Is there dehydration? It does not matter, since normally hydrated discs and desiccated discs can herniate. Herniated discs dehydrate in 8-20 weeks.
Are there osteophytes? Phytes take about a year to form, so they indicate chronic disc problems. However, they do not protect a disc against a new herniation. You can have bulging for years, osteophytes for years, and still get a new herniation at that level.
Are there endplate signal changes? There are four types, three common types and one not so common:
1. Fibrovascular changes.
2. Fatty changes.
3. Sclerotic changes.
4. Degenerative cysts.
All of these take about a year or so to form, but none protect against new herniations.
The presence of these chronic changes (phytes, endplate changes) indicates only that there have been problems at the corresponding levels for a year or so.
Absence of these changes does not mean that the disc is definitely new, but it would be hard to say a disc herniation is definitely old without these changes present or an old scan showing it was present before.
Also, while new herniations can degenerate over time, and degenerated discs can herniate acutely, there is no such thing as a "degenerative herniation." That is, degeneration of a disc cannot cause it to herniate. Only trauma can cause a herniation.
The image of two MRI scans included here shows a degenerated L4-5 disc with desiccation, narrowing, and osteophytes that herniated acutely four years after the first MR.
