Usual and unusual causes of splaying of the carotid artery bifurcation: the Lyre sign--a pictorial review.

The 'Lyre' sign describes the characteristic splaying of the carotid artery bifurcation due to a carotid body tumour (paraganglioma) on conventional carotid angiography. In this pictorial review, we describe and illustrate two cases demonstrating the equivalent Lyre sign on multi-detector computed tomography (MDCT) and ultrasound resulting from carotid body tumour and extra-cranial internal carotid artery pseudoaneurysm. Both of these pathologies can manifest acutely and warrant accurate diagnosis to prevent potential catastrophic consequences. We also emphasise the added value of MDCT in making a definitive diagnosis and discuss other differential considerations splaying the carotid bifurcation.