A New Theory to Explain the Underlying Pathogenetic Mechanism of Sudden Infant Death Syndrome

A Primer on Human Birth Theory

In the 1970s Massimo Fagioli (1931-2017) proposed a new theory of mind that he called the Human Birth Theory, based on a healthy conception of the baby and of the nonconscious mind. Fagioli made significant contributions to the understanding of mental dynamics at birth, the pathophysiology of mental illness, and the nonconscious identity of psychiatrists and psychotherapists. His original contributions to psychodynamic psychotherapy included variations on the setting and understanding of transference and dream interpretations that deviated from classical psychoanalytic techniques. This article introduces the basic tenets of Human Birth Theory, its neuropsychiatric correlates, and clinical applications.

Prenatal and postnatal factors associated with sudden infant death syndrome: an umbrella review of meta-analyses

BACKGROUND

Comprehensive quantitative evidence on the risk and protective factors for sudden infant death syndrome (SIDS) effects is lacking. We investigated the risk and protective factors related to SIDS.

METHODS

We conducted an umbrella review of meta-analyses of observational and interventional studies assessing SIDS-related factors. PubMed/MEDLINE, Embase, EBSCO, and Google Scholar were searched from inception until January 18, 2023. Data extraction, quality assessment, and certainty of evidence were assessed by using A Measurement Tool Assessment Systematic Reviews 2 following PRISMA guidelines. According to observational evidence, credibility was graded and classified by class and quality of evidence (CE; convincing, highly suggestive, suggestive, weak, or not significant). Our study protocol was registered with PROSPERO (CRD42023458696). The risk and protective factors related to SIDS are presented as equivalent odds ratios (eORs).

RESULTS

We identified eight original meta-analyses, including 152 original articles, covering 12 unique risk and protective factors for SIDS across 21 countries/regions and five continents. Several risk factors, including prenatal drug exposure [eOR = 7.84 (95% CI = 4.81-12.79), CE = highly suggestive], prenatal opioid exposure [9.55 (95% CI = 4.87-18.72), CE = suggestive], prenatal methadone exposure [9.52 (95% CI = 3.34-27.10), CE = weak], prenatal cocaine exposure [4.38 (95% CI = 1.95-9.86), CE = weak], prenatal maternal smoking [2.25 (95% CI = 1.95-2.60), CE = highly suggestive], postnatal maternal smoking [1.97 (95% CI = 1.75-2.22), CE = weak], bed sharing [2.89 (95% CI = 1.81-4.60), CE = weak], and infants found with heads covered by bedclothes after last sleep [11.01 (95% CI = 5.40-22.45), CE = suggestive], were identified. On the other hand, three protective factors, namely, breastfeeding [0.57 (95% CI = 0.39-0.83), CE = non-significant], supine sleeping position [0.48 (95% CI = 0.37-0.63), CE = suggestive], and pacifier use [0.44 (95% CI = 0.30-0.65), CE = weak], were also identified.

CONCLUSIONS

Based on the evidence, we propose several risk and protective factors for SIDS. This study suggests the need for further studies on SIDS-related factors supported by weak credibility, no association, or a lack of adequate research.

Short-term exposure to air pollution and infant mortality: A systematic review and meta-analysis

BACKGROUND AND AIM

Infant mortality is a widely reported indicator of population health and a leading public health concern. In this systematic review and meta-analysis, we review the available literature for epidemiologic evidence of the association between short-term air pollution exposure and infant mortality.

METHODS

Relevant publications were identified through PubMed and Web of Science databases using comprehensive search terms and screened using predefined inclusion/exclusion criteria. We extracted data from included studies and applied a systematic rubric for evaluating study quality across domains including participant selection, outcome, exposure, confounding, analysis, selective reporting, sensitivity, and overall quality. We performed meta-analyses, using both fixed and random-effect methods, and estimated pooled odds ratios (ORs) and 95 % confidence intervals (95%CI) for pollutants (nitrogen dioxide (NO2), sulfur dioxide (SO2), coarse particulate matter (PM10), fine particulate matter (PM2.5), ozone (O3), carbon monoxide (CO)) and infant mortality, neonatal mortality, or postneonatal mortality.

