Reproducibility and diagnostic accuracy of substantia nigra sonography for the diagnosis of Parkinson's disease

Simone van de Loo (1) , Uwe Walter (2) , Stefanie Behnke (3) , Johann Hagenah (4) , Matthias Lorenz (1) , Matthias Sitzer (1) , Rüdiger Hilker (1) , Daniela Berg (5)

1 Goethe-Universität Frankfurt am Main
2 University of Rostock
3 Department of Neurology, University of the Saarland, Homburg/Saar
4 Department of Neurology, University of Lübeck
5 Hertie Institute for Clinical Brain Research und Institute for Medical Genetics, Tübin

Objective: Transcranial sonography (TCS) shows characteristic hyperechogenicity of the substantia nigra (SN) in patients with Parkinson's disease (PD). Although this feature is meanwhile well established, sufficient observer reliability and diagnostic accuracy is a pre-requisite for advancements of this method. Methods: We investigated both aspects in a cross-sectional study with four blinded TCS raters in 22 PD patients and 10 healthy controls. Results: As expected, we found significant bilateral SN hyperechogenicity in PD patients. Quantitative computerized SN planimetry had a substantial intra- (ICC 0.97 and 0.93 respectively for both hemispheres) and inter-rater reliability (ICC 0.84 and 0.89), while visual semi-quantitative echogenicity grading of the SN revealed a moderate intra-rater (weighted kappa 0.80 ipsilateral and 0.74 contralateral) and slight (0.33) to fair (0.51) inter-rater reliability only. Diagnostic accuracy measured as the area-under curve (AUC) of ROC plots was highest in TCS of the SN opposite to the clinically most affected body side (planimetry 0.821, echogenicity grading 0.792) with a hyperechogenic area of 0.24 cm2 as the optimum cut-off value for the differentiation between PD and controls (sensitivity 79%, specificity 81%). Conclusions: The data demonstrate that the observer variability of SN planimetry is low in the hands of experienced investigators. This approach also offers adequate diagnostic accuracy. We conclude that reliable SN TCS data on PD can be achieved in clinical routine and multi-center trials when standardized analysis protocols and certain quality criteria of brain parenchyma sonography are met.

Mots clés: IMAGE ANALYSIS; PARKINSON'S DISEASE; ULTRASOUND

Simone van de Loo, Uwe Walter, Stefanie Behnke, Johann Hagenah, Matthias Lorenz, et al.. Reproducibility and diagnostic accuracy of substantia nigra sonography for the diagnosis of Parkinson's disease. Journal of Neurology, Neurosurgery and Psychiatry, 2010, 81 (10), pp.1087. ⟨10.1136/jnnp.2009.196352⟩. ⟨hal-00557430⟩