Neuroradiology
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The association of a lumbosacral transitional vertebra with accelerated degeneration of the disc above has been described. Lumbosacral transitional vertebrae have also been reported as a cause of extraforaminal entrapment of the L5 nerve root between the transverse segment of the transitional vertebra and the sacral ala optimally demonstrated by coronal MRI. The association of the lumbosacral transitional vertebra pseudoarthroses and S1 nerve root entrapment due to degenerative stenosis of the nerve root canal has never been described. ⋯ We emphasize the value of coronal T1WI MRI of the lumbosacral junction and sacrum if the cause for S1 radicular symptoms was not identified on conventional sagittal and axial MRI sequences in patients with lumbosacral transitional vertebrae.