Is an MRI subjective or Objective?

I have talked a lot about ligaments in the first 3 podcasts.  When someone has a persistent or permanent injury following trauma in their spine I typically see ligament damage or disc damage.  Disc damage and some ligament damage can be seen on MRI.  MRI is a great tool to show demonstrable evidence of an injury.  Today I want to talk about using an MRI to help with causation.  The question I get asked a lot is: Is there a way to time date an injury with MRI? 

Time dating injuries with MRI is possible to an extent.  It is done by taking many different aspects of the MRI and painting a picture.  Will the picture show us a degenerative spine that took years to develop or will it show new injuries.  A lot of times it shows us both.  A lot of times we will see a degenerative spine with new injuries superimposed.  This can be one of my favorite parts of doing an IME.  Looking into all aspects of the case and seeing what type of picture the patient is living.  I will likely do many podcasts on time dating injuries with MRI. 

Today I want to start with a review of MRIs.  I will use an article published in 2018 by Mark Buller MD titled “MRI Degenerative Disease of the Lumbar Spine: A Review”.  I want to start by giving a quick explanation of how MRIs work.   MRIs have a large magnetic field.  Once inside of the machine the magnet will cause all of the protons to align with the magnetic field.  Then the machine sends a radiofrequency pulse through the patient.  This radiofrequency pulse causes the protons to spin off of magnetic alignment.  Once the radiofrequency is stopped the protons stop spinning and alig n with the magnetic field again.  Once the protons stop spinning, they release energy.  This energy can be measured by the machine.  Every type of tissue will release different amounts of energy and at different times.  The MRI machine for spinal images typically records this energy at time 1 and time 2.  These times are often referred to as T1 or T2.  Water, bone, muscle, fat and other tissues will all look different at T1 and T2.  T2 will have a very bright signal with water and fat, which can make seeing new edema difficult.  The MRIs compensate for this problem by suppressing fat tissue on what is typically called a STIR view.  So, a typical spinal MRI will have 3 separate type of views a T1, T2 and STIR.  Sagittal and axial views are typically done to see different angels on the study.     

Today’s study talks a little about disc nomenclature by referencing one of my favorite articles published by Fardon in 2014 called the Lumber disc nomenclature 2.0.  The nomenclature shows when a disc has a symmetrical extension beyond the bone this should be called a disc bulge.  Disc bulges are typically older injuries.  When disc material extends beyond the bone in a focal area this would be called a herniation and is typically a new injury.  Herniations can be broken down into protrusion, extrusions and sequestration.  Protrusion is when the base of the herniation is wider than the apex.  An extrusion is when the base of the herniation is narrower than the apex.  A sequestration is when the herniation breaks off of the remaining disc space.   

Today’s study discusses the 2 components of an intervertebral disc.  We have the outer annulus fibrosis and the inner nucleus pulposis.  The annular fibrosis is dense fibrocartilaginous tissue made of primarily type 1 collagen.  The annular fibrosis is very strong tissue.  This will be seen on a T1 and a T2 view as low or dark signal.  The nucleus pulposis is in the center of the disc and is made of type 2 collagen and is 70-90% water and proteoglycans.  This makes the nucleus pulposis appear different on an MRI.  IT will look low on a T1 and high on a T2.  Given the lack of fat in the disc the STIR view should look just like the T2.

What will imaging of a new disc herniation vs a degenerative disc bugle look like on MRI.  A new herniation is when the center of the disc or nucleus pulposis moves outside the disc.  So, a new disc herniation will often have high T2 signal in the herniation.  This is due to the watery connective tissue moving outside of the disc.  This increased signal will not last forever.  The nucleus pulposis outside the disc will eventually dry up and no longer show the increased T2 signal.  If you have an MRI with a herniation and the herniated disc material has an increased T2 signal that is one indicator that this is a new injury.   

Today’s study showed that disc damage dramatically alters the mechanics of the spine.  These altered mechanics lead to degenerative bone changes and osteophyte formations.  Boney degenerative change can take months to even be seen on imaging and years to really develop.  These boney degenerative changes will come after disc damage.  If you have an MRI with a disc herniation and no degenerative bony changes around the disc it is much more likely than not that this is a new injury.  If you have a disc herniation with a lot of degenerative changes surrounding the disc then it may be an older injury. 

