Hypertrophy of the Anterior External Arcuate Fasciculus: A Rare Variant With Implications for the Development of the Arcuate Nucleus

Stonebridge, Renee; Taliano, Ross; Velilla, Terra D.; Anthony, Douglas C.

doi:10.3389/fnana.2020.595500

“…Somata of Arc neurons expressed CR, nNOS, and NPNFP and not CB. Expression of CR in Arc neurons was also reported by Stonebridge et al (2020). These data show again that the neurochemical pro le of the Arc is different from that in the IO in the absence of immunostaining for CB in Arc somata.…”

Section: Variability and Asymmetry Of The Arc And Ioprsupporting

confidence: 79%

“…These data show again that the neurochemical pro le of the Arc is different from that in the IO in the absence of immunostaining for CB in Arc somata. CR is expressed in somata of both structures (Baizer et al 2011b;Stonebridge et al 2020). Expression of CB and CR in IO neurons has also been seen in other species (Yu et al 2014;Celio 1990).…”

Section: Variability and Asymmetry Of The Arc And Ioprmentioning

confidence: 71%

“…The aplasia or hypoplasia of the Arc in neuropathological reports may correlate with other brainstem de cits that are more directly responsible for death. While the reevaluation of the role of the Arc in respiration has been recognized in some studies (Presti et al 2014) the idea still persists in others (Stonebridge et al 2020). Understanding the mechanisms of SIDS depends on accurate identi cation of the critical brainstem structures.…”

Section: Variability and Asymmetry Of The Arc And Ioprmentioning

confidence: 99%

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Individual variability in the size and organization of the human arcuate nucleus of the medulla

Baizer

¹

,

Witelson

²

2021

Preprint

0

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The arcuate nucleus (Arc) of the medulla is found in almost all human brains and in a small percentage of chimpanzee brains. It is absent in the brains of other mammalian species including mice, rats, cats and macaque monkeys. The Arc is classically considered a precerebellar nucleus, presumably motor in function. However, several studies have found aplasia of the Arc in babies who died of SIDS (Sudden Infant Death Syndrome) suggesting a very different role for the Arc in the control of respiration. Aplasia of the Arc, however, has also been reported in adults suggesting that it is not critical for survival. We have examined the Arc in closely-spaced Nissl-stained sections in human cases to acquire a better understanding of the degree of variability of its size and location in adults. We have also examined immunostained sections to develop a neurochemical profile of this nucleus. Our data suggest that the Arc consists of rostral and caudal subdivisions. There is some degree of left-right asymmetry in Arc position, size and shape at all rostro-caudal levels. Neurons in the Arc express calretinin (CR), neuronal nitric oxide synthase (nNOS) and nonphosphorylated neurofilament protein (NPNFP) but not calbindin (CB) or parvalbumin (PV). There is also immunostaining for GAD and GABA receptors suggesting inhibitory input to Arc neurons. We support the classical idea of the Arc as a precerebellar nucleus; its absence in SIDS cases may not be the cause of death but rather a correlate of other brainstem abnormalities.

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“…Somata of Arc neurons expressed CR, nNOS, and NPNFP and not CB, which was expressed in puncta. Expression of CR in Arc neurons was also reported by Stonebridge et al (2020). These data show that the neurochemical profile of the Arc is from that of the IO in the absence of immunostaining for CB in Arc somata.…”

Section: Neurochemical Characteristics Of the Arcsupporting

confidence: 79%

“…These data show that the neurochemical profile of the Arc is from that of the IO in the absence of immunostaining for CB in Arc somata. CR is expressed in somata of both structures (Baizer et al 2011b;Stonebridge et al 2020). Expression of CB and CR in IO neurons has also been seen in other species (Yu et al 2014;Celio 1990).…”

Section: Neurochemical Characteristics Of the Arcmentioning

confidence: 71%

Individual variability in the size and organization of the human arcuate nucleus of the medulla

Baizer

¹

,

Webster

²

,

Witelson

³

2021

View full text Add to dashboard Cite

The arcuate nucleus (Arc) of the medulla is found in almost all human brains and in a small percentage of chimpanzee brains. It is absent in the brains of other mammalian species including mice, rats, cats, and macaque monkeys. The Arc is classically considered a precerebellar relay nucleus, receiving input from the cerebral cortex and projecting to the cerebellum via the inferior cerebellar peduncle. However, several studies have found aplasia of the Arc in babies who died of SIDS (Sudden Infant Death Syndrome), and it was suggested that the Arc is the locus of chemosensory neurons critical for brainstem control of respiration. Aplasia of the Arc, however, has also been reported in adults, suggesting that it is not critical for survival. We have examined the Arc in closely spaced Nissl-stained sections in thirteen adult human cases to acquire a better understanding of the degree of variability of its size and location in adults. We have also examined immunostained sections to look for neurochemical compartments in this nucleus. Caudally, neurons of the Arc are ventrolateral to the pyramidal tracts (py); rostrally, they are ventro-medial to the py and extend up along the midline. In some cases, the Arc is discontinuous, with a gap between sections with the ventrolaterally located and the ventromedially located neurons. In all cases, there is some degree of left-right asymmetry in Arc position, size, and shape at all rostro-caudal levels. Somata of neurons in the Arc express calretinin (CR), neuronal nitric oxide synthase (nNOS), and nonphosphorylated neurofilament protein (NPNFP). Calbindin (CB) is expressed in puncta whereas there is no expression of parvalbumin (PV) in somata or puncta. There is also immunostaining for GAD and GABA receptors suggesting inhibitory input to Arc neurons. These properties were consistent among cases. Our data show differences in location of caudal and rostral Arc neurons and considerable variability among cases in the size and shape of the Arc. The variability in size suggests that "hypoplasia" of the Arc is difficult to define. The discontinuity of the Arc in many cases suggests that establishing aplasia of the Arc requires examination of many closely spaced sections through the brainstem.

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Development and Developmental Disorders of the Spinal Cord

ten Donkelaar,

Itoh,

Miyata

et al. 2023

Clinical Neuroembryology

0

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Hypertrophy of the Anterior External Arcuate Fasciculus: A Rare Variant With Implications for the Development of the Arcuate Nucleus

Cited by 4 publications

References 27 publications

Individual variability in the size and organization of the human arcuate nucleus of the medulla

Individual variability in the size and organization of the human arcuate nucleus of the medulla

Individual variability in the size and organization of the human arcuate nucleus of the medulla

Development and Developmental Disorders of the Spinal Cord

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