RESULTS

Our search returned 549 studies. We excluded 490 studies in the abstract screening phase and an additional 37 studies in the full text screening phase, leaving 22 studies for inclusion. Among these 22 studies, 14 included effect estimates for PM10, 13 for O3, 11 for both NO2 and CO, 8 for SO2, and 3 for PM2.5. We did not calculate a pooled OR for PM2.5 due to the limited number of studies available and demonstrated heterogeneity in the effect estimates. The pooled ORs (95%CI) with the greatest magnitudes were for a 10-ppb increase in SO2 or NO2 concentration in the days before death (1.07 [95%CI: 1.02, 1.12], 1.04 [95%CI: 1.01, 1.08], respectively). The pooled OR for PM10 was 1.02 (95%CI: 1.00, 1.03), and the pooled ORs for CO and O3 were 1.01 (95%CI: 1.00, 1.02) and 0.99 (95%CI: 0.97, 1.01).

CONCLUSIONS

Increased exposure to SO2, NO2, PM10, or CO is associated with infant mortality across studies.

NeuN distribution in brain structures of normal and Zika-infected suckling mice

Microcephaly is the more severe brain malformation because of Zika virus infection. Increased vulnerability of neural stem and progenitor cells to Zika infection during prenatal neurodevelopment impairs the complete formation of cortical layers. Normal development of cerebellum is also affected. However, the follow-up of apparently healthy children born to Zika exposed mothers during pregnancy has revealed other neurological sequelae. This suggests Zika infection susceptibility remains in nervous tissue after neurogenesis end, when differentiated neuronal populations predominate. The neuronal nuclear protein (NeuN) is an exclusive marker of postmitotic neurons. Changes in NeuN expression are associated with neuronal degeneration. We have evaluated immunohistochemical expression of NeuN protein in cerebral cortex, hippocampus, and cerebellum of normal and Zika-infected neonatal Balb/c mice. The highest NeuN immunoreactivity was found mainly in neurons of all cortical layers, pyramidal layer of hippocampus, granular layer of dentate gyrus and in internal granular layer of cerebellum. Viral infection caused marked loss of NeuN immunostaining in all these brain areas. This suggests neurodegenerative effects of Zika virus infection during postmitotic neuron maturation and contribute to interpretation of neuropathogenic mechanisms of Zika.

Harmful Effect of Intrauterine Smoke Exposure on Neuronal Control of "Fetal Breathing System" in Stillbirths

This article is aimed to contribute to the current knowledge on the role of toxic substances such as nicotine on sudden intrauterine unexplained deaths’ (SIUDS’) pathogenetic mechanisms. The in-depth histopathological examination of the autonomic nervous system in wide groups of victims of SIUDS (47 cases) and controls (20 cases), with both smoking and no-smoking mothers, highlighted the frequent presence of the hypodevelopment of brainstem structures checking the vital functions. In particular, the hypoplasia of the pontine parafacial nucleus together with hypoplastic lungs for gestational age were observed in SIUDS cases with mothers who smoked cigarettes, including electronic ones. The results allow us to assume that the products of cigarette smoke during pregnancy can easily cross the placental barrier, thus entering the fetal circulation and damaging the most sensitive organs, such as lungs and brain. In a non-negligible percentage of SIUDS, the mothers did not smoke. Furthermore, based on previous and ongoing studies conducted through analytical procedures and the use of scanning electron microscopy, the authors envisage the involvement of toxic nanoparticles (such as agricultural pesticides and nanomaterials increasingly used in biomedicine, bioscience and biotechnology) in the death pathogenesis, with similar mechanisms to those of nicotine.

Autonomic cardiac innervation: impact on the evolution of arrhythmias in inherited cardiac arrhythmia syndromes

The autonomic nervous system (ANS) is an essential component of arrhythmogenicity, especially in the absence of structural heart disease and channelopathy. In this article, the authors review the role and characteristics of ANS in various channelopathies. Some of these, such as most long QT syndromes and catecholaminergic polymorphic ventricular tachycardia, are highly dependent on sympathetic activation, while parasympathetic tone is an important factor for arrhythmias in other channelopathies such as Brugada syndrome or early repolarisation syndrome. Recent advances highlighting the subtle role of ANS in channelopathies are presented here, demonstrating that all is far from being so simple and straightforward and revealing some paradoxical behaviours of channelopathies in relation to discrete ANS imbalance.

