Foraminal narrowing: what it means on your MRI

What is foraminal narrowing?

Foraminal narrowing means the small opening where a nerve leaves your spine has gotten tighter.

Between each pair of spine bones there is an opening on the left and one on the right. The opening is called a foramen (plural: foramina). A spinal nerve passes through each one on its way to your arm or leg. When the opening narrows, the nerve has less room. You may also see this called "foraminal stenosis."

What causes foraminal narrowing?

Usually gradual wear over many years. Several changes can crowd the opening:

• A disc bulge or herniation pushing into it
• Bone spurs (osteophytes)
• Arthritis and enlargement of the small joints at the back of the spine (facet joints)
• Loss of disc height, which lowers the "ceiling" of the opening
• Less often, one vertebra slipping forward on another (spondylolisthesis)

What symptoms can foraminal narrowing cause?

If the narrowing pinches the nerve, it can cause pain, numbness, tingling, or weakness along that nerve's path. This is called radiculopathy.

• Neck: symptoms in the shoulder, arm, or hand
• Low back: symptoms in the buttock, leg, or foot, often called sciatica

Many people with foraminal narrowing on MRI have no symptoms at all.

What do "mild," "moderate," and "severe" mean?

They describe how much room is left for the nerve.

"Mild" means the opening is a bit smaller and the nerve usually still has space. "Severe" means very little space is left, and the report may say the nerve is "contacted" or "compressed." The MRI grade and your symptoms don't always match. A severe finding can be painless, and a mild one can hurt.

What do "left," "right," and "bilateral" mean on my report?

They tell you which side the narrowing is on. "Bilateral" means both sides.

Side matters. Narrowing on the left usually explains symptoms on the left side of your body, not the right.

Which nerve is affected at my level?

It depends on whether the narrowing is in your neck or your low back.

• Neck: the nerve is numbered for the lower bone. Narrowing at C5-6 affects the C6 nerve.
• Low back: the nerve is numbered for the upper bone. Narrowing at L4-5 affects the L4 nerve.

This trips people up, because a disc problem at L4-5 that sits more toward the center often affects the L5 nerve instead. Your clinician matches the MRI level to your exam to sort this out.

Is foraminal narrowing serious?

Usually it's not an emergency. Most arm or leg nerve pain improves over weeks to months without surgery.

It's worth seeing a clinician soon if you have weakness, like trouble lifting your foot or gripping, especially if it's getting worse.

How is foraminal narrowing treated?

Most people start with non-surgical care:

• Physical therapy and targeted exercise
• Anti-inflammatory or nerve pain medicine, if your clinician recommends it
• An injection near the nerve (epidural steroid injection or nerve root block) for pain that lingers

Surgery to widen the opening is called a foraminotomy. It may be an option when weakness is significant or getting worse. It is also an option when pain doesn't improve after a solid trial of other treatment.