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Abstract
Objective: This study assessed whether high-resolution 7 T MRI allowed direct in vivo visualization of nigrosomes, substructures of the substantia nigra pars compacta (SNpc) undergoing the greatest and earliest dopaminergic cell loss in Parkinson disease (PD), and whether any disease-specific changes could be detected in patients with PD.
Methods: Postmortem (PM) midbrains, 2 from healthy controls (HCs) and 1 from a patient with PD, were scanned with high-resolution T2*-weighted MRI scans, sectioned, and stained for iron and neuromelanin (Perl), TH, and calbindin. To confirm the identification of nigrosomes in vivo on 7 T T2*-weighted scans, we assessed colocalization with neuromelanin-sensitive T1-weighted scans. We then assessed the ability to depict PD pathology on in vivo T2*-weighted scans by comparing data from 10 patients with PD and 8 age- and sex-matched HCs.
Results: A hyperintense, ovoid area within the dorsolateral border of the otherwise hypointense SNpc was identified in the HC brains on in vivo and PM T2*-weighted MRI. Location, size, shape, and staining characteristics conform to nigrosome 1. Blinded assessment by 2 neuroradiologists showed consistent bilateral absence of this nigrosome feature in all 10 patients with PD, and bilateral presence in 7/8 HC.
Conclusions: In vivo and PM MRI with histologic correlation demonstrates that high-resolution 7 T MRI can directly visualize nigrosome 1. The absence of nigrosome 1 in the SNpc on MRI scans might prove useful in developing a neuroimaging diagnostic test for PD.
GLOSSARY
- FFE=
- fast field echo;
- FOV=
- field of view;
- FSE=
- fast spin echo;
- HC=
- healthy controls;
- MT=
- magnetization transfer;
- NSA=
- number of signal averages;
- PD=
- Parkinson disease;
- PM=
- postmortem;
- RN=
- red nucleus;
- SN=
- substantia nigra;
- SNpc=
- substantia nigra pars compacta;
- SNpr=
- substantia nigra pars reticulata;
- TE=
- echo time;
- TR=
- repetition time;
- VTA=
- ventral tegmental area
Footnotes
Go to Neurology.org for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
Supplemental data at www.neurology.org
- Received January 11, 2013.
- Accepted in final form April 17, 2013.
- © 2013 American Academy of Neurology
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