1) Description of Measurement

Lumbar lateral recess depth (or width) quantifies the available osseous space for the traversing nerve root between the pedicle medially and the superior articular facet laterally/posteriorly. Narrowing of this region is a common cause of radicular pain and may occur even when central canal dimensions appear normal.

This CT-based measurement reflects bony encroachment from facet hypertrophy, osteophytes, or congenital narrowing.

2) Instructions to Measure

• Identify the lumbar level of interest using sagittal or coronal reconstructions.

• Scroll to the axial CT slice at the pedicle level where the lateral recess is best visualized.

• Identify:

• The medial border of the pedicle (anterior boundary), and

• The anteromedial edge of the superior articular facet (posterior boundary).
  
  

• Draw a straight line between these two points following the course of the traversing nerve root.

• Measure this distance in millimeters (mm) — this is the lateral recess depth / width.

3) Normal vs. Pathologic Ranges

• Normal: ≥ 5 mm

• Relative stenosis: 3 - 5 mm

• Severe lateral recess stenosis: < 3 mm

• Critical stenosis: Root obliteration

Key point:

Values < 3 mm strongly correlate with symptomatic nerve root compression.

4) Important Reference

Munakomi S, Cruz R. Lumbar Spinal Stenosis. 2024 Jan 30. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan–.

Schonstrom NS, Bolender NF, Spengler DM. The pathomorphology of spinal stenosis as seen on CT scans of the lumbar spine. Spine (Phila Pa 1976). 1985 Nov;10(9):806-11. doi: 10.1097/00007632-198511000-00005.

Li KY, Weng JJ, Li HL, et al. Development of a Deep-Learning Model for Diagnosing Lumbar Spinal Stenosis Based on CT Images. Spine (Phila Pa 1976). 2024 Jun 15;49(12):884-891. doi: 10.1097/BRS.0000000000004903.

5) Other info....

CT-based lateral recess measurements emphasize bony pathology; correlate with MRI for ligamentous and disc-related compression.

Should be interpreted together with:

• AP canal diameter

• Canal CSA

• Foraminal dimensions