Neuropathologic substrate of cerebral palsy

Developmental regulation of the neuroinflammatory responses to LPS and/or hypoxia-ischemia between preterm and term neonates: An experimental study

Background

Preterm and term newborns are at high risk of brain damage as well as subsequent cerebral palsy and learning disabilities. Indeed, hypoxia-ischemia (HI), pathogen exposures, and associated intracerebral increase of pro-inflammatory cytokines have all been linked to perinatal brain damage. However, the developmental effects of potential variations of pro- and anti-inflammatory cytokine ratios remain unknown.

Methods

Using rat models of perinatal brain damage induced by exposures to lipopolysaccharide (LPS) and/or HI at distinct levels of maturity, we compared cytokine expression at stages of cerebral development equivalent to either preterm (postnatal day 1, P1) or term (P12) newborns.

Results

At P1, expression of anti-inflammatory cytokine within the brain was either not modulated (IL-6, IL-10) or down-regulated (IL-1ra, TGF-β1) by HI, LPS or LPS+HI. In contrast, there was at P12 an up-regulation of all anti-inflammatory cytokines studied in HI or LPS+HI condition, but not after LPS exposure. Interestingly, IL-1β was the main pro-inflammatory cytokine up-regulated moderately at P1, and strongly at P12, with a weak co-expression of TNF-α observed mainly at P12. These age-dependant inflammatory reactions were also accompanied, under HI and LPS+HI conditions, at P12 only, by combined: (i) expression of chemokines CINC-1 and MCP-1, (ii) blood-brain barrier (BBB) leakage, and (iii) intracerebral recruitment of systemic immune cells such as neutrophils. In contrast, sole LPS induced IL-1β responses mainly within white matter at P1 and mainly within gray matter at P12, that were only associated with early MCP-1 (but no CINC-1) induction at both ages, without any recruitment of neutrophils and CD68+ cells.

Conclusion

HI and LPS+HI induce pro-inflammatory oriented immune responses in both preterm and term like brains, with a maximal inflammatory response triggered by the combination of LPS+HI. The profile of these neuroinflammatory responses presented striking variations according to age: no or down-regulated anti-inflammatory responses associated with mainly IL-1β release in preterm-like brains (P1), in sharp contrast to term-like brains (P12) presenting stronger anti-and pro-inflammatory responses, including both IL-1β and TNF-α releases, and BBB leakage. These developmental-dependant variations of neuroinflammatory response could contribute to the differential pattern of brain lesions observed across gestational ages in humans. This also highlights the necessity to take into consideration the maturation stage, of both brain and immune systems, in order to develop new anti-inflammatory neuroprotective strategies.

Cell proliferation in human ganglionic eminence and suppression after prematurity-associated haemorrhage

In premature infants, germinal matrix haemorrhage in the brain is a common occurrence. However, cell proliferation and fate determination in the normal human germinal matrix is poorly understood. Human ganglionic eminence samples were collected prospectively from autopsies of premature and term infants with no evidence of pathological process (n=78; dying at post-menstrual age 14-88 weeks). The ganglionic eminence was thickest at 20-26 weeks and involuted by 34-36 weeks. Proliferating cells, detected by Ki67 immunoreactivity, were abundant throughout the ganglionic eminence prior to 18 weeks, after which a sharp boundary between the dorsal and ventral ganglionic eminence appeared with reduced cell proliferation in the dorsal region. Ki67 immunoreactivity persisted in the majority of ventral cells until ∼28 weeks, after which time the proportion of proliferating cells dropped quickly. The expression of cell lineage markers (such as Olig2, SOX2, platelet-derived growth factor receptor alpha) showed partitioning at the microscopic level. The hypothesis that germinal matrix haemorrhage suppresses cell proliferation was then addressed. In comparison to controls, germinal matrix haemorrhage (n=47; born at post-menstrual age 18-34 weeks followed by survival of 0 h to 98 days) was associated with significantly decreased cell proliferation if survival was >12 h. The cell cycle arrest transcription factor p53 was transiently increased and the oligodendroglial lineage markers Olig2 and platelet-derived growth factor receptor alpha were decreased. Cell death was negligible. A low level of microglial activation was detected. Haemorrhage-associated suppression of cell proliferation in premature human infants could partially explain the reduced brain size and clinical effects in children who suffer germinal matrix haemorrhage after premature birth.

Histopathological evaluation of the nervous system in National Toxicology Program rodent studies: a modified approach

This article outlines the changes and underlying rationale for modifications to the histopathological evaluation of the nervous system during toxicology and carcinogenesis studies conducted by the National Toxicology Program (NTP). In the past, routine evaluation of the nervous system was mostly limited to three sections of brain, and occasionally the spinal cord and peripheral nerves. Factors such as the increasing occurrence of human neurological diseases and associated economical cost burden, the role of unidentified environmental stressors in neurodegenerative disorders, multiple therapeutic drug-induced neuropathies noted in human clinical trials, and the exponential use of environmental chemicals with unknown neurotoxic potential necessitate a more extensive evaluation of the nervous system. The NTP has modified its protocol to include examination of key anatomic subsites related to neurodegenerative diseases such as Parkinson's disease. Modifications include four additional sections of the brain. Increasing the number of brain sections permits examination of a greater number of specific anatomic subsites with unique vulnerability. In addition, the spinal cord, peripheral nerves, trigeminal ganglion, and intestinal autonomic ganglia will be evaluated as needed. It is expected that this modified approach will increase the sensitivity of detecting neurotoxicants and neurocarcinogens important in human neurologic and neurodegenerative disorders.

