Detection of de novo del(18)(q22.2) and a familial of 15q13.2-q13.3 microduplication in a fetus with congenital heart defects

OBJECTIVE

We present detection of de novo del(18)(q22.2) and a familial 15q13.2-q13.3 microduplication in a fetus with congenital heart defects (CHD).

CASE REPORT

A 27-year-old, primigravid woman was referred for genetic counseling because of fetal CHD. Prenatal ultrasound at 17 weeks of gestation revealed pericardial effusion, cardiomegaly and a large ventricular septal defect. The pregnancy was subsequently terminated at 18 weeks of gestation, and a 192-g female fetus was delivered with facial dysmorphism. Cytogenetic analysis of the umbilical cord revealed a karyotype of 46,XX,del(18)(q22.2). The parental karyotypes were normal. Array comparative genomic hybridization (aCGH) of the placental tissue revealed a 2.08-Mb 15q13.2-q13.3 microduplication encompassing KLF13 and CHRNA7, and a 10.74-Mb 18q22.2-q23 deletion encompassing NFATC1. The phenotypically normal father carried the same 2.08-Mb 15q13.2-q13.3 microduplication. Polymorphic DNA marker analysis confirmed a paternal origin of the distal 18q deletion.

CONCLUSION

Prenatal diagnosis of CHD should include a complete genetic study of the embryonic tissues, and the acquired information is useful for genetic counseling.

Transplacental lidocaine intoxication

Neonatal seizures are frequent in neonatal intensive care and the most common cause is perinatal asphyxia. Among other causes, toxin exposure is rare.We present a boy with an uneventful vaginal birth, who presented one hour after birth with apnea, hypotonia, mydriasis, tongue fasciculation, and tonic seizures. There was no hypoxic ischemic encephalopathy and brain imaging was normal. Toxicology screening revealed a toxic concentration of lidocaine in his blood. The intoxication was transplacental, as a cord blood sample confirmed the toxic level. This was probably due to maternal perineal nerve block with lidocaine.Perineal local infiltration of lidocaine is not without risk for the newborn. Toxicology screen remains an important tool in the work-up of neonatal seizures and sudden unexpected postnatal collapse.

Loss of zebrafish lgi1b leads to hydrocephalus and sensitization to pentylenetetrazol induced seizure-like behavior

Mutations in the LGI1 gene predispose to a hereditary epilepsy syndrome and is the first gene associated with this disease which does not encode an ion channel protein. In zebrafish, there are two paralogs of the LGI1 gene, lgi1a and lgi1b. Knockdown of lgi1a results in a seizure-like hyperactivity phenotype with associated developmental abnormalities characterized by cellular loss in the eyes and brain. We have now generated knockdown morphants for the lgi1b gene which also show developmental abnormalities but do not show a seizure-like behavior. Instead, the most striking phenotype involves significant enlargement of the ventricles (hydrocephalus). As shown for the lgi1a morphants, however, lgi1b morphants are also sensitized to PTZ-induced hyperactivity. The different phenotypes between the two lgi1 morphants support a subfunctionalization model for the two paralogs.

Neurodevelopment in Seizure-prone and Seizure-resistant Rat Strains: Recognizing Conflicts in Management

Cytoarchitectural alterations during central nervous system (CNS) development are believed to underlie aberrations in brain morphology that lead to epilepsy. We have recently reported marked reductions in hippocampal and white matter volumes along with relative ventriculomegaly in a rat strain bred to be seizure-prone (FAST) compared to a strain bred to be seizure-resistant (SLOW) (Gilby et al., 2002, American Epilepsy Society 56th Annual Meeting). This study was designed to investigate deviations in gene expression during late-phase embryogenesis within the brains of FAST and SLOW rats. In this way, we hoped to identify molecular mechanisms operating differentially during neurodevelopment that might ultimately create the observed differences in brain morphology and/or seizure susceptibility. Using Superarray technology, we compared the expression level of 112 genes, known to play a role in neurodevelopment, within whole brains of embryonic day 21 (E21) FAST and SLOW rats. Results revealed that while most genes investigated showed near equivalent expression levels, both Apolipoprotein E (APOE) and the beta2 subunit of the voltage-gated sodium channel (SCN2beta) were significantly underexpressed in brains of the seizure-prone embryos. Currently, these transcripts have no known interactions during embryogenesis; however, they have both been independently linked to seizure disposition and/or neurodevelopmental aberrations leading to epilepsy. Thus, alterations in the timing and/or degree of expression for APOE and SCN2beta may be important to developmental cascades that ultimately give rise to the differing brain morphologies, behaviors, and/or seizure vulnerabilities that characterize these strains.

Antiepileptogenic and antioxidant effects of oil against pentylenetetrazol-induced kindling in mice

Nigella sativa oil (NSO), a herbaceous plant, has been used for thousands of years for culinary and medical purposes. This study aimed to investigate the anticonvulsant and antioxidant activities of NSO on pentylenetetrazol (PTZ) kindling seizures in mice. Nigella sativa oil was tested for its ability (i) to suppress the convulsive and lethal effects of PTZ in kindled mice (anti-epileptogenic effect), (ii) to attenuate the PTZ-induced oxidative injury in the brain tissue (antioxidant effect) when given as a pretreatment prior to each PTZ injection during kindling acquisition. Valproate, a major antiepileptic drug, was also tested for comparison. Both substances studied significantly decreased oxidative injury in the mouse brain tissue in comparison with the PTZ-kindling group. Nigella sativa oil was found to be the most effective in preventing PTZ-induced seizures relative to valproate. Nigella sativa oil showed anti-epileptogenic properties as it reduced the sensitivity of kindled mice to the convulsive and lethal effects of PTZ; valproate was ineffective in preventing development of any of these effects. The data obtained support the hypothesis that neuroprotective action of NSO may correlate with its ability to inhibit not only excessive reactive oxygen species (ROS) formation but also seizure generation.

