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.