Dural metastases responsible for benign vertebral collapses

Abstract

A 17-year-old male patient was transferred to our centre for an invasive ethmoidal carcinoma extending to both frontal lobes of the brain. Bone scintigraphy with single photon emission tomography (SPECT) showed hyperactivity at the level of the 3 to 5 and 7 to 9 vertebral bodies of the dorsal spine. Standard X-ray suggested benign bone fractures. F-fluorodeoxyglucose (FDG) positron emission tomography (PET) showed no increased uptake of the tracer in any vertebral body but there were highly hypermetabolic lesions posterior to the vertebral body at multiple levels where hyperactivity was present on the bone scan images. Magnetic resonance imaging (MRI) showed multiple metastases in the intradural extramedullary space evoking benign bone fractures, confirming the PET observations (see figure). The most probable phenomenon explaining the association of intradural metastases with benign bone fractures is vascular compression leading to vertebral infarction [1]. Indeed, vertebral infraction may accompany anterior spinal artery syndrome since the arterial supply to the dorsal part of the vertebral body derives from this artery [2]. The present observation reveals an unexpected pathophysiology for the association of bone and dural spinal lesions in advanced cancer. Classically, this association is attributed to primary bone metastasis secondarily invading the extradural space [3]. The present case unveils a possible reversed link between vertebral and dural lesions. This phenomenon is certainly far less frequent than the invasion of the extradural space by cells emanating from a vertebral metastasis. Intradural extramedullary metastasis is indeed a rare situation consequent to tumour cell spread from the blood stream and lymphatics, or from intracranial cancer sites [4], as was probably the case in our patient. Practically, the present case draws attention to the fact that “benign” vertebral collapses may be the stigmata of malignant invasion of the spinal canal in patients with cancer.