DOI: 10.1148/radiol.2232001614
(Radiology 2002;223:392-395.)
© RSNA, 2002
Case 46: Encephalomalacia in Surviving Twin after Death of Monochorionic Co-twin1
Deborah Levine, MD
1 From the Department of Radiology, Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA 02215. Received October 3, 2000; revision requested November 16; revision received December 27; accepted January 16, 2001. Supported by grant NS37945 from the National Institutes of Health. Address correspondence to the author (e-mail: dlevine@caregroup.harvard.edu).
Index terms: Diagnosis Please • Fetus, death, 856.825 • Fetus, MR, 856.1214 • Fetus, US, 856.1298 • Infants, central nervous system, 10.146 • Twins, abnormalities
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HISTORY
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A 28-year-old pregnant woman was referred for fetal evaluation at 24 weeks of gestation. Ultrasonographic (US) scans (Figs 1, 2) and magnetic resonance (MR) images (Figs 3–7) were obtained.
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Figure 1. Sagittal transabdominal US scan of the lower uterine segment with coronal view of the posterior aspect of the fetal head shows enlarged ventricles (v), with echogenic margins. The surrounding cortex was not visualized posteriorly, and this finding is consistent with enlarged cerebrospinal fluid spaces in those regions owing to cortical atrophy.
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Figure 3. Transverse half-Fourier single-shot RARE MR image (repetition time msec/echo time msec, single shot/60; field of view, 25 x 30 cm; matrix, 192 x 256; echo train length, 72; signal acquired, one; section thickness, 4 mm) of the uterus shows a single anterior placenta (P) and two fetal torsos. The fetal body at left on the image has marked skin thickening (curved arrows), pleural effusions (black arrowheads), pericardial effusion (white arrowhead), and high signal intensity within the cardiac chambers (straight black arrow). The high signal intensity in the heart suggests death, since there is no flowing blood. The fetus at right on the image has ascites (straight white arrow).
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Figure 4. Transverse half-Fourier single-shot RARE MR image (same parameters as in Figure 3) of the uterus. The fetal head (dead fetus) at left on the image is small compared with the fetal body (live fetus) at right. Skin thickening is present about the small head (open arrow). The extraaxial cerebrospinal fluid spaces are effaced. The ventricles (solid arrows) are small.
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Figure 5. Transverse half-Fourier single-shot RARE MR image (same parameters as in Figure 3) of the fetal head. There is marked cortical atrophy, with only the ventricular wall (arrows) seen in the occipital region. This head cannot be that of the dead fetus depicted in Figure 3 since the extraaxial spaces in this image are prominent, and the ventricles are enlarged.
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Figure 6. Coronal half-Fourier single-shot RARE MR image (same parameters as in Figure 3) of the fetus (oriented to fetal anatomy) shows area of porencephaly (black arrow). This corresponds to the abnormal region seen in Figure 2. The low signal intensity of flowing blood can be seen in the fetal heart (solid white arrows). Ascites (open white arrow) is seen in the fetal abdomen, a finding that confirms that this image corresponds to the fetus shown at right in Figure 3.
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Figure 7. Coronal T1-weighted MR image (114/4; flip angle, 80°; field of view, 34 x 34 cm; matrix, 160 x 256; signal acquired, one; section thickness, 4 mm) of the fetal head shows areas of increased signal intensity (arrows), findings that are consistent with either hemorrhage or mineralization.
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IMAGING FINDINGS
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The US scans (Figs 1, 2) showed an abnormal fetal head with mildly enlarged ventricles and cortical atrophy. The extraaxial spaces were enlarged, and the cortical margins were irregular and echogenic. The half-Fourier single-shot rapid acquisition with relaxation enhancement (RARE) MR images of the uterus (Figs 3, 4) showed two fetuses and a single anterior placenta. The fetus at left on the images was smaller than that at right and had high signal intensity within the heart (Fig 3), along with skin thickening and pleural effusions. The high signal intensity in the heart is consistent with death, since rapidly flowing blood is of low signal intensity when MR imaging of the fetus is performed with the single-shot RARE technique (Fig 6). Visualization of the intracranial anatomy of the dead fetus was poor, and the ventricles and extraaxial spaces were small (Fig 4), which helped distinguish between this fetal head and that seen in Figures 1, 2, 5, 6, and 7. The death of the twin occurred 3 weeks before the images in this case were obtained.
Ascites was present in the fetus at right, the live fetus, in Figures 3 and 6. The half-Fourier single-shot RARE MR images of the head (Figs 5, 6) of the live fetus showed that, in addition to the mild ventriculomegaly, there was marked diminution of the cortex with multiple regions of atrophy and cystic encephalomalacia. The T1-weighted MR image (Fig 7) showed areas of high signal intensity, which were consistent with either mineralization or hemorrhage.
