Foraminal Narrowing on MRI: What It Means — Ryan Sauber, MD

Name: Foraminal Narrowing on Your MRI: What It Means | Ryan Sauber, MD
Creator: Ryan Sauber, MD

Reviewed by Ryan Sauber, MD · Fellowship Director, AHN Orthopaedic Spine Fellowship · Last reviewed October 2026

Neural foraminal narrowing means the small opening where a spinal nerve leaves the spine has gotten tighter. The opening is called a foramen, and there is one on each side of every level of the spine. Narrowing is very common on MRI, especially after about age 40, and on its own it doesn't mean anything is wrong. It matters when it lines up with your symptoms.

Reports often arrive in a patient portal before anyone has explained them, and the language can sound alarming. This page walks through what the common phrases mean, what "mild," "moderate," and "severe" are describing, and how a spine surgeon decides whether a finding is the cause of your pain.

What the foramen is

At each level of the spine, a nerve root exits on the left and another on the right. Each one passes through a short bony tunnel, the neural foramen. The disc forms the front wall of that tunnel, the facet joint forms the back wall, and the vertebrae above and below form the roof and floor.

When any of those walls thickens or bulges, the tunnel gets smaller. Common reasons are a disc that has lost height or bulges to the side, bone spurs from the facet joint or the edge of the vertebra, and in the neck, enlargement of the small uncovertebral joints. These are mostly age-related changes, the spine's version of gray hair.

Common phrases in an MRI report

What the wording usually means. Radiologists vary in how they phrase things.
Report says	What it means
Neural foraminal narrowing, or foraminal stenosis	The exit tunnel for a nerve is smaller than usual. The two phrases mean the same thing.
Neural foraminal encroachment	Something (disc or bone) is taking up some of the space in the tunnel. Another way of describing narrowing.
Right, left, or bilateral	Which side is narrowed. Bilateral means both sides at that level.
C5-C6, L4-L5, and so on	The level, named for the two vertebrae on either side of the disc. C is the neck, T the mid back, L the low back.
Disc bulge or disc-osteophyte complex	The disc is pushing outward, sometimes with bone spur mixed in. A common cause of narrowing.
Facet arthropathy or facet hypertrophy	Arthritis and thickening of the small joints at the back of the spine, which can narrow the tunnel from behind.
Uncovertebral hypertrophy	Neck only. Enlargement of small joints next to the disc, a frequent cause of foraminal narrowing in the cervical spine.
Contacts, abuts, or approaches the nerve root	The narrowing reaches the nerve but is not described as squeezing it.
Impinges on or compresses the nerve root	The nerve appears to be pressed on. More likely to matter, but still needs to match your symptoms.
Central canal stenosis	A different finding: narrowing of the main canal in the middle of the spine, not the side tunnels. Reports often mention both.

Mild, moderate, and severe

These grades describe how much room is left around the nerve in the radiologist's judgment. There isn't one universal scale, but many radiologists read it roughly this way:

Mild: the tunnel is smaller, and there is still a cushion of fat around the nerve.
Moderate: that fat is mostly gone on one or more sides, and the nerve has less room to move.
Severe: the nerve looks crowded, sometimes flattened or changed in shape.

The grade describes a picture, not how much you hurt. People with severe narrowing on MRI can have no symptoms at all, and people with moderate narrowing can have real nerve pain. Two radiologists can also grade the same scan a step apart. The grade is one piece of information, not a verdict.

When it matters, and when it doesn't

Studies of people with no back or neck pain at all find disc bulges, arthritis, and foraminal narrowing often, and more often with each decade of age. That's why an MRI is never read on its own.

A foraminal finding is likely to matter when it fits the pattern of your symptoms:

Pain, numbness, or tingling that travels down one arm or one leg, rather than staying in the neck or back.
Symptoms on the same side as the narrowing.
Symptoms that follow the path of the nerve at that level. A C6 nerve, for example, runs toward the thumb, and an L5 nerve toward the top of the foot.
An exam that agrees: changes in strength, reflexes, or sensation in that nerve's territory.

When the side, the level, and the exam all line up with the MRI, the finding is probably the source. When they don't, it may just be part of normal aging, and the search for the real cause continues.

What treatment looks like

Treatment follows the symptoms, not the report. Narrowing that isn't causing trouble doesn't need treatment at all.

When it is causing nerve pain, most people start without surgery: physical therapy, anti-inflammatory medication when appropriate, and time. A targeted injection placed next to the irritated nerve (a transforaminal injection) can calm symptoms and also help confirm which level is responsible.

Surgery is considered when nerve pain persists despite that care, or when there is weakness that is getting worse. The usual goal is to make more room for the nerve. For many patients that can be done with a foraminotomy, which can often be performed endoscopically through a small incision. In the neck, disc replacement or ACDF are other options depending on the anatomy. Fusion is reserved for specific situations, such as a spine that isn't stable.

More detail is on the foraminal stenosis page for the low back and on the surgery for cervical radiculopathy page for the neck.

Common questions

Is foraminal narrowing serious?

Usually not. It is one of the most common findings on spine MRI and often causes no symptoms. It becomes important when it pinches a nerve and causes pain, numbness, or weakness that matches the level and side on the scan.

Why are my symptoms only on one side?

Each level has a separate foramen on the left and the right. Narrowing on one side affects only the nerve on that side. Even when a report says bilateral, it is common for only one side to cause symptoms.

Can foraminal stenosis be reversed?

Bony narrowing doesn't go away on its own, but symptoms very often do. Inflammation around the nerve settles, and the soft part of a disc bulge can shrink over time. Many people with narrowing on MRI feel well again without any procedure.

Is foraminal stenosis worse than spinal stenosis?

Neither is worse by definition. Foraminal stenosis usually affects one nerve and causes symptoms down one arm or leg. Central spinal stenosis narrows the main canal and can affect several nerves, or the spinal cord in the neck. Which one matters for you depends on your symptoms and exam.

Will I need surgery for severe foraminal stenosis?

Not necessarily. The grade on the report doesn't decide that. Surgery is considered when nerve pain persists despite non-surgical care, or when weakness develops or worsens. Plenty of people with severe narrowing on MRI never need an operation.

What kind of doctor should I see?

A primary care physician, a physiatrist (a non-surgical spine and rehabilitation specialist), or a spine surgeon can all evaluate it. Seeing a spine surgeon doesn't commit you to surgery. Much of what a surgeon does is sort out whether the MRI finding explains your symptoms at all.

Talking it through

Making more room for a pinched nerve, often endoscopically, is a large part of my practice. If you have an MRI report mentioning foraminal narrowing and symptoms going down an arm or leg, I'd be glad to go through the images with you at an appointment and sort out whether the two are connected.

Foraminal narrowing on your MRI: what it means