Functional neuroanatomy of the human pre-Bötzinger complex with particular reference to sudden unexplained perinatal and infant death

Developmental alterations of the prefrontal cerebral cortex in sudden unexplained perinatal and infant deaths

The aim of this study was to investigate the developmental patterns of the human prefrontal cortex involved in breathing control in a wide cohort of fetal and infant death victims, aged from the 22(nd) gestational week to 10 months of life, and to evaluate whether morpho-functional disorders are present in this specific cortical area in victims of sudden unexplained death. A further aim was to determine whether prenatal absorption of nicotine could also affect the maturational processes of the prefrontal cortex. A pronounced radial organization of the cerebral wall was evident from the 26(th) gestational week. By 36 gestational weeks this columnar structure disappeared, coinciding with the formation of a laminar cyto-architecture. The mature cortex, observable from the 4(th) month of life, was organized horizontally into six laminae. In 33% of the sudden death victims the prefrontal cortex showed morphological alterations with anomalous laminar patterns and delayed neuronal maturation. A significant correlation with prenatal cigarette exposure was found.

Neuropathology of the intermediolateral nucleus of the spinal cord in sudden unexplained perinatal and infant death

Experimental studies have demonstrated that breathing activity in rats is generated early in embryonic stages in rostral spinal cord, precisely in the intermediolateral nucleus, then establishing a spinal cord-brainstem network. In this study we aimed to individuate and to define the developmental steps of the intermediolateral nucleus, still inadequately known in humans, in the thoracic spinal cord of a large series of perinatal and infant death victims, aged from 17 gestational weeks to 10 months of life. Besides we investigated a possible link between alterations of this nucleus and sudden unexplained perinatal and infant death. The normal developmental pattern of the human intermediolateral nucleus consists of a progressive maturation of its neurons, that change from a round to a polygonal shape with long axons and significantly decrease in number. Various degrees of intermediolateral nucleus hypodevelopment (neuronal immaturity in a normal structure/hypoplasia/agenesis) were found almost exclusively in unexplained fetal and infant death victims. Besides, a significant correlation was found between maternal smoking in pregnancy and the neuropathological results. In conclusion this work underlines the negative effects of prenatal nicotine exposure on the development of autonomic nervous centers checking the vital functions, already in early gestational stages, when the integrity of the intermediolateral nucleus is indispensable for the first breathing bursts.

Neuropathology of the Guillain-Mollaret Triangle (Dentato-Rubro-Olivary Network) in Sudden Unexplained Perinatal Death and SIDS

The present study was undertaken to evaluate the possible alterations of the triangle of Guillain and Mollaret (G-Mt), a neuronal brainstem/cerebellum network (from the dentate nucleus to red nucleus and inferior olivary nucleus) already known for its involvement in the pathogenesis of the palatal myoclonus, in sudden unexplained perinatal and infant death. In 44 cases of perinatal and infant death victims, aged from 26 gestational weeks to 10 months of life, we investigated, besides the histological morphology of the three nuclei, the c-fos and apoptotic expression, as well as the possible effects elicited by maternal cigarette smoking.

A significant increase of lesions (hypoplasia and/or increased c-fos and apoptotic neuronal immunopositivity) of the three nuclei was found in unexplained death victims, compared with age-matched controls. These alterations were related to maternal cigarette smoking habit.

We postulated that the G-Mt is an important network involved in the pathogenesis of a wide spectrum of pathological manifestations and that maternal smoking during pregnancy can exert an adverse influence on this complex, even leading to sudden death in vulnerable periods of perinatal or infant development.

Neuromodulation and the orchestration of the respiratory rhythm

The respiratory system is continuously modulated by numerous aminergic and peptidergic substances that act at all levels of integration: from the sensory level to the level of central networks and motor nuclei. The same neuronal networks receive inputs from multiple modulators released locally as well as from distal nuclei. All parameters of respiratory control are controlled by multiple neuromodulators. By partly converging onto similar G-proteins and second messenger systems, acetylcholine, norepinephrine, histamine, serotonin (5-HT), dopamine, ATP, substance P, cholecystokinin (CCK) can increase frequency, regularity and amplitude of respiratory activity. Yet, the same modulator can also exert differential effects on respiratory activity by acting on different receptors partly in the same neurons. In the pre-Bötzinger complex (pre-BötC) modulators can differentially modulate frequency and amplitude in different types of pacemaker neurons. Similarly motoneurons located in different motor nuclei receive differential amplitude modulation from different modulators. Thus, modulators are capable of orchestrating and modulating different parameters of respiratory activity by differentially targeting different cellular targets. A disturbance in modulatory control may lead to Sudden Infant Death Syndrome (SIDS) and erratic breathing.

