Objective:
The primary objective was to evaluate the absence of nigrosome 1 in 3TMRI in a group of patients with PD according to their evolutionary time to diagnosis. And the secondary one to assess its diagnostic performance in relation to that of the midbrain ultrasound.

Background: The SWI sequence by magnetic resonance 3 tesla (MRI3T) allows to identify the area of ​​Nigrosome 1, which is absent in patients with idiopathic Parkinson’s disease (PD). In our center, this method demonstrated a sensitivity for the diagnosis of PD of 93.75% and a specificity of 87.5% when comparing patients with advanced PD vs essential tremor.

Method: All the MRI3T performed on patients diagnosed with PD in the 2018-2020 period were considered. For the diagnosis of PD, the criteria of the International Parkinson and Movement Disorders Society were followed.
The presence or absence of nigrosome 1 in the midbrain region was diagnosed. The images were evaluated by two independent neuroradiology specialists blind to diagnosis.
All patients underwent a midbrain ultrasound to assess the echogenicity of the substantia nigra.
The patients were divided into 3 subgroups according to their evolution time.
The results of MRI3T and midbrain ultrasound were compared in the three subgroups.

Results: N 68 patients.
Group 1 (up to 12 months): N: 17; mean age: 70 years; women: 8; Hoehn and Yahr: 1.47; UPDRS-MDS III: 10.5; Nigrosome 1: absent: 13 (76.4%). Mesencephalic hyperechogenicity: 9 (52.9%). Bad window: 0.
Group 2 (13 to 35 months): N: 29; mean age: 73 years; women: 14; Hoehn and Yahr: 1.6; UPDRS-MDS III: 17; Nigrosome1 absent: 26 (89.6%). Mesencephalic hyperechogenicity: 18 (66.6%). Bad window: 2 (6.89%).
Group 3 (≥36 months): N: 22; mean age: 72.5 years; women: 8; Hoehn and Yahr: 1.8; UPDRS-MDS III: 22; Nigrosome absent: 21 (95.5%). Mesencephalic hyperechogenicity: 13 (76.5%). Bad window: 5 (31.25%).

Conclusion: The percentage of positivity of the SWI sequence by MRI3T to detect the absence of Nigrosome 1 was higher as the evolutionary time increased.
After 36 months, its accuracy was close to 100%.
The performance of the midbrain ultrasound was also progressive but with a lower performance than the MRI3T in all the stages evaluated.

 this work was presented in the   57th Argentine Neurological Society VIRTUAL  Congress November 2020

References: 2. Schwarz ST, Afzal M, Morgan PS, Bajaj N, Gowland PA, Auer DP. The ‘swallow tail’ appearance of the healthy nigrosome – a new accurate test of Parkinson’s disease: a case-control and retrospective cross-sectional MRI study at 3T. PloS one 2014 3. Cosottini M, Frosini D, Pesaresi I, et al. Comparison of 3T and 7T Susceptibility-Weighted Angiography of the Substantia Nigra in Diagnosing Parkinson Disease. AJNR American journal of neuroradiology 2015;36:461-6. 4. Mahlknecht P, Krismer F, Poewe W, Seppi K .Meta-analysis of dorsolateral nigral hyperintensity on magnetic resonance imaging as a marker for Parkinson’s disease. Mov Disord. 2017 Apr;32(4):619-623 5. Noh Y, Sung YH, Lee J, Kim EY .Nigrosome 1 Detection at 3T MRI for the Diagnosis of Early-Stage Idiopathic Parkinson Disease: Assessment of Diagnostic Accuracy and Agreement on Imaging Asymmetry and Clinical Laterality..AJNR Am J Neuroradiol. 2015 Nov;36(11):2010 6. Berg D, Merz B, Reiners K, Naumann M, Becker G. Five-year follow-up study of hyperechogenicity of the substantia nigra in Parkinson’s disease. Mov Disord. 2005;20(3):383–385. 7. Perez Akly MS, Stefani CV, Ciancaglini L, Bestoso JS, Funes JA, Bauso DJ, Besada CH. Accuracy of nigrosome-1 detection to discriminate patients with Parkinson’s disease and essential tremor. Neuroradiol J. 2019 Dec;32(6):395-4005. 8. Weise D, Lorenz R, Schliesser M et al. Substantia nigra echogenicity: A structural correlate of functional impairment of the dopaminergic striatal projection in Parkinson’s disease. Mov Disord. 2009 Aug 15;24(11):1669-75. 9. Lobsein E, Schreiner s, Plotkin M. No correlation of substancia nigra echogenicity and nigroestriatal degradation in Parkinson´s disease. Mov Disord 2012 mar;27(3).450-3. 10. Bestoso JS, Pérez Akly M, Ciancaglini L, Stefani, C Rojas J, Funes J, Besada C, Bauso D. Evaluación de la ausencia de nigrosoma 1 en pacientes con enfermedad de Parkinson de Novo (EP de Novo) vs enfermedad de Parkinson avanzada (EP avanzada). Congreso Argentino de neurología. 2018

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