Astrocyte precursor response to embryonic brain injury

Penetrating traumatic insult during pregnancy is a leading cause of human fetal demise; in particular, trauma to the brain may lead to devastating long-term cognitive sequelae. Perinatal brain injury involves glial precursors, but the neural mechanisms controlling astrocyte ontogeny after injury remain incompletely understood, partly due to a lack of appropriate markers and animal models. We analyzed astrocyte precursor response to injury at the beginning (E11) and peak (E15) of gliogenesis in an avian tectal model of penetrating embryonic brain trauma, without confounding maternal and sibling effects. At both ages, lateral ventricular dilatation, necrotic foci, periventricular cysts and intraventricular hemorrhages were observed distal to stab wounds two days after a unilateral stab injury to optic tecta. Neuronal (TUBB3) and oligodendrocyte precursor (PLP) markers were down-regulated, even far-removed from the wound site. In contrast, the mature astrocyte marker, GFAP, was up-regulated at the wound site, around necrotic areas and cysts, plus in usual areas of GFAP expression. Increased inflammatory response and apoptotic cell death were also confirmed in the injured tecta. Increased expression of NFIA, SOX9 and GLAST at the wound site and in the ventricular zone (VZ) of the injured tecta indicated an astroglial precursor response. However, cell division increased in the VZ only in early (E11) injury, but not later (E15), indicating that in late injury the astrogliogenesis occurring after acute injury is predominantly due to precursor differentiation rather than precursor proliferation. The inability to replenish the glial precursor pool during the critical period of vulnerability to injury may be an important cause of subsequent developmental abnormalities.

Early microglial colonization of the human forebrain and possible involvement in periventricular white-matter injury of preterm infants

Amoeboid microglial subpopulations visualized by antibodies against ionized calcium-binding adapter molecule 1, CD68, and CD45 enter the forebrain starting at 4.5 postovulatory or gestational weeks (gw). They penetrate the telencephalon and diencephalon via the meninges, choroid plexus, and ventricular zone. Early colonization by amoeboid microglia-macrophages is first restricted to the white matter, where these cells migrate and accumulate in patches at the junctions of white-matter pathways, such as the three junctions that the internal capsule makes with the thalamocortical projection, external capsule and cerebral peduncle, respectively. In the cerebral cortex anlage, migration is mainly radial and tangential towards the immature white matter, subplate layer, and cortical plate, whereas pial cells populate the prospective layer I. A second wave of microglial cells penetrates the brain via the vascular route at about 12-13 gw and remains confined to the white matter. Two main findings deserve emphasis. First, microglia accumulate at 10-12 gw at the cortical plate-subplate junction, where the first synapses are detected. Second, microglia accumulate in restricted laminar bands, most notably around 19-30 gw, at the axonal crossroads in the white matter (semiovale centre) rostrally, extending caudally in the immature white matter to the visual radiations. This accumulation of proliferating microglia is located at the site of white-matter injury in premature neonates. The spatiotemporal organization of microglia in the immature white and grey matter suggests that these cells may play active roles in developmental processes such as axonal guidance, synaptogenesis, and neurodevelopmental apoptosis as well as in injuries to the developing brain, in particular in the periventricular white-matter injury of preterm infants.

Lame from birth: early concepts of cerebral palsy

Deformations have been attributed to supernatural causes since antiquity. Cerebral palsy was associated with God's wrath, witchcraft, the evil eye, or maternal imagination. Greek scholars recommended prevention by tight swaddling, a custom that persisted into modern times. In the Middle Ages, the midwife's negligence was held responsible as was difficult teething. Morgagni described in 1769 that the neonatal brain can liquefy, and Bednar described leukomalacia in 1850 as a distinct disorder of the newborn. In 1861, Little associated cerebral palsies with difficult or protracted labor and neonatal asphyxia, but he was challenged by Freud, who in 1897 declared that most cases are prenatal in origin. In 1868, Virchow demonstrated inflammatory changes, a view recently confirmed by Leviton and Nelson. Although a causal relationship of cerebral palsy to the birth never has been established, the habit to put the blame for cerebral palsy on someone remained a frequent attitude.

