Case report: MRI diagnosis of congenital absence of the internal carotid artery

Congenital absence or hypoplasia of the carotid artery: radioclinical issues

PURPOSE

Congenital anomaly of the carotid artery is a rare abnormality. It is usually discovered incidentally by color Doppler carotid sonography, angiography, computed tomography (CT), or magnetic resonance imaging (MRI) of the head and neck taken for some other reason. Most patients are not symptomatic because of sufficient cerebral circulation supplied to the defective area by the communicating arteries of the circle of Willis, intercavernous anastomosis, communicating arteries from external carotid artery, and by persistent embryologic arteries to the carotid artery territory. However, sometimes, this anatomic variation may eventually lead to some clinical signs and symptoms in particular circumstances in the head and neck of which surgeons are unaware. A retrospective study was designed to emphasize the characteristic radiologic and clinical picture in patients with the congenital absence (agenesis and aplasia) or hypoplasia of the carotid artery, to delineate the associated abnormalities and existing collateral vessels, and to find out its incidence.

MATERIAL AND METHODS

Five thousand one hundred cerebral MRI and/or catheter angiograms performed between February 1988 and March 2002 were reviewed for carotid artery abnormality.

RESULTS

Seven patients with congenital absence or hypoplasia (4 of these patients were presented with hypoplasia of internal carotid artery [ICA], 3 with absence of ICA) of ICA were identified (0.13%). The radiologic and clinical study of 5 patients with unilateral (3 of these patients were presented with hypoplasia and 2 with absence of ICA) and 2 patients with bilateral (1 was presented with absence of ICA, whereas the other was hypoplasia) congenital abnormality with absence or hypoplasia of ICA demonstrate that those patients are usually asymptomatic and they are diagnosed incidentally.

CONCLUSION

It has been concluded that the combined use of magnetic resonance angiography and CT scanning of the skull base may disclose small but patent ICA. Collateral vessels seem to be usual in such cases, but they may be prominent in cases of acquired vascular occlusion, or increased hemodynamic pressure in dysplastic changes in collateral arteries are known causes of aneurysms. The main vascular supply for the brain in patients with congenitally small (hypoplasia) or absent (agenesis or aplasia) ICA is the vertebrobasilar system in bilateral cases. However, contralateral carotid vessel is the dominant arterial supply for unilateral cases, which has to be borne in mind in surgical interventions to the involved side.

Persistent primitive trigeminal artery associated with absence of internal carotid artery

BACKGROUND

Both a persistent primitive trigeminal artery (PTA) and the absence of an internal carotid artery are rare developmental anomalies.

METHODS AND RESULTS

Two cases with the unusual association of a persistent PTA and absence of the internal carotid artery on the left side are reported. The left anterior cerebral artery territory was supplied from the right internal carotid artery via the anterior communicating artery, and the left middle cerebral artery territory was supplied from the vertebrobasilar system via the persistent PTA antidromically.

CONCLUSION

This is the first report of such an association of developmental anomalies of cerebral vessels. Our cases are instructive for gaining insight into the involution and evolution processes of primitive cerebral arteries in the human embryo.

Bilateral internal carotid artery agenesis in a child with psychomotor developmental delay

In a 2-year-old boy with severe psychomotor developmental delay and a dysmorphic face, a chromosome study revealed a balanced translocation: 46XY,t-(1;3)(p31.2;p21). With magnetic resonance angiography, bilateral internal carotid artery agenesis was diagnosed. Periventricular high-intensity areas were evident on T2-weighted imaging, but no major cerebral malformation was observed.