Do I Need a Lumbar Spine (low back) MRI?

by Adam Brown   BScPT, MClScPT, FCAMPT
Advanced Practice Physiotherapist – Spine
updated June 20, 2022

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Back pain and sciatica are incredibly common. Some experts have suggested that 84% of people will suffer from low back pain at some point in their lives. But just because it’s common, doesn’t mean it’s not debilitating. Many people report having difficulty working or doing their regular activities because of severe back pain.

Physiotherapy clinics and family medicine offices are full of people searching for the solution to their back pain. Naturally they have a lot of questions about diagnostic testing. In particular people tend to ask about magnetic resonance imaging (MRI). Most are curious to know if mr imaging will uncover some information that will help them recover from their back pain.

Most back pain does not require an MRI or any other imaging tests. Your doctor will do a clinical evaluation to identify some uncommon signs and symptoms indicating that an MRI of the spine may be helpful.

It can be frustrating for patients to be denied an MRI when they feel their pain warrants it. But it is important to understand the uses and limitations of spinal MRI scans. With the information in this article you will be able to better understand your doctors recommendations and perhaps advocate for yourself if you have symptoms that require imaging.

 

What Does Lumbar Magnetic Resonance Imaging Show?

MRI machines use sophisticated technology to produce detailed images of your spine. It can visualize bone, ligament, discs, nerves, the spinal cord, muscles and other surrounding soft tissue. While this sounds wonderful, it has it’s pitfalls. Most people have lots of evidence of old injuries and degenerative changes (wear and tear) that will be seen and included in your MRI report. Most of these findings will have little or nothing to do with the symptoms you are experiencing. It is only when the clinical examination and a finding on the MRI match, that there may be useful information.

For many people seeing an MRI report can be anxiety provoking. Typically they get the impression there is much more wrong with their spine than they thought. it is important for them to know that the majority of what they read in the MRI report may simply be normal wear and tear and may not be contributing to their symptoms at all.

 

Can You See Nerve Damage On An MRI?

You can’t determine if a nerve is damaged by looking at a lumbar MRI scan. However, you can see if there are any soft tissues or structures compressing the nerve. When this is correlated with your clinical exam we can determine if the nerve is likely to be producing your symptoms.

 

Do I Need To Worry About My Spinal Cord?

Patients frequently come in with concerns that their back pain will eventually progress to paralysis. The overwhelming majority of people with low back pain do not need to worry about their spinal cord at all. In the very rare instances where a persons spinal condition is a risk to their spinal cord there are some key signs and symptoms that clinicians will look for such as:

1) Profound motor weakness in the lower extremities

This is not just some weakness of a select few muscles that are supplied by a single nerve root. This presentation is quite common and does not indicate cord compression. Rather is would be widespread weakness making it very difficult to stand and walk for any length of time.

2) Widespread sensory loss in the legs

Again, this must be distinguished from a defined area of numbness in the leg corresponding to a nerve root that may be compressed. It is a general loss of sensation in the lower extremities. It is common for back pain to include leg pain. The presence of leg pain does not indicate serious pathology.

3) Bowel or bladder dysfunction

Difficulty initiating or stopping urination or the inability to hold ones bowels is a symptom that must be taken seriously and warrants further medical investigation.

4) Saddle Paresthesia

This is a specific area of numbness in the perineum or the area of your body that would normally contact a bicycle seat. Numbness in this area requires investigation.

The majority or orthopaedic low back problems occur in the lower lumbar spine. The spinal cord ends at around L1 (the upper lumbar spine). Only the lumbar and sacral nerve roots carry on down the spinal canal past this point. This protects the crucial spinal cord from this common area of spinal degeneration.

 

Why Would A Doctor Order An MRI Of The Lumbar Spine?

Most cases of low back pain do not require an MRI. There are a few instances where detailed pictures of the spine and surrounding tissues can be helpful with diagnosis and/or management. They include:

• The signs and symptoms of cord compression discussed above.
• Difficulty with walking or balance.
• Severe back pain in children.
• Recent significant physical trauma.
• When the patient is also very unwell. They may have a fever, unrelenting night pain or night sweats, weight loss, and other signs and symptoms that a more serious illness may be present.
• When a patient has mostly leg pain, has failed to manage it with a well structured trial of physiotherapy (8 weeks at least) and is considering a surgical solution. In this case the MRI exam is used to confirm the clinical presentation and appropriateness of a surgical treatment plan.

How Is A Spine MRI Done?

An MRI machine is one of the most advanced medical devices in the hospital. It is in high demand and is in constant use at most hospitals. You will be given a specific appointment time for your scan and instructions on where to check in at the hospital. In Canada musculoskeletal MRI’s are often done in the overnight hours because they do not require a radiologist to be present during the procedure, so your appointment may be in the middle of the night.

Upon arrival you will be asked to fill out some paperwork and answer some basic questions about your medical and occupational history. These questions will screen for any loose metal objects or fragments in your body that may move when subjected to magnetic fields.

Once your paperwork is complete you will change into a hospital gown. All of your clothing and jewelry will need to be removed to ensure no metal is going into the machine. If you wear hearing aids they will need to be removed.

When your appointment time comes you will be led into the room with the MRI machine. It looks like a large tube with a table that slides in and out of the opening. You will be asked to get up on the table and be positioned appropriately for the images they have been asked to obtain.

You will often be given a set of earphones so the MRI technician can talk to you during the procedure. This technician is a trained healthcare professional and they will guide you through the procedure. There will be times where the MRI technician may ask you to hold your breath for a short time to eliminate any movement of your body while images are being created. You will be required to lie still during the entire procedure so be sure you are comfortable before beginning.

You will be able to communicate with the technician throughout the procedure so if you have pain or experience any problems they will be able to assist.

 

How Long Does An MRI Of The Lumbar Spine Take?

The average spinal MRI will take between 30-60 min. if you have a contrast MRI it will take 45-90 min. You will not feel any sensations from the magnetic fields or radio waves used to create the pictures.

 

Should My Lumbar MRI Be Done With Contrast Dye?

Some MRI’s are done with a contrast dye containing the metal gadolinium. This is done to improve the visual contrast between different tissues on the images. Your physician may order an MRI with contrast if the pathology they are suspecting is typically difficult to decipher on regular MRI images.

The contrast dye used in a contrast MRI can have some rare side effects including;

• Allergic reaction causing hives, rash, dizziness and nausea or vomiting.
• People with kidney problems should not have contrast dye injected as it can lead to a rare condition called nephrogenic systemic fibrosis.
• There have been reports of joint pain and inflammation following injection with gadolinium based contrast material.

 

Can An MRI Scan Be Dangerous?

Aside from the rare side effects of contrast dye, MRI scans are a very safe noninvasive procedure. There are no known side effects from being subjected to the magnetic field or radio waves. Some people experience anxiety when inside an MRI machine because it is a small enclosed tube. If you are known to be claustrophobic discuss strategies with your doctor prior to your appointment.

 

If I Don’t Need an MRI, What Treatment Does My Back Pain Need?

Most back pain does not need an MRI scan, and a skilled physiotherapist reliably identify patients who should undergo imaging. If you are among the many patients suffering from a low back problem, you should be assessed by an experienced Physiotherapist. A detailed clinical exam will rule out pathology that requires imaging and help to categorize the type of back pain you have. Click here for a description of the types of low back pain.

 

At Cornerstone Physiotherapy we have experienced and well trained physiotherapists ready to help navigate your back pain. Give us a call.