Quantifying changes in nigrosomes using quantitative susceptibility mapping and neuromelanin imaging for the diagnosis of early-stage Parkinson's disease.

OBJECTIVE: To quantify nigral changes with a focus on their spatial variation within the substantia nigra pars compacta (SNpc) for diagnosing early-stage Parkinson's disease (PD).

METHODS: The study participants were 18 patients with early-stage PD (PD group) and 18 healthy controls (HC group) who underwent quantitative susceptibility mapping (QSM) and neuromelanin imaging. The QSM and neuromelanin values in each whole SNpc containing the entire nigrosome and dorsolateral SNpc containing nigrosome 1 were calculated. The neuromelanin area was defined as the volume with a signal-to-noise ratio higher than that of the background region. The significance of intergroup differences in the QSM value and neuromelanin area in each SNpc region was tested. Logit (p) was used to estimate the probability of PD in relation to the QSM value and the neuromelanin area, and receiver operating characteristic analyses were performed for each value.

RESULTS: In both SNpc, QSM values were significantly higher and neuromelanin areas were significantly lower in the PD group compared with the HC group (p < 0.05). The respective areas under the receiver operating characteristic curve for the two groups were 0.70/0.73 for the QSM value, 0.81/0.78 for the neuromelanin area in the whole/dorsolateral SNpc, and 0.86 for logit (p) in relation to the QSM value of the dorsolateral SNpc and the neuromelanin area of the whole SNpc.

CONCLUSION: Comprehensive MRI assessment of the abnormality involving the nigrosomes can yield a high diagnostic performance for early-stage PD. Advances in knowledge: Focusing on spatial differences in nigral changes within the SNpc can increase the sensitivity of the detection of PD-related neurodegenerative changes.