An Introduction to MRI scans

The very first MRI scan of the human body was performed in 1977. Prior to this, we were basically making educated guesses about what was wrong with the spine. Today, the modern practice of spine surgery relies heavily on the interpretation of MRI scans.

MRI scans slice the human body into thin sections

Magnetic Resonance Imaging creates thin section images of the inside of the human body. This technique allows us to visualize anatomic structures from any angle and direction. The two most common slices that we look at on MRI scans of the spine are the sagittal and coronal slices. The saggital plane sections the human body lengthwise. The axial plane creates a cross section of the human body.

MRI axial planeMRI sagittal plane

An MRI image looks like a photograph, but it is actually a computerized image of the nuclear magnetic resonance of molecules inside the human body. These images are superior to CT scans and X-rays. The resolution and clarity of the images is better, we can see more fine detail, and this test uses harmless radio waves instead of ionizing radiation.

MRI scans as a medical tool

Magnetic Resonance Imaging is an amazing tool that allows us to see deep inside the human body with a degree of clarity that is absolutely amazing. We can visualize the tiny details of normal and abnormal human anatomy. We can clearly see the intervertebral discs, spinal cord and nerve roots. In addition to normal anatomy, we have also learned to identify a number of findings that may cause neck and arm pain or back and leg pain. The list of abnormal findings that we can see on an MRI scan include the following:

disc desiccation

disc degeneration

disc bulging

disc herniations

annular tears

spinal stenosis

neuroforaminal narrowing

We are going to look at examples of each of these conditions. However, before we do, it is important that you understand that after the age of 30, essentially every MRI scan of the human body is abnormal.

Every MRI scan after the age of 30 is “abnormal”

These two pictures explain why. The natural aging process causes changes to every structure of the human body. The spine is no different. If we were to look at the skin of the gentlemen on the right with a microscope, we would see evidence of degeneration, loss of elasticity (which is called elastosis), noncancerous skin growths (called keratoacanthomas), pigment changes such as liver spots, and thickening of the skin. These findings would all be described as “abnormal”.

MRI scans reveal a natural aging process

However, we could describe the skin on the right as “normal for age”. We only describe it as abnormal when we compare it to the image of the baby on the left.  Most people, even if they don’t have any back pain, will still have evidence of abnormalities on MRI scans.  Disc degeneration, bulging disks, and herniated discs occur very commonly and they may not be causing symptoms of pain. For example, in a paper published in the journal radiology, the researches found that approximately 90% of people WITHOUT any history of back pain in the last 6 months still have evidence of annular tears, disc degeneration, and disc bulging at one or multiple levels.

Therefore, the critical task when it comes to interpreting MRI scan is CORRELATING the findings on the MRI scan with the patient’s complaints and with the physical exam.

What a normal MRI scan looks like.

This is an MRI scan of a 40 year old male. There are 5 intervertebral discs in the lumbar spine. We are going to start with a normal level which has a normal intervertebral disc. Each disc separates two bones called vertebrae in the spine. In this case, this is the L3-4 disc. Above the disc is the L3 vertebral body and below the disc is the L4 vertebral body. The center of the disc, the annulus pulpous is relatively white. The front and back of the disc, the annulus fibrosis is dark black, thick, and is not bulging into the spinal canal. The spinal canal is filled with white fluid, called cerebrospinal fluid (CSF).  Inside the CSF is the spinal cord and the nerve root that go down to the legs.

normal saggital MRI scan lumbar spine

On the axial image, the neuroforamen are wide open and there is plenty of space available for the nerve roots.

normal axial slice MRI lumbar spine

Disc dessication

Using the same MRI scan, let’s look at a dessicated disc. Desiccation is the state of dryness, or the process of drying. The theory here is that when we are young, and our discs are young, our discs have a high water content.

MRI scan lumbar disc dessicationWhen we are young, the center of the disc, called the annulus fibrosis, has an electrical charge that holds onto water very well. The disc is viscous, elastic, and is a good shock absorber. With time, the center of the disk loses water content and the disk starts to “dry out”. I tell patients that all of our intervertebral discs start out as fat plump grapes and eventually end up like raisins. Just like us.