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DISCUSSION
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The key to this case is the recognition of the monochorionic twin pregnancy, with only one of the twins being alive. Figures 3 and 4 clearly show the single anterior placenta and two fetuses. The torso at left in Figure 3 has high signal intensity within the heart. Typical single-shot RARE MR imaging of the fetus allows images to be obtained in 430 msec, which effectively freezes fetal motion. However, since blood is continuously flowing in the fetal heart, the signal intensity is low in the normal beating heart (Fig 6). The head of the fetus at left in Figure 4 shows skin thickening similar to that seen in the torso in Figure 3. The head size, ventricles, and extraaxial spaces were small in this dead fetus. The remaining images are of the head of the surviving fetus. Findings at examination of monochorionic twins, one of which was small and not alive and the other of which was alive with porencephaly, suggest the diagnosis of encephalomalacia in the surviving twin after the intrauterine death of the monochorionic co-twin.
In addition to the risks that all twin pregnancies have of preterm delivery and increased incidence of congenital anomalies, monochorionic twins are at risk for twin-twin transfusion syndrome (TTS) owing to the vascular connections in the shared placenta. In this syndrome, there is oligohydramnios and growth restriction of the small donor twin and volume overload and hydrops of the recipient twin. The surviving twin in a pair of monochorionic twins is at especially high risk of morbidity and mortality if the death of the co-twin occurs in the second or third trimester. The shared placenta puts the surviving twin at risk for sequelae, such as porencephaly, multicystic encephalomalacia, renal cortical necrosis, atresia of the small bowel, and aplasia cutis (1,2).
In a 1985 review (3) of published cases, the frequency of antepartum death of one twin varied from 0.5% to 6.8% of all deliveries of twins. In a 1998 study (4) of 31 cases of twin-twin transfusion, in 11 pairs of twins, the death of one twin occurred in utero. In these 11 pairs, the surviving twin subsequently died in three cases, the surviving twin was severely handicapped in two cases, and the surviving twin had transient changes that were demonstrated on US scans of the head after birth in two cases.
It has long been recognized that cerebral white matter necrosis and associated cerebral palsy are more common in preterm twins than in preterm singletons (1). In a study of preterm twins with US scans of the head obtained in the first 3 days of life, white matter necrosis was seen in 12 (86%) of 14 monochorionic infants and in two (3%) of 61 dichorionic infants. Since cavitary lesions appear 2 or more weeks after the initial insult and brain atrophy develops weeks later (1,5), the cause of these changes was an intrauterine event. Comparing neonates with and neonates without these findings, the authors found that white matter necrosis was associated with monochorionic twins, polyhydramnios, hydrops, placental vascular connections, and intrauterine fetal death of the co-twin (1). Lesions occurred in sets of twins in which both survived and in sets of twins in which one twin died in utero. The hypothesis for this finding is that the vascular connections in the placenta of monochorionic pairs allow ischemia to occur (1,6).
To my knowledge, Bernischke (2) was the first to describe neurologic damage in a surviving twin. He attributed the damage to the passage of thromboplastin from the dead fetus to the surviving twin through placental anastomoses. Although disseminated intravascular coagulation was initially thought to be the causal factor (7), this is now believed to be less likely since the majority of prospectively managed cases do not exhibit maternal disseminated intravascular coagulation (8,9).
There are two current theories regarding the cause of the defects seen in surviving monochorionic twins after intrauterine death of the co-twin. According to one theory, multiple emboli cause the infarctions. This theory is supported by the ongoing nature of infarcts of varying ages, from a few days to 8 weeks in one series (10), and by findings of histologic examination of initially surviving twins who subsequently died, with evidence of both new and old thrombi (11).
A second theory credits acute hypotension of the surviving twin as the cause of the organ lesions (2,9,12,13). The hypotension is thought to be caused by blood loss from the surviving twin and flow of this blood into the placenta and into the dead twin, which most likely occurred at the time of the co-twin’s death. In 1991, Fusi et al (12) proposed that acute exsanguination in the surviving twin and flow of the blood into the blood circulation of the dead twin through vascular anastomoses may cause acute hypotension and irreversible brain damage. Okamura et al (9) performed funipunctures of monochorionic twins and showed that the hematocrit level of a surviving twin prior to death of its co-twin was 54%, and 1 day later (after death of the co-twin), the level decreased to 39%, with a further decrease to 31% at delivery. Later, computed tomographic scans of the head after birth showed that the surviving twin had diffuse areas of low attenuation.
It is possible that both hypotension with anemia and emboli may play a role in the abnormalities seen in the surviving twin of a monochorionic pregnancy.
Since hydrops can develop in either a recipient or donor twin in cases of TTS, and since multiple authors have observed anemia in surviving twins after the death of the co-twin caused by TTS (9,12), it is unclear if the ascites in the live twin in this case was caused by TTS or by anemia that was owing to the death of the co-twin.
