Neonatal Fits Associated with Hypomagnesaemia

Neonatal Seizures: Gaps Between the Laboratory and the Clinic

Seizures in neonates (NBs) remain the most frequent neurological problem in the nursery. Considerable debate about their consequences exists between data and deductions reached through animal experimentations and those obtained through clinical investigations. The main conflicting issues are whether seizures in NBs can plant the roots for epileptogenesis and cause long-term deficits. The purpose of this chapter is to evaluate both laboratory and clinical results.

METHODS

Clinical data will be presented, including a 20-year-long cohort of NBs. This will be followed by the main seminal discoveries obtained in neonatal models. The phenomenon of transient or persistent dysmaturity following NB seizures will be discussed in relation to etiological factors.

RESULTS

The findings and deductions from animal models support the notions that epileptogenesis and cognitive deficits result from NB seizures. These conclusions contrast with clinical investigations maintaining that NB seizures, per se, are symptomatic markers of preexisting or of ongoing morbidities. The reasons for contrasting views will be discussed. Suggestions will be advanced for more animal models whose seizures are consistent with the etiologies and the phenotypes of human NB seizures.

Magnesium and cardiac surgery

Magnesium depletion was found to occur commonly after cardiac surgery in children and to cause significant neurological and cardiac symptoms. This discovery, in the absence of previous detailed documentation, inspired investigations to determine the relationship of cardiac surgery to changes in magnesium metabolism. A number of patient groups were studied, including both children and adults undergoing various operations. The studies demonstrated an almost universal occurrence of magnesium depletion during and after cardiac surgery, but also demonstrated that supplementation may be preventive. The patterns and aetiology of the changes and their clinical significance are presented and discussed in the light of recent reports from other authors.

Neonatal seizures: a clinician's overview

Seizures are the most frequent neurological event in newborns (NBs), provoked often by noxae not apt to cause them in later life. This is because receptor families of excitatory amino acids (EAA) are overexpressed at this stage of brain ontogenesis, which is also why most neonatal seizures rapidly abate, even when neurological deficits persist. The brain's immaturities dictate distinct seizure phenotypes. A classification proposed in the late 1960s has been criticized, and a new one has been advocated, based on correlations between EEGs and behaviors, leading to a classification of seizures into 'epileptic' and 'non-epileptic'. The taxonomic pitfalls of these classifications are discussed, and the notion advanced that many seizures fail to fulfil the criteria to label them as epileptic. While etiological factors have changed in time, the striking dichotomy in outcome has persisted. Many etiologies, often multifactorial, are unique in NBs, and they are discussed with reference to diagnosis and therapies. Four syndromes of NB seizures, accepted into the International Classification of the Epilepsies, are critically analyzed, some appearing to rest on fragile grounds. Controversies persist whether seizures per se are injurious to the immature brain. Clinical studies suggest that neither duration in days or length of seizure phenotypes correlates with outcomes, the most valid prognostic indices being offered by etiologies and by patterns of EEG polygraphy. However, because most seizures are symptomatic, it may be difficult to distinguish morbidity due to underlying pathology from that possibly added by seizures. Animal experiments suggested that they are injurious. The theory of energy failure, postulated to cause a cascade of events leading to inhibitions of DNA, proteins, lipids and disrupted neuronal proliferation, synaptogenesis, myelination, has largely been disproved. Brains of immature animals have been shown to have the oxidative machinery needed to fulfill energy demands, even during status convulsivus. They are also capable of using anaerobic metabolism and require less ATP when aerobic energy production ceases. Recent explanations for the injurious consequences of hypoxic ischemia and of prolonged convulsions postulate that neuronal damage occurs from excessive release of EAA which, by binding to their ligand-gated ionic receptors, cause a large influx of Ca2+, resulting in cell death. Because of the overabundance of EAA receptors in early ontogenesis, the excitotoxic hypothesis would appear attractive, but some observations militate against it. Among these is the dissociation found between the focal neurotoxicities induced by EAA injected into the brain and their absence following the concomitant convulsions. The latter are not blocked by pretreatment with EAA antagonists, while these prevent injuries caused by the injected EAA. There is no convincing evidence that excessive release of EAA occurs during NBs' seizures. Even if it does occur, it has been shown that immature neurons have a better capacity to self-protect from increased Ca2+ influx, and also that direct application of glutamate to immature neurons leads to significantly lower Ca2+ influx. These data raise doubts about the postulated excitotoxicity caused by NBs' seizures, being consistent with the fact that no one, so far, has observed neuronal damage from drug-induced convulsive states in NBs. Lack of overt neuronal injuries does not preclude that long-term subtle changes might be induced by noxae apt to provoke transient ictal events. Thus models developed in our laboratories demonstrate that long-term epileptogenicity results following postnatal O2 deprivation without evidence of neuronal injuries or of long-term behavioral or electrophysiological alteration. However, both age at which hypoxia occurs and specific proconvulsant methods used strictly determine whether increased epileptogenicity will occur.

