Fetal and neonatal cerebral infarcts

Protein C deficiency: a case review

Protein C (PC) deficiency is a rare but life-threatening bleeding disorder that can present in the immediate neonatal period. This article presents the case of a baby girl with acute and progressive neonatal purpura fulminans as the presenting feature of PC deficiency. Other common complications of this disease include ophthalmic problems and central nervous system (CNS) changes. Management consists of correcting the coagulopathy, intensive wound care including negative-pressure dressings and skin grafting, and supportive care for the ophthalmic and CNS issues. Long-term follow-up consists of lifelong anticoagulant therapy to avoid recurrence of these complications.

Dual effect of glutamate on GABAergic interneuron survival during cerebral cortex development in mice neonates

In term and preterm neonates, massive glutamate release can lead to excitotoxic white-matter and cortical lesions. Because of its high permeability toward calcium, the N-methyl-D-aspartic acid (NMDA) receptor is thought to play an important role in excitotoxic lesions and NMDA antagonists therefore hold promise for neuroprotection. We found that, in neonatal mouse cortex, a given NMDA concentration exerted either excitotoxic or antiapoptotic effects depending on the cortical layers. In layer VI, NMDA led to excitotoxicity, sustained calcium mobilization, and necrosis of Gad67GFP neurons. In the immature layers II-IV, NMDA decreased apoptosis and induced transient calcium mobilization. The NMDA antagonist MK801 acted as a potent caspase-3 activator in immature layers II-IV and affected gamma aminobutyric acid (GABA)ergic interneurons. The apoptotic effect of MK801-induced BAX expression, mitochondrial potential collapse and caspase-9 activation. In vivo Bax small interfering ribonucleic acid and a caspase-9 inhibitor abrogated MK801-induced apoptosis and pyknotic nucleus formation. Ketamine, an anesthetic with NMDA antagonist properties, mimicked the apoptotic effects of MK801. These data indicate a dual effect of glutamate on survival of immature and mature GABAergic neurons and suggest that ketamine may induce apoptosis of immature GABAergic neurons.

Neonatal seizures: to treat or not to treat?

The immature brain is intrinsically hyperexcitable, a feature that, despite being crucial for learning, synaptogenesis and neuronal plasticity, predisposes the neonate to seizures. Seizures represent the most common neurologic manifestation of impaired brain function in this age group. Importantly, although seizure-induced neuronal injury is minimal in the "healthy" neonatal brain, the "metabolically-compromised" brain appears more vulnerable. Even in the "healthy" brain, however, seizures result in impaired learning, enhanced susceptibility to further seizures, and increased risk of brain injury with seizures later in life, as a result of altered hippocampal circuitry. Given these findings, an aggressive approach to neonatal seizures appears warranted. However, our current conventional therapies (including phenobarbital, phenytoin, and benzodiazepines), even when used in combination, are often ineffective in controlling seizures. Lidocaine may yield better efficacy but requires more study. Recent animal data suggest that alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid (AMPA) antagonists such as topiramate may have a neuroprotective role. However, further work is needed to confirm the safety of excitatory amino acid antagonists in neonates because there remains a prevailing concern that such agents may impair normal neurodevelopmental processes.

[Interest of EEG in full-term newborns with isolated unilateral ischemic stroke]

In full-term newborns, unilateral and recurrent clonic seizures which occur during the first 48 hours of life suggest an isolated unilateral ischemic stroke. These focal seizures are isolated, occuring during a short period, or make up a status epilepticus. Electroencephalogram (EEG) is a key tool for crisis and focal cerebral process diagnosis. It also allows to assess antiepileptic drugs effectiveness. But cerebral imaging is necessary to confirm vascular origin of the cerebral impairment. Hematologic data are also needful to look for a family thromphilia. Some particular unilateral EEG abnormalities could be associated with controlateral motor sequelae or long term behavioral problems. These findings may be used for prospective studies aimed at specifying possible links between EEG abnormalities and long term outcome.

Indications de l'électroencéphalogramme en période néonatale

The electroencephalogram (EEG), an easy-to-use and non invasive cerebral investigation, is a useful tool for diagnosis and early prognosis in newborn babies. In newborn full term babies manifesting abnormal clinical signs, EEG can point focal lesions or specific aetiology. EEG background activity and sleep organization have a high prognostic value. Tracings recorded over long period can detect seizures, with or without clinical manifestations, and differentiate them from paroxysmal non epileptic movements. The EEG should therefore be recorded at the beginning of the first symptoms, and if possible before any seizure treatment. When used as a neonatal prognostic tool, EEG background activity is classified as normal, abnormal (type A and type B discontinuous and hyperactive rapid tracing) or highly abnormal (inactive, paroxysmal, low voltage plus theta tracing). In such cases, the initial recording must be made between 12 and 48 h after birth, and then between 4 and 8 days of life. Severe EEG abnormalities before 12 h of life have no reliable prognostic value but may help in the choice of early neuroprotective treatment of acute cerebral hypoxia-ischemia. During presumed hypoxic-ischemic encephalopathy, unusual EEG patterns may indicate another diagnosis. In premature newborn babies (29-32 w GA) with neurological abnormalities, EEG use is the same as in term newborns. Without any neurological abnormal sign, EEG requirements depend on GA and the mother's or child's risk factors. Before 28 w GA, when looking for positive rolandic sharp waves (PRSW), EEG records are to be acquired systematically at D2-D3, D7-D8, 31-32 and 36 w GA. It is well known that numerous and persistent PRSW are related to periventricular leukomalacia (PVL) and indicate a bad prognosis. In babies born after 32 GA with clinically severe symptoms, an EEG should be performed before D7. Background activity, organization and maturation of the tracing are valuable diagnosis and prognosis indicators. These recommendations are designed (1) to get a maximum of precise informations from a limited number of tracings and (2) to standardize practices and thus facilitate comparisons and multicenter studies.

