Alcohol-induced structural and cellular brain alterations: molecular and histopathological mechanisms

Chronic alcohol consumption is a leading cause of acquired neurodegeneration with well-documented structural and ultrastructural brain alterations. This review analyzes the cellular and molecular mechanisms underlying alcohol neurotoxicity, integrating findings from animal models, human post-mortem studies, and neuroimaging investigations. Ethanol crosses the blood-brain barrier and generates toxic metabolites including acetaldehyde and reactive oxygen species, triggering oxidative stress, lipid peroxidation, and mitochondrial dysfunction. Chronic exposure induces glutamatergic and gamma-aminobutyric acid (GABA)ergic adaptations leading to excitotoxicity during withdrawal. Cell death occurs through apoptotic, necrotic, and necroptotic pathways, while microglial and astrocytic activation perpetuates neuroinflammation. Histopathological (HP) changes include selective neuronal loss in the prefrontal cortex, hippocampus, and cerebellum, dendritic simplification, and synaptic alterations. White matter pathology manifests as demyelination and axonal degeneration. Associated thiamine deficiency produces characteristic lesions in the mammillary bodies, thalamus, and cerebellar vermis. Neuroimaging techniques provide valuable HP correlates and biomarkers for disease monitoring. While some changes demonstrate partial reversibility with abstinence through remyelination and synaptic plasticity, extensive neuronal loss remains irreversible. Understanding these mechanisms is essential for developing neuroprotective therapeutic strategies.