Neurochemistry of the Kölliker-Fuse nucleus from a respiratory perspective

The Kölliker-Fuse nucleus (KF) is a functionally distinct component of the parabrachial complex, located in the dorsolateral pons of mammals. The KF has a major role in respiration and upper airway control. A comprehensive understanding of the KF and its contributions to respiratory function and dysfunction requires an appreciation for its neurochemical characteristics. The goal of this review is to summarize the diverse neurochemical composition of the KF, focusing on the neurotransmitters, neuromodulators, and neuropeptides present. We also include a description of the receptors expressed on KF neurons and transporters involved in each system, as well as their putative roles in respiratory physiology. Finally, we provide a short section reviewing the literature regarding neurochemical changes in the KF in the context of respiratory dysfunction observed in SIDS and Rett syndrome. By over-viewing the current literature on the neurochemical composition of the KF, this review will serve to aid a wide range of topics in the future research into the neural control of respiration in health and disease.

Regulation of breathing pattern by IL-10

Proinflammatory cytokines like interleukin-1β (IL-1β) affect the control of breathing. Our aim is to determine the effect of the anti-inflammatory cytokine IL-10 οn the control of breathing. IL-10 knockout mice (IL-10^-/-, n = 10) and wild-type mice (IL-10^+/+, n = 10) were exposed to the following test gases: hyperoxic hypercapnia 7% CO₂-93% O₂, normoxic hypercapnia 7% CO₂-21% O₂, hypoxic hypercapnia 7% CO₂-10% O₂, and hypoxic normocapnia 3% CO₂-10% O₂. The ventilatory function was assessed using whole body plethysmography. Recombinant mouse IL-10 (rIL-10; 10 μg/kg) was administered intraperitoneally to wild-type mice (n = 10) 30 min before the onset of gas challenge. IL-10 was administered in neonatal medullary slices (10-30 ng/ml, n = 8). We found that IL-10^-/- mice exhibited consistently increased frequency and reduced tidal volume compared with IL-10^+/+ mice during room air breathing and in all test gases (by 23.62 to 33.2%, P < 0.05 and -36.23 to -41.69%, P < 0.05, respectively). In all inspired gases, the minute ventilation of IL-10^-/- mice was lower than IL-10^+/+ (by -15.67 to -22.74%, P < 0.05). The rapid shallow breathing index was higher in IL-10^-/- mice compared with IL-10^+/+ mice in all inspired gases (by 50.25 to 57.5%, P < 0.05). The intraperitoneal injection of rIL-10 caused reduction of the respiratory rate and augmentation of the tidal volume in room air and also in all inspired gases (by -12.22 to -29.53 and 32.18 to 45.11%, P < 0.05, respectively). IL-10 administration in neonatal rat (n = 8) in vitro rhythmically active medullary slice preparations did not affect either rhythmicity or peak amplitude of hypoglossal nerve discharge. In conclusion, IL-10 may induce a slower and deeper pattern of breathing.

Sudden Unexpected Death and the Mammalian Dive Response: Catastrophic Failure of a Complex Tightly Coupled System

In tightly coupled complex systems, when two or more factors or events interact in unanticipated ways, catastrophic failures of high-risk technical systems happen rarely, but quickly. Safety features are commonly built into complex systems to avoid disasters but are often part of the problem. The human body may be considered as a complex tightly coupled system at risk of rare catastrophic failure (sudden unexpected death, SUD) when certain factors or events interact. The mammalian dive response (MDR) is a built-in safety feature of the body that normally conserves oxygen during acute hypoxia. Activation of the MDR is the final pathway to sudden cardiac (SCD) in some cases of sudden infant death syndrome (SIDS), sudden unexpected death in epilepsy (SUDEP), and sudden cardiac death in water (SCDIW, fatal drowning). There is no single cause in any of these death scenarios, but an array of, unanticipated, often unknown, factors or events that activate or interact with the mammalian dive reflex. In any particular case, the relevant risk factors or events might include a combination of genetic, developmental, metabolic, disease, environmental, or operational influences. Determination of a single cause in any of these death scenarios is unlikely. The common thread among these seemingly different death scenarios is activation of the mammalian dive response. The human body is a complex tightly coupled system at risk of rare catastrophic failure when that "safety feature" is activated.

