Transcranial sonography of the substantia nigra in Japanese patients with Parkinson's disease or atypical parkinsonism: clinical potential and limitations.

OBJECTIVE: There is growing interest in the use of transcranial sonography (TCS) of the substantia nigra (SN) in patients with Parkinson's disease (PD), as it has been reported that SN hyperechogenicity may be present in about 90% of PD patients. However, TCS of the SN has not been applied in Japanese patients, and its clinical potential has not been determined. PATIENTS AND METHODS: TCS of the SN was performed in patients with PD, progressive supranuclear palsy (PSP), multiple system atrophy (MSA), and essential tremor (ET), and age-matched controls. Ultrasound images of the SN were assessed using semi-qualitative estimation criteria by two investigators unaware of clinical diagnosis.
RESULTS: SN hyperechogenicity was observed in approximately 83% of accessible SNs in Japanese PD patients. In comparison, SN hyperechogenicity was less frequently observed in healthy subjects or in patients with PSP, MSA, and ET. However, the rate of successful recording of the SN by TCS decreased prominently with advancing age, particularly in females.
CONCLUSION: The present study confirmed that TCS of the SN is potentially useful in the investigation of Japanese patients, and it provides a better differential diagnosis between PD and atypical parkinsonism. The recording failure of TCS in aged, particularly female subjects, may limit the clinical potential of TCS of the SN in Japanese patients.