Infant and perinatal pulmonary hypoplasia frequently associated with brainstem hypodevelopment

Recent anatomo-pathological studies have revealed a frequent associated hypoplasia of both arcuate nucleus and lungs in stillbirths. The purpose of this study is to analyze the lung and brainstem development in sudden unexplained perinatal death and sudden infant death syndrome (SIDS). A total of 51 cases were investigated. A complete autopsy was performed in each case. Anatomo-pathologic examination of the central autonomic nervous system included an in-depth study on histological serial sections of the brains where the main structures participating in control of the vital functions are located. The stage of lung development was evaluated by macroscopic and microscopic criteria. In 52.9% of cases, a pulmonary hypoplasia was detected. The pulmonary hypoplasia was significantly more frequent in the SIDS group compared to the sudden perinatal unexplained death groups (p < 0.05). In 72.5% of cases, histological examination of the brainstem on serial sections showed hypodevelopment of the brainstem nuclei, particularly hypoplasia, of the arcuate nucleus (60.8%). In 47.1% of cases, pulmonary hypoplasia was associated with brainstem hypodevelopment.

Unexpected perinatal loss versus Sids-a common neuropathologic entity

Objective: To evaluate the involvement of alterations of the central autonomic nervous system, particularly of the brainstem and cerebellum, in a wide set of victims of sudden and unexplained perinatal and infant death.

Material and Methods: The study population consisted of 63 stillbirths, 28 neonatal deaths and 140 suspected SIDS. The victims were subjected to in-depth anatomopathological examination following appropriate guidelines. The protocol included, in particular, the histological evaluation on serial sections of the cardiorespiratory autonomic nervous system.

Results: A diagnosis of “unexplained death” was established for 217 of the 231 victims (59 stillbirths, 28 newborns and 130 SIDS). In a very high percentage of these deaths (84%) we observed one or more anomalies of the nuclei and/or structures of the brainstem and cerebellum related to vital functions.

Conclusion: Unexpected perinatal loss should not be regarded as a separate entity from SIDS, given the common neuropathological substrates.

[The neuropathology of sleep in human neurodegenerative diseases]

The neuropathology of human sleep remains an ill-defined issue. The data concerning the main structures of human brain areas involved, or supposed to be implicated, in sleep organisation are reviewed. Five levels of organisation can be schematically recognized: (i) the ascending arousal system, (ii) the non REM and REM systems (iii) regulated by hypothalamic areas, (iv) and the biological clock, (v) modulated by a number of "allostatic" influences. These are briefly described, with emphasis on the location of structures involved in humans, and on the recently revised concepts. Current knowledge on the topography of lesions associated with the main sleep disorders in degenerative diseases is recalled, including REM sleep behavior disorders, restless legs syndrome and periodic leg movements, sleep apneas, insomnia, excessive daily sleepiness, secondary narcolepsy and disturbed sleep-wake rhythms. The lesions of sleep related structures observed in early and late stages of four degenerative diseases are then reviewed. Two synucleinopathies (Lewy lesions associated disorders, including Parkinson's disease and Dementia with Lewy bodies, and Multiple System Atrophy) and two tauopathies (Progressive Supranuclear Palsy and Alzheimer's disease) are dealt with. The distribution of lesions usually found in affected patients fit with that expected from the prevalence of different sleep disorders in these diseases. This confirms the current opinion that these disorders depend on the distribution of lesions rather than on their biochemical nature. Further studies might throw insight on the mechanism of normal and pathological sleep in humans, counterpart of the increasing knowledge provided by animal models. Specially designed prospective clinicopathological studies including peculiar attention to sleep are urgently needed.