The Hummingbird sign: a diagnostic clue for Steele-Richardson-Olszweski syndrome (2024)

Description

Progressive supranuclear palsy (PSP), previously known as Steele-Richardson-Olszweski syndrome, is an atypical parkinsonian syndrome with a prevalence of ∼5/100 000. It is an important differential diagnosis of more common idiopathic Parkinson's disease (iPD), where clinical differentiation is not straightforward and characteristic neuroimaging often yields a diagnostic clue. We describe a case of 75-year-old man with a history of slowness of activities and recurrent fall while walking, which was insidious in onset and gradually progressive for last 2 years. There was no history of tremor, stooping postures, urinary incontinence or hallucination. On examination supranuclear vertical gaze palsy with slow horizontal saccades, axial rigidity and bradykinesia were present. He had a slow gait with lack of associated movements and tendency to fall backwards. He had positive ‘dirty tie sign’ while eating. The patient was diagnosed as a probable case of PSP and MRI of the brain was done. Mid-sagittal T2-weighted MRI of the brain revealed characteristic selective atrophy of midbrain tegmentum (mesencephalon), with relatively preserved pons, giving an appearance of the head and body, respectively, of a hummingbird (figure 1). This is known as ‘The Hummingbird sign’ or ‘The King Penguin sign’.1 The axial T2 MRI image shows a reduction in the anterior–posterior diameter of midbrain with thinning of cerebral peduncle giving appearance of ‘morning glory sign’ or the ‘Mickey mouse sign’ (figure 2). The hummingbird sign is reported to have a sensitivity of nearly 100%.1

Patients with iPD, multisystem atrophy (MSA), corticobasal degeneration do not have midbrain atrophy, thus making this sign important in differentiating these conditions from PSP. This sign also suggests rostral interstitial nucleus of medial longitudinal fasciculus involvement in PSP.2 MR parkinsonism index, defined as the ratio of midbrain area to pons area, is another useful tool in the diagnosis of PSP patients.3 The objective of this article is to highlight the importance of neuroimaging in working up of the differential diagnosis of closely related parkinsonian disorders such as iPD, MSA and PSP.

References

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