The role of MR imaging in the evaluation of a monochorionic pregnancy after death of one of the twins has not yet been established. Use of MR imaging will likely allow prenatal diagnosis of encephalomalacia at an earlier stage compared with the time at which diagnosis with US is possible (14). However, as mentioned previously, cavitary white matter lesions and cerebral atrophy develop 2 or more weeks after the acute stage of necrosis in the remaining live twin (1). Therefore, findings on MR images and US scans will be negative until at least 2 weeks after the death of the co-twin. The individual ischemic lesions also may be too small to be detected with current imaging methods. Use of prenatal imaging is unlikely to help prevent further damage after a fetal death since by the time imaging findings are present, damage already has occurred. However, recognition of the severe brain damage seen in this case is important so that the physician can appropriately counsel the patient about the poor prognosis for the fetus and can plan appropriate management of delivery.
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FOOTNOTES
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Part 1 of this case appeared 4 months previously and may contain larger images.
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REFERENCES
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Bejar R, Vigliocco G, Gramajo H, et al. Antenatal origin of neurologic damage in newborn infants. II. Multiple gestations. Am J Obstet Gynecol 1990; 162:1230-1236.
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Bernischke K. Twin placenta in prenatal mortality. N Y State J Med 1961; 61:1499-1508.
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Enbom JA. Twin pregnancy with intrauterine death of one twin. Am J Obstet Gynecol 1985; 152:424-429.[Medline]
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Van Heteren CF, Nijhuis JG, Semmekrot BA, Mulders LGM, Van Den Berg PP. Risk for surviving twin after fetal death of co-twin in twin-twin transfusion syndrome. Obstet Gynecol 1998; 92:215-219.[CrossRef][Medline]
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Banker BQ, Larroche JC. Periventricular leukomalacia of infancy. Neurology 1962; 7:386-410.
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Hurst RW, Abbitt PL. Fetal intracranial hemorrhage and periventricular leukomalacia: complications of twin-twin transfusion. AJNR Am J Neuroradiol 1989; 10:S62-S63.
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Moore CM, McAdams AJ, Sutherland J. Intrauterine disseminated intravascular coagulation: a syndrome of multiple pregnancy with dead twin fetus. J Pediatr 1969; 74:523-528.[CrossRef][Medline]
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Cherouny PH, Hoskins IA, Johnson TRB, Niebyl JR. Multiple pregnancy with late death of one fetus. Obstet Gynecol 1989; 74:318-320.[Medline]
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Okamura K, Murotsuki J, Tanigawara S, Uehara S, Yajima A. Funipuncture for evaluation of hematologic and coagulation indices in the surviving twin following co-twin’s death. Obstet Gynecol 1994; 83:975-978.[Medline]
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Szymonowicz W, Preston H, Yu VYH. The surviving monozygotic twin. Arch Dis Child 1986; 61:454-458.[Abstract/Free Full Text]
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Larroche JC, Droulle P, Delezoide AL, Nessmann C. Brain damage in monozygous twins. Biol Neonate 1990; 57:261-278.[Medline]
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Fusi L, McParland P, Fisk N, Nicolini U, Wigglesworth J. Acute twin-twin transfusion: a possible mechanism for brain-damaged survivors after intrauterine death of a monochorionic twin. Obstet Gynecol 1991; 78:517-520.[Medline]
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Nicolini U, Pisoni MP, Cela E, Roberts A. Fetal blood sampling immediately before and within 24 hours of death in monochorionic twin pregnancies complicated by single intrauterine death. Am J Obstet Gynecol 1998; 179:800-803.[CrossRef][Medline]
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Levine D, Barnes PD, Madsen JR, Abbott J, Mehta T, Edelman RR. Central nervous system abnormalities assessed with prenatal magnetic resonance imaging. Obstet Gynecol 1999; 94:1011-1019.[CrossRef][Medline]
Our congratulations to the 11 individuals who submitted the most likely diagnosis (encephalomalacia in surviving twin after death of monochorionic co-twin) for Diagnosis Please, Case 46. The names and locations of the individuals, as submitted, are as follows:
- Kemal Demir, MD, Ataköy, Istanbul, Turkey
- Arie Franco, MD, PhD, Livingston, NJ
- Christine Glastonbury, MD, San Francisco, Calif
- Mitchell A. Klein, MD, Milwaukee, Wis
- Frank McKowne, MD, Vancouver, Wash
- Harish Panicker, MD, Madison Heights, Mich
- Paolo Siotto, MD, Cagliari, Italy
- Stephen Smith, Peoria, Ill
- Douglas L. Teich, MD, Brookline, Mass
- Jan Wajanat, United Kingdom
- Joe Yut, Olathe, Kan
TOP
HISTORY
IMAGING FINDINGS
