Can neurological injury be timed?

[Ten practical issues concerning acute poisoning with carbon monoxide in pregnant women]

BACKGROUND

The poisoning of carbon monoxide (CO) is the leading cause of death by poisoning in France. Its consequences are potentially serious to the fetus. Literature is ancient and little known.

PURPOSE AND METHOD

Make an inventory of knowledge about carbon monoxide poisoning during pregnancy.

RESULT

The CO causes maternal then fetal tissue hypoxia primarily by binding to hemoglobin with which it has a high affinity. Its transplacental passage may cause fetal harm, predominantly in the brain. Severity seems correlated with maternal symptoms during exposure. In the absence of maternal symptoms, however, the available data are reassuring. Hyperbaric oxygen therapy may reduce the risk to the fetus.

DISCUSSION

Oxygen therapy should be offered in all cases of CO poisoning, especially if there are maternal symptoms during exposure. In addition, a fetal echography directed on the cephalic pole - even a fetal magnetic resonance imaging three weeks after exposure - should also be proposed.

[Cerebral palsy and perinatal asphyxia (II--Medicolegal implications and prevention)]

Obstetric litigation is a growing problem in developed countries and its escalating cost together with increasing medical insurance premiums is a major concern for maternity service providers, leading to obstetric practice cessation by many practitioners. Fifty-four to 74 % of claims are based on cardiotocographic (CTG) abnormalities and their interpretation followed by inappropriate or delayed reactions. A critical analysis is performed about the nine criteria identified by the American College of Obstetricians and Gynecologists and the American Academy of Pediatrics in their task force on Neonatal Encephalopathy and Cerebral Palsy: four essential criteria defining neonatal asphyxia and five other suggesting an acute intrapartum event sufficient to cause cerebral palsy in term newborns. The importance of placental histologic examination is emphasized in order to confirm sudden catastrophic events occurring before or during labor or to detect occult thrombotic processes affecting the fetal circulation, patterns of decreased placenta reserve and adaptative responses to chronic hypoxia. It may also exclude intrapartum hypoxia by revealing some histologic patterns typical of acute chorioamnionitis and fetal inflammatory response or compatible with metabolic diseases. Magnetic resonance imaging (MRI) of the infant's damaged brain is very contributive to elucidate the mechanism and timing of asphyxia in conjunction with the clinical picture, by locating cerebral injuries predominantly in white or grey matter. Intrapartum asphyxia is sometimes preventable by delivering weak fetuses by cesarean sections before birth, by avoiding some "sentinel" events, and essentially by responding appropriately to CTG anomalies and performing an efficient neonatal resuscitation. During litigation procedures, it is necessary to have access to a readable CTG, a well-documented partogram, a complete analysis of umbilical cord gases, a placental pathology and an extensive clinical work-up of the newborn infant including cerebral MRI. Malpractice litigation in obstetric care can be reduced by permanent CTG education, respect of national CTG guidelines, use of adjuncts such as fetal blood sampling for pH or lactates, regular review of adverse events in Clinical Risk Management (CRM) groups and periodic audits about low arterial cord pH in newborns, admission to neonatal unit, the need for assisted ventilation and the decision-to-delivery interval for emergency operative deliveries. Considering the fast occurrence of fetal cerebral hypoxic injuries, and thus despite an adequate management, many intrapartum asphyxias will not be preventable. Conversely, well-documented hypoxic-ischemic brain insults during the antenatal period do not automatically exclude intrapartum suboptimal obstetric care.

[Cerebral palsy and perinatal asphyxia (I--diagnosis)]

