Título

Yin-Yang Sign: case report and a review

Fundamentação/Introdução

Yin-Yang signal corresponds to an incidental finding of imaging tests as contrast-enhanced CT and color Doppler echography, usually found in the brain and abdomen, but also may occur in other locations. It’s a relevant finding because it has been mainly indicative of partially thrombosed aneurysms and pseudoaneurysms.

Objetivos

The present study aimed to perform a critical review of the Yin-Yang signal and the review of two cases of giant aneurysms, one in the internal carotid artery and another in the middle cerebral artery, in which the signal was observed.

Delineamento/Métodos

MLS, 44 years old, female, domestic. It presents a history of chronic daily headache, with episodes of intense headache associated with loss of consciousness. Neurological examination: alert, no neck stiffness. Skull CT revealed lesion in the right supraclinoid internal carotid artery with calcification, being possible to observe the Yin-Yang signal. Cerebral arteriography shows presence of giant aneurysm of the internal carotid artery supraclinodea. Magnetic resonance imaging presents suprasellar lesion. Patient was submitted to embolization. He was discharged without complaints. JGHS, 48 years old, female, from home, with MRI Coronal and CTI view, showing yin yang sign with thrombus and he blood flow. The thrombous is hyperdense in CT and has Hypersignal in MRI.

Resultados

The signal presents high frequency, since 80 to 90% of the aneurysms or pseudoaneurysms present thrombus at CT. The physiopathological basis in both is the existence of hemodynamic changes of the blood flow. It presents as a rounded mass divided in half by the difference of radiological density, being hypodense the thrombus and hyperdense the intravenous contracting. The blood flow inside it’s bidirectional, anterograde during systole and retrograde in the cardiac diastole. However, the signal is not pathognomonic of aneurysms, being present in cases of cystic meningioma, craniopharyngioma, pituitary adenoma and metastasis, in cases of intracranial location. The signal may also be absent in aneurysms with concentric thrombus.

Conclusões/Considerações finais

Yin-Yang signal helps in the early identification of aneurismatic lesion, allowed diagnosis and early approach.

Palavras Chaves

Intracranial aneurysm, carotid artery lesions, computed tomography, cerebral angiography.