Congenital agenesis of internal carotid artery with ipsilateral Horner presenting as focal neurological symptoms

Abstract

Internal carotid artery (ICA) agenesis is a rare developmental anomaly and is most frequently asymptomatic, but it may also present as cerebrovascular accidents. The association with Horner's syndrome is exceptional. We present three cases of agenesis of ICA associated with Horner's syndrome and hypochromia iridum presenting as focal neurological symptoms. A system of collaterals develops as a consequence of agenesis of the ICA, making the majority of cases asymptomatic. Three types of collateral circulations have been described. These collaterals increase the risk of aneurysm formation and the occurrence of life-threatening subarachnoid hemorrhages. The association of congenital Horner's syndrome and hypochromia iridum without anhidrosis is highly suggestive of sympathetic pathway injury early in life. Such signs should prompt further diagnostic evaluation to demonstrate the presence of the agenesis of the carotid canal. Early diagnosis is essential to rule out potentially life-threatening associated vascular anomalies.

Keywords: Horner’s syndrome; carotid artery agenesis; heterochromia iridum.

Figure 1

Photographs of the patients showing miosis, ptosis, and heterochromia iridum (A, left eye; B, C, right eye).

Figure 2

A) MRA showing the circle of Willis with the absence of the left ICA, and dissection of the right ICA, ACmA supplying the left ACA, and left PCmA supplying the left MCA. B) MRA showing the circle of Willis with absence of right ICA and the multiple transcranial anastomosis with the right external carotid artery. C) CTA showing the circle of Willis with absence of right ICA with the anterior communicating artery supplying the right anterior cerebral artery and the right posterior communicating artery supplying the right middle cerebral artery. Abbreviations: MRA, magnetic resonance angiography; ICA, internal carotid artery; ACA, anterior cerebral artery; MCA, middle cerebral artery; CTA, computed tomography angiography; ACmA, anterior communicating artery; PCmA, posterior communicating artery.

Figure 3

CT scan of the base of the skull showing hypoplastic carotid canal at A) left and at B, C) right. A = case 1, B = case 2, C = case 3 Abbreviation: CT, computed tomography.