1. LABELING THE LUMBAR VERTEBRAL BODIES: IS THERE A PROCESS YOU CAN COUNT ON? L Griffin 1, M Hoch 1, Raz E 1, N Perin 1, T Naidich 2, G Fatterpekar 1 ASNR Electronic Poster Annual Meeting April 27, 2015, Chicago IL 1 NYU Langone Medical Center, New York, NY 2 The Icahn School of Medicine at Mt. Sinai, New York, NY

2. BACKGROUND Accurate, consistent numbering of the lumbar spine is necessary to communicate the level of pathology A reliable way to identify and label spines with lumbosacral transitional vertebrae (LSTV) has not been established

3. BACKGROUND Many features on MRI have been proposed 1,2 Iliolumbar ligament Disc morphology Level of anatomic structures

4. BACKGROUND Research in cadavers suggests a significant difference between the craniocaudal dimensions of the L3-L5 spinous processes 3,4

5. PURPOSE Use of spinous process height would be quick and applicable to both CT and MRI Determine if craniocaudal height can be used to reliably identify the lumbar vertebrae level in normal spines and those with LSTV

6. MATERIALS and METHODS Retrospective review of total spine MRI performed for any clinical reason from January 2013 through December 2014 Lack of a reported LSTV constituted a “normal” case LSTV cases were identified using search terms “transitional” “lumbarized” and “sacralized” Gold standard: labelling levels from C2 On sagittal whole body counter sequence, upper and lower spine counter sequences from C2, landmarks were used if a whole body counter was not available Spinous process craniocaudad dimension from T12 – S1 was measured on sagittal T1 weighted sequences From superior to inferior cortex, perpendicular to long axis of spinous process Differences in dimension were analyzed within the whole group and between the transitional and normal groups Interobserver reliability was assessed in a subset of 40 cases

7. RESULTS A total of 81 cases were reviewed 52 normal, 29 transitional (18 lumbarized L5 and 11 sacralized S1) 40 male (49%), age 54 +/- 18 years (range 17 – 92 years) Table. Comparison of Spinous Process Craniocaudal Dimensions Normal (52 cases) Transitional (29 cases) All (81 cases) Cases when L5 was smaller than L4 50 (96%)26 (90%)76 (94%) Cases when T12 was smaller than L1 43 (83%)28 (97%)71 (88%)

8. RESULTS L5 S1 L5 T12 L5 smaller than L4 (p < 0.001 for all) S1 smaller than L5 for lumbarized cases (p < 0.0001) T12 smaller than L1 (p < 0.05 for all)

9. RESULTS There was moderate agreement between readers on all cases (kappa 0.60), normal cases (kappa = 0.54) and sacralized cases (kappa = 0.48), all p < 0.0001 Substantial agreement was reached in identifying lumbarized cases (kappa 0.73, p < 0.0001) Table. Subset Reviewed by Three Reviewers NormalLumbarized S1Sacralized L5 Counting from C2121810 Clinical Report141610 Reader 1131611 Reader 219165 Reader 313198

10. Example 1: 54YO Male, Suspicion for drop mets 1. Find smallest spinous process 2. Find transition to bulbous spinous processes LABEL L5 LABEL L1 Confirmed with counting from C2

11. 2. Find transition to bulbous spinous processes LABEL L5 1. Find smallest spinous process LABEL L1 Lumbarized S1 LABEL L5 1. Find smallest spinous process 2. Find transition to bulbous spinous processes LABEL L1 3. Raises possibility of lumbarized S1 Example 2: 17-year-old male with neurofibromatosis type I

12. Example 3: 63 YO for Follow Up LABEL L5 1. Find smallest spinous process 2. Find transition to bulbous spinous processes LABEL L1 3. Sacralized L5

13. Quiz; 56-year-old male with multiple myeloma. Identify L5 Confirm L1 Check Yourself

14. CONCLUSIONS Identifying the shortest spinous process could be a reliable marker for labelling L5, obtained quickly by visual inspection L1 is larger than T12 a majority of the time and can be used to troubleshoot when question of LSTV Overall accuracy of the shortest lumbar spinous process correlating with L5 is 94%, which is the same as use of the iliolumbar ligament to identify L5 5

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