Parkinson's disease: Medical and surgical treatment

It has been over three decades since the introduction of L-dihydroxyphenyla lanine or levodopa therapy for Parkinson's disease (PD). The early levodopa trials were driven by recognition of a profound cerebral dopamine deficien cy state in this disorder. Whereas dopamine fails to cross the blood brain barrier and hence is ineffective as therapy, the amino acid precursor, dopa , is transported across this barrier and provides a substrate for dopamine synthesis. Levodopa is converted to dopamine within the brain by dopa decar boxylase, replenishing central dopamine stores and potentially reversing th e motor symptoms of PD.