‘Flip Flop phenomenon’- MRI imaging artifact (Authors- DR Monojit Mondal and Dr Suchi Gaba)
Serous atrophy of bone marrow
A 66 year old cachectic and weak female presented to the emergency department with increasing confusion and memory problems. The patient also reported muscle weakness and wasting in the lower limbs. She had previously known comorbidities of anorexia nervosa and hypothyroidism.
Whole spine MRI was done to rule out any neurological pathology. Initial MRI of the whole spine was done in 1.5 T MRI. The T1 weighted sagittal sequence images (Fig. 1A) appeared grossly abnormal. It appeared that fat saturation sequences were inadvertently selected whilst obtaining these images. The images revealed homogenous signal suppression of fatty bone marrow and subcutaneous fat in the whole spine. The T2 weighted sagittal images (Fig. 1B) revealed heterogenous variegated marrow signal, however, there was normal appearances of spinal cord and cauda equina nerve roots. The initial interpretation of the MRI was thought to be either a manifestation of systemic pathology with a diffuse skeletal infiltrative pattern or possible equipment malfunction/ inappropriate selection of sequences. Owing to concern of underlying infiltrative disorders, the patient was recalled for a repeat MRI spine on a 3 Tesla Siemens MRI scanner. T1 (Fig. 2A) and STIR W.I sequences were acquired in this scanner, which reproduced the same imaging pattern as observed in the previous 1.5 T MRI scan images. There was no difference in image comparison on two sets of scans obtained with 1.5T and 3T MRI either with or without fat saturation selection, T1 images were similar despite the manual selection of the MR parameters and frequency adjustment. Fluid sensitive STIR sequences (Fig. 2B) showed heterogeneous bone marrow which appeared as bright (hyperintense) due to incomplete suppression suggesting edema or infiltration. Spinal cord and cauda equina nerve roots appeared normal. Contrast enhanced CT of chest, abdomen, and pelvis revealed no mass lesion or generalized lymphadenopathy, however, did show almost complete non-visualization of subcutaneous and intra-abdominal fat (Fig. 3). In comparision, MRI spine performed in 2011 revealed normal appearances of bone marrow and subcutaneous fat on T1 and T2 W images (Fig 4).