A CASE OF EARLY DETECTION OF SEVERE ANOXIC-ISCHEMIC INJURY IN FETAL BRAIN OF A TWIN

1. A CASE OF EARLY DETECTION OF SEVERE ANOXIC-ISCHEMIC INJURY IN FETAL BRAIN OF A TWIN Marzia Mortilla MD, Erica del Giudice MD, Enrico Periti MD*, Claudio Fonda MD Pediatric Radiology, University Children’s Hospital A. Meyer, Firenze, Italy * Obstetrics & Gynecology, Misericordia Dolce, Prato, Italy

2. INTRODUCTION Multifetal gestations show peculiar patterns of complications. In cases of monochorionicity we can assist to abnormal vascular connections that lead to clinical problems (twin-to-twin transfusion syndrome, twin embolization with co-twin demise and twin-reversed arterial perfusion syndrome. If the twins are monoamniotic monochorionic we can also have additional complications such as conjoined twins. In dichorionic twins complications are very rare.

3. It has been described that multifetal pregnancies have two-fold higher perinatal mortality and a four to six fold higher perinatal morbidity compared to singleton pregnancies. US is the imaging of first approach and it is often reliable in evidenciating most of fetal complications. When a complication that offer challenge in diagnosis and management of the pregnancy, Magnetic Resonance (MR) can be used as a complementary technique able to detect better anatomic details and physiologic information.

4. CASE & METHODS A pregnant woman, 37 years old, at 19th gestational week. First pregnancy. Gynecologist detected an evident asymmetry of twin development by US. The smaller fetus showed slower movements and changing in heart beats rate. She was then referred to our Hospital in order to perform an MR scan.

5. A 1.5T MR scanner (Philips, Eclipse; gradients 27mT/m) with phase array abdominal coil was used. Acquisitions included Express FSE T2w images (turbo factor 128, 15 slices, 5mm thck, 128 x 128 matrix, breath hold) in transverse, sagittal and coronal planes through fetal twins brain. DWI images were acquired with Single Shot SE EPI with spectral fat saturation TR/TE 3000-6500/72-88ms, EPI factor 70-110, 4-5mm thck, 128 x128 matrix, acquisition time 18-20 sec), diffusion sensitizing gradient: b-value 0/600-800 sec/mm2.

6. RESULTS No alterations were found in the DWI images of normal developed twin. The other twin was smaller (cranial-perineum diameter 9.87cm vs. 12.28 cm and cranial area 852mm2 vs. 2146mm2). Cytotoxic edema is responsible of diffuse DWI TRACE hyperintensity. The hindered diffusion indicates the recent onset of hypoxic injury.

7. The asymmetric dimensions of the twins are evident

8. T2w images Brain of the normal fetus

9. T2w images Brain of the small fetus

10. DWI TRACE Normal fetus ADC values: - frontal WM 1,50 m2/ms - occipital 1,03 m2/ms ADC TRACE

11. DWI TRACE Small fetus ADC values: - frontal WM 2,12m2/ms - occipital 1,70 m2/ms ADC TRACE

12. In up to 20% of multifetal gestations a co-twin demise is described. This event is more common in the first trimester and in this case the loss of a twin has a negligible effect on the remaining twin. If the event occur in the second and third trimester there is a significant increase in the mortality and morbidity rate of the surviving twin (infarction, haemorrhage or necrosis of brain, liver and kidneys). It has been suggested that the underlying mechanism may involve a shunting of blood flow due to the loss of circulatory equilibrium. Other possible mechanism of infarction include embolic or thromboplastic DIC elements from demised twin.

13. A twin-reversed arterial perfusion (TRAP) occurs in 1% of monozygotic twins. The abnormal (perfused) twin receives deoxygenated blood via reversed flow of its umbilical artery and shows multiple malformations of the organs. The normal (pump) twin is at risk for high output congestive heart failure and hydrops fetalis.

14. CONCLUSIONS DWI used in MR fetal imaging may complete the morpho-functional data obtained by US about the nature and evolution of brain lesions. In this multifetal pregnancy we were able to detected in a twin a severe anoxic-ischemic injury that lead to his death.

15. Fetal MR imaging has clearly shown better details of the complications that we can find in twin gestations. DWI images are of invaluable help in demonstrating the degree of brain involvement. The normal MR findings of the other twin allowed the specialists and the pregnant woman to take the decision about continuing the gestation and the surviving twin did well after birth.

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