Paraspinal Muscles
Paraspinal muscles are the muscles that run along both sides of the spine, playing an important role in posture, movement, and spinal stability. When reviewing radiology reports, patients may come across terms related to these muscles, such as “paraspinal muscle atrophy” or “inflammation.” Understanding these findings can help you discuss your imaging results with your doctor.
Medical imaging—such as MRI (magnetic resonance imaging) and CT (computed tomography) scans—allows radiologists to assess the paraspinal muscles. Changes in muscle size, shape, or signal intensity can indicate various conditions, from normal aging to underlying disease.
What Do Paraspinal Muscles Do?
Paraspinal muscles provide essential support for the spine. They help maintain posture, assist with bending and twisting, and protect the vertebrae from excessive strain. These muscles include:
- Erector spinae – A group of long muscles that run parallel to the spine, helping with extension and rotation.
- Multifidus – A deep stabilizing muscle that plays a crucial role in spinal health.
- Quadratus lumborum – Located in the lower back, assisting with side bending and stability.
When these muscles weaken, shrink, or show abnormal signals on imaging, it can lead to back pain and mobility issues.
MRI Findings: Paraspinal Muscle Atrophy
One of the most common findings related to the paraspinal muscles on MRI is muscle atrophy, which means the muscles have lost size and bulk. This can be due to:
- Aging – Natural loss of muscle tissue over time.
- Chronic back pain – Reduced activity and disuse can lead to muscle wasting.
- Nerve damage – Conditions like spinal stenosis or disc herniation may cause nerve compression, affecting muscle function.
- Previous surgery – Muscle changes often occur after spinal procedures.
On MRI, muscle atrophy appears as a decrease in muscle volume with increased fat infiltration.
In my practice, paraspinal muscle atrophy is often noted in patients with chronic low back pain. It’s a sign that the muscles are weakening, which can contribute to ongoing discomfort and instability.
Paraspinal Muscle Edema: Signs of Inflammation
Sometimes, imaging reveals edema, or swelling, in the paraspinal muscles. This suggests an underlying issue such as:
- Muscle strain or injury – Common in athletes and those with sudden back pain.
- Infection – Rare but serious, infections like pyomyositis or discitis can affect these muscles.
- Autoimmune conditions – Diseases like polymyositis or dermatomyositis may involve muscle inflammation.
On MRI, edema appears as bright (hyperintense) areas on fluid-sensitive sequences like STIR (Short-TI Inversion Recovery). If present, further evaluation may be needed to determine the cause.
Fatty Infiltration of the Paraspinal Muscles
Fatty infiltration occurs when normal muscle tissue is replaced by fat. This is often seen in conditions such as:
- Chronic disuse – Prolonged inactivity, bed rest, or paralysis.
- Neuromuscular disorders – Diseases like muscular dystrophy.
- Post-surgical changes – Common in patients who have had spinal fusion or decompression surgery.
MRI is highly sensitive to fatty infiltration. Radiologists describe it as increased signal intensity on T1-weighted images, where fat appears bright. Severe fatty infiltration can reduce spinal stability and contribute to back pain.
Asymmetry in Paraspinal Muscles: What It Means
In some cases, imaging shows asymmetry, where one side of the paraspinal muscles is smaller or appears different than the other. Causes of asymmetry include:
- Prior surgery or trauma – Muscles on one side may atrophy due to previous damage.
- Nerve involvement – A pinched nerve or radiculopathy can cause uneven muscle wasting.
- Dominant vs. non-dominant side – Some natural variation exists, but significant differences may indicate an underlying problem.
If asymmetry is significant, your doctor may investigate further with nerve studies or additional imaging.
When to Be Concerned About Paraspinal Muscle Changes
While mild changes in the paraspinal muscles are common with age, significant abnormalities may indicate a medical issue. Consider discussing your imaging findings with a doctor if:
- You have persistent or worsening back pain.
- Imaging shows significant atrophy, edema, or asymmetry.
- There are signs of infection, nerve compression, or inflammatory disease.
Conclusion
Paraspinal muscles play a key role in spine support and movement, and radiology findings related to these muscles can provide valuable information about back health. MRI and CT scans help detect muscle atrophy, inflammation, fatty infiltration, and asymmetry, guiding treatment decisions. If your radiology report mentions paraspinal muscle changes, discussing the findings with a doctor can help determine the next steps for managing your spine health.
References
- https://www.ajronline.org/doi/pdfplus/10.2214/ajr.138.1.93
- https://www.jscimedcentral.com/public/assets/articles/radiology-8-1084.pdf
- https://radiopaedia.org/articles/paraspinal-muscles?lang=us