Morphometric Analysis of Infant and Adult Medullary Nuclei Through Optical Disector Method

Abstract

In the literature, comprehensive and comparative morphometric studies of infant and adult medullary nuclei performed with unbiased methods are still lacking. In this study, the unbiased quantitative method of the optical disector was applied to analyze neuronal densities, nuclear volumes, and total neuron numbers of the hypoglossal nucleus (XII), dorsal motor nucleus of the vagus (DMNV), nucleus tractus solitarii (NTS), medial vestibular nucleus (MedVe), cuneate nucleus (Cu), nucleus of the spinal trigeminal tract, principal inferior olivary nucleus (PION), medial inferior olivary nucleus (MION), and dorsal inferior olivary nucleus (DION) in adults (16 male, six female; mean age: 37 years) and infants (five male, five female; mean age: 5 months). In both infants and adults, higher neuronal densities were found in the more ventrally located nuclei of the spinal trigeminal tract (mean values (coefficient of variation): 20,947 (0.29) and 8,990 (0.18) neurons/mm 3 , respectively) and inferior olivary complex (PION: 20,010 (0.15) and 9,076 (0.10); MION: 18,667 (0.20) and 9,989 (0.13); DION: 22,424 (0.17) and 10,986 (0.20), respectively) than in the nuclei of the medullary tegmentum, that is, XII (2,747 (0.39) and 1,026 (0.31)), DMNV (2,876 (0.19) and 1,553 (0.26)), NTS (7,993 (0.17) and 2,877 (0.13)), MedVe (7,010 (0.17) and 2,918 (0.12)), and Cu (2,563 (0.23) and 1,038 (0.16)). All the medullary nuclei showed higher volumes and lower neuronal densities in adults than in infants, without statistically significant differences in total neuron numbers, probably because of postnatal development of the neuropil and microvascularization. Anat Rec, 292:1619Rec, 292: -1629Rec, 292: , 2009. V V C 2009 Wiley-Liss, Inc.Key words: morphometry; optical disector; medulla oblongata; human; infantThe medulla oblongata is involved in many different and complex functions as it contains nuclei involved in cardiac and respiratory control, nervous centers providing sensory and motor innervation of peripheral structures, groups of neurons receiving inputs related to the special senses of hearing, vestibular function and taste, or providing/receiving efferent/afferent cerebellar projections. There have been a few studies in the literature detailing morphometric parameters, such as neuronal density, nuclear volume, and total neuron number, in the medullary nuclei considered in this study (e.g

Review: Neuropathological features of unexplained sudden unexpected death in infancy: current evidence and controversies

“…Twenty‐eight studies have investigated structures in the medulla in SIDS [53,92,95,98,107–130] and of these, eight publications, examining a range of nuclei, met the criteria for inclusion [92,110,115–117,119–121].…”

“…Study of the nerve and its nuclei is pertinent to SIDS as they convey and process visceral sensory information [134], provide cardiac parasympathetic tone [135] and have key roles in the regulation of respiration [136]. Seven studies have examined the nuclei of the vagus nerve in SIDS [53,108,112,114,116,118,128] and of these one met the criteria for inclusion [116]. This reported no difference in volume, number or position of neurones in these nuclei in infant dying of SIDS and other causes [116].…”

“…One of these muscles, genioglossus, is essential for maintaining upper airway patency in infants [137], including after momentary occlusion as might occur during sleep [138]. Ten studies have described findings in the nucleus of the hypoglossal nerve [98,110,112,113,116–118,124,128,129], of which three met the criteria for inclusion [110,116,117]. These papers report conflicting findings: one found reduced numbers of neurones in the HGN in infants dying of SIDS when compared with controls [110], one reported no difference in volume, number or position of neurones [116] and one found increased volume of the neurones and HGN [117].…”

“…Given the reports of abnormalities in the arcuate nucleus [115,119–121] and external EGL of the cerebellum in SIDS [84], it reasonable to expect changes in the inferior olivary nuclei (ION), too, as the neural progenitor cells that migrate to populate these regions have a common origin in the rhombic lip. Three studies have examined the ION in SIDS [92,127,128] and of these one met the criteria for inclusion [92]. When adjusted for postconceptional age, infants dying of SIDS were reported to have reduced density of neurones in the ION compared with controls [92] but the same group found no significant difference in the number of neurones [92].…”

Central and peripheral chemoreceptors in sudden infant death syndrome

“…In a previous study, we performed stereological analysis of the main medullary nuclei of adults and infants according to the optical dissector method. The infant series contained both cases of SIDS and controls, but significant differences were not found, although this may have been due to the small number of cases (Porzionato et al 2009b). Further unbiased stereological studies will be necessary to verify possible morphometric changes in central and peripheral respiratory chemoreceptors of SIDS victims.…”