Article Figures & Data
Figures
- Fig 1.
Contiguous axial T2-weighted (3800/97.8) MR images through the L5–S1 level show the 3 segments of the preneural foraminal portion of the S1 nerve root. In this patient, individualization of all of the 3 segments is possible within a single zone.
A, Cranial-most image demonstrates the lateral thecal sac segment of the right S1 nerve root (arrow) in the right central zone.
B, Image shows the junctional zone segment of the right S1 nerve root (long arrow) in the right central zone. This segment, which is situated in the proximal portion of the dural root sleeve, is separated from the contents of the neighboring thecal sac by 2 adjacent layers of dura mater (arrowhead). The thickness of a single layer of dura mater is demarcated (short arrow) in the posterior portion of the thecal sac for comparison.
C, More caudally, image demonstrates the dural root sleeve of the right S1 nerve root (arrow) in the right central zone. Individualization of the contained dural root sleeve segment of the S1 nerve root is not possible in this patient.
- Fig 2.
Contiguous axial T2-weighted (3700/106.7) MR images through the L5–S1 level show the varying appearances (also refer to Fig 1B) of the proposed “junctional segment” of a lumbar nerve root.
A, Image demonstrates the junctional segment of the left S1 nerve root (long arrow) within the “pinched” portion (arrowheads) of the left ventrolateral angle of the thecal sac. The unrestricted contour of the right ventrolateral aspect of the thecal sac harbors the lateral thecal sac segment of the ipsilateral S1 nerve root (short arrow).
B, Image at a slightly more caudal level shows the proximal-most portion of the left S1 dural nerve root sleeve (arrowheads), the medial wall of which is in close apposition to the ventrolateral wall of the neighboring thecal sac. This portion of the dural root sleeve is also regarded as housing the junctional segment of the S1 nerve root (arrow).
- Fig 3.
Axial T2-weighted (4000/98) MR image at the diskal-suprapedicular level of L5–S1 demonstrates the nonparallel segmentation of the S1 nerve roots. On the right, the lateral thecal sac segment (arrow), and on the left, the junctional segment (arrowhead), of the S1 nerve roots are visualized.
- Fig 4.
Contiguous axial T2-weighted (3800/97.8) MR images through the L5–S1 level with the S1 dural nerve root sleeves (individualization of the dural root sleeve segments of the S1 nerve roots within their respective dural sleeves is not possible in this particular patient).
A, Cranial-most image demonstrates the right (long arrow) and left (short arrow) S1 dural nerve root sleeves within the subarticular zones.
B, Image at a slightly more caudal level shows a mild central-subarticular zone disk protrusion that causes a relatively severe compression of the right S1 dural nerve root sleeve (long arrow). The left-sided intact complex is demarcated (short arrow) for comparison.
C, The S1 dural nerve root sleeves (long and short arrows) assume a symmetric appearance at a slightly more caudal level.
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