Most neurological disorders seemingly have heterogenous pathogenesis, with overlapping contribution of neuronal, immune and vascular mechanisms of brain injury. The perivascular space in the brain represents a crossroad where those mechanisms interact, as well as a key anatomical component of the recently discovered glymphatic pathway, which is considered to play a crucial role in the clearance of brain waste linked to neurodegenerative diseases. The pathological interplay between neuronal, immune and vascular factors can create an environment that promotes self-perpetration of mechanisms of brain injury across different neurological diseases, including those that are primarily thought of as neurodegenerative, neuroinflammatory or cerebrovascular. Changes of the perivascular space can be monitored in humans in vivo using magnetic resonance imaging (MRI). In the context of glymphatic clearance, MRI-visible enlarged perivascular spaces (EPVS) are considered to reflect glymphatic stasis secondary to the perivascular accumulation of brain debris, although they may also represent an adaptive mechanism of the glymphatic system to clear them. EPVS are also established correlates of dementia and cerebral small vessel disease (SVD) and are considered to reflect brain inflammatory activity. In this review, we describe the “perivascular unit” as a key anatomical and functional substrate for the interaction between neuronal, immune and vascular mechanisms of brain injury, which are shared across different neurological diseases. We will describe the main anatomical, physiological and pathological features of the perivascular unit, highlight potential substrates for the interplay between different noxae and summarize MRI studies of EPVS in cerebrovascular, neuroinflammatory and neurodegenerative disorders.

多数神经系统疾病似乎具有异质发病机制，与脑损伤的神经元，免疫和血管机制重叠。大脑中的血管周围空间代表了这些机制相互作用的十字路口，也是最近发现的淋巴途径的关键解剖学组成部分，被认为在清除与神经退行性疾病有关的脑废物中起着至关重要的作用。神经元，免疫和血管因素之间的病理相互作用可以创造一种环境，促进各种神经疾病（包括主要被认为是神经退行性疾病，神经炎性疾病或脑血管疾病）的自我伤害机制的自我延续。可以监测人体血管周围空间的变化体内使用磁共振成像（MRI）。在清除淋巴管的情况下，MRI可见的扩大的血管周间隙（EPVS）被认为反映了继发于脑碎片的血管周积聚后的淋巴结淤积，尽管它们也可能代表了清除淋巴结的淋巴系统的适应性机制。EPVS也已建立为痴呆症与脑小血管疾病（SVD）的相关性，并被认为反映了脑部炎症活动。在这篇综述中，我们将“血管周单元”描述为大脑损伤的神经元，免疫和血管机制之间相互作用的关键解剖学和功能性底物，这在不同的神经系统疾病中是共享的。我们将描述血管周单元的主要解剖，生理和病理特征，