Many hypotheses have been postulated to define the etiology of sporadic Parkinson's and Alzheimer's disorders (PD and AD) but there is no consensus on what causes these devastating age-related diseases. Braak staging of both pathologies helped researchers to better understand the progression and to identify their prodromal and symptomatic phases. Indeed, it is well accepted that Lewy body pathology and neurofibrillary tangles appearance correlates with disease progression and severity of symptoms in PD and AD, respectively. Additionally, several studies in PD and AD models try to disclose which cellular mechanisms are defaulted and trigger the neurodegenerative process that culminates with neuronal death causing PD and AD classical symptomatology. Herein, we determined expression levels of proteins involved in microtubule assembly, autophagic-lysosomal pathway and unfolded protein response in the cortex, hippocampus and SNpc of PD and AD patients, vascular dementia patients and aged-match controls. The differential expression allowed us to determine which pathways are determinant to synaptic dysfunction and to establish a time line for disease progression. Our results allow us to challenge the hypothesis that both PD and AD pathologies are caused by α-synuclein or Aβ pathology propagation throughout the brain in a prion-like manner.