Myotonic dystrophy is a significant cause of idiopathic polyhydramnios

Congenital hypotonia: systematic approach for prenatal detection

OBJECTIVES

Congenital hypotonic conditions are rare and heterogeneous, and some are severely debilitating or lethal. Contrary to its prominent postnatal manifestation, the prenatal presentation of hypotonia is frequently subtle, inhibiting prenatal detection. We aimed to characterize the prenatal sonographic manifestation of congenital hypotonia throughout pregnancy, evaluate the yield of diagnostic tests and propose diagnostic models to increase its prenatal detection.

METHODS

This was a retrospective observational study of singleton pregnancies with congenital hypotonia, diagnosed either prenatally or immediately after birth, at a single tertiary center between the years 2012 and 2020. Prenatally, hypotonia was diagnosed if a fetus showed sonographic or clinical signs suggestive of hypotonia and had a confirmed underlying genetic condition, or in the absence of a known genetic abnormality if the fetus exhibited multiple prominent signs suggestive of hypotonia. Postnatally, it was diagnosed in neonates displaying reduced muscle tone leading to reduced spontaneous movement, reduced swallowing or feeding difficulty. We reviewed the medical records of pregnant patients carrying fetuses subsequently diagnosed with congenital hypotonia and assessed the yield of ultrasound scans, fetal magnetic resonance imaging, computed tomography and genetic tests. The detection rate of sonographic signs suggesting fetal hypotonia was calculated. The prevalence of non-specific signs, including polyhydramnios, persistent breech presentation, intrauterine growth restriction and maternal perception of reduced fetal movement, were compared between the study group and the local liveborn singleton population. Potential detection rates of different theoretical semiotic diagnostic models, differing in the threshold for referral for a targeted scan, were assessed based on the cohort's data.

RESULTS

The study group comprised 26 cases of congenital hypotonia, of which 10 (38.5%) were diagnosed prenatally, and the controls included 95 105 singleton live births, giving a prevalence of congenital hypotonia of 1:3658. Nuchal translucency thickness and the early anomaly scan at 13-17 weeks were normal in all 22 and 23 cases, respectively, in which this was performed. The mid-trimester scan performed at 19-25 weeks was abnormal in four of 24 (16.7%) cases. The overall prenatal detection rate of congenital hypotonic conditions in our cohort was 38.5%. Only cases which underwent a targeted scan were detected and, among the 16 cases which underwent this scan, the prenatal detection rate was 62.5% compared with 0% in pregnancies that did not undergo this scan (P = 0.003). An abnormal genetic diagnosis was obtained in 21 (80.8%) cases using the following modalities: chromosomal microarray analysis (CMA) in two (9.5%), whole-exome sequencing (WES) in 14 (66.7%) and methylation analysis in five (23.8%). CMA was abnormal in 8% (2/25) of the cases and WES detected a causative genetic mutation in 87.5% (14/16) of the cases in which these were performed. Comparison of non-specific signs in the study group with those in the local singleton population showed that hypotonic fetuses had significantly more polyhydramnios (64.0% vs 3.0%, P < 0.0001), persistent breech presentation (58.3% vs 4.2%, P < 0.0001), intrauterine growth restriction (30.8% vs 3.0%, P < 0.0001) and maternal perception of reduced fetal movement (32.0% vs 4.7%, P < 0.0001). Prenatally, the most commonly detected signs supporting a diagnosis of hypotonia were structural anomaly (62.5%, 10/16), reduced fetal movement (46.7%, 7/15), joint contractures (46.7%, 7/15) and undescended testes ≥ 30 weeks (42.9%, 3/7 males). Proposed diagnostic strategies that involved performing a targeted scan for a single non-specific ultrasound sign or two such signs, and then carrying out a comprehensive genetic evaluation for any additional sign, offered theoretical detection rates in our cohort of 88.5% and 57.7%, respectively.

CONCLUSIONS

Congenital hypotonic conditions are rare and infrequently detected prenatally. Sonographic signs are visible from the late second trimester. A targeted scan increases prenatal detection significantly. Comprehensive genetic testing, especially WES, is the cornerstone of diagnosis in congenital hypotonia. Theoretical diagnostic models which may increase prenatal detection are provided. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Congenital Myotonic Dystrophy: An Overlooked Diagnosis Not Amenable to Detection by Sequencing

OBJECTIVE

To increase the clinical awareness of the need for genetic evaluation for congenital myotonic dystrophy in cases of fetal akinesia sequence and idiopathic polyhydramnios.

