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Abstract
Objective: To assess the value of baseline clinical and imaging biomarkers in a cohort of asymptomatic LRRK2 G2019S carriers for predicting conversion to Parkinson disease (PD) at 4 years.
Methods: Thirty-two asymptomatic carriers of LRRK2 G2019S mutation underwent baseline and 4-year evaluation including clinical examination (Unified Parkinson's Disease Rating Scale, part III, olfaction University of Pennsylvania Smell Identification Test [UPSIT]) and dopamine transporter (DaT) SPECT (123I-ioflupane). Visual and semiquantitative analysis of images was performed. The specific striatal binding ratio was calculated (striatal region of interest [ROI] − occipital ROI/occipital ROI).
Results: Three carriers, asymptomatic at baseline, had converted to PD at 4-year evaluation. Twenty-three participants were fully evaluated. PD converters had lower striatal DaT binding at baseline than nonconverters (p = 0.002). A baseline scan with a ratio of bilateral striatal uptake below 1 predicted conversion to PD within the 4-year period with high sensitivity and specificity (area under the curve 1; p = 0.006). The slope of DaT binding decline between the 2 scans was similar in PD converters and nonconverters. Age-adjusted UPSIT score at baseline and at 4 years was similar in both groups.
Conclusions: Semiquantitative DaT-SPECT could be used to predict early conversion to PD in asymptomatic carriers of the LRRK2 G2019S mutation. Rate of conversion to PD at 4 years in this cohort aged ∼64 years was 12%. The slope of DaT binding decline on DaT-SPECT imaging seems to be similar across different stages of the premotor period.
GLOSSARY
- DaT=
- dopamine transporter;
- PD=
- Parkinson disease;
- ROI=
- region of interest;
- SN=
- substantia nigra;
- UPDRS-III=
- Unified Parkinson's Disease Rating Scale, part III;
- UPSIT=
- University of Pennsylvania Smell Identification Test
Footnotes
Go to Neurology.org for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
- Received January 14, 2017.
- Accepted in final form May 10, 2017.
- © 2017 American Academy of Neurology
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