Humans have a tendency to see patterns and images where none exist. Many of these patterns were created (or evolved, depending on your view) as early warning systems against the many predators that plot our early demise as they lurk in dark and sinister shadows.

By Diego Delso, CC BY-SA 4.0, Link

The commonest image the brain imagines is of the face, and it doesn’t require much prompting for the brain to make faces at you. Take the image below for example:

Pareidolia. Tup Wanders on Flikr.

The brains of social media users require even less prompting to conjure up a smiley or a frownie (if that is the word for it). All it takes is a comma and a colon.

The ‘ability’ to see what isn’t there has also served less life-preserving functions than gearing us up for the flight or fight response. Where, for example, would astronomy be without this important delusion?

Sky walk constellations. John on Flikr.

Medicine, surely more important than astronomy, has also made excellent use of this self-deception. This phenomenon that enables us to see non-existent faces and objects comes under the umbrella term of pareidolias.

By Aleph79 – Own work, CC BY-SA 3.0, Link

There are many very useful clinical pareidolias in neurology, for example the classical inverted champagne bottle appearance which describes the shape of the leg in Charcot Marie Tooth disease (CMT). The most intriguing patterns are however seen on brain imaging. And the favourite neuroradiological pareidolias are, no surprise here, of animal shapes and faces. How many of these signs do you know? What diseases do they signify? Test yourself with our 50 most fascinating neuroradiological pareidolias. Links to the answers are at the end of the list.

Banana sign

Bare/empty orbit sign

Bright tongue sign

Boxcar ventricle sign

Butterfly sign

Champagne bottle neck sign

Chasing the dragon sign

By David Revoy / Blender Foundation – Own work, CC BY 3.0, Link

Corpus callosum splenium sign

Dense middle cerebral artery sign

Double panda sign

Double rim sign

Dural tail  sign

Ears of the lynx sign

Profile of the lynx. Tambako the Jaguar on Flikr.

Elephant sign

Empty delta sign

Eye of the tiger sign

Face of the giant panda sign

Smithsonian’s National Zoo’s Giant Panda Turns Four! Smithsonian’s National Zoo on Flikr.

Figure of eight sign

Haemosiderin cap sign

Harlequin eye sign

Hockey stick sign

Hot cross bun sign

Hummingbird sign

By Joseph C Boone – Own work, CC BY-SA 4.0, Link

Hypodense artery sign

Infundibulum sign

Ivy sign

Lemon sign

Lentiform fork sign

Leopard skin sign

Medusa head sign

By Miguel Hermoso Cuesta – Own work, CC BY-SA 4.0, Link

Middle cerebellar peduncle (MCP) sign

Molar tooth sign

Omega/trident sign

Puff of smoke sign

Pulvinar sign

Punched-out corpus callosum sign

Radial band sign

Salt and pepper sign

Scalpel sign

Snake eyes sign

Snake eyes. Thomas Hawk on Flikr.

Spot sign

Spring sign

Starfield sign

Starry sky/swiss cheese sign

Swallow tail sign

Swirl sign

Tigroid sign

Tram track sign

Wine glass sign

Zebra sign

By Clipartqueen – Own work, CC0, Link

OK, we admit a few of the signs are not really pareidolias, but they do help to take the number up to a round 50! How many did you know? Why not check the answers and references in these Neurochecklists:


Neuroradiological signs: classic types

Neuroradiological signs in stroke

Neuroradiological signs: miscellaneous types


And why not explore more neuroradiology pearls in our other 35 neuroradiology checklists such as:

Basal ganglia calcification

Bilateral thalamic lesions

Cerebellopontine angle (CP angle) lesions

Cortical abnormalities

Corticospinal tract hyperintensity

Enhancing meningeal lesions

Headache imaging pathologies


MRI T1 high signal lesions

Radiation necrosis v tumour recurrence

Reversible splenial lesions

Sellar and parasellar lesions

Third ventricle lesions

White matter lesions

By Thomas Schultz – Own work, CC BY-SA 3.0, Link

And that’s not all: neuroradiology gems are sprinkled extensively in all the neurology topics covered by Neurochecklists. Go on then, explore and please leave a feedback!

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