Purpose or Case Report: Fetal demise (FD) occurs in 1/1000 pregnancies after 20 weeks gestation. MRI is increasingly being used after ultrasound to assess fetal pathology. FD may occur in the interval between ultrasound and MRI, and various organ systems have been described as having changes on fetal MRI. Although ultrasound findings of FD have been well described, criteria for FD on MRI have not. Diffusion MRI evaluates Na⁺/K⁺ channel viability and can be used to evaluate tissue death. Flowing blood produces signal loss on MRI, and along with fetal heart activity results in MRI signal loss of the cardiac chambers. FD with no heart motion and increased signal within non-flowing blood in the heart should result in increased signal in the chambers relative to the myocardium. Either of these findings can be seen with different fetal pathology, but the combination of brain and cardiac changes may allow for a diagnosis of FD. We hypothesize that restricted brain diffusion in certain brain lobes along with increased signal within heart chambers is specific for FD.
Methods & Materials: An IRB approved review of the 1374 pregnant women studied with MRI in a single institution between 2005 and 2015 found 13 FD, 8 of which had imaging of both their heart and brain. The other 5 FD only had imaging of their thorax and were excluded. The remaining 1361 fetuses were either born alive or were alive at a subsequent ultrasound, and were the comparison group for the 8 FD cases.
Results: Restricted diffusion was seen in brain regions including the lateral anterior half of the cerebral hemispheres (CH), lateral posterior half of the CH, temporal lobes, medial cortex of the CH, brainstem, and cerebellum in all 8 patients except for 1 patient who did not demonstrate restricted diffusion in the medial cortex. Of the patients whose deep grey matter was well seen, 5/6 showed restricted diffusion. All 8 demised fetuses showed increased signal within the cardiac chambers as compared with the fetal myocardium. None of the patients in the comparison group had both increased signal within the cardiac chambers and restricted diffusion in the lateral CH, temporal lobes, and cerebellum. The combination of restricted diffusion in the lateral cortex of the CH, temporal lobes, and cerebellum along with increased signal in the heart chambers differentiates between demised and alive fetuses (p<0.0001) using a Fisher exact test (two tailed), with a sensitivity of 100%.
Conclusions: Brain and cardiac changes can diagnose fetal demise on MRI.