Anterior decompression for far-out syndrome below a transitional vertebra: a report of two cases

Background contextImpingement of the L5 nerve between the transverse process of L5 and the ala of sacrum has been described as the far-out syndrome. Posterior decompression is often performed for this pathology.PurposeTo describe rare cases of far-out syndrome below a transitional vertebra who underwent anterior decompression.Study design/settingA case report and a review of the literature.MethodsReview of the hospital medical record, history, physical examination, and imaging studies.ResultsA 70-year-old woman and a 53-year-old man presented with prolonged and progressive leg pain and/or low back pain. Both of the patients showed muscle weakness and sensory disturbance at L5 level and lumbosacral transitional vertebra on the plain radiography. Magnetic resonance imaging showed huge osteophytes, and there was severe impingement of the L5 nerve at the anterior exit zone of the foramen. Anterior decompression was performed for both cases using a Fraser incision and resulted in successful resolution of the symptom and neurological status.ConclusionIn the extraforaminal stenosis of the L5 nerve with far-out syndrome below the transitional vertebra, entrapment occurs more anterior of exit zone of the L5 nerve foramen than in the other pathologies; anterior decompression brings in more complete decompression.