2013년 9월 2일 월요일

Spine update lumbar foraminal stenosis


Title: Spine Update, Lumbar Foraminal Stenosis

1. Introduction
About Lateral nerve root canal
             >> Tubular-Shaped Region
             >> Passing Nerve Root from thecal sac to intervertebral foramen

Previous definitions of Foramen
1) Lee et al (19): 3 distinct areas in figure 1A
             >> Entrance or Lateral recess zone
             >> Midzone
             >> Exit zone
2) Crock (6): Single sagittal slice or "window" in figure 1B
3) Current: Vertical interpedicular zone incorporating portions of lateral recess and exit zone (19) in figure 1C

Figure 1
>> A: Diagram of lumbar spine, depicting region of the lateral nerve root canal
>> B: Depicting the foramen or "window"
>> C: Depicting the intervertebral foramen or vertical interpedicular zone

What is the Lateral spinal canal stenosis?
             >> common etiology of lumbar radicular symptomatology
             >> 8~11% incidence of lateral root entrapment (18, 26, 31)
             >> sometimes, associated with failed back surgery syndrome (3, 22)

Why did the authors do this research?
       >> to review anatomy, clinical presentation, neuroradiographic evaluation, treatment of pathology located in the intervertebral foramen

2. Anatomy
Foramen
>> oval, round, or inverted teardrop-shaped "window" in lumbar spine
>> different aspects between upper lumbar spine and lower lumbar spine

Dorsal Root Ganglion (DRG) in foramen
>> associated with symptomatology
>> potential mediator of low back pain
>> exiting nerve root compression in foramen -- radicular symptoms

3. Pathoanatomy
Why does the foraminal stenosis develop? (Incidence)
1) related to the process of lumbar spondylosis
             *normal Foraminal height: 20~23 mm
             *normal width of superior foramen: 8~10 mm, 40~160
             *references: 8, 30
>> compressed nerve root: 15mm (FH) or less, 4 mm (posterior DH) or less
             might be indicators of foraminal stenosis
>> subluxation of superior facet alteration of biomechanical forces development of hypertrophic ligamentum flavum and bony spurs diminishing foramen volume

2) cranio-caudal compression (vertical stenosis)
>> posterolateral osteophytes from vertebral endplates
  >> protrude into foramen along with laterally bulging anulus fibrosis or herniated disc
    >> compress nerve root against the superior pedicle

3) according to the positions (13)
>> 21% in neutral position
>> 15.4% in flexion position
>> 33.3% in extended position

4) according to the parts of lumbar spine (1)
>> 75% in 5th lumbar root
>> 15% in 4th lumbar root
>> 5.3% in 3rd lumbar root
>> 4.0% in 2nd lumbar root

4. Imaging studies
>> Plain radiographic lateral view: depict intervertebral foramen
       * caution for misleading because of oblique direction of foramen in lumbar spine
>> Myelography: documentation of central canal stenosis
>> CT and MRI: evaluating and quantifying the degree of foraminal stenosis
       1) CT: detection of bony encroachment of the zone
              *better detection of the space available for nerve root in parasagittal image
       2) MRI: Central and lateral spinal canal pathology
        *better detection of foramina along the length of lumbar spine in parasagittal image

5. Treatment
   1) conservative treatment
   2) Epidural steroid injection/selective nerve root blocks
   3) Limited decompressive procedures
                   >> laminotomy or laminectomy
                   >> medial facetectomy
                   >> medial foraminotomy
                   >> muscle splitting Wiltse or lateral approach to foramen with foraminotomy
   4) Direct decompressive procedure alone: most patients with Foraminal stenosis
   5) Concomitant indirect foraminal "enlargement", fusion or both: subset of patients
                   >> in fusion: increasing the foramen size and maintaining or restoring lordosis

6. Summary
>> Although no pathognomonic clinical findings, High index of suspicion for any patients with exacerbation of leg pain from lumbar extension

>> Surgical considerations: location of compression of exiting nerve root/ presence of concomitant areas requiring decompression

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