The human olfactory system in two proteinopathies: Alzheimer's and Parkinson's diseases.

Alzheimer's and Parkinson's diseases are the most prevalent neurodegenerative disorders. Their etiologies are idiopathic, and treatments are symptomatic and orientated towards cognitive or motor deficits. Neuropathologically, both are proteinopathies with pathological aggregates (plaques of amyloid-ß peptide and neurofibrillary tangles of tau protein in Alzheimer's disease, and Lewy bodies mostly composed of α-synuclein in Parkinson's disease). These deposits appear in the nervous system in a predictable and accumulative sequence with six neuropathological stages. Both disorders present a long prodromal period, characterized by preclinical signs including hyposmia. Interestingly, the olfactory system, particularly the anterior olfactory nucleus, is initially and preferentially affected by the pathology. Cerebral atrophy revealed by magnetic resonance imaging must be complemented by histological analyses to ascertain whether neuronal and/or glial loss or neuropil remodeling are responsible for volumetric changes. It has been proposed that these proteinopathies could act in a prion-like manner in which a misfolded protein would be able to force native proteins into pathogenic folding (seeding), which then propagates through neurons and glia (spreading). Existing data have been examined to establish why some neuronal populations are vulnerable while others are resistant to pathology and to what extent glia prevent and/or facilitate proteinopathy spreading. Connectomic approaches reveal a number of hubs in the olfactory system (anterior olfactory nucleus, olfactory entorhinal cortex and cortical amygdala) that are key interconnectors with the main hubs (the entorhinal-hippocampal-cortical and amygdala-dorsal motor vagal nucleus) of network dysfunction in Alzheimer's and Parkinson's diseases.

Cranial Pair 0: The Nervus Terminalis.

Originally discovered in elasmobranchs by Fritsh in 1878, the nervus terminalis has been found in virtually all species, including humans. After more than one-century debate on its nomenclature, it is nowadays recognized as cranial pair zero. The nerve mostly originates in the olfactory placode, although neural crest contribution has been also proposed. Developmentally, the nervus terminalis is clearly observed in human embryos; subsequently, during the fetal period loses some of its ganglion cells, and it is less recognizable in adults. Fibers originating in the nasal cavity passes into the cranium through the middle area of the cribiform plate of the ethmoid bone. Intracranially, fibers joint the telencephalon at several sites including the olfactory trigone and the primordium of the hippocampus to reach preoptic and precommissural regions. The nervus terminalis shows ganglion cells, that sometimes form clusters, normally one or two located at the base of the crista galli, the so-called ganglion of the nervus terminalis. Its function is uncertain. It has been described that its fibers facilitates migration of luteinizing hormone-releasing hormone cells to the hypothalamus thus participating in the development of the hypothalamic-gonadal axis, which alteration may provoke Kallmann's syndrome in humans. This review summarizes current knowledge on this structure, incorporating original illustrations of the nerve at different developmental stages, and focuses on its anatomical and clinical relevance. Anat Rec, 302:394-404, 2019. © 2018 Wiley Periodicals, Inc.

Síndromes conversivos en neurología: características clínicas de 16 pacientes / Conversion syndromes in neurology: clinical characteristics of 16 patients

El trastorno de conversión (término que describe lo que anteriormente se llamaba histeria) se refiere a los síntomas motores, sensitivos o ambos, que se asemejan a una enfermedad neurológica, pero que no tienen origen en una enfermedad física conocida, ni se pueden explicar por ella, dándose la particularidad de que el enfermo no es consciente de lo que le ocurre. La incapacidad funcional para los pacientes a veces es mayor que la observada en los casos en los que, con una semiología similar, hay un sustrato orgánico. Material y método: Presentamos 16 pacientes, valorados en consulta externa de neurología, con un trastorno motor o sensitivo, sin evidencia de enfermedad orgánica subyacente, con al menos un año de seguimiento. Discusión: Se comentan las características semiológicas. La fisiopatología de los síndromes conversivos está todavía en discusión. Las técnicas de neuroimágenes funcionales parecen mostrar alteraciones que nos permiten acercarnos a la fisiopatología de estos trastornos. Es importante señalar que aunque la fisiopatología de los síndromes conversivos está todavía en discusión, lo cierto es que se trata de pacientes de diagnóstico difícil, pero posible; es responsabilidad del médico intentar entender el sustrato neurológico de un problema que implica una gran incapacidad funcional e instaurar un tratamiento adecuado, buscando, si es necesario, la colaboración de un psiquiatra con experiencia en el abordaje de estos trastornos...