Neurobiological Alterations Of The Substantia Nigra In Sudden Infant Death Syndrome

Abstract Background - The purpose of this study was to research possible morphological and functional alterations of the substantia nigra in SIDS. Methods - Brainstems of 46 victims of sudden infant death, aged from 1 to 7 months, 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 10% of controls and 77% of SIDS. Histopathological examination of the substantia nigra was done on midbrain 5-µm-thick sections stained with hematoxylin-eosin and Klüver-Barrera. Densitometry, immunohistochemistry and histochemistry were applied to highlight the neuronal concentration, the expression of tyrosine hydroxylase and neuromelanin, respectively. Results - Hypoplasia of the pars compacta of the substantia nigra was observed in SIDS but not in controls. Tyrosine hydroxylase expression in the substantia nigra was significantly higher in controls than in SIDS. Neuromelanin was observed as dark granules only in 4 infants of the control group but never in SIDS. A significant correlation was found between hypoplasia/low neuronal density, low tyrosine hydroxylase expression in the substantia nigra pars compacta and maternal smoking. Conclusion - The substantia nigra pars compacta, that is the main dopamine center in the brain, is involved in the control of many functions, including the sleep-arousal phase, and hence, its structural and/or functional alterations may explain the pathogenesis of SIDS, that often occurs during sleep. This study also indicates that maternal smoking can may have strongly influenced the SN altered development. Trial registration – not applicable for this study