Expression of soluble Fas in the cerebrospinal fluid of preterm infants with posthemorrhagic hydrocephalus and cystic white matter damage

Perinatal brain damage may result in impaired neurological development in extremely preterm infants. The underlying pathophysiological mechanisms are complex, and biomarkers of prognostic value are not available. The aim of this study was to analyze soluble Fas (sFas) concentrations in the cerebrospinal fluid (CSF) representative for involvement of apoptotic processes in preterm infants developing posthemorrhagic hydrocephalus (PHHC) and to link them to white matter damage (WMD) diagnosed by cranial ultrasound. A total of 29 preterm infants with PHHC were included in the study; 17 of them had signs of cystic WMD (cWMD) on ultrasound examinations. CSF samples were obtained at first ventriculostomy, and results were compared to those of a reference group of 24 preterm and term infants without neurologic diseases. sFas concentrations were elevated in CSF samples of PHHC patients compared to the reference group. In patients with cWMD, sFas concentrations were significantly higher than in patients without cWMD. These results indicate that apoptosis via the Fas pathway is involved in the pathogenesis of cWMD in the context of PHHC, and that sFas in the CSF may serve as a marker of cWMD development.

Excitability and synaptic communication within the oligodendrocyte lineage

The mammalian CNS contains an abundant, widely distributed population of glial cells that serve as oligodendrocyte progenitors. It has been reported that these NG2-immunoreactive cells (NG2(+) cells) form synapses and generate action potentials, suggesting that neural-evoked excitation of these progenitors may regulate oligodendrogenesis. However, recent studies also suggest that NG2(+) cells are comprised of functionally distinct groups that differ in their ability to respond to neuronal activity, undergo differentiation, and experience injury following ischemia. To better define the physiological properties of NG2(+) cells, we used transgenic mice that allowed an unbiased sampling of this population and unambiguous identification of cells in discrete states of differentiation. Using acute brain slices prepared from developing and mature mice, we found that NG2(+) cells in diverse brain regions share a core set of physiological properties, including expression of voltage-gated Na(+) (NaV) channels and ionotropic glutamate receptors, and formation of synapses with glutamatergic neurons. Although small amplitude Na(+) spikes could be elicited in some NG2(+) cells during the first postnatal week, they were not capable of generating action potentials. Transition of these progenitors to the premyelinating stage was accompanied by the rapid removal of synaptic input, as well as downregulation of AMPA and NMDA receptors and NaV channels. Thus, prior reports of physiological heterogeneity among NG2(+) cells may reflect analysis of cells in later stages of maturation. These results suggest that NG2(+) cells are uniquely positioned within the oligodendrocyte lineage to monitor the firing patterns of surrounding neurons.

Hypoxic-ischemic encephalopathy in the term infant

Hypoxia-ischemia in the perinatal period is an important cause of cerebral palsy and associated disabilities in children. There has been significant research progress in hypoxic-ischemic encephalopathy over the last 2 decades, and many new molecular mechanisms have been identified. Despite all these advances, therapeutic interventions are still limited. In this article the authors discuss several molecular pathways involved in hypoxia-ischemia, and potential therapeutic targets.

Mutation in the AP4M1 gene provides a model for neuroaxonal injury in cerebral palsy

Cerebral palsy due to perinatal injury to cerebral white matter is usually not caused by genetic mutations, but by ischemia and/or inflammation. Here, we describe an autosomal-recessive type of tetraplegic cerebral palsy with mental retardation, reduction of cerebral white matter, and atrophy of the cerebellum in an inbred sibship. The phenotype was recorded and evolution followed for over 20 years. Brain lesions were studied by diffusion tensor MR tractography. Homozygosity mapping with SNPs was performed for identification of the chromosomal locus for the disease. In the 14 Mb candidate region on chromosome 7q22, RNA expression profiling was used for selecting among the 203 genes in the area. In postmortem brain tissue available from one patient, histology and immunohistochemistry were performed. Disease course and imaging were mostly reminiscent of hypoxic-ischemic tetraplegic cerebral palsy, with neuroaxonal degeneration and white matter loss. In all five patients, a donor splice site pathogenic mutation in intron 14 of the AP4M1 gene (c.1137+1G-->T), was identified. AP4M1, encoding for the mu subunit of the adaptor protein complex-4, is involved in intracellular trafficking of glutamate receptors. Aberrant GluRdelta2 glutamate receptor localization and dendritic spine morphology were observed in the postmortem brain specimen. This disease entity, which we refer to as congenital spastic tetraplegia (CST), is therefore a genetic model for congenital cerebral palsy with evidence for neuroaxonal damage and glutamate receptor abnormality, mimicking perinatally acquired hypoxic-ischemic white matter injury.

Antenatal magnesium sulfate for the prevention of cerebral palsy in preterm infants less than 34 weeks' gestation: a systematic review and metaanalysis

We conducted a systematic review and metaanalysis of randomized controlled trials to determine whether magnesium sulfate administered to women at risk of preterm delivery before 34 weeks of gestation may reduce the risk of cerebral palsy in their children. Six trials involving 4796 women and 5357 infants were included. Antenatal magnesium sulfate was associated with a significant reduction in the risk of cerebral palsy (relative risk [RR], 0.69; 95% confidence interval [CI], 0.55-0.88), moderate or severe cerebral palsy (RR, 0.64; 95% CI, 0.44-0.92), and substantial gross motor dysfunction (RR, 0.60; 95% CI, 0.43-0.83). There was no overall difference in the risk of total pediatric mortality (RR, 1.01; 95% CI, 0.89-1.14). Minor side effects were more frequent among women receiving magnesium sulfate. In conclusion, magnesium sulfate administered to women at risk of delivery before 34 weeks of gestation reduces the risk of cerebral palsy.

