Category: Drug-Induced Movement Disorders
Objective: To asses the role of transcranial sonography in suspected drug-induced parkinsonism.
Background: Differential diagnosis between drug-induced parkinsonism (DIP) and Parkinson’s disease (PD) is challenging, as 15% of suspected DIP are actually PD unmasked by drug exposure. Substantia nigra hyperechogenicity (SN+) as detected with transcranial sonography (TCS) has proved useful for PD diagnosis. In a previous study (n:60), we assessed the role of TCS in suspected DIP, obtaining a positive predictive value (PPV) of SN+ of 49.9% for underlying PD. We hypothesized a longer follow-up could increase the PPV if more incidental PD cases were registered.
Method: At the end of the previous study 16 patients had PD diagnosis, and 44 DIP (7 SN+, 37 SN-), being clinical resolution after drug withdrawal the diagnostic gold standard. 44 DIP patient’s records were analysed 5 years after the completion of the study.
Results: After a mean follow up of 2.1 years (0-5), incidental PD diagnosis occurred in 2 SN+ patients (28.6%) and 1 (2.7%) SN-. Ten patients died (1 SN+, 9 SN-). Accuracy of SN+ to distinguish PD from DIP improved in terms of sensitivity 88% (82.4%), specificity 88 % (previous 85.4%) and PPV 54.5% (49.9%); with similar negative predictive value 96.2% (96.5%), area-under-the-curve 0.83.The hazard ratio for final PD diagnosis in SN+ subjects with suspected DIP was 11.4 (95% confidence interval 3.7-34.8, p<0.0002).
Conclusion: This study strengthens the role of TCS in the assessment of suspected DIP, not only for differential diagnosis but also as a prognostic tool. In our study, PPV of SN+ improved by 5%, even if follow-up was potentially insufficient in some patients
To cite this abstract in AMA style:B. Baena Álvarez, R. Sainz Amo, F. Rodríguez Jorge, J. Gómez Corral, F.J Buisán Catevilla, N. García Barragán, I. Corral Corral, A. Felipe Mimbrera, M.C Matute Lozano, J. Masjuán Vallejo, J.C Martínez Castillo, J.L López-Sendón, A. Alonso Cánovas. Substantia nigra echogenicity as a predictor of drug withdrawal response in suspected drug-induced parkinsonism: a five year follow-up study [abstract]. Mov Disord. 2020; 35 (suppl 1). https://www.mdsabstracts.org/abstract/substantia-nigra-echogenicity-as-a-predictor-of-drug-withdrawal-response-in-suspected-drug-induced-parkinsonism-a-five-year-follow-up-study/. Accessed December 2, 2023.
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MDS Abstracts - https://www.mdsabstracts.org/abstract/substantia-nigra-echogenicity-as-a-predictor-of-drug-withdrawal-response-in-suspected-drug-induced-parkinsonism-a-five-year-follow-up-study/