Moebius syndrome and holoprosencephaly following exposure to misoprostol

Echoencephalography of Möbius sequence: A congenital cranial dysinnervation disorder with brainstem calcifications

BACKGROUND AND PURPOSE

Möbius sequence (MBS) previously known as Möbius syndrome is a rare nonprogressive developmental defect of the rhombencephalon leading to congenital abducens (VIth) and facial (VIIth) nerve palsy. Echoencephalography is the first, safe, noninvasive, and cost-effective imaging modality available at bedside. No study on the use of echoencephalography in neonates for the diagnosis of MBS has been previously reported.

METHODS

In this single tertiary center study, more than 18,000 neonates underwent echoencephalographic imaging over the span of two decades. Imaging was performed through the anterior, posterior, and lambdoid fontanelles. All neonates found to have calcifications of brainstem tegmental nuclei underwent additional imaging studies. Each neonate with MBS was carefully examined by the same investigator.

RESULTS

Five neonates were shown to have punctate, bilateral, symmetrical tegmental pontine calcifications through all three acoustic windows. These calcifications extended caudally in most patients, and rostrally in 2 patients. Brainstem hypoplasia was best seen through the posterior fontanelle. Three out of five infants were noted to have brainstem hypoplasia with straightening of the floor of the fourth ventricle. In two children, facial collicular bulges and hypoglossal eminences were present. All five infants fulfilled clinical diagnostic criteria of MBS. In addition, a wide array of cerebral defects is identified. Echoencephalographic findings were confirmed by other imaging modalities.

CONCLUSION

Knowledge of echoencephalographic features of MBS should improve its early recognition. A detailed description of the various imaging phenotypes of MBS is necessary to characterize the etiology of this heterogeneous congenital cranial dysinnervation disorder.

Neuroimaging Findings in Moebius Sequence

BACKGROUND AND PURPOSE

Moebius sequence comprises a spectrum of brain congenital malformations predominantly affecting the function of multiple cranial nerves. Reported neuroimaging findings are heterogeneous and based on case reports or small case series. Our goal was to describe the neuroimaging findings of Moebius sequence in a large population of patients scanned with MR imaging.

MATERIALS AND METHODS

An observational cross-sectional study was performed to assess brain MR imaging findings in 38 patients with Moebius syndrome studied between 2013 and 2016.

RESULTS

Retrospective analysis of MR imaging studies showed flattening of the floor of the fourth ventricle floor secondary to a bilateral absent facial colliculus in 38 patients (100%) and unilateral absence in 1. A hypoplastic pons was found in 23 patients (60.5%). Mesencephalic malformations consisted of tectal beaking in 15 patients (39.5%) and increased anteroposterior midbrain diameter with a shallow interpeduncular cistern in 12 (31.6%). Infratentorial arachnoid cysts were found in 5 patients (13.2%), and cerebellar vermis hypoplasia, in 2 (5.3%). Supratentorial findings included the following: thalamic fusion (26.3%), periventricular nodular heterotopias (26.3%), ventriculomegaly (26.3%), callosal abnormalities (23.7%), and hippocampal malrotations (23.7%).

CONCLUSIONS

Findings seen in this large patient cohort agreed with previously published reports. Flattening of the fourth ventricle floor secondary to a bilaterally absent facial colliculus was the most frequent MR imaging finding. The presence of other brain stem and cerebellar malformations as well as supratentorial abnormalities may help explain clinical symptoms and achieve a correct diagnosis.

Misoprostol exposure during the first trimester of pregnancy: Is the malformation risk varying depending on the indication?

OBJECTIVE

To report the prospective follow-up of pregnancies exposed to misoprostol during the first trimester and analyse the teratogenic risk depending on the indication for use.

STUDY DESIGN

Prospective observational study of 265 women exposed to misoprostol during the first 12 weeks of pregnancy and followed until the delivery. Women were included if they or their physician had contacted a French pharmacovigilance centre before 22 weeks of gestation (WG) to obtain information on the risk of misoprostol exposure, and if there had been misoprostol exposure before 13 WG. Data were collected at the time of the first contact, and the pregnancy outcome was recorded at follow-up. Women were prospectively enrolled from January 1988 to December 2013.

RESULTS

The main indication for misoprostol was voluntary abortion (60.9%). Ten major malformations (5.5%) (95% CI 2.65-9.82%) were reported and five of them were consistent with the pattern of malformations attributed to misoprostol: Möbius sequence, hydrocephalus, terminal transverse limb reduction associated with a clubfoot, syndactyly, and complete posterior encephalocele. The rate of malformations was higher, but not significantly, in women exposed to misoprostol for voluntary abortion (7.9%) compared with women exposed to misoprostol for other or unknown indications (3.2%).

