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Table of Contents    
Year : 2017  |  Volume : 65  |  Issue : 3  |  Page : 673-674

Humming bird sign, a significant sign

Department of Neurology, KMC Hospital, Dr. Ambedkar Circle, Mangalore, Karnataka, India

Date of Web Publication9-May-2017

Correspondence Address:
Saumya H Mittal
Department of Neurology, KMC Hospital, Dr Ambedkar Circle, Mangalore, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/neuroindia.NI_45_17

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How to cite this article:
Mittal SH, Rakshith K C, Misri Z K, Pai S, Shenoy N. Humming bird sign, a significant sign. Neurol India 2017;65:673-4

How to cite this URL:
Mittal SH, Rakshith K C, Misri Z K, Pai S, Shenoy N. Humming bird sign, a significant sign. Neurol India [serial online] 2017 [cited 2020 Jan 21];65:673-4. Available from:

Humming bird sign is a sign commonly expected in a patient with progressive supranuclear palsy (PSP). In this neuroimaging section, we discuss how it is formed, and the other possible differential diagnoses that also show this sign.

Humming bird sign is largely considered a sensitive sign significant in the diagnosis of PSP. This is an interesting radiological sign that occurs due to midbrain atrophy. Is humming bird sign the only radiological feature of PSP? Moreover, is PSP the only diagnosis suggested by the humming bird sign?

A 68-year old gentleman presented to the hospital with the complaints of recurrent falls and restricted vision. The patient was found to have tremors, stiffness, axial rigidity and cogwheel rigidity, and restricted up and down gaze. The patient had been previously initiated on syndopa, but showed no significant response to the medicine. Magnetic resonance imaging (MRI) revealed significant midbrain atrophy without pontine atrophy suggestive of the humming bird sign [Figure 1].
Figure 1: Humming bird sign seen in our patient

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Humming bird sign is known to differentiate PSP from multiple system atrophy and Parkinson's disease.[1] With the atrophy of the midbrain (confirmed by midbrain to pons ratio, which is reduced from a normal of 0.24 to 0.12), the preserved pons assumes the shape of the body of the bird and the atrophic midbrain forms the head of the bird with the beak extending towards the optic chiasm. Also known as the Penguin sign or the King Penguin sign, this sign is known to be 99% sensitive for PSP, previously known as Steele–Richardson–Olszweski syndrome.[2]

Other features seen in MRI of a PSP patient are elevated diffusion coefficient in caudate nucleus, putamen, and globus pallidus. MR  Parkinsonism More Details index, an abnormal superior profile of the midbrain, and maximal diameter of midbrain in mid-sagittal plane can indicate the correct diagnosis.[2] One may also see the Mickey Mouse sign in the scans.[3] In advanced stages, a Squint sign may be seen in patients with PSP due to the development of complete ophthalmoplegia leading to a divergent squint.[4]

Humming bird sign may also be seen with normal pressure hydrocephalus [5] or fragile X-associated tremor/ataxia syndrome.[6]

Humming bird sign caused by the midbrain atrophy with normal pons is highly sensitive, however, probably not entirely specific to PSP. However, PSP remains the most frequent diagnosis suggested by the Humming bird sign.

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There are no conflicts of interest.

  References Top

Graber JJ, Staudinger R. Teaching NeuroImages: ''Penguin'' or ''humming bird'' sign and midbrain atrophy in progressive supranuclear palsy. Neurology 2009;72:e81.  Back to cited text no. 1
Sonthalia N, Ray S. The humming bird sign: A diagnostic clue for Steele-Richardson-Olszweski syndrome. BMJ Case Rep 2012;2012.  Back to cited text no. 2
Itolikar SM, Salagre SB, Kalal CR. 'Humming bird sign', 'penguin sign' and 'mickey mouse sign' in progressive supranuclear palsy. J Assoc Phys India 2012;60:52.  Back to cited text no. 3
Anam AM, Rabbani R, Shumy F. Humming bird sign and squint eyes. Bangladesh Crit Care J 2015;3:42.  Back to cited text no. 4
Kobayashi, Tsuruoka S, Numasawa Y, Tomimitsu H, Shintani S. Disappearance of the humming bird sign after shunt surgery in a case of idiopathic normal pressure hydrocephalus. Intern Med 2016; 55:815-7.  Back to cited text no. 5
Immovilli P, Rota E, Morelli N, IIafelice I, Cavallotti F, Michieletti E, et al. “humming bird sign” in fragile x-associated tremor/ataxia syndrome. Mov Disord Clin Pract 2015;2:328-9.  Back to cited text no. 6


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