Foraminal stenosis

In one minute

Foraminal stenosis is a narrowing of the tunnel (the foramen) through which a nerve root leaves the spine; lateral recess stenosis is narrowing of the corner just inside the canal where the root turns toward that tunnel. Both squeeze one root and produce sciatica-like pain in one leg. They are conditions of the worn spine, mostly in later life, and a common cause of one-sided leg pain when there is no disc herniation to blame. The pain is often present at rest, worse on standing straight, arching backward or lying on the painful side, and less tied to sitting than a disc herniation. MRI (magnetic resonance imaging) with a standard grading confirms it. Many people manage with activity changes, exercise and an injection; when the pain persists, the tunnel is reopened, which we do through a 7 mm incision, without screws or implants.

What it is

Each lumbar root leaves the canal through a foramen bounded above and below by the pedicles of two vertebrae, in front by the disc and behind by the facet joint. A 2023 scoping review gives the normal foramen a height of 20 to 23 mm and a width of 8 to 10 mm, with a height under 15 mm or a disc height at the back under 4 mm indicating severe compression. Surgeons divide the side of the canal into three zones: the lateral recess (from the edge of the dural sac to the inner edge of the pedicle), the foramen (between the pedicles) and the extraforaminal zone beyond it. The root that runs through the lateral recess at one level is the one that will exit at the level below, so a narrowing at L4-L5 pinches the L5 root in the recess and the L4 root in the foramen. Regional reports may say "фораминальный стеноз" or "латеральный стеноз", or bundle it into "остеохондроз".

Causes and risk factors

The scoping review lists the usual suspects: loss of disc height, which brings the pedicles closer together; enlargement of the facet joint and its capsule; osteophytes (bone spurs) on the back edge of the vertebra, commonest at L5-S1; thickening of the ligamentum flavum; synovial cysts; and a vertebra that has slipped forward or, after previous surgery, become unstable. A disc fragment can also herniate straight into the foramen or beyond it; in the 2022 BMJ discectomy trial, 12% to 13% of herniations were inside the foramen and 6% to 8% beyond it. All of these are consequences of age and load, so the risk factors are those of disc degeneration in general.

How it develops

A disc that has lost height lets the vertebra above settle onto the one below, and the foramen loses height with it. The facet joint behind, now carrying more load, thickens and grows spurs. The part of the tunnel level with the disc, already the narrowest, is the first to close. Standing upright and arching backward narrow the foramen further; the review cites a 30% reduction in its cross-section in extension, which is why patients learn to lean forward. Because the squeeze is constant rather than triggered by movement, the pain tends to be there at rest, and because what squeezes is bone and ligament rather than disc, the body cannot digest it the way it digests a herniated fragment.

Symptoms

Leg pain in the territory of one root is the rule; most patients also have back pain felt in the buttock. The review describes the distinguishing pattern: pain at rest, aggravated by lying flat, by sitting and by lying on the affected side, while a central disc herniation is aggravated by bending forward and produces positive nerve stretch tests. Weakness, numbness or a lost reflex in the same root may be present. Because the pattern is less obvious than a disc herniation, diagnosis is often delayed; in one series cited by the review, leg symptoms had lasted a mean of 15 months. Neighbours to tell apart: a disc herniation (sudden onset, worse sitting, positive straight leg raise), central spinal stenosis (both legs, worse walking, better sitting) and hip arthritis (groin pain, limited hip rotation).

Diagnosis

The examination maps the root: strength, sensation and reflex for L4, L5 and S1, plus a check of the hip. MRI is the test; the North American Spine Society (NASS) suggests it as the most appropriate non-invasive test for degenerative narrowing and adds that any grading of lateral recess or foraminal stenosis should describe loss of the fat around the root, displacement of the root and compression of it. The side-view (sagittal) images show the foramen most clearly. Radiologists use the Lee grading: grade 0 is a normal foramen; grade 1 (mild) loses the fat around the root in two opposing directions (above and below, or in front and behind); grade 2 (moderate) loses it in all four directions with the root still normal in shape; grade 3 (severe) shows the root flattened or collapsed. Conventional MRI is sensitive but not specific: the review quotes 96% sensitivity and 67% specificity for symptomatic foraminal stenosis, so a grade 1 or 2 finding without matching symptoms means little. CT (computed tomography) shows the bone spurs; standing X-rays in flexion and extension show whether the segment moves. When the picture and the symptoms disagree, a selective nerve root block (an injection of anaesthetic around one root under X-ray) tells the surgeon whether that root is the one that hurts.

