Spinal stenosis is narrowing of the spinal canal, lateral recesses, or neural foramina due to degenerative or congenital causes. Degenerative (acquired) spinal stenosis is the most common form, with aging-related disc bulging, ligamentum flavum hypertrophy, facet joint hypertrophy, and osteophytes contributing together. Central stenosis leads to cauda equina compression and neurogenic claudication (bilateral leg pain/numbness worsened by walking, relieved by sitting or forward flexion) is characteristic. Foraminal stenosis affects the exiting nerve root and causes radiculopathy. Lateral recess stenosis affects the traversing root. MRI is the gold standard modality; trefoil configuration and thecal sac compression on axial T2 sections are typical findings. Thecal sac AP diameter <10 mm is considered relative stenosis, <7 mm absolute stenosis. CT better demonstrates bone details and osteophytes than MRI. In the lumbar region, L3-4, L4-5, and L5-S1 are the most commonly affected levels. In cervical stenosis, myelopathy (cord compression) poses additional risk.
Age Range
50-85
Peak Age
65
Gender
Equal
Prevalence
Very Common
Degenerative spinal stenosis is the final stage of the spinal degenerative cascade. Pathological process: disc degeneration → disc height loss → segmental instability → increased load on facet joints → facet hypertrophy and osteophytes → ligamentum flavum hypertrophy (elastic fiber loss, collagen accumulation, fibrosis) → 360-degree narrowing of the canal. Disc bulging contributes anteriorly, ligamentum flavum hypertrophy posteriorly, facet hypertrophy posterolaterally → trefoil shape forms on axial section. Ligamentum flavum thickens 2-3 times normal (normal 2-4 mm → pathological >5 mm); particularly buckles toward the canal in extension → dynamic stenosis. Nerve root ischemia is the critical mechanism in spinal stenosis: canal narrowing + venous congestion → nerve root nutritional compromise → increased oxygen demand during walking cannot be met → neurogenic claudication. In forward flexion, canal diameter widens (ligamentum flavum stretches, facets open) → symptoms relieve. This mechanism differs from vascular claudication (peripheral artery disease): position change makes no difference in vascular type.
Trefoil (clover/triangular) shape of the spinal canal on axial T2-weighted MRI resulting from 360-degree narrowing. Formed by anterior disc bulging, posterior bilateral ligamentum flavum hypertrophy, and lateral facet joint hypertrophy. Pathognomonic imaging finding of degenerative spinal stenosis.
The spinal canal takes on a trefoil (clover/triangular) shape on axial T2-weighted MRI. This represents loss of normal oval/round canal shape. CSF space narrows anteriorly from disc bulging, is compressed posterolaterally by bilateral ligamentum flavum hypertrophy, and lateral recesses narrow from facet joint hypertrophy. Cauda equina roots within the thecal sac appear clumped (redundant nerve roots).
Report Sentence
The spinal canal shows trefoil configuration on axial T2 at __ level with central canal AP diameter measuring __ mm; consistent with __[relative/absolute] central stenosis.
Ligamentum flavum is bilaterally posterolaterally located and appears as hypointense thickened band on T2. Normal thickness is 2-4 mm; >4-5 mm is considered pathological. Hypertrophic ligamentum flavum buckles toward the spinal canal compressing the thecal sac posteriorly and posterolaterally. It is the main cause of posterior canal narrowing on axial images.
Report Sentence
Bilateral ligamentum flavum hypertrophy at __ level with maximum thickness measuring __ mm; contributing to posterior spinal canal narrowing.
On T1-weighted sagittal MRI, the neural foramen is normally filled with hyperintense fat tissue and the nerve root sits freely within this fat. In foraminal stenosis, disc bulging, osteophytes, and facet hypertrophy cause foraminal fat plane obliteration → foramen size decreases → nerve root is compressed. Foraminal fat obliteration on T1 is considered the earliest and most sensitive finding of foraminal stenosis.
Report Sentence
Foraminal fat plane obliteration in the __[left/right] __[L4-5/L5-S1] neural foramen on T1-weighted sagittal images, consistent with foraminal stenosis.
CT is the best imaging modality for facet joint degeneration. Facet joint hypertrophy, osteophytes, joint space narrowing, subchondral sclerosis, and vacuum phenomenon (intra-articular gas) are typical findings. Hypertrophic facets grow toward lateral recess and central canal contributing to stenosis. Bone anatomy and osteophyte relationship to spinal canal are visualized much more clearly on CT axial sections than MRI.
Report Sentence
Bilateral facet joint hypertrophy, osteophytes, and subchondral sclerosis at __ level on CT, contributing to lateral recess narrowing and central stenosis.
In severe spinal stenosis, cauda equina roots buckle and appear clumped proximal to stenosis — 'redundant nerve roots' sign. On sagittal T2, nerve roots show serpentine (snake-like) curves instead of normal parallel course. This finding indicates chronic, severe stenosis and suggests nerve roots have been under compression for prolonged period.
Report Sentence
Cauda equina root clumping and serpentine course proximal to __ level on sagittal T2, suggesting redundant nerve roots consistent with chronic severe stenosis.
Criteria
Narrowing of central spinal canal, thecal sac AP diameter <10 mm (relative) or <7 mm (absolute)
Distinct Features
Causes neurogenic claudication (bilateral leg pain, worsened by walking, relieved by sitting). Risk of cauda equina syndrome in severe cases
Criteria
Neural foramen narrowing, foraminal fat plane obliteration, exiting nerve root compression
Distinct Features
Affects exiting nerve root → causes radiculopathy of one level above. T1 sagittal foraminal fat obliteration is most sensitive finding. Disc osteophytes and facet hypertrophy are main causes
Criteria
Lateral recess (subarticular zone) depth <3 mm, traversing nerve root compression
Distinct Features
Affects traversing root (root going to level below). Facet hypertrophy and disc bulging together cause it. Lateral recess depth <3 mm is pathological
Distinguishing Feature
Disc herniation is usually single-level focal pathology with disc material extending beyond the canal; stenosis is multilevel diffuse canal narrowing
Distinguishing Feature
Spondylolisthesis has vertebral slippage with canal narrowing predominant at slippage level; stenosis shows degenerative narrowing without slippage
Distinguishing Feature
Synovial cyst is focal cystic lesion with facet joint relationship and rim enhancement; stenosis is diffuse canal narrowing without expected enhancement
Urgency
routineManagement
conservativeBiopsy
Not NeededFollow-up
6-monthSpinal stenosis is a chronic progressive condition. Mild-moderate symptoms respond to conservative treatment (physical therapy, NSAIDs, epidural steroid injection). Decompression surgery (laminectomy) is indicated for severe stenosis, neurogenic claudication refractory to conservative treatment, and progressive neurological deficit. Cauda equina syndrome is an emergency surgical indication. The SPORT trial showed surgical treatment to be superior to conservative treatment in the short term.
Spinal stenosis is an important cause of mobility limitation in the elderly population. Neurogenic claudication (decreased walking distance, relief with forward flexion) is characteristic. Mild-moderate stenosis is treated conservatively (physical therapy, epidural injection). Laminectomy/decompression surgery is indicated for severe stenosis or progressive neurological deficit. Cauda equina syndrome requires emergency surgery.