Seven tesla MRI of the substantia nigra in patients with rapid eye movement sleep behavior disorder

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Introduction: Susceptibility-weighted imaging of the substantia nigra (SN) both at 7 and 3 Tesla (T) has shown high accuracy in distinguishing patients with Parkinson's disease (PD) and healthy subjects (HS). Patients with rapid eye movement (REM) behavior disorder (RBD) can develop synucleinopathies, and such risk is higher with dopamine transporter single photon emission tomography (123I-FP-CIT SPECT) evidence of nigro-striatal dysfunction. We aimed at evaluating SN 7T magnetic resonance imaging (7T-MRI) in patients with RBD and determining the agreement between MRI and 123I-FP-CIT SPECT. Methods: Fifteen patients with idiopathic RBD confirmed by polysomnography and a recent 123I-FP-CIT SPECT underwent a 7T MR by using three-dimensional gradient-recalled-echo multiecho susceptibility-weighted imaging of the SN; the findings were randomly presented with those of 14 HS and 28 patients with PD and blindly evaluated by an expert neuroradiologist, according to recently published criteria. MRI and SPECT results were also compared. Results: Nine subjects with RBD had abnormal SPECT; among them, the findings of 7T-MRI were rated abnormal in eight. Out of six subjects with RBD with normal SPECT, the 7T-MRI findings of five were rated normal. The Cohen's kappa statistic value of agreement was 0.722. Conclusion: Gradient-recalled-echo multiecho susceptibility-weighted imaging of the SN at 7T is abnormal in 60% of patients with RBD. The 7T-MRI and 123I-FP-CIT SPECT results showed good agreement. 7T-MRI of the SN could represent a safe marker for neurodegenerative disease in patients with RBD, however longitudinal study is warranted.

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