Cerebral palsy (CP) is a group of disorders of the development of movement and posture, causing activity limitations, that are attributed to nonprogressing disturbances that occurred in the developing fetal or infant brain. The motor abnormalies are often accompanied by disturbances of sensation, perception, cognition, behavior and/or by a seizure disorder. The prevalence of CP has not decreased in developed countries over the past 30 years, despite the widespread use of electronic fetal heart rate monitoring and a 5- to 6-fold increase in the cesarean delivery rate. In the term newborn, CP may be attributed to perinatal asphyxia in case of metabolic acidosis in the cord blood (pH<7,00 and base deficit>12 mmol/L), followed by a moderate or severe neonatal encephalopathy within 24 hours and a further neurological impairement characterized by spastic quadriplegia and dyskinesia/dystonia. Dating the time of fetal asphyxia during delivery is possible when there are acute catastrophic complications during labor and unexpected acute or progressive fetal heart rate anomalies after a normal admission test, when there is a need for intensive neonatal resuscitation, a multi-organ failure within 72 hours of birth and visualization of acute non focal cerebral abnormalities, mainly by early magnetic resonance imaging (MRI). MRI sequences show either a brain-damaged pattern of the central basal ganglia, thalami and posterior limbs of internal capsules with relative cortical sparing, in acute, near-total asphyxial insults manifested by a continuous bradycardia or a pattern of cortical injury in the watershed zones and relative sparing of the central grey matter, in prolonged partial asphyxia, manifested by late or atypical variable decelerations with progressive fetal tachycardia, loss of reactivity and absent fluctuation. Prolongation of either type of asphyxial insult results in more global brain damage. In order to differentiate a CP occurring after perinatal asphyxia from other neurological sequelae in relation with infection, hemorrhage, stroke, malformations, genetic or metabolic diseases, it is essential that a definitive information from the brain by MRI and an extensive histological examination of the placenta are at disposal.

The Timing of Neonatal Brain Damage

Although neonatal morbidity and mortality are less than in the past, the risk of pre-natal and neonatal brain damage has not been eliminated. In order to optimize pre-natal, perinatal and neonatal care, it is necessary to detect factors responsible for brain damage and obtain information about their timing. Knowledge of the timing of asphyxia, infections and circulatory abnormalities would enable obstetricians and neonatologists to improve prevention in pre-term and full-term neonates. Cardiotocography has been criticized as being too indirect a sign of fetal condition and as having various technical pitfalls, though its reliability seems to be improved by association with pulse oximetry, fetal blood pH and electrocardiography. Neuroimaging is particularly useful to determine the timing of hypoxic-ischemic brain damage. Cranial ultrasound has been used to determine the type and evolution of brain damage. Magnetic resonance has also been used to detect antenatal, perinatal and neonatal abnormalities and timing on the basis of standardized assessment of brain maturation. Advances in the interpretation of neonatal electroencephalograms have also made this technique useful for determining the timing of brain lesions. Nucleated red blood cell count in cord blood has been recognized as an important indication of the timing of pre-natal hypoxia, and even abnormal lymphocyte and thrombocyte counts may be used to establish pre-natal asphyxia. Cord blood pH and base excess are well-known markers of fetal hypoxia, but are best combined with heart rate and blood pressure. Other markers of fetal and neonatal hypoxia useful for determining the timing of brain damage are assays of lactate and markers of oxidative stress in cord blood and neonatal blood. Cytokines in blood and amniotic fluid may indicate chorioamnionitis or post-natal infections. The determination of activin and protein S100 has also been proposed. Obstetricians and neonatologists can therefore now rely on various methods for monitoring the risk of brain damage in the antenatal and post-natal periods.

Screening for infectious diseases

INTRODUCTION

Fetal brain injury is an essential cause of lifelong morbidity. Infection appears as a cause of brain damage. Apart from chorioamnionitis, screening for infectious diseases must be considered in pregnancies with a risk of congenital infection or cases with abnormal cerebral ultrasound findings.

DISCUSSION

Congenital infections include most of the major components of the TORCH complex: toxoplasmosis, rubella, cytomegalovirus, herpes, and varicella. Seronegative mothers can develop primary infection, which carries a risk of vertical transmission. The timing of the infection is a critical point, because fetal damage often depends on the gestational age at which acute maternal infection took place and occurs more likely in the first half of pregnancy. Antenatal ultrasound can detect brain abnormalities, like hydrocephalus, periventricular leukomalacia, calcifications or hemorrhage. Maternal serologic tests must be performed to look for an infectious etiology; the most frequent agents are the components of the TORCH complex. But additional serology must include parvovirus B19, HIV, and coxsackieviruses.