CONCLUSIONS

Our results confirmed a specific pattern of malformations due to misoprostol use in early pregnancy, even with low dose of misoprostol. Despite the small number of cases, we observed a higher proportion of major malformations in fetuses born to women who continued their pregnancy after a failed voluntary abortion with misoprostol. Further studies should be conducted to evaluate other potential factors, such as combination treatment with mifepristone and the socio-environmental characteristics in this group of women.

Examining the genetics of congenital facial paralysis--a closer look at Moebius syndrome

OBJECTIVES

The molecular underpinnings of Moebius syndrome (MBS) are diverse. This article provides a comprehensive summation of the genetic and etiologic literature underlying this disorder. Elucidating the genetic causes of the disorder can aid in earlier detection and treatment planning.

DESIGN

Articles from 1880-2013 were selected and reviewed by six researchers to understand all of the molecular theories and chronicity of advancements in the literature.

RESULTS

Mutations in the MBS1, MBS2, and MBS3 gene loci all have contributed to the development of MBS through various pathways. HOX family genes coding for homeobox domains, also, have been implicated in the abnormal development of the human brain. These are among the numerous genes that have been linked to the development of MBS.

CONCLUSION

Our study codified nascent findings of the molecular determinants of MBS. These findings add to a growing database of MBS-associated mutations and can be used to diagnose MBS and clarify pathogenesis.

Mid-hindbrain malformations due to drugs taken during pregnancy

Although genetic defects are the leading cause of central nervous system malformations including in the posterior fossa, specific malformative patterns should alert the clinician to consider rather a teratogenic etiology. We discuss the imaging features of 2 mid-hindbrain malformations consecutive to the intake of isotretinoin (Roaccuatane®; case 1) and misoprostol (Cytotec®; case 2) during pregnancy and review the pertinent literature. We correlate the morphological appearance of the mid-hindbrain malformation, as seen on high-resolution magnetic resonance imaging to possible drug-induced pathogenetical mechanisms. The recognition of characteristic imaging patterns enables diagnosis of and/or confirmation of suspected drug-induced hindbrain malformations. This has important medicolegal implications and also clinical significance to avoid unsuccessful and misleading genetic testing.

[Pharmacology of misoprostol (pharmacokinetic data, adverse effects and teratogenic effects)]

Misoprostol is a synthetic analogue of prostaglandin E1. It is used in gynaecology because of its properties of myometrium smooth muscle cells contraction and its effects on the cervix. Misoprostol oral bioavailability is low and several authors have assessed whether the administration by other routes increased its pharmacodynamic effects. This paper summarizes the pharmacokinetic studies after other routes of administration: vaginal, sublingual, buccal or rectal. It also provides an update on its adverse effects and teratogenic effects.

Novel FGF8 mutations associated with recessive holoprosencephaly, craniofacial defects, and hypothalamo-pituitary dysfunction

CONTEXT

Fibroblast growth factor (FGF) 8 is important for GnRH neuronal development with human mutations resulting in Kallmann syndrome. Murine data suggest a role for Fgf8 in hypothalamo-pituitary development; however, its role in the etiology of wider hypothalamo-pituitary dysfunction in humans is unknown.

OBJECTIVE

The objective of this study was to screen for FGF8 mutations in patients with septo-optic dysplasia (n = 374) or holoprosencephaly (HPE)/midline clefts (n = 47).

METHODS

FGF8 was analyzed by PCR and direct sequencing. Ethnically matched controls were then screened for mutated alleles (n = 480-686). Localization of Fgf8/FGF8 expression was analyzed by in situ hybridization in developing murine and human embryos. Finally, Fgf8 hypomorphic mice (Fgf8(loxPNeo/-)) were analyzed for the presence of forebrain and hypothalamo-pituitary defects.

RESULTS

A homozygous p.R189H mutation was identified in a female patient of consanguineous parentage with semilobar HPE, diabetes insipidus, and TSH and ACTH insufficiency. Second, a heterozygous p.Q216E mutation was identified in a female patient with an absent corpus callosum, hypoplastic optic nerves, and Moebius syndrome. FGF8 was expressed in the ventral diencephalon and anterior commissural plate but not in Rathke's pouch, strongly suggesting early onset hypothalamic and corpus callosal defects in these patients. This was consolidated by significantly reduced vasopressin and oxytocin staining neurons in the hypothalamus of Fgf8 hypomorphic mice compared with controls along with variable hypothalamo-pituitary defects and HPE.

CONCLUSION

We implicate FGF8 in the etiology of recessive HPE and potentially septo-optic dysplasia/Moebius syndrome for the first time to our knowledge. Furthermore, FGF8 is important for the development of the ventral diencephalon, hypothalamus, and pituitary.