Discordant imaging findings in dizygotic twins with known exposure to maternal ZIKV infection during initial stages of pregnancy

Abstract

Zika virus (ZIKV) is an arbovirus commonly transmitted to humans through the bite of an infected Aedes mosquito. Clinically, ZIKV is known to cause a wide range of symptoms, from febrile rash to severe neurological conditions, with congenital microcephaly being one of the most notable. Herein, we present a case of concurrent ZIKV infection in dizygotic twins, where only one twin developed microcephaly and severe encephalic malformations, while the other exhibited normal encephalic architecture. Our findings shed light on the complex interplay between ZIKV infection and the manifestation of neurological disorders while providing potential insights into the underlying pathological basis of ZIKV neuropathogenicity, particularly in relation to its association with the development of Dandy-Walker malformation. By examining the differential outcomes in twins exposed to the same viral infection, we contribute to the understanding of factors that may influence the development of severe neurological complications in ZIKV-infected individuals. Further research in this direction is crucial for developing targeted interventions and preventive strategies to mitigate the devastating effects of ZIKV infection, especially in pregnant women and their offspring.

Introduction

Zika virus (ZIKV) is a single-stranded RNA arbovirus in the Flavivirus genus. Primarily transmitted by Aedes mosquitoes [1], it can also spread through sexual contact, saliva, animal bites, intrauterine transmission, blood transfusions, and breast milk [1], [2]. Initially associated with mild febrile rashes, ZIKV gained attention in 2015 due to severe birth defects in Brazil, including microcephaly [3]. The World Health Organization (WHO) has proposed a new congenital syndrome caused by ZIKV, known as congenital Zika syndrome (CZS). Microcephaly is the main manifestation observed in CZS, which is usually severe and associated with other neurological injuries [4]. CZS has also been reported in newborns of twin pregnancies [5], [6], [7], [8].

Microcephaly is a condition characterized by an extremely small head circumference, typically associated with an underdeveloped cerebral cortex. The cerebral cortex is responsible for higher-order processes, such as language, memory, and perception. Infants with severe microcephaly often experience developmental delays, intellectual disabilities, and other neurological disorders. Microcephaly can result from various environmental or genetic factors, including maternal ZIKV infection. In fact, ZIKV has been shown to cause microcephaly by disrupting fetal neural development. Genetic studies have demonstrated that ZIKV infection leads to the deregulation of signaling pathway genes. For instance, ZIKV infection of neural cells upregulates immune-response-related and apoptosis pathways, while downregulating the Akt-mTOR pathway. The Akt-mTOR pathway is essential for neural stem cells proliferation and differentiation, linking prenatal ZIKV infection to microcephaly [9].

Other brain abnormalities reported to occur in CZS comprise calcifications, cortical development malformations, impaired neuronal migration, abnormalities of the corpus callosum, ventriculomegaly, as well as brainstem and cerebellum abnormalities including the rare anatomical structural disorder known as Dandy-Walker Syndrome (DWS) [8].

DWS is a congenital brain malformation that commonly affects the cerebellum and the third and fourth ventricles of the brain. There are four subtypes of DWS: (1) Dandy-Walker malformation (DWM), characterized by the complete agenesis or underdevelopment of the cerebellar vermis, cystic enlargement of the fourth ventricle, and an enlarged posterior fossa. DWM is often associated with hydrocephalus, a condition in which excess cerebrospinal fluid builds up in the ventricles, causing increased pressure within the head; (2) Dandy-Walker variant (DWV), characterized by partial underdevelopment of the cerebellar vermis, cystic enlargement of the fourth ventricle, and a normal posterior fossa. DWV is much less severe than DWM; (3) Mega cisterna magna, characterized by a normal cerebellar vermis and fourth ventricle, and an enlarged posterior fossa; and (4) Posterior fossa arachnoid cyst. In all four instances, patients often exhibit neurological symptoms, but the severity of the symptoms can vary [10].