[EEG and ischemic stroke in full-term newborns]

The aims of this study were to describe EEG anomalies in unilateral neonatal ischemic stroke without hypoxic-ischemic encephalopathy, and to determine possible links between these abnormalities and long-term outcome. In 6 full-term newborns without severe fetal distress ischemic stroke was confirmed by computed tomography and/or magnetic resonance imaging. Twenty EEGs were recorded during the neonatal period, 5 in acute stage and 15 later. The duration of the follow-up ranged from 3 to 9 years. All newborns developed unilateral clonic seizures, right-sided (5 cases) or left-sided (1 case); seizures began between 14 and 48 h of life. At follow-up, 3 children were normal at 2 and 6 years of age, while the 3 others had sequelae: epilepsy at 9 years of age in one, and unilateral mild cerebral palsy in the 2 others (3 and 4 years of age), with behavioral problems in one of them. Critical EEG discharges, rhythmic sharp waves and/or slow waves were recorded on the injured side. Abnormalities of interictal activity were excess of alpha or theta rhythms, transitory EEG discontinuity or low voltage. The 2 children with cerebral palsy had numerous unilateral post-ictal positive rolandic slow sharp waves (PRSSWs), which were similar to the positive rolandic sharp waves of premature infants; the child with behavioral problems had numerous positive left-sided temporal fast sharp waves. PRSSWs could be associated with contralateral motor sequelae, while positive left temporal fast sharp waves were associated with long term behavioral problems. These findings may be used for future prospective studies aimed at specifying the relation between EEG abnormalities and long-term outcome.

Prenatal infection obliterates glutamate-related protection against free hydroxyl radicals in neonatal rat brain

Prenatal infection constitutes an important risk factor for brain injury, in both premature and full-term infants. Unfortunately, as the mechanisms involved are far from understood, no therapeutic strategy emerges to prevent the damage. We tested the hypothesis that administration of lipopolysaccharide (LPS) to gravid female rats enhanced glutamate-induced oxidative stress in brain of pups. A microdialysis probe was implanted into the striatum of 14-day-old animals and the release of hydroxyl radicals (.OH) in the perfusion medium was evaluated. Glutamate promoted a delayed.OH release in the offspring of dams given LPS, contrasting with the.OH decreases observed in control animals. A similar response occurred after infusion of (R,S)-3,5-dihydroxyphenylglycine (DHPG), a Group I metabotropic glutamate receptor (mGluR) agonist. This response was not consecutive to a remote activation of N-methyl-D-aspartate (NMDA) receptors, as it was unaffected by an NMDA receptor antagonist. Furthermore, the response to NMDA itself decreased in the offspring of dams given LPS. Massive amounts of DHPG, however, likely internalizing the mGlu receptor, still blunted the response to NMDA, as in controls. No quantitative variation occurred in mGluR1, mGluR5, or the NR1 subunit of the NMDA receptor between controls and neonates born from LPS-treated dams. Direct LPS injection into age-matched pups, by contrast, affected the response to neither glutamate nor DHPG. These results confirm that normally during perinatal development, the brain is protected from any oxidative stress resulting from excess glutamate, and the results support the hypothesis that maternal infection before delivery may lead to critical brain damage via the release of toxic free radicals.

Cerebral infarctions in the fetus and neonate: maternal-placental-fetal considerations

Historical data, clinical examination findings, and laboratory information must be integrated along a variable timeline that includes antepartum, intrapartum, and postnatal time periods when cerebral infarction can occur, in the context of the neonates genetic endowment. Genetic susceptibility or prenatal acquired vulnerabilities regarding stroke syndromes may set in motion a cascade of molecular pathways that ultimately cause or exacerbate brain injury when the vulnerable child experiences adverse medical conditions. The clinician must consider maternal, placental, and fetal conditions on which a stroke syndrome may be superimposed, with or without additional brain injury from other pathogenic mechanisms. Evaluation of fetal and neonatal cerebral infarction requires knowledge of mechanisms of brain injury that cross medical disciplines and may involve consultation with maternal/fetal specialists, placental and pediatric pathologists, neonatologists, geneticists, and other pediatric subspecialties. Comprehensive evaluations of survivors of cerebral infarction are needed to better understand structural and functional plasticity of the developing brain after a cerebrovascular event in the fetal and neonatal periods.

Animal models of neonatal stroke

Neonatal stroke occurs in approximately 1 in 4,000 to 1 in 10,000 newborns, and more than 80% involve the vascular territory supplied by the middle cerebral artery. Neonatal stroke is associated with many acquired and genetic prothrombotic factors, and follow-up studies indicate that as many as two thirds of neonates develop neurologic deficits. In the past two decades unilateral carotid occlusion with 8% hypoxia has been used to study focal and global ischemia in the newborn, and recently a filament model of middle cerebral artery occlusion has been developed. This review describes the results of studies in these two newborn models covering aspects of the injury cascade that occurs after focal ischemia. A likely requirement is that therapeutic efforts be directed less at using thrombolytic therapy and more toward treatment of events associated with reperfusion injury, the inflammatory cascade, and apoptosis. Additional areas of research that have received attention in the past year include inhibition of nitric oxide and free-radical formation, use of iron chelating agents, the potential role of hypoxia-inducible factors and mediators of caspase activity, use of growth factors, hypothermia, and administration of magnesium sulfate.