METHODS

Retrospective case review.

RESULT

A 27 y.o. G1P0 with no significant family history presented for ultrasound at 25 weeks gestation. Notable findings included lack of extension of the fetal arms and legs with bilateral talipes consistent with fetal akinesia sequence. Polyhydramnios with an amniotic fluid index of 32.2cm was also present. Amniotic fluid obtained by amniocentesis revealed normal results for a chromosomal microarray and a next generation sequencing panel for arthrogryposis. The patient underwent serial amnioreductions for recurrent severe polyhydramnios with removal of a total of 9.3 L. Further amniotic fluid testing for CDM1 identified >200 repeats in one copy of the fetal DMPK gene, consistent with a diagnosis of congenital myotonic dystrophy type 1. The patient was delivered at 35 weeks gestation and neonatal demise occurred on the second day of life.

CONCLUSION

Congenital myotonic dystrophy should be a consideration for cases of severe polyhydramnios identified on ultrasound. Myotonic dystrophy is detected using PCR and southern blot and is not typically included on next generation sequencing panels that test for similar conditions. This article is protected by copyright. All rights reserved.

Fetal Macrocephaly: A Novel Sonographic Finding in Congenital Myotonic Dystrophy

Objective  Sonographic clues to the diagnosis of congenital myotonic dystrophy (CDM) are limited, particularly in the absence of family history of myotonic dystrophy (DM). We reviewed cases of CDM for unique prenatal findings. Study Design  A single-center case series of fetuses with CMD with characteristic prenatal findings confirmed postnatally. Results  Four fetuses with pre- or postnatally diagnosed CDM presented with macrocephaly in utero. While head measurements were appropriate for gestational age until midgestation, third-trimester head circumference and biparietal diameter were both >2 standard deviation (SD) above the mean in all. Abdominal and femur measurements were otherwise appropriate for gestation. Postnatally, the occipitofrontal circumference was >2 SD above the mean in all, confirming the diagnosis of macrocephaly. Conclusion  CDM should be included in the differential diagnosis of third-trimester macrocephaly, especially in the presence of additional sonographic clues and when maternal medical history and physical examination are suggestive of DM.

Obstetrical, maternal and neonatal outcomes in pregnancies affected by muscular dystrophy

Objective:

Pregnancies in women affected by a muscular dystrophy are at an increased risk of adverse maternal and neonatal outcomes due to the effect of the disease on the muscular, cardiac and respiratory systems. We sought to evaluate the risk of adverse outcomes within a large population-based cohort study.

Methods:

We used the data extracted from the Nationwide Inpatient Sample (NIS) to conduct a retrospective population-based cohort study consisting of over 12 million births that occurred in the United States between 1999 and 2013. Births to mothers with muscular dystrophy were identified using the International Classification of Diseases, Ninth Revision (ICD-9) codes and were compared with births to mothers with no maternal muscular dystrophy. Unconditional logistic regression analysis was used to evaluate the adjusted effect of muscular dystrophy on maternal and neonatal outcomes.

Results:

During the 14-year study period, there was an increasing trend in the incidence of muscular dystrophy, with a cumulative incidence of 7.26 in 100,000 births. Women with muscular dystrophy and their neonates were at a significantly increased risk of adverse pregnancy outcomes: specifically, an increased risk of preeclampsia, preterm premature rupture of membranes, preterm labor, venous thromboembolism, cardiac dysrhythmia, requiring a blood transfusion and giving birth by cesarean section. Neonates born to affected mothers were at a significantly higher risk of being born preterm, with a congenital malformation and suffering intrauterine growth restriction.

Conclusion:

The risk of several adverse maternal and neonatal outcomes is increased in pregnant women with muscular dystrophy. As such, additional surveillance in order to mitigate the risk of adverse outcomes is warranted in these pregnancies.

Maternal Genetic Disorders in Pregnancy

The life expectancy and quality of life of women with genetic disorders continues to improve, resulting in more women reaching reproductive age and desiring fertility. It is becoming increasingly important that obstetricians become familiar with common genetic disorders and their associated risks in pregnancy. The authors review pregnancy in women with various genetic disorders, including review of pregnancy outcomes, management recommendations, and genetic risk assessment. Most data on pregnancies in women with genetic conditions are based on case reports and literature reviews. Additional studies, including pregnancy registries, are needed to improve our understanding and care of this patient population.

