Neuropathology of the area postrema in sudden intrauterine and infant death syndromes related to tobacco smoke exposure

New Step in Understanding the Pathogenetic Mechanism of Sudden Infant Death Syndrome: Involvement of the Pontine Reticular Gigantocellular Nucleus

This study aimed to investigate, for the first time, the potential role of the gigantocellular nucleus, a component of the reticular formation, in the pathogenetic mechanism of Sudden Infant Death Syndrome (SIDS), an event frequently ascribed to failure to arouse from sleep. This research was motivated by previous experimental studies demonstrating the gigantocellular nucleus involvement in regulating the sleep-wake cycle. We analyzed the brains of 48 infants who died suddenly within the first 7 months of life, including 28 SIDS cases and 20 controls. All brains underwent a thorough histological and immunohistochemical examination, focusing specifically on the gigantocellular nucleus. This examination aimed to characterize its developmental cytoarchitecture and tyrosine hydroxylase expression, with particular attention to potential associations with SIDS risk factors. In 68% of SIDS cases, but never in controls, we observed hypoplasia of the pontine portion of the gigantocellular nucleus. Alterations in the catecholaminergic system were present in 61% of SIDS cases but only in 10% of controls. A strong correlation was observed between these findings and maternal smoking in SIDS cases when compared with controls. In conclusion we believe that this study sheds new light on the pathogenetic processes underlying SIDS, particularly in cases associated with maternal smoking during pregnancy.

The Role of Maternal Smoking in Sudden Fetal and Infant Death Pathogenesis

Maternal smoking is a risk factor for both sudden infant death syndrome (SIDS) and sudden intrauterine unexplained death syndrome (SIUDS). Both SIDS and SIUDS are more frequently observed in infants of smoking mothers. The global prevalence of smoking during pregnancy is 1.7% and up to 8.1% of women in Europe smoke during pregnancy and worldwide 250 million women smoke during pregnancy. Infants born to mothers who smoke have an abnormal response to hypoxia and hypercarbia and they also have reduced arousal responses. The harmful effects of tobacco smoke are mainly mediated by release of carbon monoxide and nicotine. Nicotine can enter the fetal circulation and affect multiple developing organs including the lungs, adrenal glands and the brain. Abnormalities in brainstem nuclei crucial to respiratory control, the cerebral cortex and the autonomic nervous system have been demonstrated. In addition, hypodevelopment of the intermediolateral nucleus in the spinal cord has been reported. It initiates episodic respiratory movements that facilitate lung development. Furthermore, abnormal maturation and transmitter levels in the carotid bodies have been described which would make infants more vulnerable to hypoxic challenges. Unfortunately, smoking cessation programs do not appear to have significantly reduced the number of pregnant women who smoke.

Area postrema syndrome as initial manifestation in neuromyelitis optica spectrum disorder patients: A retrospective study

BACKGROUND

Area postrema syndrome (APS) is recognized as a core feature in neuromyelitis optica (NMO) diagnosis. Isolated APS can occur at NMO onset and frequently results in a delay of diagnosis, along with devastating secondary neurologic deficits. To date, few studies have characterized APS-onset neuromyelitis optica spectrum disorder (APSO-NMOSD).

OBJECTIVE

We aimed to describe the clinical and radiologic features of patients with APSO-NMOSD who are initially misdiagnosed in a cohort of patients from Zhengzhou, China.

MATERIALS AND METHODS

We identified 15 patients who presented with APS as an initial manifestation, based on the 2015 international consensus diagnostic criteria for NMOSD, and reviewed their demographic, clinical, laboratory, and magnetic resonance imaging (MRI) data.

RESULT

Fifteen patients (3 men, 12 women) aged 14-50 years old were included in our study. All patients presented with APS that included intractable nausea, vomiting, or hiccups (INVH) as the initial manifestation; many experienced a delay in diagnosis. Serum AQP4 was positive in eleven patients and myelin oligodendrocyte glycoprotein (MOG) in one patient. All patients had a linear medullary lesion or a linear medulla-spinal lesion on sagittal MRI. An "inverted V sign" on axial medulla oblongata images, representing a lesion involving the area postrema, was noted in seven patients in this study.

CONCLUSIONS

APS can occur as a sole and initial manifestation of NMOSD, often leading to misdiagnosis in the early process of disease. Identifying patients with an "inverted V" sign and a linear medullary lesion upon MRI examination can help to quickly identify APS patients and avoid further diagnostic delays.

