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 48
Oct 2010 fusion T8-sacrum w/ pelvic fixation
Feb 2012 lumbar revision for broken rods @ L2-3-4
Sept 2015 major lumbar A/P revision for broken rods @ L5-S1
mom of Leah, 14 y/o, diagnosed '08 with 26* T 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
4/15 stable 5 yrs post-op, 18* T/ 22* L, Risser 2
also mom of Torrey, 10 y/o son, 16* T, stable