If you send us images, include the report, the side-view images at the level named, and a sentence on which positions hurt.

Treatment without surgery

First-line care is the same as for any radicular pain: stay active, avoid the positions that arch the back, a supervised exercise programme (in our experience one that favours flexion and hip strength), short courses of anti-inflammatory medication decided by the doctor, and manual therapy as part of an exercise package. NICE (the English guideline body) advises against belts, traction and acupuncture.

A transforaminal epidural steroid injection places the steroid where the root is pinched and doubles as a diagnostic test. Its benefit is real but modest and short: the 2020 Cochrane review of 25 trials found a small advantage over placebo for leg pain and disability in the short term, about 5 points on a 100-point scale. It buys weeks to months and clarifies the diagnosis; it does not reopen the tunnel. Because the narrowing is bone and ligament rather than a disc fragment the body can digest, spontaneous resolution is less likely than with a herniation, and the weeks of conservative care that precede any surgical decision serve to control pain and confirm the diagnosis rather than to wait for a cure.

When surgery is considered

Jenis and An, in their Spine review, set the criteria that still apply: significant leg pain refractory to conservative treatment, and concordance between the area of stenosis on imaging and the root implicated by symptoms and signs. NICE frames it the same way for sciatica of any cause: consider decompression when non-surgical treatment has not improved pain or function and the radiological findings match. Progressive weakness brings the decision forward. Timing is about quality of life rather than a closing window, but long-standing compression can leave lasting numbness, and the scoping review lists undertreated or ignored foraminal stenosis among the commonest reasons for pain that persists after spine surgery.

Surgical options

• Open foraminotomy: through a midline incision, or through a muscle-splitting incision about 3 cm to the side (the Wiltse approach) when only the foramen is involved. Bone at the edge of the joint is removed to free the root. The surgeon must leave more than half of each facet joint intact; taking more risks instability and a later fusion.
• Microscopic or tubular foraminotomy: the same steps through a tube, with less muscle damage.
• Transforaminal endoscopic foraminotomy: the endoscope is docked at the safe triangle beside the exiting root, and the bone spur and the front edge of the facet are shaved with minimal removal of the joint. A 2022 single-arm meta-analysis of nine studies and 316 patients reported a 12-month improvement of 5.4 points on a 10-point pain scale and 40 points on the 100-point disability index, with 11.5% adverse events, mostly transient tingling in about 11% of patients. See endoscopic foraminotomy. Where the recess is the problem, the operation is an endoscopic lumbar decompression.
• Decompression with fusion: needed when the segment is unstable, when a slipped vertebra has closed the foramen, or when freeing the root would remove too much joint. A fusion with an interbody cage restores disc height and opens the foramen indirectly. NASS suggests decompression alone for leg-dominant symptoms without instability. We perform fusion fully endoscopically with a cage and percutaneous screws: endoscopic lumbar fusion.

How we treat it at spine.uz

Endoscopic spine surgery in Tashkent for a pinched nerve root

Send your MRI on Telegram or WhatsApp. The remote opinion is free; a doctor from the team replies by voice within 48 hours and tells you whether the tunnel, the recess or the disc is the problem. The in-person consultation and the operation are paid.

When surgery is indicated, we reopen the foramen through a 7 mm incision, most often under local anaesthesia with sedation rather than general anaesthesia; the anaesthetist and surgeon decide per patient. Decompression uses no screws or implants. Most patients walk on the day of surgery and go home within 24 hours. We are Tashkent's first endoscopic spine team, five surgeons operating as one team, with 27,600+ endoscopic and spine operations and a complication rate well below 1% in our own series. You leave with a written team conclusion.

Recovery and outcomes

Radicular pain from a mechanical squeeze usually eases within days of decompression. In the meta-analysis above, leg pain and disability at 12 months were both substantially improved, and the commonest problem was temporary tingling in the leg, seen in about one in ten patients, which settles over weeks. Numbness that was present for many months before surgery improves more slowly and may persist in part; that is the argument against waiting years. Reoperation becomes necessary when instability declares itself or a neighbouring level narrows; keeping the joint intact at the first operation is the surgeon's main lever on that risk.

Living with it and prevention

Avoid sustained arching of the back: standing for long periods, sleeping flat on the stomach, overhead work. In our experience, sleeping on the side with a pillow between the knees, or on the back with the knees raised, is more comfortable. Keep the hips strong and the weight down. Stop smoking. If the leg pain returns after a good result, ask for a review rather than assuming it is the same problem; a neighbouring level is often the reason.