Inhibition of gelatinase activity reduces neural injury in an ex vivo model of hypoxia-ischemia

Perinatal hypoxia-ischemia (H-I) often manifests as cognitive and/or motor disturbances that appear early in development. Growing evidence indicates that neuroinflammation may exacerbate H-I injury. Resident microglia release proinflammatory cytokines and proteases in response to ischemia. Matrix metalloproteinases (MMPs), in particular, activate cytokines and degrade basement membrane proteins. These actions ultimately permit entry of peripheral leukocytes into the CNS neuropil, enhancing neuroinflammation and cell death. Currently, the relative contributions of resident and peripheral immune cells to ischemic brain injury are unclear. The present study employed an ex vivo model of H-I through oxygen glucose deprivation (OGD) to identify the cellular localization of MMP-9 in organotypic hippocampal slices from rat, and to determine whether inhibiting gelatin-degrading MMPs affords neuroprotection in the absence of peripheral immune cells. Immunohistochemistry revealed ubiquitous neuronal MMP-9 expression in both normoxic and hypoxic slices. Increased MMP-9 expression was detected in CD11b-positive microglia after 48 h exposure to OGD relative to normoxic controls. Consistent with these data, in situ zymography showed increased gelatinolytic activity after OGD. Gelatin-cleaved fluorescence localized to astrocytic processes and somata of various cellular morphologies. Treatment with either the MMP inhibitor AG3340 (prinomastat) or minocycline dampened OGD-induced gelatinolytic activity and neural injury, as measured by Fluoro-Jade staining, relative to vehicle controls. These results show that resident microglia, in the absence of peripheral immune cells, were sufficient to enhance neural injury after OGD in the organotypic hippocampal slice. Additionally, these effects were associated with upregulation or secretion of MMP-9, and were blocked after treatment with either the gelatinase-selective compound AG3340 or the anti-inflammatory compound minocycline. These data, coupled with the effectiveness of these compounds previously shown in vivo, support the selective targeting of gelatin-degrading MMPs and activated microglia as potential therapeutic approaches to combat neonatal H-I injury.

Delayed neural network degeneration after neonatal hypoxia-ischemia

OBJECTIVE

Clinical magnetic resonance studies show delayed and ongoing neurodegeneration after neonatal hypoxia-ischemia (HI), but the mechanisms and timing of this neurodegeneration remain unclear. We used ex vivo diffusion tensor imaging (DTI) and brain neuropathology to determine whether selective injury to white matter tracts occurs after neonatal HI in mice resulting in neural system-associated attrition in remote regions and at delayed times.

METHODS

The Rice-Vannucci model (unilateral carotid ligation + 45 minutes of hypoxia FiO(2) = 0.08) was used to cause brain injury in postnatal day 7 (p7) C57BL6 mice, and ex vivo DTI and correlative neuropathology were performed at p8, p11, p15, p21, p28, and p42.

RESULTS

DTI provides excellent contrast visualization of unmyelinated white matter in the immature mouse brain. Severe ipsilateral injury to the hippocampus is seen with both histopathology and diffusion-weighted magnetic resonance imaging 24 hours after injury. Injury to axons is evident 24 hours after HI in the hippocampal alveus. By p11 and continuing until p28, the ipsilateral fimbria fornix degenerates. At p15, there is injury and loss of axons entering the ipsilateral septal nucleus followed by ipsilateral septal atrophy. Volume loss in the hippocampus is rapid and severe, but is subacute and significantly slower in the ipsilateral septum. Neonatal HI also interrupts the normal developmental increase in fractional anisotropy in the ipsilateral fimbria but not in the contralateral fimbria from p8 to p42.

INTERPRETATION

In neonatal brain, there is progressive systems-preferential injury after HI. DTI allows unparalleled visualization of this neural network-associated attrition so that it can be followed longitudinally in developing brain.

Plasticity and injury in the developing brain

The child's brain is more malleable or plastic than that of adults and this accounts for the ability of children to learn new skills quickly or recovery from brain injuries. Several mechanisms contribute to this ability including overproduction and deletion of neurons and synapses, and activity-dependent stabilization of synapses. The molecular mechanisms for activity-dependent synaptic plasticity are being discovered and this is leading to a better understanding of the pathogenesis of several disorders including neurofibromatosis, tuberous sclerosis, Fragile X syndrome and Rett syndrome. Many of the same pathways involved in synaptic plasticity, such as glutamate-mediated excitation, can also mediate brain injury when the brain is exposed to stress or energy failure such as hypoxia-ischemia. Recent evidence indicates that cell death pathways activated by injury differ between males and females. This new information about the molecular pathways involved in brain plasticity and injury are leading to insights that will provide better therapies for pediatric neurological disorders.

