Bertolotti Syndrome: Role of SPECT/CT in Distinguishing Benign Anatomical Variants from Suspicious Bone Lesions

Abstract: Bertolotti syndrome corresponds to a congenital lumbosacral transitional anomaly, characterized by a partial or complete articulation between the L5 mega-transverse process and the sacrum or iliac wing. Although common, it often remains underdiagnosed and can represent a true imaging pitfall, particularly in patients monitored for neoplastic disease, where any osseous uptake is initially suggestive of a secondary lesion. We report the case of a female oncology patient in whom technetium-99m bone scintigraphy revealed a suspicious lumbar focus of increased uptake. The contribution of SPECT/CT allowed correlation of the osteoblastic hyperactivity with a neo-articulation between L5 and the sacrum, thus confirming Bertolotti syndrome and ruling out metastatic involvement. This case highlights the major value of SPECT/CT in the differential diagnosis of atypical bone uptakes. By integrating morphological and functional information, SPECT/CT enables differentiation between a benign anatomical variant and a tumor lesion, thereby avoiding invasive investigations or inappropriate therapeutic decisions.