Hypomagnesemia in diabetic children

Serum concentrations of iron, copper, zinc and magnesium were determined in 27 Swedish children with well controlled diabetes without longterm diabetic complications. Thirteen of the diabetic children had age- and sex-matched healthy controls. Significantly lower serum magnesium concentrations were found in the diabetic children than in the matched healthy controls (p less than 0.01). The levels of iron, copper and zinc did not differ in the diabetic children from those in the controls. A negative correlation between serum magnesium level and duration of diabetes was found (p less than 0.05). This is seemingly the first report of hypomagnesemia in diabetic children.

The role of magnesium in protein-energy malnutrition

The present study was aiming to explore further the variations in the levels of Mg in both serum and CSF of PEM children, hoping a better understanding revealed decreased values of both blood serum and CSF levels of Mg in PEM children which denote some abnormalities in brain metabolism. Such abnormalities add further support for assumption of the link between dietary insufficiency and subnormal mental performance in PEM.

Clinical and biochemical assessment of a modified evaporated milk for infant feeding

A clinical and biochemical evaluation has been made of a new milk formula, Modified Carnation milk (MCM), based on cows' milk but with the mineral content and concentration of caloric nutrients altered to make it correspond more closely to human milk. MCM produced higher plasma calcium and magnesium concentrations in 6-day-old infants than those produced by unmodified evaporated and dried milks, achieving concentrations closer to those of breast milk. Plasma free amino acid concentrations in MCM-fed infants are nearer breast-fed values than those in unmodified milk-fed infants where higher individual plasma amino acid concentrations persist during the first 3 months. MCM-fed infants had low plasma urea concentrations and lower urine osmolalities at 6 days, 3 weeks, 6 weeks, 3 months, and 6 months than infants fed on the evaporated and dried milks, and similar plasma urea and urine osmolalities to those of breast-fed infants. MCM is likely to be superior to unmodified evaporated and dried milks in preventing convulsions of the hypocalcaemic/hypomagnesaemic/hyperphosphataemic type, and seems less likely to cause hypertonic dehydration. MCM is easily prepared, readily accepted by babies, and appears to be nutritionally adequate for the feeding of term infants.

Effect of magnesium deficiency on nonspecific excitability level (NEL) and audiogenic seizure susceptibility

Magnesium deficiency in weanling rats caused an increase in NEL and in audiogenic seizure susceptibility. These behavioral effects were apparent after eight days of magnesium restriction and could be reversed by dietary rehabilitation. Serum magnesium declined rapidly from 1.87 +/- 0.10 mEq/L to 0.91 +/- 0.24 mEq/L in two days. Cerebrospinal fluid (CSF) magnesium decreased gradually from 1.86 mEq/L, becoming significantly lower (1.44 +/- 0.23 mEq/L) after eight days. When deficient rats were injected IP with MgCl2, raising the serum magnesium concentration to 6.6 mEq/L, NEL decreased to normal while audiogenic seizure susceptibility remained. Both NEL and audiogenic seizure susceptibility in rats reflect central nervous system magnesium concentration, except when serum magnesium concentration is very high. Very high serum magnesium concentration lowers NEL but does not reduce audiogenic seizure susceptibility if CSF magnesium is low.

