Parkinson’s disease can be present for many years in an asymptomatic phase before becoming clinically evident. Therapeutic approaches might be more effective in the preclinical phase. The possible utility of imaging biomarkers in this case would be to perform a preclinical diagnosis as well as a differential diagnosis with other confounding diseases. Unfortunately there is still no consensus on criteria for validating a biomarker.
Some of the imaging tests that show promise are:
1) MRI measurements of structural changes in the Substantia Nigra. This shows that fractional anisotropy (which is reduced in Parkinson’s disease) can differentiate from Multiple System Atrophy.
2) SPECT using FP-CIT and IBZM shows these to be reduced in Parkinson’s disease, but significantly less in Essential Tremor.
3) Classical Parkinson’s disease as well as Multiple System Atrophy and Progressive Supranuclear Palsy should reveal a decreased uptake of F18-DOPA using PET. Also F18-DOPA can be used as a marker for disease progression. Patients on treatments show a slowing on the decrease of uptake of F18-DOPA.
A review on this subject can be found on a paper by Chrystalina Antoniades and Roger a Barker “The search for Biomarkers in Parkinson’s disease, a critical review” Expert Rev Neurotherapy 8(12), 1841-1852 (2008).
Adolfo Cotter, MD