Acquired Lumbar Central Stenosis

KEY FACTS

Terminology

Spinal canal narrowing in lumbar spine
- Secondary to multifactorial degenerative changes, being progressive and dynamic process

Imaging

Trefoil appearance of lumbar spinal canal on axial imaging
Sagittal diameter of bony lumbar canal < 10 mm

Top Differential Diagnoses

Disc herniation
Metastatic disease
Paget disease
Epidural hemorrhage

Clinical Issues

Chronic low back pain
Neurogenic claudication
- Leg pain (80%)
- Bilateral lower extremity pain, paresthesia, and weakness
- Relief of pain by squatting or sitting (flexion) in 80%
Bladder dysfunction and sexual difficulty (10%)
Radicular pain (10%)
Rare but important presentation: Legs suddenly “giving out”
Operative treatment includes surgical decompression or X-Stop interspinous implant-like devices
Natural history: Majority of symptomatic patients stable over months to years (40-70%)
- 1/3 improve with nonoperative treatment
- 1/3 deteriorate

Diagnostic Checklist

Axial T2WI mandatory for stenosis identification

Axial T2WI MR demonstrates severe central canal stenosis with marked facet degenerative arthropathy

. The thecal sac has assumed a trefoil appearance

Axial T1WI MR in another case shows central canal stenosis

primarily related to facet

and ligamentous hypertrophy/thickening

with little ventral epidural disease.

Sagittal T2WI MR shows severe central stenosis at L4-L5 due to marked posterior ligamentum flavum thickening

. Hyperintensity within the interspinous ligament denotes degeneration

, which is also called Baastrup disease or interspinous bursitis.

Sagittal T2WI MR shows canal stenosis at L3-L4 with a bulging disc and ligamentous thickening

. Note serpentine areas of low signal within the cephalad thecal sac due to redundant nerve roots

TERMINOLOGY

Synonyms

Spondylosis, central canal stenosis, lumbar canal stenosis

Definitions

Spinal canal narrowing in lumbar spine
Secondary to multifactorial degenerative changes, being a progressive, and dynamic, process

IMAGING

General Features

Best diagnostic clue
- Trefoil appearance of lumbar spinal canal on axial imaging
Location
- Most common in lower lumbar spine where there is the most mobility (L4-L5)
Size
- Sagittal diameter of lumbar canal < 12 mm relative stenosis
- Sagittal diameter of lumbar canal < 10 mm absolute stenosis
Morphology
- Obliterated perineural fat in lumbar neural foramina on sagittal imaging
- Narrowed lumbar lateral recess on axial imaging

Radiographic Findings

Radiography
- Disc space narrowing, osteophytes
- Facet osteoarthritis, spondylosis, spondylolisthesis
- Interpedicular distance narrowing if combined with congenital stenosis

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