Potential Involvement of Impaired Venous Outflow from the Brain in Neurodegeneration: Lessons Learned from the Research on Chronic Cerebrospinal Venous Insufficiency

About 10 years ago, the so-called chronic cerebrospinal venous insufficiency syndrome was discovered. This clinical entity, which is associated with extracranial venous abnormalities that impair venous outflow from the brain, was initially found exclusively in multiple sclerosis patients. Currently, we know that such venous lesions can also be revealed in other neurological pathologies, including Alzheimer’s and Parkinson’s diseases. Although direct causative role of chronic cerebrospinal venous insufficiency in these neurological diseases still remains elusive, in this paper, we suggest that perhaps an abnormal venous drainage of the brain affects functioning of the glymphatic system, which in turn results in the accumulation of pathological proteins in the cerebral tissue (such as β-synuclein, β-amyloid and α-synuclein) and triggers the venous outflow from the cranial cavity and circulation of the cerebrospinal fluid in the settings of neurodegenerative disease.