Variability of the medullary arcuate nucleus in humans.

Beatrice Paradiso,Anna Maria Lavezzi,Stefano Ferrero,Gaetano Thiene

doi:10.1002/brb3.1133

Abstract

IntroductionThe arcuate nucleus is a component of the ventral medullary surface involved in chemoreception and breathing control. The hypoplasia of this nucleus is a very frequent finding in victims of sudden unexplained fetal and infant death (from the last weeks of pregnancy to the first year of life). On the contrary, this developmental alteration is rarely present in age‐matched controls who died of defined causes. These observations lead to hypothesize that a well‐developed and functional arcuate nucleus is generally required to sustain life. The aim of this study was to investigate whether the arcuate nucleus maintains the same supposed function throughout life.MethodsWe carried out neuropathological examinations of brainstems obtained from 25 adult subjects, 18 males and 7 females, aged between 34 and 89 years, who died from various causes.ResultsFor almost half of the cases (44%) microscopic examinations of serial histological sections of medulla oblongata showed a normal cytoarchitecture of the arcuate nucleus, extending along the pyramids. For the remaining 56% of cases, various degrees of hypodevelopment of this nucleus were observed, validated through the application of quantitative morphometric investigations, from decreased area, neuron number and volume, to full aplasia.ConclusionsThese unexpected findings indicate that the involvement of the arcuate nucleus in chemoreception in adulthood is questionable, given the possibility of living until late age without this nucleus. This opens new perspectives for researchers on the role and function of the arcuate nucleus in humans from birth to old age.

Highlights

The arcuate nucleus is a component of the ventral medullary surface involved in chemoreception and breathing control
The arcuate nucleus (AN) is a group of neurons located in the brainstem on both sides of the midline at the ventral surface of the medulla oblongata, which extends between the caudal border of the pons and the caudal pole of the olive (Mikhail & Ahmed, 1975)
A first examination was performed under a light microscope at dif‐ ferent magnifications on serial histological sec‐ tions obtained from the medulla oblongata, with the plates from VIII to XVIII of the classic Atlas of Olszewski and Baxter (1982) and the sections from E to J of the online Atlas of the Brainstem of Swenson (RRID:SCR_005967) used as references for the AN analysis

Summary

| INTRODUCTION

The arcuate nucleus (AN) is a group of neurons located in the brainstem on both sides of the midline at the ventral surface of the medulla oblongata, which extends between the caudal border of the pons and the caudal pole of the olive (Mikhail & Ahmed, 1975) This nucleus has been proposed as the homologue of the chemo‐ receptive areas in the ventral medullary surface (VMS) reported in experimental researches, responsible for mediating the ventilator responsiveness to carbon dioxide (CO2) (Bruce & Cherniack, 1987; Filiano, Choi, & Kinney, 1990; Millhorn & Eldridge, 1986; Paterson, Thompson, & Kinney, 2006; Zec, Filiano, & Kinney, 1997). With the aim to determine whether this was merely an isolated and inexplicable finding and that a well‐developed and functional AN is essential throughout the entire life span, we decided to ana‐ lyze the AN in a cohort of adults who died of various causes

| MATERIALS AND METHODS

| Ethics statement

Findings

| DISCUSSION