Does a long preclinical period occur in Parkinson's disease?

Koller, W.C.; Langston, J.W.; Hubble, J.P.; Irwin, I.; Zack, M.; Golbe, L.; Forno, L.; Ellenberg, J.; Kurland, L.; Ruttenber, A.J.

Neurology 41(5 Suppl 2: 8-13


ISSN/ISBN: 0028-3878
PMID: 2041599
Document Number: 18175
Evidence from a variety of sources support the concept of a long preclinical period in PD. Thus, PD may be an example of a long-latency neurologic disease. Both objective and subjective clinical observations of the motor and non-motor manifestations of PD indicate the existence of a preclinical period. The degree of dopamine depletion needed before symptoms occur and the presence of incidental Lewy bodies strongly support a preclinical period. Furthermore, the neurochemical lesion of parkinsonism can be identifed in the asymptomatic individual. These observations and other data support the conclusion that a long preclinical period occurs in PD. This may have practical implications. If a prolonged preclinical phase does indeed exist in PD and ways can be found to detect it, this could greatly facilitate epidemiologic studies and efforts to find ways to prevent the disease. A search for biological markers of the disease is underway and hopefully in the future the diagnosis of PD can be made by laboratory methods. It is conceivable, therefore, that protective therapy could be initiated even before symptoms occur. As a final note, however, we should point out that the evidence for a long preclinical period is inferential and indirect. Several observations appear to contradict the notion of a preclinical period. Lewy bodies are almost never seen in individuals before the age of 50 years. Why are they not seen earlier if there is a long preclinical period? Recent observations of McGeer and coworkers suggest that because nigral cell death may be an active pathological process, the degeneration may be a fast rather than a slow process. Thus it would be wise to at least keep an open mind to the possibility that the preclinical phase of PD could be more fulminant than we now think.

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Does a long preclinical period occur in Parkinson's disease?