Lumbar Foraminal Stenosis

What it is

Each nerve in your lower back leaves the spine through a small side doorway called the foramen. In foraminal stenosis, that doorway narrows and pinches the single nerve passing through it. The narrowing usually comes from the ordinary wear of aging — the disc loses height and settles, a bone spur forms, or the nearby joint enlarges — all of which crowd the exit. It is a focused pinch of one nerve, which is different from central stenosis, where the main canal narrows and crowds many nerves at once.

What it feels like

Because one specific nerve is involved, symptoms usually follow that nerve’s path down one leg — pain, numbness, tingling, and sometimes weakness in a particular zone of the leg or foot. Many people notice it is worse when they stand or lean backward, which closes the doorway further, and eases when they sit or bend forward, which opens it.

How we diagnose it

Your description of where the symptoms travel tells me a great deal, and a focused exam helps pinpoint which nerve is involved. An MRI confirms the narrowed doorway and the level. As always, I treat the patient in front of me: the imaging and your symptoms have to point to the same nerve.

How we treat it

My first goal is almost always to settle this without surgery, and most of the time that works. A pinched nerve hurts not only from the physical pressure but from inflammation around the nerve — and that inflammation is often what makes the pain so severe. Calming it with a targeted (transforaminal) steroid injection, anti-inflammatory medication, and time is frequently enough, as long as the nerve is not being re-irritated. I usually want to give this a fair trial of at least six weeks, and often longer, because most people improve and avoid an operation:

• Activity adjustments and physical therapy
• Anti-inflammatory medication for a limited period
• A targeted nerve-root (transforaminal) steroid injection, which calms the inflammation and confirms the level

If severe nerve pain persists after a fair trial, surgery is reasonable — this kind of pain can be genuinely debilitating, and you do not have to wait indefinitely. I choose the approach carefully, because it depends on why the doorway is narrowed. A decompression from the back relieves the main canal and the side gutter and can open the foramen somewhat; when the pinch is from a bone spur or disc fragment and enough of the joint can be preserved, that may be all that is needed — and it has the real advantage of not destabilizing the level. But when the doorway is narrow mainly because the disc has lost height, reopening it usually takes one of two things: rebuilding the disc height with a spacer (which spreads the bones apart and lifts the roof of the doorway), or removing the facet joint to unroof the nerve directly. Both make the level unstable, so both require a fusion.

The science — for the curious

I work hard to avoid fusion when I responsibly can. Fusing a level stops it from moving, which shifts extra load onto the levels above and below and can speed their wear — and in a spine that has already begun to age, I want to do as little as possible to accelerate that. So I favor the least destabilizing operation that will solve the problem, and I push non-surgical care first. It also helps to know how the spine ages: some degeneration is normal, and when it happens slowly the spine usually stiffens and settles on its own — it may look arthritic on an X-ray yet never cause symptoms, as is true for many people. Trouble tends to come when a level breaks down faster than the body can stabilize it, and one worn level then hands stress to the next. Careful, staged treatment aims to keep you comfortable while disturbing that process as little as possible.

Learn more

American Academy of Orthopaedic Surgeons — OrthoInfo: orthoinfo.aaos.org

North American Spine Society — KnowYourBack: knowyourback.org

This handout is general education about a common condition and does not replace the personalized advice we discuss in clinic. If anything here does not match what we talked about, what we talked about wins — please ask me.