Utility of transcranial sonography in the diagnosis of drug-induced parkinsonism: a prospective study.

Background And Purpose: Drug-induced parkinsonism usually resolves after discontinuation of the causative agent. However, it persists in some patients, who actually have subclinical neurodegenerative parkinsonism. Identification of this condition is important because these patients could benefit from therapeutic measures. The objective of this study was to prove whether transcranial sonography, a technique used in the diagnosis of neurodegenerative parkinsonism, can be used for the said identification.

Methods: In this prospective study, patients with drug-induced parkinsonism were followed for at least 6 months after discontinuation of the causative drug and performance of blinded transcranial sonography. Patients were categorized as having iatrogenic parkinsonism if the clinical presentation had resolved or subclinical drug-exacerbated parkinsonism if it persisted. Once the patient was classified into one of the two groups, an expert assessed the transcranial sonography findings and their agreement with the clinical diagnosis.

Results: Twenty patients composed the group for analysis of results. Assessing hyperechogenicity in the substantia nigra >20 mm2 and/or hyperechogenic lentiform nucleus, differences were detected between the iatrogenic parkinsonism and the subclinical drug-exacerbated parkinsonism groups, although they did not reach statistical significance (Fisher’s exact test 0.09). Joint assessment of sonographic alterations in both structures had a negative predictive value of 85.7% for diagnosis of drug-induced parkinsonism, with a negative likelihood ratio of 0.3.

Conclusions: Although in our study statistically significant differences were not found between the transcranial sonography characteristics of subclinical drug-exacerbated parkinsonism and iatrogenic parkinsonism patients, we believe that transcranial sonography is a valid technique for diagnosis of drug-induced parkinsonism.