Neonatal high pressure hydrocephalus is associated with elevation of pro-inflammatory cytokines IL-18 and IFNgamma in cerebrospinal fluid

Background

In human neonatal high pressure hydrocephalus (HPHC), diffuse white matter injury and gliosis predispose to poor neuro-developmental outcome. The underlying mechanism for diffuse white matter damage in neonatal HPHC is still unclear. Analogous to inflammatory white matter damage after neonatal hypoxemia/ischemia, we hypothesized that pro-inflammatory cytokines could be involved in neonatal HPHC. If so, early anti-inflammatory therapy could ameliorate white matter damage in HPHC, before irreversible apoptosis has occurred. In HPHC and control neonates, we therefore aimed to compare cerebrospinal fluid (CSF) concentrations of IL18, IFNγ and sFasL (interleukin 18, interferon gamma and apoptosis marker soluble-Fas ligand, respectively).

Methods

In neonatal HPHC (n = 30) and controls (n = 15), we compared CSF concentrations of IL18, IFNγ and sFasL using sandwich ELISA. HPHC was grouped according to etiology: spina bifida aperta (n = 20), aqueduct stenosis (n = 4), and fetal intra-cerebral haemorrhage (n = 6). Neonatal control CSF was derived from otherwise healthy neonates (n = 15), who underwent lumbar puncture for exclusion of meningitis.

Results

In all three HPHC groups, CSF IL18 concentrations were significantly higher than control values, and the fetal intracranial haemorrhage group was significantly higher than SBA group. Similarly, in all HPHC groups CSF-IFNγ concentrations significantly exceeded the control group. In both HPHC and control neonates, CSF FasL concentrations remained within the range of reference values.

Conclusion

Independent of the pathogenesis, neonatal HPHC is associated with the activation of the pro-inflammatory cytokines (IL-18 and IFNγ) in the CSF, whereas CSF apoptosis biomarkers (sFasL) were unchanged. This suggests that anti-inflammatory treatment (in addition to shunting) could be helpful to preserve cerebral white matter.

Sulfonylurea receptor 1 in the germinal matrix of premature infants

Germinal matrix (GM) hemorrhage (GMH) is a major cause of mortality and of life-long morbidity from cerebral palsy. GMH is typically preceded by hypoxic/ischemic events and is believed to arise from rupture of weakened veins in the GM. In the CNS, hypoxia/ischemia up-regulate sulfonylurea receptor 1 (SUR1)-regulated NCCa-ATP channels in microvascular endothelium, with channel activation by depletion of ATP being responsible for progressive secondary hemorrhage. We hypothesized that this channel might be up-regulated in the GM of preterm infants at risk for GMH. Here, we studied expression of the regulatory subunit of the channel, SUR1, and its transcriptional antecedent, hypoxia inducible factor 1 (HIF1), in postmortem tissues of premature infants who either were at risk for or who sustained GMH. We found regionally specific up-regulation of HIF1 and of SUR1 protein and mRNA in GM tissues, compared with remote cortical tissues. Up-regulation was prominent in most progenitor cells, whereas in veins, SUR1 was found predominantly in infants who had sustained GMH compared with those without hemorrhage. Our data suggest that the SUR1-regulated NCCa-ATP channel may be associated with GMH, and that pharmacological block of these channels could potentially reduce the incidence of this devastating complication of prematurity.

Cranial sonography in term and near-term infants

Sonographic patterns of brain injury in the term and near-term infant are quite different from those in the premature infant. Although periventricular leukomalacia and germinal matrix hemorrhage are rarely seen in term infants, selective neuronal injury, parasagittal infarction, focal stroke, diffuse hypoxic-ischemic injury, and deep parenchymal hemorrhages are more common lesions. In addition, congenital brain tumors, hamartomatous lesions, such as hemimegalencephaly, and tuberous sclerosis can mimic ischemic and hemorrhagic injury. Sonography remains an important tool in the initial evaluation of intracranial abnormalities in critically ill term and near-term infants. An understanding of the differences in etiology, sonographic patterns, and limitations of sonography in the term infant is essential for accurate and effective diagnoses in this age group.

Pathogenesis of cerebral white matter injury of prematurity

Cerebral white matter injury, characterised by loss of premyelinating oligodendrocytes (pre-OLs), is the most common form of injury to the preterm brain and is associated with a high risk of neurodevelopmental impairment. The unique cerebrovascular anatomy and physiology of the premature baby underlies the exquisite sensitivity of white matter to the abnormal milieu of preterm extrauterine life, in particular ischaemia and inflammation. These two upstream mechanisms can coexist and amplify their effects, leading to activation of two principal downstream mechanisms: excitotoxicity and free radical attack. Upstream mechanisms trigger generation of reactive oxygen and nitrogen species. The pre-OL is intrinsically vulnerable to free radical attack due to immaturity of antioxidant enzyme systems and iron accumulation. Ischaemia and inflammation trigger glutamate receptor-mediated injury leading to maturation-dependent cell death and loss of cellular processes. This review looks at recent evidence for pathogenetic mechanisms in white matter injury with emphasis on targets for prevention and treatment of injury.