The type B brevetoxin (PbTx-3) adversely affects development, cardiovascular function, and survival in Medaka (Oryzias latipes) embryos

Brevetoxins are produced by the red tide dinoflagellate Karenia brevis. The toxins are lipophilic polyether toxins that elicit a myriad of effects depending on the route of exposure and the target organism. Brevetoxins are therefore broadly toxic to marine and estuarine animals. By mimicking the maternal route of exposure to the oocytes in finfish, we characterized the adverse effects of the type B brevetoxin brevetoxin-3 (PbTx-3) on embryonic fish development and survival. The Japanese rice fish, medaka (Oryzias latipes), was used as the experimental model in which individual eggs were exposed via microinjection to various known concentrations of PbTx-3 dissolved in an oil vehicle. Embryos injected with doses exceeding 1.0 ng/egg displayed tachycardia, hyperkinetic twitches in the form of sustained convulsions, spinal curvature, clumping of the erythrocytes, and decreased hatching success. Furthermore, fish dosed with toxin were often unable to hatch in the classic tail-first fashion and emerged head first, which resulted in partial hatches and death. We determined that the LD(50) (dose that is lethal to 50% of the fish) for an injected dose of PbTx-3 is 4.0 ng/egg. The results of this study complement previous studies of the developmental toxicity of the type A brevetoxin brevetoxin-1 (PbTx-1), by illustrating in vivo the differing affinities of the two congeners for cardiac sodium channels. Consequently, we observed differing cardiovascular responses in the embryos, wherein embryos exposed to PbTx-3 exhibited persistent tachycardia, whereas embryos exposed to PbTx-1 displayed bradycardia, the onset of which was delayed.

Nitric oxide synthase inhibition and delayed cerebral injury after severe cerebral ischemia in fetal sheep

After transient cerebral ischemia in fetal sheep, delayed disruptions in cerebral energetics are represented by a delayed increase in cortical impedance, a progressive decrease in the concentration of oxidized cytochrome oxidase as measured by near-infrared spectroscopy, and cortical seizures. Because the production of nitric oxide (NO), a potent mediator of neuronal death, is increased during this phase, the present study investigated whether inhibition of NO synthesis could ameliorate the delayed disruption in cerebral energetics. Eleven late gestation fetal sheep were subjected to 30 min of transient cerebral ischemia in utero. Two hours later, the treatment group (n = 5) received a continuous infusion of N(G)-nitro-L-arginine, a competitive inhibitor of NO synthase, whereas the control group (n = 6) received PBS. Changes in concentration of oxidized cytochrome oxidase, cortical impedance, and electrocortical activity were observed for 3 d. A delayed increase in cortical impedance of similar magnitude and duration commenced at 14+/-4 h in the control and at 15+/-3 h in the treatment groups. The progressive decrease in oxidized cytochrome oxidase signal, by -2.2+/-0.2 micromol/L in the control and -2.0+/-0.4 micromol/L in the treatment group at 72 h postischemia, was similar in both groups. In both groups, delayed cortical seizures were indicated by intense low-frequency electrocortical activity. In the treatment group, duration of cortical seizures was increased and the intensity of the final electrocortical activity was more depressed (-19+/-1 dB versus -10+/-2 dB). The results indicate that after cerebral ischemia in fetal sheep, NO synthase inhibition does not ameliorate the delayed disruptions in cerebral energetics. However, the effect of NO synthase inhibition on delayed cortical seizures may improve our understanding of the role of NO during this phase.

Perinatal observations in forty-eight neurologically impaired term infants

OBJECTIVE

Our goal was to review the perinatal characteristics of 48 singleton term infants with central nervous system neurologic impairment.

STUDY DESIGN

Medical records were retrospectively reviewed for maternal characteristics, prenatal and intrapartum care patterns, neonatal course, and long-term outcome. Those patients without evidence of an obvious acute asphyxial event, traumatic delivery, or preterm birth were excluded. The study population was then subclassified according to the admission fetal heart rate pattern.

RESULTS

Of these 48 term infants the admission fetal heart rate pattern was nonreactive in 33 (69%) and reactive in 15 (31%). Maternal characteristics, prenatal care, and long-term outcome were statistically similar between the two groups. However, the nonreactive group exhibited significantly more characteristics consistent with a prior asphyxial event: thick "old" meconium, "fixed" nonreactive baseline fetal heart rate, meconium-stained skin, and meconium aspiration syndrome. In contrast, in the reactive group a fetal heart rate pattern developed that was consistent with Hon's theory for intrapartum asphyxia and manifested by a prolonged tachycardia in association with persistent nonreactivity, diminished fetal heart rate variability, and fetal heart rate decelerations.

CONCLUSIONS

Among fetuses later found to be neurologically impaired, a persistent nonreactive fetal heart rate tracing obtained from admission to delivery appears to be evidence of prior neurologic injury.

Antenatal and intrapartum factors associated with the occurrence of seizures in term infant

To identify antenatal and intrapartum risk factors associated with seizures in term newborns, 40 infants who had seizures within 72 hours of birth were compared with 400 controls using logistic regression analysis. The risk of seizure in the term newborn was approximately one per 1000 in the population studied. The logistic regression model identified a group of infants in whom the risk of seizure was approximately one per 100. The risk factors included in the model were antepartum anemia, antepartum bleeding, asthma, meconium-stained amniotic fluid, presentation other than occiput anterior, fetal distress, and shoulder dystocia. Consistent with other studies, our analysis confirmed a strong association between seizures and factors that increase the risk of fetal asphyxia.