Parkinson's Disease in Patients with Essential Tremor: A Prospective Clinical and Functional Neuroimaging Assessment

Abstract

Introduction: Patients with essential tremor (ET) have 3.5 times greater risk of developing Parkinson's disease (PD) throughout their lives, also known as PD with antecedent ET (ET-PD). Single photon emission computed tomography with radiotracer imaging of dopamine transporters (TRODAT-SPECT) can help differentiate these two diseases. Method: Relate the results of TRODAT-SPECT imaging in patients with ET to potential progress to ET-PD. Thirty-six patients with ET were evaluated by neurological examination, the Archimedes spiral, and the MDS-UPDRS III scale on two occasions, after a mean interval of three years. SPECT was performed on all patients after the first visit. Results: Overall, six patients (16.6%) progressed clinically to ET-PD. Patients with ET-PD were older, and the age of tremor onset was later. The ET-PD group scored higher on the MDS-UPDRS III scale, especially for the presence of bradykinesia. SPECT imaging was altered in 83.3% of the ET-PD patients compared to 33% of the ET patients (p=0.034). Changes on the SPECT with asymmetrical hypouptake suggested progress to ET-PD (p=0.025). Conclusion: Advanced age at the onset of tremor, the presence of bradykinesia, and asymmetrical alterations in SPECT may be related to progression to PD in patients with ET. Changes in neuroimaging suggest that SPECT-TRODAT can be used to predict progression to PD in selected patients.