Homocysteine in neurological disease: a marker or a cause?

Hyperhomocysteinemia is increasingly recognized as an independent risk factor for several cerebral, vascular, ocular, and agerelated disorders. Whether it is a cause or a consequence or a mere marker necessitates further clarification. This review focuses on the pathophysiological aspects of homocysteine's involvement in neurodegenerative and neuropsychiatric disorders and complications. The pharmacological agents (antiepileptic drugs, L-DOPA) augment the homocysteine levels, thus, raising concern for physicians. The mechanisms underlying the enhanced homocysteine levels and its related pathophysiological cascades remain poorly understood, inspite of numerous epidemiological and research studies that have been carried out in recent years. This article will review the current understanding of these underlying mechanisms and the research being carried with homocysteine as a core molecule.