Permeability of the amniotic membranes to the natural vanilla molecule

Purpose: We studied natural vanilla permeability through amniotic membranes.Methods: We studied natural vanilla permeability through amniotic membranes obtained from 45 spontaneous normal deliveries at term. The ferric chloride test (FeCL₃) was used to determine the presence or absence of phenols in a given sample. Vanilla is a polyphenol so it gives a reaction to FeCL₃ with an intense color change. The diffusion of the vanilla was checked by dropping ferric chloride solution on the gauze once the membranes are lifted with care to avoid contamination. If vanilla has passed through the membranes the distilled water papers would change from an initial ferric yellow in the drops toward a marked gray/greenish color on the papers (positive test).Results: In all cases, the swabs were stained, all the membranes in both directions were permeable to the whole vanilla molecule.Conclusions: This experiment allows us to reevaluate the importance of molecular diffusion through the amniotic membranes with no placental metabolism existing between maternal and fetal environment.

The Sudden Infant Death Syndrome mechanism of death may be a non-septic hyper-dynamic shock

BACKGROUND

Sudden Infant Death Syndrome (SIDS) mechanisms of death remains obscured. SIDS' Triple Risk Model assumed coexistence of individual subtle vulnerability, critical developmental period and stressors. Prone sleeping is a major risk factor but provide no clues regarding the mechanism of death. The leading assumed mechanisms of death are either an acute respiratory crisis or arrhythmias but neither one is supported with evidence, hence both are eventually speculations. Postmortem findings do exist but are inconclusive to identify the mechanism of death. WHAT DOES THE PROPOSED HYPOTHESIS BASED ON?: 1. The stressors (suggested by the triple risk model) share a unified compensatory physiological response of decrease in systemic vascular resistant (SVR) to facilitate a compensatory increase in cardiac output (CO). 2. The cardiovascular/cardiorespiratory control of the vulnerable infant during a critical developmental period may be impaired. 3. A severe decrease in SVR is associated with hyper-dynamic state, high output failure and distributive shock.

THE HYPOTHESIS

Infant who is exposed to one or more stressors responds normally by decrease in SVR which increases CO. In normal circumstances once the needs are met both SVR and CO are stabilized on a new steady state. The incompetent cardiovascular control of the vulnerable infant fails to stabilize SVR which decreases in an uncontrolled manner. Accordingly CO increases above the needs to hyper-dynamic state, high output heart failure and hyper-dynamic shock.

CONCLUSIONS

The proposed hypothesis provides an appropriate alternative to either respiratory crises or arrhythmia though both speculations cannot be entirely excluded.

Loss of Atoh1 from neurons regulating hypoxic and hypercapnic chemoresponses causes neonatal respiratory failure in mice

Atoh1-null mice die at birth from respiratory failure, but the precise cause has remained elusive. Loss of Atoh1 from various components of the respiratory circuitry (e.g. the retrotrapezoid nucleus (RTN)) has so far produced at most 50% neonatal lethality. To identify other Atoh1-lineage neurons that contribute to postnatal survival, we examined parabrachial complex neurons derived from the rostral rhombic lip (rRL) and found that they are activated during respiratory chemochallenges. Atoh1-deletion from the rRL does not affect survival, but causes apneas and respiratory depression during hypoxia, likely due to loss of projections to the preBötzinger Complex and RTN. Atoh1 thus promotes the development of the neural circuits governing hypoxic (rRL) and hypercapnic (RTN) chemoresponses, and combined loss of Atoh1 from these regions causes fully penetrant neonatal lethality. This work underscores the importance of modulating respiratory rhythms in response to chemosensory information during early postnatal life.

