Combination of transcranial sonography, olfactory testing, and MIBG myocardial scintigraphy as a diagnostic indicator for Parkinson's disease

Background: Appropriate diagnostic biomarkers are useful for improving speed and accuracy of a diagnosis. Substantia nigra (SN) hyperechogenicity visualized by transcranial sonography (TCS), olfactory dysfunction, and the reduced uptake of 123I-metaiodobenzylguanidine (MIBG) in myocardial scintigraphy have been suggested as potential biomarkers for the identification of Parkinsons disease (PD). Objectives: To evaluate the diagnostic potential of these tests and to determine whether combining them increases their diagnostic power. Methods: Subjects were 44 patients with clinically diagnosed PD and 36 healthy controls. TCS of the SN, the odor stick identification test for Japanese (OSIT-J), and MIBG myocardial scintigraphy were conducted. Results: Eleven patients with PD (25%) and four controls (11%) were excluded because of an insufficient acoustic temporal bone window in the TCS. Thus, 33 patients with PD and 32 healthy controls were finally included. The diagnostic sensitivity of TCS, OSIT-J, and MIBG myocardial scintigraphy was 78.8%, 84.8%, and 60.6%, respectively. The specificity of TCS and OSIT-J was 93.8% and 78.1%, respectively. The combination of TCS of the SN and OSIT-J substantially increased the sensitivity to a sufficient level for discriminating patients with PD from controls. Conclusion: TCS of the SN and olfactory testing play complementary roles in increasing diagnostic power in PD. As both tests are easy to perform, noninvasive, and inexpensive, the combination of TCS of the SN and olfactory testing may contribute to early and accurate diagnosis of PD.