fusion T8-sacrum w/ pelvic fixation, TLIF at L4/5.
Feb 2012 major A/P revision for broken rods
mom of Leah, 12 y/o, diagnosed Jan '08 with 26* thoracic JIS (age 6)
4/08 26 degrees, brace 16 hrs/day
9/08 17 deg. OOB - brace discontinued
9/09 30 deg, resuming brace
5/10 VBS Dr Luhmann Shriners St Louis
11/13 stable 3.5 yrs post-op, 15 deg
also mom of Torrey, 9 y/o son, 12* T, decreasing spontaneously (from 19*)