Myotonic dystrophy: disease repeat range, penetrance, age of onset, and relationship between repeat size and phenotypes

Myotonic dystrophy (DM) is an autosomal dominant neuromuscular disease primarily characterized by myotonia and progressive muscle weakness. The pathogenesis of DM involves microsatellite expansions in noncoding regions of transcripts that result in toxic RNA gain-of-function. Each successive generation of DM families carries larger repeat expansions, leading to an earlier age of onset with increasing disease severity. At present, diagnosis of DM is challenging and requires special genetic testing to account for somatic mosaicism and meiotic instability. While progress in genetic testing has been made, more rapid, accurate, and cost-effective approaches for measuring repeat lengths are needed to establish clear correlations between repeat size and disease phenotypes.

Prenatal diagnosis of congenital myopathies and muscular dystrophies

Congenital myopathies and muscular dystrophies constitute a genetically and phenotypically heterogeneous group of rare inherited diseases characterized by muscle weakness and atrophy, motor delay and respiratory insufficiency. To date, curative care is not available for these diseases, which may severely affect both life-span and quality of life. We discuss prenatal diagnosis and genetic counseling for families at risk, as well as diagnostic possibilities in sporadic cases.

Idiopathic polyhydramnios and postnatal findings

OBJECTIVE

Our objective was to investigate the outcome of neonates with idiopathic polyhydramnios in the first year after birth.

METHODS

All patients diagnosed in the Erasmus Medical Centre Rotterdam and the University Medical Centre Utrecht between January 2000 and April 2005 with idiopathic polyhydramnios were studied. The outcome variables included mode of delivery, pre-term delivery, birth weight, macrosomia, large-for-gestational-age (weight > p90), neonatal or infant mortality and infant morbidity at 1 year after delivery. These were related to antenatal findings, including the onset of polyhydramnios and ultrasonographic evidence of macrosomia (estimated fetal weight > p90).

RESULTS

Polyhydramnios was diagnosed at a mean gestational age (+/- s.d.) of 31.0 +/- 4.9 weeks. The mean gestational age at birth (+/- s.d.) was 37.9 +/- 3.7 weeks. Macrosomia at birth was present in 25.3% (22/88). Sixty-three of 88 infants were in good health 1 year after birth; 20 infants had an abnormality and 5 children had died. Macrosomia and detection of polyhydramnios in the third trimester was associated significantly with a good outcome.

CONCLUSION

In neonates with idiopathic polyhydramnios, abnormalities were detected during the first year of life in 28.4%. Detection of polyhydramnios in the second trimester and low or normal birth weight are risk factors for associated abnormalities.

Congenital myotonic dystrophy: prenatal ultrasound findings and pregnancy outcome

OBJECTIVE

The objective of this study was to assess the maternal and prenatal ultrasound findings and outcome in pregnancies complicated by congenital myotonic dystrophy Type 1 (DM1).

METHODS

A retrospective chart review of all patients with a diagnosis of DM1 and pregnancy presenting to the Oxford Radcliffe Hospital between 1990 and 2004 was undertaken. Obstetric case notes were reviewed and details of all pregnancies obtained. This included data on prenatal diagnostic tests and obstetric ultrasound scans performed as well as pregnancy complications and pregnancy outcome. Maternal and fetal CTG expansion size was also recorded where available. Maternal genetic case notes were reviewed for details of maternal grip myotonia.

RESULTS

Sixty pregnancies among 26 couples in which one of the parents was a carrier of DM1 were identified during the study period. These resulted in 36 (60%) pregnancies affected by congenital DM1 and 19 (31.7%) unaffected pregnancies. There were four miscarriages and one termination of pregnancy for non-medical reasons. Nineteen of the 36 affected pregnancies ended in termination following the antenatal diagnosis of congenital DM1 by either chorionic villus sampling (CVS) or amniocentesis. In the remaining 17 affected pregnancies (16 singleton and one twin) there was one miscarriage of an affected fetus with co-existing Down syndrome and eight perinatal deaths. The principal cause of perinatal death was respiratory failure in the early neonatal period. Antenatally noted clinical/sonographic abnormalities in these pregnancies included polyhydramnios (100%), talipes (26.6%) and borderline ventriculomegaly (13.3%). Uni- or bilateral talipes was noted at delivery in 10 of 16 (62.5%) neonates. Maternal grip myotonia was present in all but one of these cases.

CONCLUSION

The antenatal findings of polyhydramnios and talipes should prompt a search for maternal grip myotonia. If present, definitive testing for congenital DM1 should be considered.

