Objective: To determine clinical correlates which differentiate drug induced Parkinsonism (DIP) from IPD and other forms of Parkinsonism using DaT-SPECT imaging.

Background: DaT-SPECT imaging is currently approved in the US for differentiating ET from IPD and other forms Parkinsonism. DIP is a common and a relatively under diagnosed condition. DaT scans are normal in most drug induced forms of Parkinsonism which are related to DRBA’s while being abnormal in IPD and other forms of Parkinsonism.

Methods: A retrospective chart review of 160 consecutive patients who had DaT scans performed from 2013 to 2016 was conducted. Of the 160 scans, 30 were performed to differentiate DIP from other forms of Parkinsonism. History of prodromal Parkinsonism, clinical features, and medications used were obtained from the patient’s records.

Results: In 18 patients with a positive scan result, 11 (61%) had bilateral tremors. In 10 patients with a negative result, 6 (60%) had bilateral tremors. In the negative group, only 2 (20%) had asymmetric tremors while in the positive group 8 (73%) were asymmetric. All 5 patients with leg tremors had positive scans. In 5 patients who had REM behavior disorder, 4 scans were positive while 1 was negative. All 4 patients on aripiprazole alone had negative DaTscan results, while all 6 patients who were on quetiapine alone had positive DaTscans. The difference in proportions is significant, (χ² (1, N = 10) P= 0.004, < 0.010) using a Fisher Exact test with P value of 0.010 (Šidák-modified Bonferroni correction used to control for error).

Conclusions: Although not statistically significant, we found a correlation between positive DaTscans and asymmetric tremor, leg tremor and REM behavior disorder. The presence of these clinical markers in patients on neuroleptics may indicate a presynaptic/degenerative disorder rather than DIP. The use of quetiapine is an unlikely cause of DIP while aripiprazole is more likely to cause DIP. Bilateral hand tremors should not be considered a feature of DIP, while tremor asymmetry is a likely marker of IPD and other forms of Parkinsonism. We propose a prospective study of a larger cohort of patients exposed to neuroleptics in order to confirm these findings.

References: Fuente-Fernandez, R. D. (2012). Role of DaTSCAN and clinical diagnosis in Parkinson disease. Neurology, 78(10), 696-701. doi:10.1212/wnl.0b013e318248e520

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MDS Abstracts - https://www.mdsabstracts.org/abstract/utility-of-datscan-imaging-in-differentiating-drug-induced-parkinsonism-from-ipd-and-other-forms-of-parkinsonism/