Biological tissues in nature are fractal due to their self-similarity and porosity properties. These properties change with the progress of some diseases, including brain tissue in leading neurological disorders such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). Thus, there is an unmet clinical need to develop a tool for accurate and early diagnosis of AD and PD conditions. Although the whole brain tissues in AD and PD have been extensively studied, their local structural alterations at the nano-to-submicron levels have not been explored. In this paper, we measure the local structural alterations in different brain regions of AD and PD patients by measuring their change in fractal dimensions via optical microscopy. Our results show an increase in the fractal dimension value of ~5–10% in the affected regions of the brain tissues relative to their respective controls. For AD cases, the structural alteration is attributed to the aberrant deposition of amyloid beta protein and neurofibrillary tangles in the brain, and for PD, the gradual loss of dopaminergic neurons and abnormal accumulation of α-synuclein in the brain. The work will enhance the further understanding of alterations in the brain structures in AD and PD and its detection.