Altered cortical inhibitory function in children with spastic diplegia: a TMS study

Periventricular leukomalacia (PVL) is the most frequent cause of spastic diplegia. The movement disorder is attributed to damage to the corticospinal tract, but there is increasing evidence of additional cortical dysfunction associated with PVL. Aim of the present study was to evaluate the integrity of the corticospinal tract and cortical inhibitory function using transcranial magnetic stimulation. Fifteen children with bilateral PVL and spastic diplegia and twenty-two healthy children underwent single-pulse stimulations to the right tibial anterior muscle. We compared central motor conduction time and amplitudes of motor evoked potentials as markers for corticospinal integrity and the postexcitatory silent period (SP), representing cortical inhibitory interneurons. The patients' parameters of corticospinal tract function did not differ significantly from those in the control children. In contrast, the SP was significantly shortened in children with PVL (mean 25.6 +/- 6.9 ms; controls: mean 47.6 +/- 23.2 ms, P = 0.018). This suggests cortical involvement with reduced cortical inhibitory function in PVL. This could be due to impaired functioning of the cortical interneurons themselves, or to decreased input from activating fibres, e.g. thalamocortical or cortico-cortical connections.

Cerebral palsy

Cerebral palsy (CP) is a group of disorders of movement and posture resulting from nonprogressive disturbances of the fetal or neonatal brain. More than 80% of cases of CP in term infants originate in the prenatal period; in premature infants, both prenatal or postnatal causes contribute. The most prevalent pathological lesion seen in CP is periventricular white matter injury (PWMI) resulting from vulnerability of the immature oligodendrocytes (pre-OLs) before 32 wk of gestation. PWMI is responsible for the spastic diplegia form of CP and a spectrum of cognitive and behavioral disorders. Oxidative stress and excitotoxicity resulting from excessive stimulation of ionotropic glutamate receptors on preOLs are the most prominent molecular mechanisms for PWMI. Asphyxia around the time of birth in term infants accounts for less than 15% of CP in developed countries but the incidence is higher in underdeveloped areas. Asphyxia causes a different pattern of brain injury and CP than is seen after preterm injuries. This type of CP is associated with the clinical syndrome of hypoxic-ischemic encephalopathy shortly after the insult, and the cortex, basal ganglia, and brainstem are selectively vulnerable to injury. Experimental models indicate that neurons in the neonatal brain are more likely to die by delayed apoptosis extending over days to weeks than those in the adult brain. Neurons die by glutamate-mediated excitotoxicity involving downstream caspase-dependent and caspase-independent cell death pathways. Recent reports indicate that males and females preferentially utilize different pathways. Clinical trials indicate that mild hypothermia reduces death or disability in term infants following asphyxia and basic research suggests that this approach might be combined with pharmacological strategies in the future.

Diffusion tensor imaging in children with periventricular leukomalacia: variability of injuries to white matter tracts

BACKGROUND AND PURPOSE

Conventional MR imaging shows evidence of brain injury and/or maldevelopment in 70%-90% of children with cerebral palsy (CP), though its capability to identify specific white matter tract injury is limited. The great variability of white matter lesions in CP already demonstrated by postmortem studies is thought to be one of the reasons why response to treatment is so variable. Our hypothesis is that diffusion tensor imaging (DTI) is a suitable technique to provide in vivo characterization of specific white matter tract lesions in children with CP associated with periventricular leukomalacia (PVL).

MATERIALS AND METHODS

In this study, 24 children with CP associated with PVL and 35 healthy controls were evaluated with DTI. Criteria for identification of 26 white matter tracts on the basis of 2D DTI color-coded maps were established, and a qualitative scoring system, based on visual inspection of the tracts in comparison with age-matched controls, was used to grade the severity of abnormalities. An ordinal grading system (0=normal, 1=abnormal, 2=severely abnormal or absent) was used to score each white matter tract.

RESULTS

There was marked variability in white matter injury pattern in patients with PVL, with the most frequent injury to the retrolenticular part of the internal capsule, posterior thalamic radiation, superior corona radiata, and commissural fibers.

CONCLUSION

DTI is a suitable technique for in vivo assessment of specific white matter lesions in patients with PVL and, thus, a potentially valuable diagnostic tool. The tract-specific evaluation revealed a family of tracts that are highly susceptible in PVL, important information that can potentially be used to tailor treatment options in the future.

