A semi-quantitative evaluation of substantia nigra hyperechogenicity in Parkinson’s disease and Parkinsonian syndrome using the Gray Scale Median ultrasound analysis

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Objective: Hyperechogenicity in the midbrain substantia nigra (SN) on transcranial sonography (TCS) images has been reported in Parkinson’s disease (PD). We used a semi-quantitative evaluation method, the Gray Scale Median, to quantify echogenic changes.Subjects: Hospitalized patients with PD (n = 7) or Parkinsonian syndrome (PS) (n = 7) and in-hospital control subjects (n = 6) were included. The PS group consisted of cases of progressive supranuclear palsy (n = 3), multiple system atrophy (n = 2), and corticobasal degeneration (n = 2).Methods: The subjects were evaluated using TCS. The SN was identified within the midbrain and the areas with echogenic signals were circled and measured. Next, echogenic signals in the SN and dorsal midbrain (DM) were converted into gray scale using Photoshop software (Adobe Systems Inc., Tokyo, Japan) and the median gray scale values of the SN and DM were obtained using a histogram. The SN-to-DM ratio was calculated.Results: Compared with the PS and control groups, the PD group had an increased SN-to-DM ratio and a larger SN hyperechogenic area. The SN-to-DM ratio correlated positively with the SN hyperechogenic area.Conclusion: A semi-quantitative evaluation of echogenic signal changes using the SN-to-DM ratio may be useful for the objective evaluation of SN signal changes.