In this context, this report details discordant CZS and DWS in dichorionic, dizygotic twins following maternal ZIKV infection during pregnancy.

Case presentation

A 35-year-old gravida 3, para 2 woman underwent prenatal ultrasound at 9 weeks, which showed a dichorionic, dizygotic pregnancy with embryos in both sacs. The Crown Rump Length was 72.4 mm and 78.1 mm for embryo No. 1 and embryo No. 2, respectively. Ultrasonography at 34 weeks revealed that the female fetus (twin 1) presented with a biparietal diameter and a cephalic circumference (CC) below the 3rd percentile, indicating microcephaly, mild ventriculomegaly, and an abdominal circumference below the 3rd percentile. The male fetus (twin 2) appeared structurally normal. Repeat ultrasonography at 36 weeks additionally revealed abnormalities in twin 1. Cesarean section was performed due to failure to descend. Twin 1 was 1900 g weight and 40 cm long and twin 2 was 2050 g weight and 41 cm long. Both lengths fell below the 3rd percentile. At birth, the CC for twin 1 was 26 cm, indicating severe microcephaly, whereas the CC for twin 2 was within normal limits.

The mother’s pregnancy was relevant for a body-spread maculopapular rash accompanied by fever, conjunctival injection, malaise, generalized joint pain, and myalgia on the 9th week of gestation lasting 7 days. Notably, the father of the twins presented similar symptoms during the same period. Clinical and epidemiological assessment led to the presumptive diagnosis of ZIKV fever. ZIKV serology was performed three days after symptoms’ onset resulting positive for IgM and negative for IgG. In addition, IgM and IgG serology for T. gondii, Rubella virus, Cytomegalovirus, Herpes Simplex, and T. pallidum was negative. Post-partum maternal serology using the indirect immunofluorescence test Arboviral Fever Mosaic 2 Euroimmun AG® IgG, IgM Test System (Euroimmun AG® Luebeck, Germany) was positive for ZIKV IgG. No antibodies to Chikungunya virus or Dengue virus serotypes 1–4 were detected. The sample was tested for plaque reduction neutralization test (PRNT) confirmation for ZIKV at a regional reference laboratory, which was positive (≥ 1:10). Convalescent samples collected 8 months later showed a seven-fold increase in neutralizing antibody titers to ZIKV. Per the Pan American Health Organization (PAHO), the mother met criteria for probable ZIKV infection and twin 1 met criteria for probable congenital syndrome associated with ZIKV. Placental, neonatal, and molecular testing were not available due to resource limitations.

Maternal history revealed hypothyroidism treated with levothyroxine. Her therapeutic TSH levels during the 1st and 3rd trimesters of pregnancy were 1.3 mcg/dL and 1.2 mcg/dL, respectively. Urinary tract infection was diagnosed and treated during the second trimester. There were no other reported personal or family history infections. The mother denied radiation exposure, use of teratogenic agent or other exposures during pregnancy.

On follow-up at 5-months of age, twin 1 physical examination revealed psychomotor developmental delay. Electroencephalogram (EEG) findings showed normal sleep architecture but demonstrated diffuse, paroxysmal slow activity with a pattern suggestive of hypsarrhythmia. Twin 2 neurological development exam was reported as within normal limits.

At 15 months of age, Twin 1 visual evoked potentials (VEP) results indicated adequate bilateral maculocortical conduction; however, a visual deficit was identified secondary to macular lesions and cortical pigmentary changes. Visual stimulation therapy was subsequently recommended. For Twin 2, visual development and VEP findings were reported as normal.

At 18-months of age, the twins underwent brain magnetic resonance imaging. Twin 1 displayed widening of the subarachnoid space in the posterior fossa that communicated extensively with the fourth ventricle, and inferior cerebellar vermis hypoplasia, indicating Dandy Walker Malformation (DWM) (Fig. 1). Significant dilation of the supratentorial ventricular system was observed, specifically involving the cerebral aqueduct and the third ventricle. Temporal and occipital horns were also visualized. The brain appeared significantly thinned, with sparse sulci, widening of the subarachnoid space surrounding both cerebral hemispheres, myelination abnormalities, and marked thinning of the corpus callosum. Furthermore, the optic nerve sheath diameter was 5 mm. Twin 2 exhibited no abnormalities (Fig. 2). The chronology of the case is summarized in Fig. 3.