Ischemic perinatal stroke: summary of a workshop sponsored by the National Institute of Child Health and Human Development and the National Institute of Neurological Disorders and Stroke

Ischemic perinatal stroke is a disorder associated with significant long-term neurologic morbidity. With an estimated incidence of 1 in 2300 to 5000 births, stroke is more likely to occur in the perinatal period than at any time in childhood. The incidence of ischemic perinatal stroke ranks second only to that of strokes in the elderly population. Although ischemic perinatal stroke is a well-recognized disorder, many aspects remain to be studied. There is no consensus on its terminology, definition, or classification. Several risk factors have been identified, but their precise roles in causing stroke are not well understood. There are no reliable predictors of ischemic perinatal stroke on which to base prevention or treatment strategies. To review these important issues and propose a research agenda, the National Institute of Child Health and Human Development and the National Institute of Neurological Disorders and Stroke convened a workshop in August 2006. This article provides a summary of the workshop.

Diffuse white matter injury and neurologic outcomes of infants born very preterm in the 1990s

Neurocognitive outcomes of infants born very preterm (less than 32 weeks gestation) remain a major concern in perinatal practice. Very preterm birth rates have increased, with enhanced survival since 1990. As focal brain lesions become less common, diffuse injury to both gray and white matter is now the primary focus for improving neurologic outcomes in survivors. Recent evidence supports preoligodendrocytes as the principal cellular target of diffuse white matter injury due to their susceptibility to hypoxic-ischemic and inflammatory insults. An understanding of their development and vulnerability can inform acute nursing care of very preterm infants.

Activated protein C reduces endotoxin-induced white matter injury in the developing rat brain

Periventricular leukomalacia (PVL), the dominant form of brain injury in premature infants, is characterized by white matter injury (WMI) and is associated with cerebral palsy. The pathogenesis of PVL is complex and likely involves ischemia/reperfusion, free radical formation, excitotoxicity, impaired regulation of cerebral blood flow, a procoagulant state, and inflammatory mechanisms associated with maternal and/or fetal infection. Using an established animal model of human PVL, we investigated whether activated protein C (APC), an anti-coagulant factor with anti-inflammatory, anti-apoptotic, anti-oxidant, and cytoprotective activities, could reduce endotoxin-induced WMI in the developing rat brain. Intraperitoneal injections of lipopolysaccharide (LPS) (0.5 mg/kg body weight) were given at embryonic days 18 (E18) and 19 (E19) to pregnant Sprague-Dawley rats; control rats were injected with sterile saline. A single intravenous injection of recombinant human (rh) APC (0.2 mg /kg body weight) was given to pregnant rats following the second LPS dose on embryonic day 19 (E19). Reduced cell death in white matter and hypomyelination were shown on TUNEL and myelin basic protein (MBP) staining, respectively, on late postnatal days (P7) in APC-treated groups. There were significantly fewer TUNEL+nuclei in the periventricular WM in the APC+LPS group than in the untreated LPS group. Compared to the APC+LPS and control group, MBP expression was weak in the LPS group on P7, indicating endotoxin-induced hypomyelination in the developing rat brain. APC attenuated the LPS-induced protein expression of inflammatory cytokines, tumor necrosis factor-alpha, and interleukin-6, as evaluated by ELISA in neonatal rat brains. A single intraperitoneal injection of rhAPC (0.2 mg/kg body weight) to neonatal rats on P1 also had similar protective and anti-inflammatory effects against maternally administered LPS. Collectively, these data support the hypothesis that APC may provide protection against an endotoxin-evoked inflammatory response and WMI in the developing rat brain. Moreover, our results suggest that the possible use of APC in treatment of preterm infants and pregnant women with maternal or placental infection may minimize the risk of PVL and cerebral palsy.

Auditory event-related potentials and cognitive function of preterm children at five years of age

OBJECTIVE

In our previous study, auditory event-related potentials (AERPs) in preterm 1-year-old children had a positive deflection at 150-350 ms that correlated positively with their 2-year neurodevelopmental outcome. In a study of the same subjects at age 5, our aim was to assess AERPs and their relationship to neuropsychological test results.

METHODS

Preterm small (SGA, n=13), appropriate for gestational age (AGA, n=15), and control (n=13) children were assessed with an Easy paradigm presenting a large frequency change accompanied with occasional novel sounds, and a Challenging paradigm presenting small frequency and duration changes with a rapid rate. The preterm children underwent neurocognitive tests.

RESULTS

Easy paradigm. The P1 response to frequency deviant was smaller and MMN larger in the preterm than in the control children. Challenging paradigm. The P1 response to standard, frequency, and duration deviants was smaller in the preterm than in the control children. The N2 response to frequency deviant was larger in the preterm than in the control children. AGA and SGA children had similar AERPs. The P1, N2, and MMN amplitudes correlated with verbal IQ and NEPSY language subtests.

CONCLUSIONS

Small P1 response(s) appears to be typical for preterm children.

SIGNIFICANCE

Small P1 response in preterm children may suggest altered primary auditory processing.

Changes in echogenicity in the fetal brain: a prevalence study in fetuses at risk for preterm delivery

OBJECTIVES

To study the incidence of echodensities in the periventricular white matter, ventricular system, basal ganglia and thalamus of the brain in fetuses at risk for preterm delivery.

