When scans are performed for ? Discitis, often both a T2 and T2 Fat Sat/ STIR sequence are performed. Which is better for assessing for early discitis?
One of the features of discitis on MRI is increased T2 signal in the disc. But often, there are no other features of discitis/ osteomyelits, the disc signal on T2 is normal or decreased, but the T2 Fat Sat / STIR sequences shows a bright disc? Is this a sign of very early discitis seen only on the fat saturated scans or is it aretefact and can be ignored? Which sequence to believe?
The image above, is from a person who does not have discitis. You can see that discs normally demonstrate brighter signal on the T2 fat sat/ STIR sequence than on standard T2 scans. Even the discs that are quite degenerate such as at L5/S1 are brighter. This is a normal finding on T2 Fat saturated scans that the disc signal looks brighter than on standard T2 scans and does not mean its early discitis.
- So when you are assessing the disc signal for very early discitis, base your decisions on disc signal on the T2 scan and not on the T2 fat sat or STIR sequence.
- If there are no other features of discitis/ osteomyelitis, the disc signal is dark or normal on standard T2 scans and the only finding is increased T2 signal on the T2 fat saturated scan, ignore it. Its not early discitis.