Role of L5 Nerve Root Morphology in Identification of Lumbosacral Transitional Vertebra. Is it a Reliable Indicator?

  Objective: To determine whether L5 nerve root morphology can assist in identification Lumbosacral Transitional vertebra. Study Design: Cross sectional study. Place and Duration of Study: Radiology Department, Combined Military Hospital, Multan Pakistan, Apr 2019 to Apr 2020. Methodology: Patients of both genders, 15 to 50 years age who underwent whole spine MRI were included in the study. Patients were referred from Combined Military Hospital Multan, from neighboring Combined Military Hospitals and Civil. Sagittal and axial T1WS and T2WS were performed along with coronal T2WS/FS sequences. Axial images were assessed for identification of L5 nerve root arising from LV5-SV1 level and hence vertebra was identified as LV5. Correlation was done with sagittal images for presence of Transitional vertebra, further confirmed by counting vertebral bodies from C2 vertebra upto sacrum using cross referencing tool. Results: A total of 135 patients were included in the study. Out of these, transitional vertebra was confidently labeled in 23 patients by nerve identification method which was confirmed on vertebral counting method. However, in four patients, L5 nerve root morphology was not clear and we had to rely on vertebral counting method for identification of transitional vertebra. Conclusion: Neuroanatomy and morphology of exiting L5 nerve roots can act as a reliable method for numbering of lumbosacral vertebra and identification of transitional vertebra.