METHODS

This was a prospective study of 124 fetuses with a gestational age between 26 and 34 weeks in pregnancies affected by either pregnancy-induced hypertensive disorders or preterm labor. Transvaginal ultrasound examination of the fetal brain in coronal and sagittal planes was performed weekly until delivery and the neonatal brain was examined within 24 h after delivery.

RESULTS

In 66% of all fetuses, echodensities were found in one or more areas of the brain. They were present in the periventricular area in 52% of cases, the intraventricular area in 18% and in the basal ganglia and thalamus area in 28%. Changes in echogenicity were seen throughout the entire gestational-age period studied. Of the periventricular echodensities that exceeded in echodensity that of the choroid plexus, at least 50% persisted after delivery; at least 38% of the intraventricular echodensities and at least 32% of the basal ganglia and thalamus echodensities persisted after delivery.

CONCLUSIONS

In high-risk fetuses, echodensities are a frequent finding in several areas in the brain. How far these echodensities are related to future outcome of the infant needs to be investigated.

The neuropathology of acquired pre- and perinatal brain injuries

Acquired pre- and perinatal brain injuries comprise a significant proportion of perinatal neuropathology. They are associated with placental abnormalities, maternal factors, multiple gestations, and preterm labor, as well as with the later development of cerebral palsy and developmental delay. The patterns of perinatal brain injury depend on the etiology (often hypoxic-ischemic) and the timing relative to the development of the fetal nervous system, since the vulnerabilities of gray and white matter differ across postconceptional age and by neuroanatomic site. Nevertheless, characteristic features allow determination of the approximate age and cause of each pattern of injury in the perinatal brain.

The lymphotoxin Cys13Arg polymorphism and cognitive functioning in individuals with schizophrenia

Genetic factors that modulate the immune response have been implicated as risk factors for schizophrenia and cognitive impairment. We assessed the correlation between cognitive functioning and the LTA Cys13Arg polymorphism in 351 individuals with schizophrenia, 122 with bipolar disorder, and 160 controls. There was a significant association between cognitive functioning and the LTA Cys13Arg polymorphism within the schizophrenia (p<0.008) but not the other diagnostic groups. There was no association between cognitive functioning and the two other polymorphisms in the same gene complex. The LTA Cys13Arg polymorphism may represent a risk factor for cognitive impairment in individuals with schizophrenia.

Antioxidant Status Alters Levels of Fas-Associated Death Domain-Like IL-1B-Converting Enzyme Inhibitory Protein following Neonatal Hypoxia-Ischemia

Activation of Fas death receptor (Fas DR) signaling cascade is seen after neonatal hypoxia-ischemia (HI). Cell survival is favored when signaling through the death-inducing signaling complex and cleavage of caspase 8 to its active form is blocked by FLIP, a dominant negative of caspase 8. H2O2 quickly downregulates expression of FLIP. Neonatal mice overexpressing glutathione peroxidase (GPx) have less injury and less H2O2 accumulation compared with neonatal mice overexpressing superoxide dismutase (SOD) or wild-type (WT) littermates. Expression of both FLIP(L) and FLIP(S) is increased in GPx-oxerexpressing mice relative to WT mice at 24 h and relative to SOD-overexpressing mice at 2 and 24 h following neonatal HI (ANOVA, p < 0.05). There is an increase in Fas DR expression at 24 h in both WT and GPx-overexpressing mice and significant differences between WT and SOD-overexpressing mice (ANOVA, p < 0.01). There is no difference in FADD expression among the 3 groups 24 h after HI. At 24 h following HI, the ratio of FLIP to Fas DR expression supports a significant negative correlation with injury score (r2 = 0.99, slope = -4.01), and expression of both the active fragment of caspase 8 and caspase 8 activity is increased in SOD overexpressors compared to GPx overexpressors at 24 h after HI (ANOVA, p < 0.05). The overall degree of injury previously seen in these 3 strains correlates well with changes in expression of Fas DR signaling proteins favoring neuroprotection in the GPx-overexpressing mice, i.e. increased FLIP expression and decreased caspase 8 activity compared to SODtg mice. The mechanism by which antioxidant status alters FLIP levels following neonatal HI may be related to the ability to detoxify H2O2 produced following neonatal HI.

Maternal infection and white matter toxicity

Studies examining maternal infection as a risk factor for neurological disorders in the offspring have suggested that altered maternal immune status during pregnancy can be considered as an adverse event in prenatal development. Infection occurring in the mother during the gestational period has been implicated in multiple neurological effects. The current manuscript will consider the issue of immune/inflammatory conditions during prenatal development where adverse outcomes have been linked to maternal systemic infection. The discussions will focus primary on white matter and oligodendrocytes as they have been identified as target processes. This white matter damage occurs in very early preterm infants and in various other human diseases currently being examined for a linkage to maternal or early developmental immune status. The intent is to draw attention to the impact of altered immune status during pregnancy on the offspring for the consideration of such contributing factors to the general assessment of developmental neurotoxicology.