Substantia Nigra Abnormalities Provide New Insight on the Neural Mechanisms Underlying the Sleep-Arousal Phase Dysfunctions in Sudden Infant Death Syndrome

The purpose of this study was to research possible developmental alterations of the substantia nigra (SN) in sudden infant death syndrome (SIDS), a syndrome frequently attributed to arousal failure from sleep. Brain stems of 46 victims of sudden infant death, aged from 1 to about 7 months (4 to 30 postnatal weeks), were investigated. Twenty-six of these cases were diagnosed as SIDS, due to the lack of any pathological finding, while the remaining 20 cases in which the cause of death was determined at autopsy served as controls. Maternal smoking was reported in 77% of SIDS and 10% of controls. Histopathological examination of the SN was done on 5-µm-thick sections of caudal midbrain stained with both hematoxylin-eosin and Klüver-Barrera. Densitometry, immunohistochemistry and histochemistry were applied to highlight the neuronal concentration, the tyrosine hydroxylase (TH) expression, and the presence of neuromelanin (NM) in this structure. Hypoplasia of the pars compacta portion of the SN was observed in 69% of SIDS but never in controls; TH expression was significantly higher in controls than in SIDS; and NM was observed only in 4 infants of the control group but not in SIDS. A significant correlation was found between SIDS, hypoplasia/low neuronal density, low TH expression in the pars compacta, and maternal smoking. Because the SN pars compacta, being the major dopamine brain center, controls many functions, including the sleep-arousal phase, its alterations, especially concurrently with smoking exposure, may contribute to explain the pathogenesis of SIDS that occur in the great part of cases at awakening from sleep.

Bedsharing and Breastfeeding: The Academy of Breastfeeding Medicine Protocol #6, Revision 2019

A central goal of the Academy of Breastfeeding Medicine is the development of clinical protocols for managing common medical problems that may impact breastfeeding success. These protocols serve only as guidelines for the care of breastfeeding mothers and infants and do not delineate an exclusive course of treatment or serve as standards of medical care. Variations in treatment may be appropriate according to the needs of an individual patient.

Toxic Effect of Cigarette Smoke on Brainstem Nicotinic Receptor Expression: Primary Cause of Sudden Unexplained Perinatal Death

Among the neurotoxicants contained in tobacco smoke, if absorbed during pregnancy, nicotine significantly affects α7-nicotinic acetylcholine receptors, which play essential roles in the development of the brainstem regions receiving cholinergic projections in perinatal life. Immunohistochemical procedures for analysing formalin-fixed and paraffin-embedded brainstem samples from 68 fetuses and early newborns, with smoking and non-smoking mothers, who died of known and unknown causes, were carried out in order to determine if nicotine had activated the α7-nicotinic acetylcholine receptors. High α7-nicotinic acetylcholine receptor expression levels were only observed in the victims with smoking mothers. Frequently, these findings were associated with the hypoplasia of the brainstem structures controlling vital functions. The results of this study indicate that the exposition to nicotine in pregnancy exerts a strong direct effect on α7-nicotinic acetylcholine receptor activity especially in perinatal life and may be one of the primary risk factors leading to the sudden unexplained death of fetuses and newborns.

Cardiovascular autonomic dysfunction in sudden infant death syndrome

A failure of cardiorespiratory control mechanisms, together with an impaired arousal response from sleep, are believed to play an important role in the final event of sudden infant death syndrome (SIDS). The 'triple risk model' describes SIDS as an event that results from the intersection of three overlapping factors: (1) a vulnerable infant, (2) a critical developmental period in homeostatic control and (3) an exogenous stressor. In an attempt to understand how the triple risk hypothesis is related to infant cardiorespiratory physiology, many researchers have examined how the known risk and protective factors for SIDS alter infant cardiovascular control during sleep. This review discusses the association between the three components of the triple risk hypothesis and major risk factors for SIDS, such as prone sleeping, maternal smoking, together with three "protective" factors, and cardiovascular control during sleep in infants, and discusses their potential involvement in SIDS.

Sudden Infant Death With Area Postrema Lesion Likely Due to Wrong Use of Insecticide

We report a noteworthy case of a 7-month-old infant who suddenly and unexpectedly died during her sleep. After a complete postmortem examination, review of the clinical history, and detailed death scene investigation, the death remained unexplained, leading to a diagnosis of sudden infant death syndrome. However, an extensive review of the brainstem neuropathology revealed a severe alteration in the area postrema (a highly vascular structure lying at the base of the fourth ventricle outside of the blood-brain barrier). The alteration was likely due to massive and repeated to a common household insecticide in the last few weeks of life. These results provide an explanation for this sudden infant death, allowing a differential diagnosis from sudden infant death syndrome.

