Discordance Between Anatomical Nerve Root Compression and Functional Radiculopathy in Patients with Lumbosacral Transitional Vertebrae

Background/Objectives: Lumbosacral transitional vertebrae (LSTV) are associated with alterations in spinal anatomy and biomechanics that may complicate localization of symptomatic nerve root pathology. However, the relationship between anatomically defined nerve root compression on magnetic resonance imaging (MRI) and electrophysiologically identified radiculopathy on electromyography (EMG) remains insufficiently characterized. This study aimed to evaluate concordance between MRI-identified nerve root compression and EMG-identified radiculopathy and to investigate whether transitional morphology influences this relationship. Methods: A retrospective analysis was performed in patients with LSTV who underwent both MRI and needle EMG for single-level lumbosacral radiculopathy. Transitional vertebrae were classified as lumbarization or sacralization and further categorized as complete or partial. Concordance between the anatomical level of nerve root compression and the electrophysiological level of radiculopathy was assessed. Clinical and radiographic variables potentially associated with discordance were analyzed. Results: Twenty-nine patients were included. Concordance between MRI-defined nerve root compression and EMG-identified radiculopathy was observed in 27.6% of cases, whereas 72.4% demonstrated discordance. The degree of transitional morphology significantly influenced concordance patterns, with complete transitional vertebrae showing a higher rate of discordance compared with partial transitions. Conclusions: In this exploratory cohort, patients with LSTV showed a high rate of anatomical–functional discordance between MRI and EMG findings. Complete transitional morphology is associated with increased discordance, suggesting altered functional expression of nerve root pathology. These findings suggest that anatomical and electrophysiological assessments may provide complementary information during diagnostic evaluation in selected patients with LSTV.