Objective: We investigated the substantia nigra (SN) echogenicity in drug-induced parkinsonism (DIP), Parkinson’s disease (PD), and healthy controls. A subgroup analysis of DIP by clinical symptoms was conducted for the early transcranial sonography (TCS) finding to predict the prognosis of DIP.

Background: DIP is the second most common cause of parkinsonism. DIP is most commonly caused by dopamine receptor blocking agents and the symptoms are improved after offending drug withdrawal. However, in several subjects, parkinsonism is not regressed and persisted or exacerbated after drug withdrawal. TCS of SN has been widely used for the diagnosis of PD and differentiating PD from DIP.

Methods: A total of 50 PD, 69 DIP, and 74 healthy controls were enrolled in this study. Patients with DIP were categorized into clinically improved after drug withdrawal (pure DIP) and clinically remained or aggravated parkinsonism after drug withdrawal (unmasked PD) subgroups. TCS was performed to all included subjects to detect SN echogenic area. We also obtained the ratio of the sum of the bilateral SN echogenic areas to the total midbrain area to compare the relative areas of echogenicity in each individual.

Results: Transcranial sonographic SN echogenicity was significantly increased in PD (0.24 ± 0.09 cm², p = 0.006), while DIP (0.18 ± 0.06 cm²) and controls (0.14 ± 0.05 cm²) had similar SN echogenicity. The ratio of the sum of both sides of the SN echogenic area to the whole midbrain area was also significantly increased in PD than other groups (PD: 0.06 ± 0.02, DIP: 0.04 ± 0.01, controls: 0.03 ± 0.01, p < 0.001). Of the subgoups analysis, Transcranial sonographic SN echogenicity was significantly increased in PD and unmasked PD (PD: 0.24 ± 0.09 cm², unmasked PD: 0.24 ± 0.04 cm²) than in pure DIP and controls (pure DIP: 0.15 ± 0.04 cm², controls: 0.14 ± 0.05 cm², p < 0.001). The ratio of the sum of both sides of the SN echogenic area to the whole midbrain area was also increased in PD and unmasked PD than in pure DIP and controls (PD: 0.06 ± 0.02, unmasked PD: 0.05 ± 0.01, pure DIP: 0.04 ± 0.01, controls: 0.03 ± 0.01, p < 0.001).

Conclusions: SN echogenicity could be a useful tool for differentiating PD from DIP. Pure DIP and unmasked PD showed different SN echogenicity. Early finding of SN echogenicity may be a biomarker for the expectation of clinical prognosis of DIP.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/transcranial-sonography-in-the-prognosis-of-drug-induced-parkinsonism/