Transcranial imaging of substantia nigra hyperechogenicity in a Taiwanese cohort of Parkinson's disease

Transcranial Doppler imaging (TCDI) has been used as a noninvasive diagnostic tool to differentiate Parkinson's disease (PD) from atypical parkinsonism by detecting hypere- chogenicity in the substantia nigra (SN). To our knowledge, no TCDI data are available for Asian populations, and TCDI sensitivity is uncertain across populations. Early-onset PD (EOPD) represents a specific PD subtype based on clinical features and pathogenic mechanisms. It is not known if EOPD patients have abnormal echogenicity in SN comparable to late-onset PD (LOPD) patients. We assessed the area of SN hyperechogenicity (hyper-SN) and a ratio of hyper-SN over ipsilateral midbrain (S/M ratio) with TCDI in 164 healthy Taiwanese, 40 EOPD patients, and 40 LOPD patients. The upper 95th percentile values for hyper-SN and S/M ratio were 0.20 cm 2 and 0.07. Our results indicate that S/M ratio is a more sensitive measure than hyper-SN in diagnosing PD. Approxi- mately 92.5% of the LOPD patients and 57.5% of the EOPD patients had S/M ratios 0.07. Enlarged hyperechogenicity of SN is a common finding in LOPD, but not in EOPD. Iron- independent mechanisms of SN cell degeneration in EOPD distinct from that in LOPD might contribute to the sonographic findings. © 2007 Movement Disorder Society