Asymmetry index of blink reflex recovery cycle differentiates early parkinson’s disease from atypical parkinsonian syndromes

Abstract

Differential diagnosis between Parkinson’s Disease (PD) and Atypical Parkinsonian Syndromes (APS), such as Multiple System Atrophy (MSA) and Progressive Supranuclear Palsy (PSP) is often difficult, because of overlap of common clinical features. We evaluated R2 Blink Reflex Recovery Cycle (R2BRRC) in drug-naive PD patients with hemiparkinson syndrome, MSA and PSP patients to differentiate early PD from APS. We prospectively enrolled 43 patients: 12 PSP, 16 MSA and 15 drug-naive PD patients. R2BRRC was evaluated at interstimulus intervals (ISIs) of 100, 150, 200, 300, 400, 500 and 750 ms, stimulating both more affected side (MAS) and less affected side (LAS). An asymmetry index (AI) for each ISI was calculated in all enrolled patients. R2BRRC of PD showed an increased brainstem excitability for LAS stimulation at ISI of 100, 150, 200 (p<0.001) and 300 ms (p=0.03) (Fig.1), whereas no differences between MAS and LAS were found in APS. R2BRRC of PD was significantly different for MAS stimulation compared to APS at ISIs of 100, 150 and 200 ms (p<0.001) (Fig.2), whereas there were no differences for LAS stimulation between groups. AI of 0.68 at ISI of 100 ms differentiated PD from PSP with a specificity of 99.9% and a sensitivity of 86.7%, whereas AI of 0.72 at ISI of 100 ms permitted to differentiate PD from MSA with a specificity of 100% and a sensitivity of 86.7% (Fig.3).View Large Image Figure ViewerDownload Hi-res image Download (PPT) AI of R2BRRC may represent a reliable tool in differentiating PD from APS, especially at the early stage of the disease.