Pathophysiology of Parkinson's Disease: The MPTP Primate Model of the Human Disorder

Autografting of dopamine-producing adrenal medullary tissue to the striatal region of the brain is now being attempted in patients with Parkinson's disease. Since the success of this neurosurgical approach to dopamine-replacement therapy may depend on the selection of the most appropriate subregion of the striatum for implantation, we examined the pattern and degree of dopamine loss in striatum obtained at autopsy from eight patients with idiopathic Parkinson's disease. We found that in the putamen there was a nearly complete depletion of dopamine in all subdivisions, with the greatest reduction in the caudal portions (less than 1 percent of the dopamine remaining). In the caudate nucleus, the only subdivision with severe dopamine reduction was the most dorsal rostral part (4 percent of the dopamine remaining); the other subdivisions still had substantial levels of dopamine (up to approximately 40 percent of control levels). We propose that the motor deficits that are a constant and characteristic feature of idiopathic Parkinson's disease are for the most part a consequence of dopamine loss in the putamen, and that the dopamine-related caudate deficits (in "higher" cognitive functions) are, if present, less marked or restricted to discrete functions only. We conclude that the putamen--particularly its caudal portions--may be the most appropriate site for intrastriatal application of dopamine-producing autografts in patients with idiopathic Parkinson's disease.

This synthetic review was performed to demonstrate the utility of frontal-subcortical circuits in the explanation of a wide range of human behavioral disorders. Reports of patients with degenerative disorders or focal lesions involving frontal lobe or linked subcortical structures were chosen from the English literature. Individual case reports and group investigations from peer-reviewed journals were evaluated. Studies were included if they described patient behavior in detail or reported pertinent neuropsy-chological findings and had compelling evidence of a disorder affecting frontal-subcortical circuits. Information was used if the report from which it was taken met study selection criteria. Five parallel segregated circuits link the frontal lobe and subcortical structures. Clinical syndromes observed with frontal lobe injury are recapitulated with lesions of subcortical member structures of the circuits. Each prefrontal circuit has a signature behavioral syndrome: executive function deficits occur with lesions of the dorsolateral prefrontal circuit, disinhibition with lesions of the orbitofrontal circuit, and apathy with injury to the anterior cingulate circuit. Depression, mania, and obsessive-compulsive disorder may also be mediated by frontal-subcotical circuits. Movement disorders identify involvement of the basal ganglia component of frontal-subcortical circuits. Frontal-subcortical circuits mediate many aspects of human behavior.