title: Substantia nigra neuromelanin-MR imaging differentiates essential tremor from Parkinson's disease.
abstract: BACKGROUND
  Essential tremor (ET) is a very common movement disorder that has no diagnostic markers. Differentiation with Parkinson's disease (PD) can be clinically challenging in some cases, with a high rate of misdiagnosis. Magnetic resonance imaging (MRI) studies have been able to identify neuromelanin changes in the substantia nigra (SN) of PD patients, but they have thus far not been investigated in ET. In this study, we aimed to characterize neuromelanin-MR signal changes in ET and evaluate its diagnostic accuracy in the differential diagnosis with PD.
  
  
  METHODS
  The inclusion criteria were patients with ET and untreated "de novo" PD patients; in addition, age-matched controls were enrolled. These were studied with a high-resolution T1-weighted MRI sequence at 3.0 Tesla to visualize neuromelanin. The primary outcomes were the area and width of the SN region with high signal.
  
  
  RESULTS
  A total of 15 ET patients and 12 "de novo" PD patients were evaluated. The area and width of the T1 high signal in the SN region were markedly decreased in the PD group compared with the ET and age-matched controls, and a greater decrease was seen in the ventrolateral segment. The neuromelanin measures in the ET group, although slightly lower, were not significantly different from the healthy control group. We obtained a sensitivity of 66.7% and a specificity of 93.3% in discriminating ET from early-stage PD.
  
  
  CONCLUSIONS
  Neuromelanin-sensitive MRI techniques can discriminate ET from early-stage tremor-dominant PD and can be a useful clinical tool in the evaluation of tremor disorders. © 2015 International Parkinson and Movement Disorder Society.
authors.affiliation: Neurological Imaging Department, Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, Portugal.|Clinical Pharmacology Unit, Instituto de Medicina Molecular, Faculty of Medicine, University of Lisbon, Portugal.
authors.forename: Sofia
authors.initials: S
authors.lastname: Reimão
authors.affiliation: Clinical Pharmacology Unit, Instituto de Medicina Molecular, Faculty of Medicine, University of Lisbon, Portugal.|Neurology Department, Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, Portugal.|CNS-Campus Neurológico Sénior, Torres Vedras, Portugal.
authors.forename: Patrícia
authors.initials: P
authors.lastname: Pita Lobo
authors.affiliation: Clinical Pharmacology Unit, Instituto de Medicina Molecular, Faculty of Medicine, University of Lisbon, Portugal.|Neurology Department, Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, Portugal.
authors.forename: Dulce
authors.initials: D
authors.lastname: Neutel
authors.affiliation: Clinical Pharmacology Unit, Instituto de Medicina Molecular, Faculty of Medicine, University of Lisbon, Portugal.|Neurology Department, Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, Portugal.|CNS-Campus Neurológico Sénior, Torres Vedras, Portugal.
authors.forename: Leonor Correia
authors.initials: LC
authors.lastname: Guedes
authors.affiliation: Clinical Pharmacology Unit, Instituto de Medicina Molecular, Faculty of Medicine, University of Lisbon, Portugal.|Neurology Department, Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, Portugal.
authors.forename: Miguel
authors.identifier: http://orcid.org/0000-0002-4008-8110
authors.initials: M
authors.lastname: Coelho
authors.affiliation: Clinical Pharmacology Unit, Instituto de Medicina Molecular, Faculty of Medicine, University of Lisbon, Portugal.|Neurology Department, Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, Portugal.|Laboratory of Clinical Pharmacology and Therapeutics, Faculty of Medicine, University of Lisbon, Portugal.
authors.forename: Mário M
authors.initials: MM
authors.lastname: Rosa
authors.affiliation: Instituto de Biofísica e Engenharia Biomédica, Faculdade de Ciências, Universidade de Lisboa, Portugal.
authors.forename: Pedro
authors.initials: P
authors.lastname: Azevedo
authors.affiliation: Instituto de Biofísica e Engenharia Biomédica, Faculdade de Ciências, Universidade de Lisboa, Portugal.
authors.forename: Joana
authors.initials: J
authors.lastname: Ferreira
authors.affiliation: Clinical Pharmacology Unit, Instituto de Medicina Molecular, Faculty of Medicine, University of Lisbon, Portugal.
authors.forename: Daisy
authors.initials: D
authors.lastname: Abreu
authors.affiliation: Clinical Pharmacology Unit, Instituto de Medicina Molecular, Faculty of Medicine, University of Lisbon, Portugal.
authors.forename: Nilza
authors.initials: N
authors.lastname: Gonçalves
authors.affiliation: Instituto de Biofísica e Engenharia Biomédica, Faculdade de Ciências, Universidade de Lisboa, Portugal.
authors.forename: Rita G
authors.initials: RG
authors.lastname: Nunes
authors.affiliation: Neurological Imaging Department, Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, Portugal.
authors.forename: Jorge
authors.initials: J
authors.lastname: Campos
authors.affiliation: Clinical Pharmacology Unit, Instituto de Medicina Molecular, Faculty of Medicine, University of Lisbon, Portugal.|Neurology Department, Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, Portugal.|CNS-Campus Neurológico Sénior, Torres Vedras, Portugal.|Laboratory of Clinical Pharmacology and Therapeutics, Faculty of Medicine, University of Lisbon, Portugal.
authors.forename: Joaquim J
authors.initials: JJ
authors.lastname: Ferreira
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D020329:Essential Tremor / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000592:standards; D008297:Male; D008543:Melanins; D008875:Middle Aged; D010300:Parkinson Disease / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D013378:Substantia Nigra / Q000473:pathology*
chemical_list: D008543:Melanins; C014121:neuromelanin
keywords: MRI; Parkinson's disease; essential tremor; neuromelanin; substantia nigra