Etiology of convulsions in neonatal and infantile period

1) Etiology of convulsions starting prior to two years of age was discussed in 418 cases. Neonatal seizures before 30 days old appeared in 86 cases (53 boys and 33 girls). Three hundred and thirty-two patients (172 boys and 160 girls) had convulsions in infancy. Twelve patients (9 boys and 3 girls) suffered from convulsions both in neonatal and infantile period. 2)Etiology of convulsions was prenatal in 67 cases (16%), natal in 49 cases (12%), postnatal in 158 cases (38%) and unknown in 144 cases (34%). Prenatal factors consisted of cerebral malformation (23 cases, 6%), associated physical minor anomaly such as cataracta or finger abomaly (11 cases, 3%), abnormal pernatal history (8 cases, 2%), congenital heart disease 3) cases, 1%), tuberose scleorsis (7 cases, 2%) and positive family history (13 cases, 3%). Postnatal causes included hypocalcemia or hypoglycemia (7 cases, 2%), brain tumors (3 cases, 1%), breath-holding spells (21 cases, 5%), febrile convulsion (44 cases, 11%), bathing (3 cases, 1%), afebrile colds (3 cases, 1%), purulent meningitis (17 cases, 4%), DPT immunization (10 cases 2%), vaccination (7 cases, 2%) and acute hemiplegia (10 cases, 2%). The group of unknown etiology were as fns (38 cases, 9%), epilepsy associated with interictal signs (23 cases, 6%), benign infantile convulsions (57 cases, 14%), neonatal convulsion of unknown etiology (12 cases, 3%) and miscellaneous categories (4%). 3) Pregnancy was abnormal in 53% of cases with cerebral malformation. Asphyxia at birth was noted in 43% of patients with tuberose sclerosis and in 35% of congenital cerebral abomaly. 4) Pneumoencephalographic examinations revealed midline anomaly in 50% of cerebral malformation. It was abnormal in all cases with tuberose sclerosis, head injury and epilepsy with interseizure neurological signs. 5) There were no correlations between the seizure pattern and the etiology in neonatal convulsion. In infancy, focal-unilateral convulsions and infantile spasms were frequently associated with organic damages. Generalized seizures were seen in organic lesions as well as functional ones although approximately half of the cases were febrile convulsion, benign infantile convulsion or breath-holding spell. 6) EEG features of cerebral malformation were asymmetrical or multifocal dischages in neonatal period and hypsarhythmia or focal-unilateral spike discharges in infancy. Tuberose sclerosis showed hypsarhythmia in infancy. In birth injury or cerebral anoxia, EEG mostly revealed focal-unilateral abnormality or suppression-burst activity in newborns and hypsarhythmia or focal features in infants. 7) The occurrence rate of neonatal seizures in autopsy cases with intracranial pathology was demonstrated. EEG with intravenous diazepam was useful to know pathophysiology of infantile spasms.

The effects of aliphatic alcohols on the biophysical and biochemical correlates of membrane function

The simplicity of the structure of aliphatic alcohols suggests that their interaction with receptors in the classical sense is unlikely. The actions of alcohols may involve a relatively nonspecific disruption of cell membranes, possibly physically dissolving into neuronal membranes especially, resulting in the malfunction of normal physiological processes. Studies of alcohol-membrane interactions have employed the use of artificial and nonneural membranes, invertebrate neurons for electrophysiological measurements and brain tissue for studying ion fluxes and enzymatic activities. For the most part these studies have been inclusive because high concentrations of alcohols were needed to elicit any effect. Also, it is difficult to extrapolate the data to in vivo mammalian systems, especially relative to the clinical signs of depression of the central nervous system.

Neonatal convulsions associated with primary disturbance of calcium, phosphorus, and magnesium metabolism

Images

Plasma calcium and magnesium in newborn babies

Normal values for plasma calcium and magnesium levels during the first week of life, in breast- and bottle-fed babies, have been determined. It has been shown on the sixth day that plasma levels of calcium, magnesium, and protein are all significantly lower in bottle-fed babies than in breast-fed babies, while the reverse is true of the plasma inorganic phosphorus. The normal babies have been compared with 30 babies who had convulsions, beginning towards the end of the first week of life. In only six of the babies was the plasma calcium outside our normal range and only four had abnormally low magnesium levels. As so many of these babies had calcium and magnesium levels within the normal range it must seriously be questioned whether hypocalcaemia or hypomagnesaemia could have been the sole cause of the convulsions.