The aim of this study was to present the current knowledge on the aetiopathogenesis of neurodegenerative disorders, devoting attention not only to neurophysiological and clinical aspects, but above all to the genetic and extra-genomic conditions underlying these diseases. The dynamic development of knowledge and technological progress in medical and related sciences is resulting in changes in the demographic structure of the human population (ageing populations). One of the consequences of these changes is an increase in the incidence of neurodegenerative disorders. Neurodegenerative diseases include Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease. They belong to a group of disorders whose common feature is a pathological process leading to the loss of nerve cells through apoptosis or necrosis. The aetiology of neurodegenerative diseases is multifactorial and, in addition to the involvement of genomic factors, extra-genomic mechanisms have been postulated to be involved in their aetiopathogenesis. The aetiology of numerous neurodegenerative diseases is still not fully understood. Therefore, intensive research has been ongoing for years, focusing, among other aspects, on the causes and course of such conditions. An important direction of research into the pathogenesis of neurodegenerative diseases is assessment of their potential genetic aspect. Many studies also focus on non-genomic factors, highlighting that many of them can have a significant impact on the course of these diseases.