Substantia nigra hyperechogenicity in Polish patients with Parkinson's disease

Hyperechogenicity of the substantia nigra (SN) measured by transcranial sonography (TCS) is a characteristic feature observed in patients with Parkinson's disease (PD). To our knowledge, no SN hyperechogenicity data are available for Polish population. Moreover most of studies come from few centres, which used the one type of ultrasound device. The main aim of the study was to investigate the association between PD and SN hyperechogenicity measured by sonographic machine, not assessed so far.

In this study cross-sectional study SN hyperechogenicity was evaluated in 102 PD patients and 95 control subjects. Midbrain was visualised by Aloka Prosound 7 ultrasound device. SN area measurement, the relation to the clinical features of PD, inter- and intra-observer reliability were evaluated.

We confirmed that SN echogenicity is significantly increased in PD patients compared to control subjects (p < 0.001). The area under curve for PD patients vs. controls was 0.93. Receiver operating characteristic analysis indicated a cut-offs for SN echogenicity at 0.19 cm² with accuracy equal to 90%, specificity - 86% and sensitivity - 93.7%. The SN hyperechogenicity was not related to PD clinical findings. Reliability was good if an experienced sonographer performed the SN measurements.

This study shows that the SN abnormality observed by TCS isa specific feature, which can be helpful in the process of PD diagnosing.