Fig. 1.

Sagittal (A), Axial (B), and Coronal (C) sequences of twin 1 brain MRI at 18 months of age exhibiting CNS malformations compatible DWM, including widening of the subarachnoid space in the posterior fossa with extensive communication the fourth ventricle and inferior cerebellar vermis hypoplasia, showed a significant ventricular cephalic system dilation towards the cerebral aqueduct, resulting in third ventricle, temporal and occipital horns widening. The brain cortex was significantly thin, with sparse sulci and widening of the subarachnoid space surrounding both cerebral hemispheres. The optic nerve sheath diameter was 5 mm (B).

Fig. 2.

Sagittal brain MRI of twin 2 at 18 months. Cortical folding and sulcation were appropriate for age, with no evidence of myelination or cortical defects. The ventricular and cisternal systems, as well as midline structures, were within normal limits. These findings were consistent with a neuroanatomically normal brain for the patient's age.

Fig. 3.

Timeline of maternal exposure, prenatal findings, neonatal presentation of the twins, diagnostic workup, and clinical course leading to the diagnosis of congenital ZIKV infection with Dandy–Walker spectrum malformation in twin 1.

Discussion

Dandy Walker Malformation is part of the spectrum of DWS [8] consisting of cerebellar dysplasia, posterior fossa enlargements, and cystic dilation of the fourth ventricle [11]. Although DWM has been observed in congenital ZIKV in single pregnancies [12], to our knowledge, this is the first report of dichorionic dizygotic twins exposed to maternal ZIKV infection during the first trimester, followed by CZS, microcephaly, and DWM in only one twin. Discordant outcomes have been reported in the spectrum of ZIKV in utero [5], [6]. Potential mechanisms for these discordances might be explained by fetal susceptibility and differences in the placental function in dizygotic pregnancies [6].

The female twin in the pair we describe was diagnosed with severe microcephaly due to biparietal diameter and cephalic circumference measurements below the 3rd percentile. Previous reports have established the relationship between ZIKV and microcephaly [5], [13]. In cases of ZIKV infection with microcephaly, transfontanellar ultrasonography typically exhibits reduced corpus callosum and cerebral parenchyma, enlargement of the subarachnoid space, multiple punctiform calcifications, and enlargement of the atria and occipital horns of the lateral ventricles [5]. ZIKV infections during pregnancy have also been linked to cortical thinning, Guillain-Barre syndrome, and most notably anomalies consistent with DWM [5].

Van der Linden et al. [6] described two cases of dichorionic dizygotic twin pregnancies following maternal ZIKV exposure. One twin exhibited symptoms of DWM. In both cases, the affected twin presented with calcifications in the subcortical region, ventriculomegaly, and cortical underdevelopment, all of which are signs of DWM. Typically, this kind of discordant outcome is seen in dichorionic pregnancies, which suggests that the variability in outcome of congenital ZIKV infection is likely influenced by placental factors [14].

Several studies have investigated the ZIKV neuropathogenicity, particularly viral-triggered host protein responses [8]. Zinc-finger proteins, including ZNRF2, ZNF830, ZSWIM8, and ZPR1, show increased levels during early ZIKV infection and are closely linked to neurosensory dysregulation during in-utero viral exposure [15], [16]. The ZIC gene family encodes zinc-finger transcription factors and has been associated with DWM. ZIC1 and ZIC4 genes’ deletions have been identified as potential substrates for the disease [17]. It remains unclear if ZIKV alters ZIC gene function during infection. FOXC1 is a transcription factor member of the forkhead family, is crucial for cerebellar neurogenesis, whose downregulation has been observed in ZIKV-infected neural stem cells, and its loss has been linked to the development of microcephaly and DWM [18] (Fig. 4). It should be noted that while some of these mechanisms have been demonstrated in ZIKV infection, their relevance to other contexts to congenital CNS damage remains hypothetical and requires further experimental confirmation.

