THE PATHOGENESIS OF EXPERIMENTAL PERIVENTRICULAR CEREBRAL NECROSIS AND ITS POSSIBLE RELATION TO THE PERIVENTRICULAR LEUCOMALACIA OF BIRTH TRAUMA

Vertically acquired neonatal citrobacter brain abscess - case report and review of the literature

Vertically acquired citrobacter meningitis in the neonate is very rare and carries a very high mortality and morbidity. Overall, approximately 30% of neonates with Citrobacter meningitis die and 50% sustain some damage to the CNS. The authors describe a case of a newborn with Citrobacter koseri meningitis with multiple brain abscesses, with a successful outcome following multiple burr-hole aspirations and prolonged antibiotic therapy. An aggressive surgical approach combined with intravenous antibiotics (including imipenems, to which the organism is very sensitive) for a minimum of 4 weeks appears to improve the outcome of infection with this virulent organism.

Periventricular leukomalacia, inflammation and white matter lesions within the developing nervous system

Periventricular leukomalacia (PVL) occurring in premature infants, represents a major precursor for neurological and intellectual impairment, and cerebral palsy in later life. The disorder is characterized by multifocal areas of necrosis found deep in the cortical white matter, which are often symmetrical and occur adjacent to the lateral ventricles. There is no known cure for PVL. Factors predisposing to PVL include birth trauma, asphyxia and respiratory failure, cardiopulmonary defects, premature birth/low birthweight, associated immature cerebrovascular development and lack of appropriate autoregulation of cerebral blood flow in response to hypoxic-ischemic insults. The intrinsic vulnerability of oligodendrocyte precursors is considered as central to the pathogenesis of PVL. These cells are susceptible to a variety of injurious stimuli including free radicals and excitotoxicity induced by hypoxic-ischemic injury (resulting from cerebral hypoperfusion), lack of trophic stimuli, as well as secondary associated events involving microglial and astrocytic activation and the release of pro-inflammatory cytokines TNF-alpha and IL-6. It is yet unclear whether activated astrocytes and microglia act as principal participants in the development of PVL lesions, or whether they are representatives of an incidental pathological response directed towards repair of tissue injury in PVL. Nevertheless, the accumulated evidence points to a pathological contribution of microglia towards damage. The topography of lesions in PVL most likely reflects a combination of the relatively immature cerebrovasculature together with a failure in perfusion and/or hypoxia during the greatest period of vulnerability occurring around mid-to-late gestation. Mechanisms underlying the pathogenesis of PVL have so far been related to prenatal ischemic injury to the brain initiated within the third trimester, which result in global cognitive and developmental delay and motor disturbances. Over the past few years, several epidemiological and experimental studies have implicated intrauterine infection and chorioamnionitis as causative in the pathogenesis of PVL. In particular, recent investigations have shown that inflammatory responses in the fetus and neonate can contribute towards neonatal brain injury and development-related disabilities including cerebral palsy. This review presents current concepts on the pathogenesis of PVL and emphasizes the increasing evidence for an inflammatory pathogenic component to this disorder, either resulting from hypoxic-ischemic injury or from infection. These findings provide the basis for clinical approaches targeted at protecting the premature brain from inflammatory damage, which may prove beneficial for treating PVL, if identified early in pathogenesis.

Hypoxic-ischemic encephalopathy with cystic brain stem necroses and thalamic calcifications in a preterm twin

A severe and rare ischemic brain lesion in a preterm twin boy is reported. The boy was born after two weeks of anhydramnios and amnionic infection at 24 weeks of gestation. Following a difficult Caesarean section and prolonged umbilical cord compression he developed prenatal acidosis with an umbilical cord pH of 6.96. At the age of 7 h, heart rate variability narrowed due to severely disturbed brain stem function and the patient developed clinical signs of hypoxic-ischemic encephalopathy. Sonography demonstrated extensive symmetrical brain stem and basal ganglia lesions. After a prolonged comatose and apneic state, death occurred at the age of 25 days. Autopsy confirmed columnar bilateral cavitation of basal ganglia, diencephalon, brain stem and spinal gray matter, as well as focal calcifications in the palladium, thalamus, and brain stem. The findings highly resemble those observed after experimental or clinical cardiac arrest.

Bilateral carotid artery occlusion causes periventricular leukomalacia in neonatal dogs

At 14 days of age, seven mongrel puppies were anesthetized and bilateral carotid arteries, not only the common but also the external and internal carotid arteries, were ligated with sutures. Seven sham-operated littermates served as controls. They were sacrificed at 3 months of age, and their brains were examined macro- and microscopically. Neuropathological examination revealed dilated posterior communicating and basilar arteries in bilateral carotid artery occlusion (BCAO) animals. Six out of 7 BCAO brains had uni- or multiloculated cysts in the periventricular white matter which were surrounded by a band of GFAP-positive glial cells. Scattered small areas of gliosis were found in all experimental animals. Four BCAO brains also showed ventricular dilatation. Although the cerebral cortex seemed to be intact, the periventricular white matter and the corpus callosum were reduced in width in experimental animals. Myelination in the white matter was significantly reduced in BCAO animals compared with the controls. This study directly demonstrates that cerebral hypoperfusion alone can produce periventricular leukomalacia in neonatal dogs.

