Morphometric analysis of the lumbosacral nerve roots and dorsal root ganglia by Magnetic Resonance Imaging [Spine 1996;21:1005-1009]

[Spine 1996;21:1005-1009] (link!!)

Summary

1. Study design: Imaging Study using MRI

2. Objectives:

           1) To determine the normal anatomic parameters of lumbosacral nerve root and DRG

           2) To compare above parameters to degenerative or pathologic changes

3. Summary of background data

           1) Various modalities in studying anatomic details of lumbar nerve root and DRG

           2) Conflicting data because of individual variations and different degree of degeneration

4. Methods

           1) 20 male volunteers with no back pain or radiculopathy

           2) Underwent MRI

           3) Mean age: 30.4 y (22-38)

           4) L1~S1 T1-weighted coronal MRI

           5) 233 nerve roots including 36-L1, 40-L2, 40-L3, 39-L4, 40-L5, 38-S1

5. Results

           1) Nerve root origin >> more cephalad level for caudad nerve root, specially S1

           2) Take-off angle change at L1 and S1 acutely

           3) Increasing the nerve root progressively to max at L5, but decreased at S1

           4) DRG center >> more cephalad at S1

           5) DRG average dimension >> gradually increased from L1 to S1

           6) S1 Root >> takes off more cephalad, shortest length of any nerve roots

           7) S1 DRG >> Largest and frequently located intraspinally *Unique!!

7. Conclusions

S1 radiculopathy may involve both nerve root and DRG because of disc herniation or degenerative L5-S1 facet changes.

Larger DRG, Greater DRG/foramen height rations in lower lumbar region >> higher incidence of L5 or S1 radiculopathy.

For the correct diagnosis, we need to know the spatial relationships of nerve root and DRG, then we could understand pathologic anatomy in degenerative disorders and proper surgical dissection of this region.

Figure 2: Lumbosacral nerve root and DRG

1. level of the nerve root origin

2. nerve root sleeve angulations (NRA)

3. length of the nerve root (NRL)

4. position of DRG

5. dimensions of DRG (DRGW= midpoint width; DRGL= midpoint length)

6. Height of DRG

7. Dimensions of pedicle (W= pedicle midpoint width; H= pedicle midpoint height)

8. Height of the intervertebral foramen (FH), IS =intraspinal, F= foraminal, EF= extraforaminal,

  AP= above the pedicle, U= upper third of the pedicle, M= middle third of the pedicle,

  L= lower third of the pedicle, BP= below the pedicle

About Foramens

[Foraminal Height]

 1) L1-2 >> 17.1±2㎜

 2) L2-3 >> 18.4±1.7㎜

 3) L3-4 >> 18.1±1.5㎜

 4) L4-5 >> 17.1±3.6㎜

[Rations of height of DRG/foraminal height]

1. mean rations of DRG Height/foraminal height

 1) L1-2 >> 25.2%±4.9%

 2) L2-3 >> 30.5%±6.7%

 3) L3-4 >> 40.9%±9.6%

 4) L4-5 >> 47.7%±7.9%

 5) L5-S1 >> 51.2%±14.2%

2. more caudad ration of DRG height/foraminal height

 1) L1-L2 and L2-L3 >> P < 0.0005

 2) L2-L3 and L3-L4 >> P < 0.0001

 3) L3-L4 and L4-L5 >> P < 0.005

 4) L4-L4 and L5-S1 >> similar

have a nice day~