Clinical criteria for the diagnosis of idiopathic Parkinson's disease, and akinetic-rigid syndromes accompanying cerebral arteriosclerosis and senile dementia, are discussed. The clinical features, levodopa response, cerebrospinal fluid homovanillic acid, and 5-hydroxy-indole acetic acid concentration, and E.E.G. changes of 42 elderly akinetic patients in these three diagnostic groups are reviewed. Extrapyramidal features of akinesia and a flexed posture were similar in all patient groups, but the rigidity of patients with Parkinson's disease was different in nature from the increase in muscle tone, equal in both flexion and extension and varying with the force applied, of patients with senile dementia and cerebral arteriosclerosis. A resting rhythmic hand tremor may be unique to Parkinson's disease.
The cerebrospinal fluid homovanillic acid concentration of most patients with Parkinson's disease is low, in contrast to near-normal values of most akinetic patients with cerebral arteriosclerosis or senile dementia. A therapeutic response to levodopa only occurred in the patients studied, in those with a clinical diagnosis of Parkinson's disease.
Frequency analysis of the E.E.G. gave normal values in patients with Parkinson's disease in contrast with an excess of slow frequencies in those with cerebral arteriosclerosis. The term arteriosclerotic Parkinsonism, although useful in clinical description, has been superseded with the recognition of idiopathic Parkinson's disease as a single condition, not caused by cerebral arteriosclerosis.