Brain metabolic correlates of hypoxic-ischemic cerebral necrosis in mid-gestational sheep fetuses: significance of hypotension

Mid-gestational sheep fetuses exposed to marked hypoxia for 2 h remain brain intact if MABP is maintained above 30 mm Hg. On the other hand, similarly hypoxic fetuses, if they experience reductions in MABP below 30 mm Hg, develop foci of necrosis that predominantly affect hemispheric white matter and neostriatum. Cortex damage is more restricted and is usually associated with more massive underlying white matter damage. The present study examines the brain metabolic basis for the important role of hypotension in brain injury development in marked hypoxia. Sheep fetuses rendered hypoxic by respiring their ewes with 11% oxygen (fetal PaO2 = 8-12 mm Hg) in which MABP was maintained above 30 mm Hg showed increases in brain lactic acid concentrations to 7-13 mumol/g but unaltered energy charge. In contrast, fetuses that sustained MABP reductions below 30 mm Hg showed increases in lactic acid concentrations in vulnerable structures to 16-24 mumol/g accompanied by marked decreases in energy charge. The vulnerable structures also showed reductions in fructose concentrations but a variable behavior of other brain metabolites including phosphocreatine, glycogen, and glucose. Thus, the present findings suggest a relation between hypotension during marked hypoxia, low energy charge, lactic acid accumulation in brain at high concentrations, and fetal brain injury. The ewes of hypoxic hypotensive fetuses received pentobarbital at lower doses than did those of fetuses that maintained blood pressure. This suggests that pentobarbital plays an important role in protecting the fetal brain from asphyxia by extending the hypoxic fetus's ability to maintain blood pressure in addition to reducing its brain metabolism.

Ventricular shapes, distortions, and deformities: mirrors of past cerebral insults. A study based on early sonographic follow-up studies

Ventricular distortions and deformities often represent the endpoint of neuropathologic reactions that evolve early in life. Once fully developed, they may offer no clues as to preceding etiologic agents or pathogenesis. Serial sonography in the neonatal period of 14 patients with periventricular leukomalacia provided documentation of the evolution of certain ventricular patterns. When recognized early, these ventricular changes have prognostic significance because periventricular leukomalacia can produce serious neurologic sequelae. If found later in childhood, periventricular leukomalacia can be suggested as the original pathology. Ventricular deformities can be generalized (12 patients) or focal (11 patients); the various types of distortions are seen frequently in combination. The generalized form of ventricular expansion consisted of uniform expansion of the parieto-occipital components (hydroporencephaly), following extensive periventricular white matter necrosis. Hydroporencephaly is a new form of ex vacuo hydrocephalus in the pediatric age group. Focal changes are caused by more localized white matter cavitations with ventricularization of ensuing porencephalic cysts. These changes result in a footprint-shaped ventricular pattern (10 patients) or in frontal/occipital (polar) ventricular pointing (4 patients). White matter necrosis in other areas may lead to ventricles with bumpy contours (5 patients).

Neonatal Citrobacter meningitis: pathogenesis of cerebral abscess formation

In 2 premature infants with brief survival, the major pathological feature of Citrobacter meningitis consisted of vasculitis and infarction with necrosis and liquefaction of large portions of the white matter of the hemispheres. Areas of decreased density demonstrated on computed tomographic head scan represented infarction with necrosis, liquefaction, and cavitation and not a classic abscess. This finding has clinical significance, because surgical drainage of liquefied infarcts is rarely indicated and could further damage the relatively preserved cortex.

Acquired perinatal leukoencephalopathy

Between 36 and 44 weeks after conception, telencephalic white matter in the newborn appears to be particularly vulnerable to insults that result in morphological disturbances. Available evidence indicates that this disorder (or group of disorders), named acquired perinatal leukoencephalopathy, reflects a decrease in blood flow through the distal vessels supplying paraventricular white matter and/or a metabolic disturbance produced by, or in response to, an infectious agent. Major advances in our understanding of the causes, mechanisms, and sequelae of acquired perinatal leukoencephalopathy may be made in the next decade because of improvement in brain imaging techniques, improved survival of high-risk babies, and relatively routine follow-up of these high-risk babies.

Radiological Diagnosis of Periventricular and Subcortical Leukomalacia

Nine newborn infants with histories of perinatal asphyxia are presented. The pneumoencephalographic findings which led to the diagnosis are typical and constant. They include marked subcortical atrophy with rounded, dilated, and undisplaced lateral ventricles. Cystography with 3 cc of air demonstrated multiple subcortical and pareventricular cavities, without communication with the ventricular system, but with the typical honeycomb appearance of paraventricular and subcortical leukomalacia described in postmortem findings. The CT findings are typical, and provide the location of the cavities as well as their density.

Multiple cystic and focal encephalomalacia in infancy and childhood with brain stem damage

Two cases are described in which damage to the brain stem was associated with extensive necrosis of the cerebral hemisphere. In the first case--a monochorionic twin--there was clear evidence that injury of an ischaemic or hypoxic type had occurred during fetal life and some evidence that an inadequate share of the placental circulation was an important aetiological factor. In the second case death occurred 4 yr after an asphyxial episode at birth. The lesions in the hemispheres and brain stem were extensive, although less than in the first example. The lesions are discussed in the context of our knowledge of the anatomy and physiology of the developing nervous system. Although they cannot as yet be fitted into the concepts of "critical periods" and "vulnerable periods" of development, this is perhaps because observations on human cases are scanty in comparison with the extensive animal studies which have been reported. The lesions are contrasted and compared with those seen in animals.

Periventricular leucomalacia in neonates. Complications and sequelae

Periventricular leucomalacia was examined in a total of 28 infants. These foci of infarction were attributed to episodes of failure of perfusion due to hypotension in a border zone between ventriculofugal and ventriculopetal circulations. We describe haemorrhage occurring into these infarctions as a complication occurring in 7 infants. In 2 infants with a bleeding diathesis the haemorrhage was massive and fatal. Descending degeneration of the corticospinal tract was present as a sequel of a large area of periventricular leucomalacia in another case.