Hummingbird sign and Mickey Mouse sign.

Hummingbird sign is a rather interesting sign seen in mid-sagital view of MRI brain in patient with progressive supranuclear palsy(PSP) [ref1]. PSP is characterized by akinetic rigid parkinsonism, dizziness, unsteadiness, slowness, falls, and pseudobulbar dysarthria, and also supranuclear eye movement abnormalities which presented as downward, or upward, or combination gaze palsy[ref2]. Pathology of PSP includes tissue loss in the frontal cortex, subcortical nuclei; which includeds midbrain, caudate and thalamic; as well as periventricular white matter. This pathological changes correlate with the clinical presentation [ref3]; and the midbrain atrophy is able to be detect by CT and MRI [ref4].

The shape of the atrophy looks like the bill of a hummingbird, and thus the hummingbird sign. This is caused by the atrophy of the midbrain tegmentum and a relative increase in the length of the interpeduncular fossa over the anteroposterior diameter of the midbrain tegmentum. This sign has nearly 100% sensitivity according to one study[ref5]. This correlate with another study giving a result of sensitivity of 100% and specificity of 90.5% of diagnosing and differentiating PSP from other conditions[ref6]. It is also stated that midbrain atrophic changes on mid-sagittal view on MRI is a reliable test and can differentiate PSP from Parkinson’s disease(PD), Multiple system atrophy of parkinson type(MSI-P) [ref7].

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Image above shown a T2-weighted MRI image of the brain, the selective atrophy of midbrain with preservation of pons (divided by the black line). Image obtained from [ref8]. Try comparing to a hummingbird.

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Image above shows the T1-weighted for comparison. Image obtained from [ref9].

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Image above shows Hummingbird sign (left) with comparison of normal (right) on midsagittal view MRI. Image obtained from [ref10].

Mickey mouse sign is referring to the axial MRI view of the brainstem, showing a selective atrophy of the midbrain tegmentum, with relative sparing of the midbrain tectum and cerebral peduncles, hence giving you the Mickey Mouse symbol. [ref11]

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Image above shows an axial T2-weighted image shows the atrophy of the midbrain tegmentum. Image obtained from [ref8].

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Image above shows the comparison between axial view of midbrain MRI of PSP (left) and normal (right). Image obtained from [ref12]. I personally do no think it look like the three circle of Mickey mouse symbols.

References
1. Rakesh Shukla, Manish Sinha, Rajesh Kumar, and Dilip Singh. ‘Hummingbird’ sign in progressive supranuclear palsy. Ann Indian Acad Neurol. 2009 Apr-Jun; 12(2): 133.
doi: 10.4103/0972-2327.53087

2. Mahlon R. DeLong and Jorge L. Juncos. PARKINSON’S DISEASE AND OTHER EXTRAPYRAMIDAL MOVEMENT DISORDERS. In: Stephen L. Hauser, HARRISON’S Neurology in Clinical Medicine. 2nd ed.

3. N. J. Cordato, A. J. Duggins, G. M. Halliday et al. Clinical deficits correlate with regional cerebral atrophy in progressive supranuclear palsy. Brain (June 2005) 128 (6): 1259-1266. doi: 10.1093/brain/awh508

4. Duvoisin RC, Golbe LI, Lepore FE. Progressive supranuclear palsy. Can J Neurol Sci. 1987 Aug;14(3 Suppl):547-54.

5. Kato N, Arai K, Hattori T. Study of the rostral midbrain atrophy in progressive supranuclear palsy. J Neurol Sci. 2003 Jun 15;210(1-2):57-60.

6. M. Cosottini, R. Ceravolo, L. Faggioni et al. Assessment of midbrain atrophy in patients with progressive supranuclear palsy with routine magnetic resonance imaging. Acta Neurologica Scandinavica. Volume 116, Issue 1, pages 37–42, July 2007

7. Oba H, Yagishita A, Terada H et al. New and reliable MRI diagnosis for progressive supranuclear palsy. Neurology. 2005 Jun 28;64(12):2050-5.

8. Nikhil Sonthalia and Sayantan Ray. The Hummingbird sign: a diagnostic clue for Steele-Richardson-Olszweski syndrome. BMJ Case Reports 2012; doi:10.1136/bcr-2012-006263.

9. Graber JJ and Staudinger R. Teaching NeuroImages: “Penguin” or “hummingbird” sign and midbrain atrophy in progressive supranuclear palsy. Neurology. 2009 Apr 28;72(17):e81. doi: 10.1212/WNL.0b013e3181a2e815.

10. Pandey S. Hummingbird sign in progressive supranuclear palsy disease. J Res Med Sci 2012; 17(2): 197-8

11. JM Schott. A neurological MRI menagerie. Pract Neurol 2007;7:186-90.

12. Lehéricy S, Hartmann A, Lannuzel A et al. Magnetic resonance imaging lesion pattern in Guadeloupean parkinsonism is distinct from progressive supranuclear palsy. Brain. 2010 Aug;133(Pt 8):2410-25. doi: 10.1093/brain/awq162.

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