Severe Hypoplasia/Aplasia of the Medullary Arcuate Nucleus in a Further Patient with Sudden Infant Death Syndrome

The aim of this study was to verify and confirm the close correlation between the absence of the medullary arcuate nucleus and sudden death in a 4-month-old infant. Careful neuropathological examination of the cerebral hemispheres, basal ganglia and cerebellum was irrelevant to the death. The brainstem region, normally occupied by the nuclei was cut into several serial sections so as not to lose any details. The largest median part of the medullary arcuate nucleus was completely absent and only very small groups of residual neurons in its most lateral part were still detectable; the rest of the brainstem showed no abnormalities. In the absence of other lesional, degenerative or malformative causes, the sudden and unexpected death of this infant was likely due to severe hypoplasia/aplasia of the medullary arcuate nucleus with our evidence. The anatomo-functional development of the nucleus and its crucial role in the control of respiratory and cardiac autonomic reactivity in sleep during the first year of life may provide an important contribution to the pathogenic interpretation.