Cranial ultrasonography has a low sensitivity for detecting arterial ischemic stroke in term neonates

The aim of this study was to investigate the sensitivity of cranial ultrasonography for detecting acute arterial ischemic stroke in term neonates. Thirty-six neonates with gestational age > or = 36 weeks who had cranial ultrasonography followed by computed tomography (CT) or magnetic resonance imaging (MRI) confirming arterial ischemic stroke were identified from a consecutive cohort study of all children diagnosed with arterial ischemic stroke by CT or MRI and seen at Chedoke McMaster Hospital between January 1992 and December 1998 or at The Hospital for Sick Children between January 1992 and December 2000. Cranial ultrasonography demonstrated focal abnormalities in 11 patients, giving the initial cranial ultrasonography a sensitivity of 30.56% for identifying neonates with infarction (95% CI 15.5-45.5%). The sensitivity of cranial ultrasonography performed in the two pediatric referral centers (Chedoke McMaster Hospital and Hospital for Sick Children; n = 19) was higher than that in community hospitals (n = 17) (47.3% versus 11.7%; P =.031). Neonates with suspected infarction should be evaluated with CT or MRI.

Proinflammatory cytokines: a link between chorioamnionitis and fetal brain injury

OBJECTIVE

To review the etiology of impaired fetal neurodevelopment - in particular, the relationship between chorioamnionitis, cytokines, and cerebral palsy.

DATA SOURCES

A MEDLINE search was performed for all clinical and basic science studies published in the English literature from 1966 to 2002. Key words or phrases used were chorioamnionitis, cerebral palsy, fetal brain damage, fetal CNS injury, infection in pregnancy, proinflammatory cytokines in pregnancy, proinflammatory cytokines in infection, and preterm labour or birth. All relevant human and animal studies were included.

STUDY SELECTION

Fetal brain injury remains a major cause of lifelong morbidity, incurring significant societal and health care costs. It has been postulated that chorioamnionitis stimulates maternal/fetal proinflammatory cytokine release, which is damaging to the developing fetal nervous system. Elevated cytokine concentrations may interfere with glial cell development and proliferation in the late second trimester of pregnancy, when the central nervous system is most vulnerable. Increasing numbers of epidemiological and basic science studies found through MEDLINE searches support this hypothesis. Treatment options aimed at etiologic factors may lead to improved neurodevelopmental outcomes.

CONCLUSIONS

Clearly, some relationship exists between chorioamnionitis, cytokines, and the development of cerebral palsy, but the severity and duration of exposure required to produce fetal damage remains unknown. Future research addressing these issues may aid in clinical decision-making. As well, the elucidation of mechanisms of cytokine action may aid in early treatment options to prevent or limit development of fetal brain injury.

Long-term developmental outcome of asphyxiated term neonates

Asphyxia remains one of the main causes of later disability in term infants. Despite many publications identifying possible predictors of outcome in this population of interest, little is known of the long-term developmental outcome of asphyxiated term neonates. Observational studies have largely focused on short-term outcomes, with an emphasis on significant neurologic sequelae and intellectual impairments. This article reviews the literature that has described the developmental outcome of asphyxiated term newborns. As part of this review, we have also highlighted the evolution of the definition of asphyxia and delineated appropriate markers that should be used in future research on this population.

The pediatric neurologist as expert witness with particular reference to perinatal asphyxia

The frequency of litigation related to alleged medical malpractice is increasing in Canada. For the neurologist, involvement in such litigation most often takes place in the context of acting as an expert witness and, for the pediatric neurologist, the most common clinical situation for which expertise is requested is that of possible perinatal asphyxia. The medical expert's primary role is to provide necessary guidance and assistance to the court, which may permit the rendering of decisions that are scientifically valid. This article will review the attributes of the medical expert witness. Aspects of perinatal asphyxia cases under litigation that commonly require the assistance of pediatric neurology expertise such as etiology, timing, extent of disability and life expectancy will also be reviewed in detail. The aim is to provide for the neurologist a clearer understanding of the responsibilities inherent in this increasing professional role.