Familial diseases revealed by a fetal anomaly

OBJECTIVES

The recognition of a fetal anomaly can lead to the same diagnosis being made in one of the asymptomatic parents unaware of the problem. We analyzed cases in which the discovery of a fetal anomaly led to the discovery of a genetic familial disorder.

METHODS

Families in which the recognition of a fetal anomaly led to the same diagnosis being made in one of the asymptomatic parents were included.

RESULTS

Twenty couples were included in the study. The fetal anomalies were cleft lip and palate (4), cardiac anomalies (2), cerebral anomalies (1), bilateral club feet with polyhydramnios, akinesia or camptodactily (5), nuchal anomalies (2), micromelia (3), polydactyly (2), and limited elbow extension (1). Genetic counselling helped establish nine maternal diseases as follows: Steinert disease (3), spinal muscular atrophy (1), antecubital pterygium (1), DiGeorge (1), Wardenburg type II (1), Charge (1) and Greig syndromes (1). Eleven paternal diseases were discovered, which were Noonan-like syndrome (1), paternal cervical anomalies (1), Goldenhar syndrome (1), dominant autosomal arthrogryposis (1), osteogenesis imperfecta (3), tuberous sclerosis (1), dominant transposition of great vessels (1), Weyers acrofacial dysostosis (1), and autosomal dominant holoprosencephaly (1). Twelve couples continued with pregnancy and eight opted for termination of pregnancy.

CONCLUSION

The fetus is central in giving the first insight into a familial disorder. It can reveal familial diseases undiscovered in the parent and help understand the mode of transmission of an anomaly, mainly the autosomal dominant diseases with variable expressions.

Neuromuscular disorders in pregnancy

Many neuromuscular conditions occur more frequently during pregnancy and include carpal tunnel syndrome, Bell's palsy, lumbosacral radiculopathy, meralgia paresthetica, intercostal neuralgia, and other compression neuropathies. Preexisting or coincident neuromuscular diseases, including demyelinating polyneuropathies, inflammatory muscle disease, myasthenia gravis, and inherited nerve and muscle disease present specific problems during pregnancy. We review management of neuromuscular disorders during pregnancy, labor, delivery, and the early postpartum period.

Congenital Myotonic Dystrophy

We describe a case of severe congenital myotonic dystrophy (CDM). A 38-year-old primigravida, who was known to suffer from mild myotonic dystrophy (DM), conceived spontaneously and booked for confinement at 11 weeks in our unit. The couple had been fully counseled about the risks of transmission of this condition to their offspring before embarking on this pregnancy. Despite being fully aware of the risks, they declined prenatal diagnosis. The pregnancy was monitored by serial ultrasound scans. The diagnosis of CDM was suspected by ultrasound markers of borderline ventriculomegaly, polyhydramnios, and reduced fetal movements. The pregnancy ended prematurely at 33 weeks in an emergency caesarean section because of severe fetal compromise. The neonate died almost immediately after birth. The genetic analysis of cord blood confirmed severe DM. This case highlights the importance of ultrasound markers for the diagnosis of CDM in the absence of definitive prenatal diagnosis.

Neuromuscular ultrasound

High-resolution ultrasound now is capable of imaging muscle and nerve in fine detail. It is sensitive in detecting chronic myopathies and neurogenic atrophy and may be able to detect subtle changes associated with acute denervation. It is particularly well suited to the study of fasciculations and kinesiology. Recent studies show that ultrasound also is capable of imaging most peripheral nerves,including small branches, and of sensitively measuring the swelling that follows chronic compression. This noninvasive technology holds considerable promise for providing anatomic information to complement other tests of nerve and muscle function.

Chapter 25 Imaging nerve and muscle with ultrasound

Over the last two decades significant advances in ultrasound have made it possible for investigators to image and interpret pathologic changes in muscle and nerve. In addition to being able to assess the pathologic changes in these structures themselves, ultrasound also provides the unique ability to identify anatomic lesions responsible for nerve or muscle injury. They can be correlated with changes in neural structures or affected muscles. Like electrodiagnostic studies, ultrasound is portable and inexpensive, but it is even less invasive, and surprisingly sensitive in detecting a variety of unusual and common causes of neuromuscular dysfunction. Given recent developments in the field, ultrasound shows promise as the technique most suitable for clinical neurophysiologists and neuromuscular clinicians in the growing field of imaging. Such involvement is required to best adopt and exploit the potential of imaging for the research and clinical evaluation of neuromuscular disorders.