The diagnostic accuracy of the hummingbird and morning glory sign in patients with neurodegenerative parkinsonism

Abstract

Introduction: The hummingbird sign and the morning glory flower sign, reflecting midbrain pathology on MRI, have previously been shown to separate patients with progressive supranuclear palsy (PSP) from those with Parkinson's disease (PD) and multiple system atrophy (MSA). The aim of the present study was to determine the diagnostic accuracy and reproducibility of visual assessment of midbrain atrophy patterns in a large cohort of patients with neurodegenerative parkinsonism.

Methods: Retrospective analysis of midbrain atrophy patterns on T1-weighted MRI in a large cohort of patients with neurodegenerative parkinsonism and healthy controls who underwent MR imaging during their diagnostic work-up.

Results: 481 patients with neurodegenerative parkinsonism and 79 healthy controls were included in the present study. The presence of the hummingbird sign had a specificity of 99.5% and a positive predictive value of 96.1% for a diagnosis of PSP while sensitivity was suboptimal with 51.6%. Similarly, the presence of the morning glory flower sign yielded a specificity of 97.7% for a diagnosis of PSP, but sensitivity was only 36.8%. Sensitivity of both signs was 35.3% in early, clinically unclassifiable parkinsonism. Visual assessment of these midbrain alterations showed excellent inter-rater agreement.

Conclusion: Midbrain atrophy patterns are useful in the differential diagnosis of neurodegenerative parkinsonism but both the hummingbird sign and more so the morning glory flower sign suffer from low sensitivity, especially in early disease stages.

Keywords: Hummingbird sign; MR parkinsonism index; Midbrain-to-pontine area ratio; Multiple system atrophy; Parkinson's disease; Parkinsonism; Progressive supranuclear palsy.