Actualización en la fisiopatología de la hidrocefalia crónica del adulto idiopática: ¿nos enfrentamos a otra enfermedad neurodegenerativa? / Current concepts on the pathophysiology of idiopathic chronic adult hydrocephalus: Are we facing another neurodegenerative disease?

INTRODUCCIÓN: Desde la descripción hace 5 décadas de la hidrocefalia crónica del adulto idiopática (HCAi), su fisiopatología ha sido considerada básicamente relacionada con el efecto que la dilatación ventricular ejerce sobre las estructuras adyacentes al sistema ventricular. Sin embargo, las alteraciones en el flujo sanguíneo cerebral (FSC) y, sobre todo, la reducción en el recambio licuoral parecen emerger como componentes fisiopatológicos principales de esta enfermedad. DESARROLLO: En la HCAi se observa una compresión del tracto piramidal, de los circuitos cortico-subcorticales fronto-estriatales y fronto-reticulares, y de las fibras profundas del fascículo longitudinal superior. En el cuerpo calloso se objetiva un descenso en el número de fibras comisurales, que son reemplazadas por gliosis. El FSC se encuentra alterado, con un patrón de última pradera en la región subcortical adyacente a los ventrículos, correspondiente a la intersección entre las arterias subependimarias y las arterias perforantes dependientes de los grandes troncos arteriales de la circulación anterior. El recambio diario del LCR se ve disminuido en un 75%, lo que conlleva una reducción del aclaramiento de neurotóxicos y la interrupción de las señalizaciones neuroendocrinas y paracrinas que ocurren a través del LCR. CONCLUSIONES: La HCAi emerge como una entidad nosológica compleja, en la que los efectos de la microangiopatía subcortical y la disminución del recambio de LCR desempeñan un papel fundamental. Esta base fisiopatológica aleja la HCAi del concepto clásico de hidrocefalia y la acerca al perfil de otras enfermedades neurodegenerativas, como la enfermedad de Alzheimer o la enfermedad de Binswanger

INTRODUCTION: Since its description five decades ago, the pathophysiology of idiopathic chronic adult hydrocephalus (iCAH) has been traditionally related to the effect that ventricular dilatation exerts on the structures surrounding the ventricular system. However, altered cerebral blood flow, especially a reduction in the CSF turnover rate, are starting to be considered the main pathophysiological elements of this disease. DEVELOPMENT: Compression of the pyramidal tract, the frontostriatal and frontoreticular circuits, and the paraventricular fibres of the superior longitudinal fasciculus have all been reported in iCAH. At the level of the corpus callosum, gliosis replaces a number of commissural tracts. Cerebral blood flow is also altered, showing a periventricular watershed region limited by the subependymal arteries and the perforating branches of the major arteries of the anterior cerebral circulation. The CSF turnover rate is decreased by 75%, leading to the reduced clearance of neurotoxins and the interruption of neuroendocrine and paracrine signalling in the CSF. CONCLUSIONS: iCAH presents as a complex nosological entity, in which the effects of subcortical microangiopathy and reduced CSF turnover play a key role. According to its pathophysiology, it is simpler to think of iCAH more as a neurodegenerative disease, such as Alzheimer disease or Binswanger disease than as the classical concept of hydrocephalus

Current concepts on the pathophysiology of idiopathic chronic adult hydrocephalus: Are we facing another neurodegenerative disease? / Actualización en la fisiopatología de la hidrocefalia crónica del adulto idiopática: ¿nos enfrentamos a otra enfermedad neurodegenerativa?

INTRODUCTION: Since its description five decades ago, the pathophysiology of idiopathic chronic adult hydrocephalus (iCAH) has been traditionally related to the effect that ventricular dilatation exerts on the structures surrounding the ventricular system. However, altered cerebral blood flow, especially a reduction in the CSF turnover rate, are starting to be considered the main pathophysiological elements of this disease. DEVELOPMENT: Compression of the pyramidal tract, the frontostriatal and frontoreticular circuits, and the paraventricular fibres of the superior longitudinal fasciculus have all been reported in iCAH. At the level of the corpus callosum, gliosis replaces a number of commissural tracts. Cerebral blood flow is also altered, showing a periventricular watershed region limited by the subependymal arteries and the perforating branches of the major arteries of the anterior cerebral circulation. The CSF turnover rate is decreased by 75%, leading to the reduced clearance of neurotoxins and the interruption of neuroendocrine and paracrine signalling in the CSF. CONCLUSIONS: iCAH presents as a complex nosological entity, in which the effects of subcortical microangiopathy and reduced CSF turnover play a key role. According to its pathophysiology, it is simpler to think of iCAH more as a neurodegenerative disease, such as Alzheimer disease or Binswanger disease than as the classical concept of hydrocephalus.