MRI scan (saggital view) of a 75 year old male patient. There is significant visible atrophy of the midbrain with the ‘hummingbird’ or ‘penguin’ sign clearly evident. The atrophy of the midbrain results in a profile of the brainstem as seen in the above image. The preserved or normal volume pons forms the body of the bird. The pons is an area of the hindbrain that sits directly above the medulla and connects the upper and lower parts of the brain. The atrophied midbrain forms the head and the beak extending towards the optic chiasm. The optic chiasm is the part of the brain where the optic nerves partially cross. Findings: Progressive Supranuclear Palsy.
Detail of Hummingbird or Penguin sign from the above MRI case of Progressive Supranuclear Palsy. The ‘Hummingbird or ‘penguin’ sign has almost a 100% sensitivity in diagnosing Progressive Supranuclear Palsy which makes it also very useful in differentiating this condition from other similar neurological disorders.(1)
Progressive Supranuclear Palsy (PSP)
Progressive Supranuclear Palsy is a degenerative brain disease that involves the gradual deterioration and death of increasing numbers of brain cells in the areas that involve body movement and thinking. Progressive Supranuclear Palsy is also sometimes called ‘Steele-Richardson-Olszewski Syndrome’ after the three Canadian doctors who described the disease in 1963. Symptoms of Progressive Supranuclear Palsy can vary widely, as can the rate of progression of the disease. Early symptoms include, problems with balance and mobility, behavioural changes such as apathy or irritability and an inability to control eye and eyelid movement, particularly vertical movement of the eyes. The disease damages parts of the brain located above the nuclei (called the supranuclear) which are small, pea-sized structures that control eye movements.
MRI (axial) image of a 75 year old male patient (same patient as seen in Image 1) reveals atrophy of the midbrain tegmentum with thinning of the cerebral peduncles that result in a concave (rather than the normally convex) dorso-lateral midbrain margin (purple arrow pointing downwards). There is a deep interpeduncular cistern as well (indicated by the two upward pointing purple arrows). The interpeduncular cistern (basal cistern or Fossa interpeduncularis) is a wide cavity where the arachnoid extends across between the two temporal lobes. These neurological changes combined give the classic radiological sign seen here, which for obvious reasons, has become known as the ‘Mickey Mouse’ symbol. Findings: Progressive Supranuclear Palsy.
The 75 year old male patient, whose MRI scans are featured in Images 1 and 2 above, presented with a history of mobility problems, especially gait instability with Parkinsonian features, he had been unresponsive to levodopa (medication used to treat Parkinson’s Disease). The symptoms of Progressive Supranuclear Palsy are often confused with that of other more common, degenerative brain disorders, particularly Parkinson’s disease (because of the movement and gait difficulty) and Alzheimer’s (because of the behavioural changes). Accurate diagnosis is extremely important as Progressive Supranuclear Palsy does not respond to levodopa, this factor together with a symmetrical onset of Progressive Supranuclear Palsy, can help differentiate the disease from that of Parkinson’s.(2) Progressive Supranuclear Palsy is a rare disease that is more prevalent in elderly patients (although it has been found in patients as young as 40 years old) it is usually diagnosed in people in their 60’s and older. The prevalence of Progressive Supranuclear Palsy has been estimated around 1.39 cases per 100,000 in the United States.(3) The results of a recent study however, suggest that the true prevalence of Progressive Supranuclear Palsy has been underestimated because many patients remain both undiagnosed and misdiagnosed.(4)
1. 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.
2. Litvan I, Campbell G, Mangone CA, Verny M, McKee A, Chaudhuri KR, Jellinger K, Pearce RK, D’Olhaberriague L. (Jan 1997). “Which clinical features differentiate progressive supranuclear palsy (Steele-Richardson-Olszewski syndrome) from related disorders? A clinicopathological study”. Brain. 120 (1): 65–74. doi:10.1093/brain/120.1.65. PMID 9055798.
3. Golbe LI, Davis PH, Schoenberg BS, Duvoisin RC. Prevalence and natural history of progressive supranuclear palsy. Neurology 1988; 38:1031.
4. A Schrag, MDa, Y Ben-Shlomo, MRCPb, Prof NP Quinn, MDa ‘Prevalence of progressive supranuclear palsy and multiple system atrophy: a cross-sectional study.’ The Lancet: Volume 354, Issue 9192, 20 November 1999, Pages 1771–1775