Towards Better Understanding of the Pathogenesis of Neuronal Respiratory Network in Sudden Perinatal Death

Sudden perinatal death that includes the victims of sudden infant death syndrome, sudden intrauterine death syndrome, and stillbirth are heartbreaking events in the life of parents. Most of the studies about sudden perinatal death were reported from Italy, highlighting two main etiological factors: prone sleeping position and smoking. Other probable contributory factors are prematurity, male gender, lack of breastfeeding, respiratory tract infections, use of pacifiers, infant botulism, extensive use of pesticides and insecticides, etc. However, extensive studies across the world are required to establish the role of these factors in a different subset of populations. Previous studies confirmed the widely accepted hypothesis that neuropathology of the brainstem is one of the main cause of sudden perinatal death. This study is an effort to summarize the neuropathological evaluation of the brainstems and their association to sudden perinatal death. Brainstem nuclei in vulnerable infants undergo certain changes that may alter the sleep arousal cycle, cardiorespiratory control, and ultimately culminate in death. This review focuses on the roles of different brainstem nuclei, their pathologies, and the established facts in this regard in terms of it's link to such deaths. This study will also help to understand the role of brainstem nuclei in controlling the cardiorespiratory cycles in sudden perinatal death and may provide a better understanding to resolve the mystery of these deaths in future. It is also found that a global initiative to deal with perinatal death is required to facilitate the diagnosis and prevention in developed and as well as developing countries.

Substance P/Neurokinin 1 and Trigeminal System: A Possible Link to the Pathogenesis in Sudden Perinatal Deaths

Sudden demise of a healthy fetus or a neonate is a very tragic episode in the life of parents. These deaths have been a mystery since ages but still remain unexplained. This review proposes the involvement of trigeminal nerve, neurotransmitter substance P (SP), and its receptor neurokinin 1 (NK-1R) in regulation of cardiorespiratory control in fetuses and newborns. Anomalies and immaturity of neuroregulatory systems such as trigeminal system in medulla oblongata of brainstem may provide a possible mechanism of sudden perinatal deaths. Vulnerable infants are born with respiratory center immaturity which in combination with any stressor such as cold, hypoxia, and smoking may lead to cessation of breathing and ventilatory response. SP/NK-1R may be involved in regulating the ventilatory control in neonates while it is decreased in fetal and adult life in humans, and any alterations from these may lead to irreversible sleep apnea and fatal breathing, ultimately sudden death. This review summarizes the studies performed to highlight the expression of SP or NK-1R in sudden perinatal deaths and proposes the involvement of trigeminal ganglion along with its nerve and SP/NK-1R expression alteration as one of the possible pathophysiological underlying mechanism. However, further studies are required to explore the role of SP, NK-1R, and trigeminal system in the pathogenesis of sudden infant deaths, sudden intrauterine deaths, stillbirths, and sudden deaths later in human life.

Key Brainstem Structures Activated during Hypoxic Exposure in One-day-old Mice Highlight Characteristics for Modeling Breathing Network in Premature Infants

We mapped and characterized changes in the activity of brainstem cell groups under hypoxia in one-day-old newborn mice, an animal model in which the central nervous system at birth is particularly immature. The classical biphasic respiratory response characterized by transient hyperventilation, followed by severe ventilation decline, was associated with increased c-FOS immunoreactivity in brainstem cell groups: the nucleus of the solitary tract, ventral reticular nucleus of the medulla, retrotrapezoid/parafacial region, parapyramidal group, raphe magnus nucleus, lateral, and medial parabrachial nucleus, and dorsal subcoeruleus nucleus. In contrast, the hypoglossal nucleus displayed decreased c-FOS immunoreactivity. There were fewer or no activated catecholaminergic cells activated in the medulla oblongata, whereas ~45% of the c-FOS-positive cells in the dorsal subcoeruleus were co-labeled. Approximately 30% of the c-FOS-positive cells in the parapyramidal group were serotoninergic, whereas only a small portion were labeled for serotonin in the raphe magnus nucleus. None of the c-FOS-positive cells in the retrotrapezoid/parafacial region were co-labeled for PHOX2B. Thus, the hypoxia-activated brainstem neuronal network of one-day-old mice is characterized by (i) the activation of catecholaminergic cells of the dorsal subcoeruleus nucleus, a structure implicated in the strong depressive pontine influence previously reported in the fetus but not in newborns, (ii) the weak activation of catecholaminergic cells of the ventral reticular nucleus of the medulla, an area involved in hypoxic hyperventilation, and (iii) the absence of PHOX2B-positive cells activated in the retrotrapezoid/parafacial region. Based on these results, one-day-old mice could highlight characteristics for modeling the breathing network of premature infants.

