Bone marrow metastases in children's neuroblastoma studied by magnetic resonance imaging

Forty-one patients (pts) presenting with a neuroblastoma underwent 52 MRI to detect bone marrow metastases. Mean age was 4 years. Acquisitions were done with a 1.5 tesla unit. T1 and T2 weighted images were obtained in coronal (legs and pelvis) and sagittal (dorso-lumbar spine) sections. In 13 cases MRI was performed for initial staging, in 30 during the follow-up. 43/52 examinations were evaluable. Out of 24 anatomically proven medullary involvement (19 pts), MRI showed focal abnormal signals in 23 (18 pts): foci hypersignal in T2 weighted images and hyposignal in T1 weighted images compared to the normal bone marrow (BM) and fat tissue. The lesions were more often detected in lower limbs than dorso-lumbar vertebral body or iliac bone. Nineteen examinations were performed in 15 pts with cytologically and histologically normal BM. MRI raised suspicion of BM metastases in 5 pts (7 MRI). Out of those 5 pts, 1 (2 MRI) had BM relapse 9 months later; 1 (2 MRI) had intra cranial relapse 6 months later; 1 (1 MRI) is disease free 1 1/2 year later; the follow-up is too short for 2 remaining pts (2 MRI). MRI's specificity was 88.9% and sensitivity 84.4%.