Neuromelanin imaging analyses of the substantia nigra in patients with Machado-Joseph disease.

PURPOSE: Machado-Joseph disease (MJD/SCA3) is the most frequent spinocerebellar ataxia worldwide. Pathological studies revealed less melanin-containing dopaminergic neurons in the substantia nigra (SN) pars compacta in MJD/SCA3 patients. The purpose of this study was to quantify the damage in the SN reported for MJD/SCA3 patients in vivo using neuromelanin MR imaging. METHODS: We retrospectively reviewed the clinical information and MR imaging in sixteen MJD/SCA3 patients and fourteen healthy controls. High-resolution T1-WI of the SN were acquired using a 3-T MR system. The neuromelanin-related contrast (NRC), which was defined as the number of pixels of high-signal-intensity areas on T1-WI in the SN, was calculated semi-automatically. The NRC values were compared between MJD/SCA3 patients and normal controls. RESULTS: The NRC values were significantly lower in MJD/SCA3 patients than in healthy controls. In MJD/SCA3 patients, a significant negative correlation existed between disease durations and NRC values. No significant difference in the NRC values was revealed between the MJD/SCA3 patients with and without parkinsonism. CONCLUSION: Neuromelanin in the SN may decrease at the early stage of the disease and continue to decrease over time with the disease duration in MJD/SCA3 patients. The NRC may be a useful biological index for monitoring MJD/SCA3.