Do you know why this patient has resting tremor and diplopia?

Imaging signs on MR can be a helpful tipoff toward the correct diagnosis. Take a look at this textbook example in today’s neurological imaging case.

This 71-year-old male presents with resting tremor and diplopia. Is the most likely diagnosis Parkinson’s disease, Lewy body dementia, Progressive supranuclear palsy, Alzheimer’s disease, or Frontobasal degeneration? Have a look at images 1 and 2, and see if you can generate a diagnosis.

Clue: Do you have a hummingbird feeder in your yard?


T1 Sagittal

Image 2 supplement – “Hummingbird Sign”


This patient was diagnosed with progressive supranuclear palsy (PSP), also known as Steele-Richardson-Olszewski syndrome or Richardson’s syndrome. The condition is associated with supranuclear ophthalmoplegia, pseudobulbar palsy, nuchal dystonia, dementia, gradual progressive monophasic disease onset at age 40 or older, and prominent posterior instability in the first year of the disease.

PSP is a tauopathy like frontotempolobar dementia (formerly known as Pick’s disease). Tau is a microtubule-associated protein which, in the normal human brain, is distributed by axons. Neurofibrillary tangles and tau protein filaments are found in cases of Alzheimer’s disease.

Sometimes, PSP has early brainstem involvement with a frontal predominance. It is typical for there to be more posterior fossa and brainstem involvement than in classic Parkinson’s disease. Midbrain atrophy, divergence of the red nuclei, dilatation of the third ventricle, atrophy of the superior cerebellar peduncle, and frontocortical atrophy are common. The hummingbird sign is used to describe mid-sagittal imaging appearance of PSP, at the midbrain level (image 2, yellow arrows).

In addition to the midbrain atrophy in PSP, the dentate nucleus (not shown) is markedly involved. This leads to its main efferent pathway, the brachium conjunctivum or superior cerebellar peduncle being affected and atrophic.  Its fibers pass into the brainstem and decussate at the inferior colliculi before synapsing at the red nucleus and ventrolateral nucleus of thalamus.

Q1 – What diseases found in the brain are linked to tau proteins?

(a) Pick’s disease
(b) Alzheimer’s
(c) Progressive supranuclear palsy (PSP)
(d) Wilson’s disease
(e) a, b, and c

Q2 – The “hummingbird sign” is typical of:

(a) Parkinson’s disease
(b) Progressive supranuclear palsy (PSP)
(c) Wilson’s disease
(d) Hurler’s disease
(e) None of the above

Q3 – The “big panda sign” is typical of:

(a) Parkinson’s disease
(b) Progressive supranuclear palsy (PSP)
(c) Wilson’s disease
(d) Hurler’s disease
(e) NF-2

Q4 – The “swallow tail sign” is typical of:

(a) Parkinson’s disease
(b) Progressive supranuclear palsy (PSP)
(c) Wilson’s disease
(d) Multisystem atrophy
(e) None of the above


For more advanced nuanced thoughts (“putaminal slit sign” and “the smudging sign”), read on. Differential subtle features of similar diseases:

  • PSP can be differentiated from multisystem atrophy-P (Parkinson type) using a midbrain diameter of less than 14mm on the sagittal scan in the AP dimension.
  • Multisystem atrophy cerebellar-type (MSA-C) may be differentiated from PSP and idiopathic Parkinson’s disease by the “hot-cross bun sign” or “pontine cross sign” seen in MSA-C.
  • Putaminal low signal intensity helps differentiate MSA from idiopathic Parkinson’s disease.
  • The “putaminal slit sign” differentiates a parkinsonian-type or MSA-P type from progressive supranuclear palsy and standard idiopathic Parkinson’s disease.
  • Zona compacta atrophy results in confluence or “the smudging sign” between the substantia nigra and red nucleus hypointensity in classic Parkinson’s disease.
  • Corticobasal degeneration is characterized by global atrophy or asymmetric atrophy which helps differentiate it from the other entities.
  • Classic Parkinson’s or idiopathic Parkinson’s disease should be suspected when there is resting tremor, rigidity, hypokinesia, but not upward gaze palsy as in PSP.
  • Some later stage Parkinson’s patients may have visual hallucinations, but this is more typical of Lewy body dementia.


A1 – (e) a, b, and c

A2 – (b) Progressive supranuclear palsy (PSP)

A3 – (c) Wilson’s disease

A4 – (a) Parkinson’s disease


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For more case review, check out MRI Online.


1. Kornenko, Aronin.  Neuroradiology

2. Cossotini M et al. MRI of the Substantia Nigra. Radiology 2014.  Jun;271(3): 831-838.

3. Quattrone A et al. MR Imaging Differentiation of PSP from Parkinson’s. Radiology 2008; 246: 214-221.

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