Fig. 4.

Potential neuropathogenic mechanisms of CNS damage in congenital Zika Virus (ZIKV) Syndrome. Early ZIKV infection may induce neurosensory dysregulation by upregulating Zinc-finger proteins (ZNRF2, ZNF830, ZSWIM8, and ZPR1). Deletions in ZIC1 and ZIC4 genes, which encode zinc-finger transcription factors, might serve as the substrate for Dandy-Walker Malformation. However, the precise role of these factors remains to be elucidated. FOXC1 is a transcription factor that has shown downregulation in ZIKV-infected neural cells. Another mechanism involves the inflammatory immune response mediated by microglia, as well as the induction of neural stem cell apoptosis through cell cycle dysregulation or activation of caspase-3. Activation of Caspase-3 has been observed in infections with the ZIKV_SMGC-1 strain, leading to microphthalmia, optic nerve hypoplasia, and visual deficiencies [19], [20].

In addition, we recognize that definitive diagnosis of ZIKV infection with molecular methods would have been ideal. However, at the time of the study, molecular ZIKV testing was unavailable in the state and could only be performed at the national reference laboratory, in Caracas, Venezuela’s capital, hundreds of kilometers from where the case occurred. In Venezuela, sample transportation logistics largely depend on the patient’s own resources and are typically at their expense. In this case, the cost and logistical burden were prohibitively high for both the clinical team and the patient. Unfortunately, such circumstances are common given the limited allocation of resources for ZIKV infection monitoring, management, and research, particularly in developing countries. Therefore, reliance on clinical and epidemiological data for diagnosis and management remains essential.

In sum, we describe severe CZS and DWM in one twin of a dichorionic twin pregnancy, while the other twin was healthy, in the setting of prior maternal ZIKV infection. This discordance suggests additional factors beyond placental protection may influence ZIKV outcomes. Further studies on ZIKV in twin pregnancies are necessary to understand the molecular mechanisms behind DWM and other congenital neurological complications.

CRediT authorship contribution statement

Alberto E. Paniz Mondolfi: Writing – review & editing, Writing – original draft, Supervision, Project administration, Methodology, Investigation, Formal analysis, Conceptualization. Gabriela M Blohm: Writing – original draft, Methodology, Conceptualization. Sordillo Emilia Mia: Writing – review & editing, Writing – original draft, Methodology, Conceptualization. Ascanio Luis C: Writing – review & editing, Visualization, Methodology, Investigation, Formal analysis. Lednicky John A: Writing – review & editing. Fabio Adami-Teppa: Writing – review & editing, Supervision, Resources, Project administration, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Marilianna Marquez: Supervision, Project administration, Methodology, Investigation, Formal analysis, Data curation. Maria Alejandra Escalona-Rodriguez: Supervision, Investigation, Formal analysis, Data curation.

Contributions

FAT, MM, MAER, and AEPM examined and followed the patient. FAT, MM, and UR performed imaging studies. AEPM, GMB, and EMS designed the study approach to the case and wrote the draft. FAT, MM, MAER, UR, LCA and AEPM participated in the planning of this report and contributed to the acquisition, analysis, and interpretation of the clinical data. GMB, EMS, LCA, JAL, and AEPM helped draft the final version manuscript. MM generated Fig. 3. LCA generated Fig. 4. All authors read and approved the final manuscript.

Compliance with ethical standards

The study is a retrospective observational single-case report, which does not require approval from the institutional review boards of our institute. However, written consent was obtained from the patient’s family.

Informed consent

Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Funding sources

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability

No datasets were generated or analyzed during the current study.