Today’s study showed that with altered mechanical changes we not only get bone spurring around the disc, but loss of disc space height.  If we have a new herniation, we will not typically see loss of disc space height. 

Today’s study also discusses changes seen on MRI to the vertebra with injuries.  When discs herniate, we often seen damage to the vertebra surrounding the disc.  We often seen endplate fractures or edema or increased fluid or inflammation.  The endplate fractures or just increased fluid or edema in the vertebra will change it’s appearance on an MRI.  This was first studies by Dr. Modic and his name has stuck with classification.  This fluid or edema from a new injury has been called a type 1 modic change.  This will change the appearance of bone to look more like fluid and will have an increased signal on T2 and a decreased signal of T1.  Given there is not fat the STIR view will also be increased. 

Eventually the edema will be gone and the bone can return to normal healthy bone or it may heal with an increase of fatty tissue.  Fatty tissue in vertebra has been called a type 2 modic change.  This typically happens months to years after an injury.  The fat tissue will be bright on the T1 and T2, but suppressed or dark on the STIR view.  This type 2 modic change can last for years.

Overtime injured bone that had fatty infiltration can harden and become very sclerotic.  This hardened sclerotic bone will look dark on the T1, T2 and STIR views.  This hardened bone will be called a type 3 modic change. 

The ligamentum flavum will often show thickening on an MRI.  Today’s study has shown that this is a common finding with degenerative changes. 

Today’s study has shown us a few ways to review an MRI and paint a picture of a new injury that can be related to trauma or if the MRI paints the picture of a degenerative spine with no new injuries.  Or a lot of times I see the MRI that shows indications of degenerative changes and new superimposed injuries related to trauma. 

Today’s study showed us if we have an increased signal inside of the herniated material this is the inside of the disc herniating outside and this is a new injury.  This study showed us that disc herniations are focal and degenerative bulges are circumferential.  Today’s study showed that following a disc herniation we will have degenerative bony changes over time.  If we have a new herniation without bony degenerative changes this is likely a new injury.  Today’s study discussed modic changes.  If we have a new disc herniation with type 1 modic changes surrounding the disc then we have a new disc herniation. 

For my real-world example, I want to use a worker’s compensation IME I did last week.  The patient was lifting a heavy item at work and felt instant pain in his low back and right leg.  This got worse over time and he had an MRI a few months later.  The radiologist reported and I quote “there are minimal degenerative changes in the lumbar spine, the examination is normal for the patient’s age” end quote.   He was 59 years-old at the time.  He continued to have low back and right leg pain and had another MRI 2 years later.  This time the radiologist said and I quote “There is right-sided radicular disc extrusion with inferior migration and impingement of the descending right s1 nerve root” end quote.

According to the radiologist this patient’s L5-S1 following the work place injury was normal for his age.   Then 2 years later the L5-S1 disc has an extrusion type disc herniation with nerve root impingement.  The attorney got me this case with 2 days for me to get a report before he has a court hearing for the workers compensation claim.    After reviewing hundreds of pages of medical records I knew the original MRI was crucial for this case.  Fortunately, they were able to get me a copy of the MRI to review. 

His MRI showed a right sided focal herniation.  There were no bony degenerative changes surrounding L5-S1.  The herniation showed a bright signal on T2 and STIR view.  As we went over today this shows that this is a new herniation where the inside nucleus pulposis herniated outside the disc.  He also did not have disc space loss at L5-S1 indicative of a new injury. 

This herniation was abutting the right nerve root which is indicative of right leg symptoms he was having.  This is clearly a new herniation and likely directly related to his work place injury. 

Unfortunately, I see a lot of missed pathology on MRI reports.  This is an easy case for me to show demonstrable new injuries.  I am able to take the MRI pictures and show the increased signal in the herniation, lack of degenerative changes, lack of disc space loss and nerve abutment.  This MRI in almost every way shows a new disc herniation which correlated perfectly with his work place injury. 

Thanks for listening to today’s podcast.  Be sure to subscribe so you don’t miss out on more ways to demonstrably show injuries.