The cold vertebral lesion on ¹⁸F-Fluoride PET/CT: Do not forget vertebral osteonecrosis (Kuemmell's disease)

A 75-year-old woman presented with a history of severe backache and spinal cord compression syndrome. MRI revealed a well-circumscribed, homogeneous, wedge-shaped lesion involving T11 vertebral body, which was hypointense on T1- and hyperintense on T2-weighted images with bulging posterior border. Patient benefited from a decompressive T10-T12 laminectomy. Four months later, a new vertebral collapse of T10 was evidenced on plain X-rays. A second MRI exam displayed worrisome diffuse signal abnormalities of T10 pointing to a space-occupying lesion. A (¹⁸F)-NaF PET/CT was ordered and disclosed an hypometabolic ('cold') activity of T10 and T11 vertebral bodies with a partial postero-lateral hypermetabolic rim. Twined low dose CT evidenced fracture sequelae and air-filled cleft within vertebral bodies. Histopathologic examination of the biopsy specimen of T10 revealed thinned out trabeculae surrounded by hyalinized fatty marrow cells and fibrovascular tissue, thus ascertaining the diagnosis of avascular necrosis of the vertebra. The radiographic and CT sine qua non for Kuemmell's disease is intraosseous vacuum phenomenon. That is to say, vacuum clefts (VCs) of the vertebral bodies are radiographically recognized as a vacuum or air-filled cleft within the collapsed vertebrae. This sign is felt to be suggestive of ischemic necrosis but not specific as VCs of the vertebral bodies have also been associated with delayed union or non-union of osteoporotic fractures. Because of often misleading MRI abnormalities, integrative interpretation of (¹⁸F)-NaF PET/CT pattern should be undertaken in order to suspect Kuemmell's disease and to discard some of the differentials. (authors)