Occurrence of specific environmental risk factors in brain tissues of sudden infant death and sudden intrauterine unexpected death victims assessed with gas chromatography-tandem mass spectrometry

Sudden infant death syndrome (SIDS) and sudden intrauterine unexpected death syndrome (SIUDS) are an unresolved teaser in the social-medical and health setting of modern medicine and are the result of multifactorial interactions. Recently, prenatal exposure to environmental contaminants has been associated with negative pregnancy outcomes, and verification of their presence in fetal and newborn tissues is of crucial importance. A gas chromatography-tandem mass spectrometry (MS/MS) method, using a triple quadrupole analyzer, is proposed to assess the presence of 20 organochlorine pesticides, two organophosphate pesticides, one carbamate (boscalid), and a phenol (bisphenol A) in human brain tissues. Samples were collected during autopsies of infants and fetuses that died suddenly without any evident cause. The method involves a liquid-solid extraction using n-hexane as the extraction solvent. The extracts were purified with Florisil cartridges prior to the final determination. Recovery experiments using lamb brain spiked at three different concentrations in the range of 1-50 ng g(-1) were performed, with recoveries ranging from 79 to 106%. Intraday and interday repeatability were evaluated, and relative standard deviations lower than 10% and 18%, respectively, were obtained. The selectivity and sensitivity achieved in multiple reaction monitoring mode allowed us to achieve quantification and confirmation in a real matrix at levels as low as 0.2-0.6 ng g(-1). Two MS/MS transitions were acquired for each analyte, using the Q/q ratio as the confirmatory parameter. This method was applied to the analysis of 14 cerebral cortex samples (ten SIUDS and four SIDS cases), and confirmed the presence of several selected compounds.

Cytoarchitectural and functional abnormalities of the inferior colliculus in sudden unexplained perinatal death

The inferior colliculus is a mesencephalic structure endowed with serotonergic fibers that plays an important role in the processing of acoustic information. The implication of the neuromodulator serotonin also in the aetiology of sudden unexplained fetal and infant death syndromes and the demonstration in these pathologies of developmental alterations of the superior olivary complex (SOC), a group of pontine nuclei likewise involved in hearing, prompted us to investigate whether the inferior colliculus may somehow contribute to the pathogenetic mechanism of unexplained perinatal death. Therefore, we performed in a wide set of fetuses and infants, aged from 33 gestational weeks to 7 postnatal months and died of both known and unknown cause, an in-depth anatomopathological analysis of the brainstem, particularly of the midbrain. Peculiar neuroanatomical and functional abnormalities of the inferior colliculus, such as hypoplasia/structural disarrangement and immunonegativity or poor positivity of serotonin, were exclusively found in sudden death victims, and not in controls. In addition, these alterations were frequently related to dysgenesis of connected structures, precisely the raphé nuclei and the superior olivary complex, and to nicotine absorption in pregnancy. We propose, on the basis of these results, the involvement of the inferior colliculus in more important functions than those related to hearing, as breathing and, more extensively, all the vital activities, and then in pathological conditions underlying a sudden death in vulnerable periods of the autonomic nervous system development, particularly associated to harmful risk factors as cigarette smoking.

Vulnerability of fourth ventricle choroid plexus in sudden unexplained fetal and infant death syndromes related to smoking mothers

The human choroid plexuses in the ventricular system represent the main source of cerebrospinal fluid secretion and constitute a major barrier interface that controls the brain's environment. The present study focused on the choroid plexus of the fourth ventricle, the main cavity of the brainstem containing important nuclei and/or structures mediating autonomic vital functions. In serial sections of 84 brainstems of subjects aged from 17 gestational weeks to 8 postnatal months of life, the deaths due to both known and unknown causes, we examined the cytoarchitecture and the developmental steps of the fourth ventricle choroid plexus to determine whether this structure shows morphological and/or functional alterations in unexplained perinatal deaths (Sudden Infant Death Syndrome and Sudden Intrauterine Unexplained Death Syndrome). High incidence of histological and immunohistochemical alterations (prevalence of epithelial dark cells, the presence of cystic cells in the stroma, decreased number of blood capillaries, hyperexpression of Substance P and apoptosis) were prevalently observed in unexplained death victims (p<0.05 vs. controls). A significant correlation was found between maternal smoking in pregnancy and choroidal neuropathological parameters (p<0.01). This work underscores the negative effects of prenatal exposure to nicotine on the development of the autonomic nervous system, and in particular of the fourth ventricle choroid plexus that is a very vulnerable structure in the developing CSF-brain system.