Imaging the Substantia Nigra in Parkinson Disease and Other Parkinsonian Syndromes

Abstract

which results in a trilaminar pattern (Fig 1). The use of 3-T SWI has yielded similar nigrosome 1 findings (Fig 2, A-D) (22)(23)(24)(25)(26)(27)(28). Across the literature, different terms, such as swallow tail sign, SN dorsolateral hyperintensity, or simply nigrosome 1, refer to nigrosome 1 appearance. Nigrosome Imaging in PDOn both 3-and 7-T MRI scans, patients with PD show nigral hyperintensity loss (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28). This loss of nigral hyperintensity reflects signal hypointensity due to iron deposition associated with dopaminergic neuronal loss. When using 7-T MRI, the diagnosis of PD based on nigral hyperintensity loss compared with the healthy population has shown high diagnostic performance, with sensitivity and specificity of up to 100% (21). The diagnostic performance for PD using nigral hyperintensity loss at 3-T SWI compared with healthy control subjects varies but is generally satisfactory (22-28). Moreover, the asymmetric nigrosome involvement correlates with asymmetry in clinical motor symptoms (24,28). This variability in diagnostic performance may be due to diversity in the imaging protocols and study populations (Table ). However, a meta-analysis of 3-T SWI studies on the diagnosis of PD reported sensitivity of 94.6% and specificity of 94.4%, which provide sufficient evidence for the high diagnostic performance of 3-T SWI (29). When comparing 3-and 7-T MRI of the SN, the sensitivity, specificity, and diagnostic accuracy for PD diagnosis were higher with 7-T MRI (93%, 100%, 96%, respectively) than with 3-T MRI (79%, 94%, 86%, respectively) (19).Rapid eye movement sleep behavior disorder (RBD) is a common sleep-related symptom in patients with PD. Especially idiopathic RBD is known as the premotor disease prior to the development of synucleinopathy, such as PD or dementia with Lewy bodies (DLB) (30,31). A high rate of loss of nigral hyperintensity was observed in patients with idiopathic RBD (30,31). Bae et al (31) showed that patients with idiopathic RBD with loss of nigral hyperintensity had lower dopamine transporter uptake at SPECT than those with intact nigral signal, progressing into overt PD or DLB, suggesting that nigrosome imaging could be a marker for synucleinopathy conversion risk in premotor disease. Further studies with larger and more diverse prodromal cohorts with longitudinal followup will provide greater insights.

Differential Effects of Tau Stage, Lewy Body Pathology, and Substantia Nigra Degeneration on18F-FDG PET Patterns in Clinical Alzheimer Disease

“…However, such associations had neither been assessed using neuropathologic evaluations nor in the context of clinical AD. Additional studies combining FDG-PET with imaging modalities aimed to evaluate SN degeneration in-vivo (44)(45)(46)(47) would be of great interest for replicating and studying these associations in larger observational cohorts.…”

Normative values of neuromelanin-sensitive MRI signal in older adults obtained using a standard protocol for acquisition and analysis

“…[1][2][3][4][5] The method has been most broadly applied in research studies of neurodegenerative illnesses such as Parkinson's disease and Alzheimer's disease as a marker of degeneration of these nuclei. 2,3,6,7 More recently it has been applied in psychiatric conditions, where the NM-MRI signal has been shown to correlate to important aspects of psychopathology, consistent with evidence that the signal may assay aspects of the function of these neurotransmitter systems, even in the absence of neurodegeneration. 1,8,9 Many research studies support the potential of NM-MRI as a neuroimaging biomarker that could prove useful in clinical applications such as diagnosis or treatment of neurodegenerative and psychiatric disorders.…”

Identification of Immune-Related Hub Genes in Parkinson’s Disease

“…Mounting evidence indicates that immune dysfunction is involved in the pathogenesis of PD. The physiological function of the axon guidance pathway includes neuronal network formation during central nervous system development and the maintenance and plasticity of neural synapses (Bae et al, 2021). Abnormal axon-guidancemolecule signaling can lead to loss of connectivity and eventually trigger PD (Lin et al, 2009;Tomiyama, 2011).…”