This document describes several radiological signs named after animal ears: - The "mouse ear sign" describes bone erosions at finger joints resembling mouse ears. - The "bladder ears" sign refers to normal protrusion of the bladder into the groin resembling ears. - The "dog ear sign" identifies fluid in the pelvis separating from the bladder, resembling a dog's face and ear. - The "rabbit ear sign" describes slit-like ventricles displaced inward, resembling a rabbit's ears.

1. ALL EARS!
DR BHAVANA K

2. MOUSE EAR SIGN

3. MOUSE EAR SIGN
• Erosions will usually begin at the
peripheral articular surfaces and
extend centrally.
• Marginal erosions and bony
overgrowth at the interphalangeal
joints can create an appearance
which resembles "mouse ears".

4. BLADDER EARS
• Normal protrusion of lateral aspect of
bladder is seen into the inguinal
canal, called "bladder ears“
• Seen in infants.

5. DOG EAR SIGN

6. DOG EAR SIGN
• Dog ear sign of fluid in the pelvic
peritoneal recess.
• Supine abdominal radiograph shows
a full bladder which represents the
face of the dog.
• The convex soft-tissue opacity
representing blood in the left lateral
pelvic peritoneal recess and
separated from the bladder by a thin
hyperlucent strip of extraperitoneal
fat is the dog ear.
John H. Harris, Jr. Reflections: Emergency Radiology. Radiology 2001; 218(2): 309-316.

7. RABBIT EAR SIGN

8. RABBIT EAR SIGN
• Bilateral subdural hematomas may
lead to slit like ventricles displaced
medially.
• Also called squeezed ventricle or
hare’s ears sign

9. INVERTED RABBIT EAR SIGN

10. INVERTED RABBIT EAR SIGN
• Hyperintensities in the dorsal column
due toVitamin B12 deficiency.
• About 50% resolve completely after
vitamin B12 therapy
• Also called InvertedV sign

11. EARS OFTHE LYNX SIGN

12. EARS OFTHE LYNX SIGN
• Periventricular cone shaped
hyperintensities near the frontal horn
resembling the tuft of hair on the ears
of the lynx.

13. EARS OFTHE LYNX SIGN
• Seen in hereditary spastic paraplegia
with thin corpus callosum and
Marchiafava bignami.

14. Thank you!