MRI reveals disc dessicationDisc Degeneration

Disc degeneration is a more advanced form of disc dessication. In addition to the nucleus pulposus drying out, the disc starts to collapse.  Bone spurs form around the edges of the intervertebral disc. Disc degeneration is the same thing as degenerative arthritis. This condition is inevitable. It’s just as certain as death and taxes, and it will happen to everyone if they live long enough. The one thing that predicts whether or not you will have degeneration of your discs is the number of birthdays you have had. The more birthdays, the more evidence you are certain to have of disc degeneration.

MRI scan shows disc space degeneration

Disc bulging and herniations

Disc bulges and herniations come in all sorts of sizes and shapes. As the disc starts to degenerate, it can bulge out towards the spinal canal and the nerve roots. This first example is described by the radiologist as a “herniation”.  This herniation is still contained by the annulus.  As such, it is probably more accurate to describe this as a disc bulge.

MRI scans focal disk herniation

In contrast, this example shows a really large disc herniation.  In this case, the nucleus pulposus has herniated completely through the annulus and there is a large free fragment of disc material filling the neural foramen and completely obstructing the normal path for the exiting and traversing nerve roots.

 MRI scan large disc herniationAnnular tears on MRI scan

Annular tears are a particularly interesting finding on MRI scans. They represent a partial disc herniation where only a few of the fibers of the annulus fibrosis remain. Here is a short video illustrating the typical findings in an annular tear.


Spinal Stenosis and neuroforaminal narrowing: what that looks like on the MRI scan

The end result of all of these changes is spinal stenosis. Stenosis mean “narrowing”.  The process of disc bulging, degenerative disc disease, and the development of arthritis of the spine all cause narrowing of the space available for the nerve roots. Here is a short video where I review the MRI scan of someone with two level severe spinal stenosis and illustrates this process.

Making Sense of your MRI scan

Recently, it has become much more common to give the patient a copy of the MRI and report from the radiologist.  Unfortunately, this often creates a lot of confusion and concern.

I have been practicing spine surgery in Monterey, California for more than 12 years.  About 4 or 5 years ago, ObamaCare mandated that patients be given a health care summary document when they finished seeing the doctor.  This applied to MRI scanners as well.  Now, it is very common for the patient to see the radiologists report, usually before they see the doctor who ordered the scan.

By the time that a patient sees me, they usually have had the opportunity to read their own MRI report which typically sounds something like:

  • “disc dessication is prominent at L5/S1.”
  • “There is broad based disk bulging at L4/5 and L5/S1 and degenerative disk disease at these two levels.”
  • “Complete disc space collapse with prominent osteophytosis is noted at L5-S1”

Patients love Google.  After an hour or two of typing the words they don’t recognize on their MRI report into the Google search bar they are scared.  They arrive in my office CONVINCED that there is something dramatically wrong with their back.

I begin by explaining that these findings can be considered a normal part of aging and that they frequently occur in patients without back pain or sciatica.

While there is a healthy debate about what constitutes an abnormal versus a normal MRI scan of the spine, there are a few key findings that reveal a problem that we know will require surgery.

If your MRI scan does not show evidence of severe stenosis, spondylolisthesis, neuroforaminal narrowing, or a large extruded disk hernation, chances are that you can probably get better without surgical treatment.

However, the opposite is also true.  If you MRI scan shows that you have a large disk herniation, a free fragment, severe neuroforaminal narrowing, severe spinal stenosis, or a severe spondylolisthesis, chances are, you may need to have an operation after all.  The important thing to do is make sure that you have the right operation.

I specialize in non-fusion, outpatient, microscopic surgery for herniated disks, spinal stenosis, spondylolisthesis, and sciatica. If you think you may be a candidate, I will review your MRI scan to see if we can help you.

If you are interested in having me review your MRI scan, you can follow this link:

[button url=”” target=”_blank” color=”blue” size=”large” border=”true” icon=”MRI review”]MRI review[/button]

I have also prepared a short video explaining some of your options so that you can make the right decision about spine surgery.