Abstract
Hypoplasia of the internal carotid artery is a rare congenital abnormality that can present with an ischemic stroke or transient ischemic attacks. We present the case of a 17-year-old male who presented with right hemiparesis and dysarthria. The imaging revealed hypoplasia of the left internal carotid artery and narrowing of the left carotid duct. The patient was managed conservatively. This case highlights the importance of considering ICA hypoplasia as a cause of ischemic stroke in patients with a narrowed osseous canal. Early diagnosis and management can help prevent recurrent strokes.
Keywords: Ischemic vascular accident, Hypoplasia of the internal carotid artery, Narrowed bony canal, Congenital abnormality, Collateral circulation, Cerebral blood flow
Introduction
Hypoplasia of the internal carotid artery (ICA) is a rare congenital condition characterized by a blood vessel with an abnormally tiny diameter. This anatomical variation can significantly reduce cerebral blood flow, increasing the risk of ischemic stroke [1].
Despite its potential for severe neurological consequences, ICA hypoplasia often remains asymptomatic due to the development of collateral circulation. Consequently, the condition is typically discovered incidentally on imaging studies rather than through clinical presentation. While some patients may experience intermittent symptoms such as headaches, torticollis, visual disturbances, or cranial nerve palsies, others may present with catastrophic events like cerebral hemorrhage, ischemic stroke, or seizures [1].
Given the potential for devastating neurological outcomes, early diagnosis and appropriate management are crucial. This case highlights the importance of considering ICA hypoplasia as a cause of ischemic stroke in patients with a narrowed osseous canal [2].
Case presentation
A 17-year-old male patient with no significant medical or surgical history presented to the emergency department with a 1-week history of right-sided weakness (hemiparesis) and difficulty speaking (dysarthria). The patient reported no associated symptoms.
A physical examination revealed right hemiparesis and increased tone in the right upper and lower limbs. Deep tendon reflexes were higher on the right side. The sensory assessment was unremarkable. The cranial nerve testing revealed dysarthria without other deficits. The cardiopulmonary examination was unremarkable.
Initial laboratory investigations, including complete blood count, basic metabolic panel, and coagulation studies, were within normal limits.
The patient underwent a radiological workup. Cerebral CT scan returning in favor of an ischemic stroke involving the superficial and deep left sylvian territory (Fig. 1).
Fig. 1.
C- cerebral CT scan showing a left total sylvian ischemic stroke (red arrow).
The bone window at the base of the skull revealed a reduction in the caliber of the left carotid duct, measuring 3 mm in diameter versus 7 mm on the right (Fig. 2).
Fig. 2.
Cerebral CT scan through the skull base in a bone window: reduced caliber of the left carotid artery measuring 3 mm in diameter versus 7 mm on the right (red arrow).
Contrast injection showed defective opacification of the M1 and M2 portions of the left sylvian artery, as well as the formation of opposite collaterals, rarefaction of the cortical branches of the M3 and M4 portions, and hypoplasia of the left internal carotid artery on a narrowed bony canal (Fig. 3).
Fig. 3.
Cerebral scan with injection; defective opacification of the M1 and M2 portions of the left sylvian artery (red arrow).
Given the difficulty of accessing the carotid canal of bone, as well as the operative risks involved, the neurosurgical team suggested therapeutic abstention.
Discussion
Hypoplasia of the internal carotid artery is a rare congenital anomaly characterized by diffuse narrowing of the arterial lumen, affecting the internal carotid artery from 1 to 2 centimeters above the bifurcation. The anomaly may be bilateral or unilateral.
The real prevalence is likely underestimated due to the presence of asymptomatic patients owing to the sufficient cerebral circulation provided by the polygon of Willis and its anastomoses. It affects adults aged 17 to 64, with an average of 35 years [3].
The circumstances of discovery are highly variable: ischemic stroke, cerebromeningeal hemorrhage, headache, seizure, but very often, it is discovered accidentally.
Internal carotid arterial hypoplasia on the retreci osseous canal is investigated by cerebral MRI coupled with angio-arterial sequences and a skull-base CT scan.
When carotid hypoplasia is suspected on MRI, time-of-flight and fast 3D gradient echo magnetic resonance angiography sequences with Gadolinium contrast enhancement are used to assess the various bypass tracts and their pathways [4].
The discovery of a tiny carotid canal corresponding to a hypoplastic artery on CT is widely recognized and reported in almost all cases. Angioscan with 3D reconstruction confirms the small caliber of hypoplastic internal carotid arteries, collateral circulation, and, above all, the presence of associated intracranial aneurysms.
It is important to identify brain collateral circulation to predict neurological outcome and plan appropriate long-term follow-up.
Vascular supply is variable, and 3 types have been described in the literature.
The first type, the hypertrophied vertebrobasilar circulation, takes over hemispheric vascularization via the large posterior communicating arteries.
The second type, "admirable carotid networks," is also frequent. These networks are usually bilateral. Their afferents are either the internal carotid itself, branches of the external carotid, notably the internal maxillary artery, or both, sometimes joined by the ophthalmic artery.
The third type are the gray nuclei's pseudoangiomatous anastomoses. They receive afferents from the posterior cerebral and posterior choroidal arteries, and they contribute to vascularizing the Willis polygon's anterior branches [5].
The main causes of mortality are associated intracranial vascular events. The most common event is aneurysm formation in the posterior circulation, which causes increased hemodynamic stress across the collateral circulation.
Another vascular complication is acute ischemic stroke, particularly in patients with an incomplete circle of Willis and inadequate collateral circulation. Cerebral artery thrombosis has also been reported.
Management of these patients with acceptable operative risks remains a challenge, requiring aneurysm clipping or endovascular embolization, antiplatelet agents, and long-term follow-up.
For the treatment of carotid hypoplasia, antiplatelet therapy has been chosen for most asymptomatic patients with no vascular complications [6].
Conclusion
Congenital hypoplasia of the internal carotid artery is a rare anomaly. Its recognition is critical for avoiding incorrect management. Echo-Doppler combined with angio-MRI and/or angioscanner suggests congenital hypoplasia of the internal carotid artery. A CT scan of the skull base can confirm the diagnosis by revealing a tiny carotid artery.
Patient consent
Consent was obtained from the patient for publication of this case report and accompanying images.
Footnotes
Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
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