Congenital absence of bilateral Internal Carotid Artery: A case report

R. Bhuvaneshwari*, R. Gayathri

Senior Consultant, Neurology and Neurophysiology, Kauvery Hospital, Chennai, India

Physician assistant, Department of Neurology, Kauvery Hospital, Chennai, India



Agenesis of bilateral Internal Carotid Artery (ICA) is a rare and infrequent abnormality. People with this abnormality would have adequate collateral circulation and remain asymptomatic. It is usually diagnosed after a stroke, seizure, transient ischemic attack or headache, when images are analyzed.

Case Presentation

A 45-years-old male, with no background medical illness, presented to the emergency department with right sided weakness and speech impairment. He lived alone, and was found to be unconscious at home and was later brought to emergency department.

On examination, he had right hemiplegia and global aphasia.

Magnetic Resonance Imaging (MRI) of brain showed large areas T2/Flair hyperintensity, with diffusion restriction in left fronto-tempero-parietal, subcortical left centrum semiovale and corona radiata, which indicated large acute left Middle Cerebral Artery (MCA) territory infarct, with mass effect and midline shift of 7 mm to right. It also showed multiple lacunar infarcts of left cerebellum and right frontoparietal region, with minimal uncal herniation; also, mass effect on midbrain was seen but no hemorrhage (Fig. 1).




Fig. 1. Axial MRI brain showing acute infarcts of the left MCA and bilateral ACA.

MR Angiogram (MRA) brain showed occluded left MCA and bilateral Anterior Cerebral Artery (ACA). Left MCA M1 segment was just visualized with occlusion of distal M1, and sparse cortical branches. Right MCA was supplied by posterior circulation.

MRA neck vessels showed thin caliber of bilateral Common Carotid Arteries, at origin and proximal third, and narrowing of bilateral carotid bulbs with non-visualization bilateral ICA origin, representing congenital absence of both Internal Carotid Artery. Vertebral arteries appeared normal. The collateral flow was through vertebrobasilar supply and posterior circulation (Figs. 2-4).




Fig. 2. Loss of Flow related signals of the Bilateral intracranial ICA. There was a large calibre right PCOM perfusing both middle cerebral arteries.




Fig. 3. Large PCOM perfusing middle cerebral artery.




Fig. 4. Axial CT brain in bone windows showing agenesis of the bilateral carotid canals.

He arrived outside the “window” period, hence high dose of Aspirin and Statin was given, and started on antiedema measures in view of malignant infarct.

On the next day, he had deterioration in his conscious level. Follow up CT Brain showed no new changes.

In view of massive stroke and drop in consciousness level, left fronto-tempero-parietal decompression craniotomy surgery was done. He was on mechanical ventilator. Despite maximal therapy patient continued to deteriorate and died because of his massive stroke and poor blood supply to brain with congenital agenesis of bilateral ICA.


Bilateral ICA agenesis is a rare congenital anomaly. This condition occurs more often unilateral, and often on the left side. Our case is peculiar because it is bilateral. ICA agenesis has to be distinguished from acquired stenosis, as the management for the two conditions is different. The absences are not common, and oftentimes remain undetected and unexplored due to sufficient collateral blood flow. Origin of such bilateral absence is congenital, with lack of proper channel and vessel development during the fetal period.

Patients with bilateral internal carotid artery agenesis are at high risk of development of aneurysms and cerebrovascular events. It is estimated that the prevalence of intracranial aneurysms in the general population ranges from 2 to 4%. In contrast, among patients with congenital absence of the ICA, this range increases to 24 to 34% [1,2].

The diagnosis of congenital absence of ICA can be made by imaging like computed tomography angiography (CTA) and magnetic resonance angiography (MRA). Congenital hypoplasia/aplasia of the ICA should be suspected on imaging when the ICA is not visualized 1-2 cm beyond the carotid bulb along with a narrow or aplastic carotid canal. The finding of an absent or hypoplastic carotid canal is also radiological sign of congenitally anomalous ICA.

No specific treatment is possible to re-establish ICA. Diagnosis of anomalies involving the carotid system should be the signal for rigorous follow-up focused on early identification of potentially fatal changes, such as cerebral aneurysms.


(1)       Steer AC, Rowe PW. Bilateral agenesis of the internal carotid artery: case report and approach to management. J Paediatr Child Health. 2008;44(9):511-3.

(2)       Elazab NE, Riel-Romero RM, Gonzalez-Toledo E. Internal carotid artery agenesis and basilar artery aneurysm with third nerve palsy. Pediatr Neurol. 2010;42(6):451-4.



Dr. Bhuvaneshwari Rajendran

Senior Consultant – Neurology & Neurophysiology



Ms. R. Gayathri

Physician assistant