Sacral nerve root entrapment demonstrated on computed tomography--'the winking ogre'.

Pictorial analogies are a descriptive modality often employed to convey radiological (as well as clinical and pathological) appearances. Examples of this useful descriptive device abound and many anatomical terms take their origin from such analogies. The cauda equina (horse's tail) and the uvula (grape) are but two classic examples. A radiographic appearance resembling a 'winking ogre' on computed tomography of the lumbosacral junction is described. This appearance is encountered in cases scanned following myelography, where one of the (left or right) first sacral nerve roots is compressed by herniated disc material.