Safe Sleep Infant Care Practices Reported by Mothers of Twins

BACKGROUND

The high prevalence of prematurity and low birth-weight places twin infants at increased risk for sudden unexpected infant death (SUID) and/or sudden infant death syndrome (SIDS). Risk for these SUID and SIDS is affected by a combination of nonmodifiable intrinsic risk factors and modifiable extrinsic stressors including infant care practices related to sleep. Although adherence to the full scope of American Academy of Pediatrics (AAP) 2011 recommendations is intended to decrease risk, these recommendations are aimed at singleton infants and may require tailoring for families with multiple infants.

PURPOSE

The study describes infant care practices reported by mothers of twins in the first 6 months postpartum.

METHODS

Mothers caring for twin infants (N = 35) were surveyed online both longitudinally (at 2, 8, 16, and 24 weeks after infant hospital discharge) and cross-sectionally. AAP recommendations (2011) guided survey content.

RESULTS

The degree of adherence to AAP recommendations varied over time. For example, mothers of twins reported 100% adherence to placing twins supine for sleep initially, but many reported putting babies on their stomachs for naps as twins became older. Sharing a parent's bedroom decreased over time as did frequency of crib sharing. Fewer than half of mothers offered a pacifier most or all of the time for sleep.

IMPLICATIONS FOR PRACTICE

Opportunities exist for development of an educational program geared specifically for postpartum parents of twins.

IMPLICATIONS FOR RESEARCH

Barriers affecting adherence to AAP recommendations and effectiveness of educational programs addressing needs of this unique population need further exploration.

Updates on the Methodological Approaches for Carrying Out an In-Depth Study of the Cardiac Conduction System and the Autonomic Nervous System of Victims of Sudden Unexplained Fetal and Infant Death

This article contains a set of protocols for histopathological techniques that can be used for carrying out in-depth studies of cases of sudden infant death syndrome and sudden intrauterine unexplained fetal death syndrome. In order to enable researchers to advance hypotheses regarding the causes of the unexpected death of infants and fetuses, the authors propose three innovative and accurate methodologies for studying the cardiac conduction system, the peripheral cardiac nervous system, and the central autonomic nervous system. Over the years, these protocols have been developed, modified, and improved on a vast number of cases which has enabled pathologists to carry out the microscopic analyses of the structures which regulate life, in order to highlight all the possible morphological substrates of pathophysiological mechanisms that may underlie these syndromes.

In memory of our research professor Lino Rossi (1923–2004).

Immunohistochemical Analysis of Brainstem Lesions in the Autopsy Cases with Severe Motor and Intellectual Disabilities Showing Sudden Unexplained Death

It is known that patients with severe motor and intellectual disabilities (SMID) showed sudden unexplained death (SUD), in which autopsy failed to identify causes of death. Although the involvement of brainstem dysfunction is speculated, the detailed neuropathological analysis still remains to be performed. In order to clarify pathogenesis, we investigated the brainstem functions in autopsy cases of SMID showing SUD. We immunohistochemically examined expressions of tyrosine hydroxylase, tryptophan hydroxylase, substance P, methionine-enkephalin, and c-fos in the serial sections of the midbrain, pons, and medulla oblongata in eight SUD cases and seven controls, having neither unexplained death nor pathological changes in the brain. Expressions of tyrosine hydroxylase and tryptophan hydroxylase were reduced in two of eight cases, and those of substance P and/or methionine-enkephalin were augmented in the pons and medulla oblongata in seven of eight cases, including the aforementioned two cases, when compared with those in controls. The hypoglossal nucleus and/or the dorsal vagal nucleus demonstrated increased neuronal immunoreactivity for c-fos in seven of eight cases, although there was no neuronal loss or gliosis in both the nuclei. Controls rarely showed immunoreactivity for c-fos in the medulla oblongata. These data suggest the possible involvement of brainstem dysfunction in SUD in patients with SMID, and consecutive neurophysiological evaluation of brainstem functions, such as all-night polysomnography and blink reflex, may be useful for the prevention of SUD, because some parameters in the neurophysiological examination are known to be related to the brainstem catecholamine neurons and the spinal tract nucleus of trigeminal nerve.