Agenesis of the internal carotid artery with transcavernous anastomosis presenting with an anterior communicating artery aneurysm--a case report and review of the literature

Proposed new classification for internal carotid artery segmental agenesis based on embryologic and angiographic correlation

BACKGROUND AND PURPOSE

Internal carotid artery (ICA) agenesis is a rare anatomical variant that can involve different segments of the ICA. Although many authors proposed their own classifications of this variant basing on different criteria, none of these allows to include all the cases described in the literature. The aim of the authors is to propose a new classification that allows to include all cases of ICA agenesis described until now.

MATERIALS AND METHODS

The study is based on the review of all the cases of ICA agenesis described in the literature and of the classifications already proposed. After the analysis of these cases, we looked for the limits of each classification to elaborate a new more complete one.

RESULTS

We found 228 cases of ICA agenesis. Among them 40 were not includible in the existing classifications. For this reason, we proposed a new classification based on the type of flow compensation and on the embryological events that determine the different variants. The flow is compensated in Type I by the Circle of Willis; in Type II by the non-regression of an embryonic artery; in Type III by the presence of an arterio-arterial anastomosis and in Type IV by external-internal carotid arteries anastomoses.

CONCLUSION

After the literature review, we proposed a new comprehensive classification based on the detailed analysis of arterial embryology. Even if all the embryological details that determine this complex variant are not completely understood yet, this classification allows to include all the cases described in literature.

ICA agenesis with transcavernous anastomosis: a systematic review

PURPOSE

To present two cases of Internal Carotid Artery (ICA) agenesis and conduct a systematic review to assess for associations with other anomalies and intracranial aneurysms.

METHODOLOGY

We performed a retrospective review of published cases of patients with ICA agenesis with intercavernous anastomosis in MEDLINE database on August 2022 using search terms "internal carotid artery", "agenesis" and "transcavernous anastomosis". We also included two cases of ICA agenesis with type D collateral that we encountered.

RESULTS

Total of 45 studies that included 47 patients and two of our cases resulted in 49 patients. Only 70% of studies reported the location of a collateral vessel of which more than two-thirds were on the floor of sella. More than half of the vessels connected cavernous segments of ICA. A1 segment ipsilateral to the side of ICA agenesis was absent in most of the cases but was not true for all cases. Aneurysm was seen in more than one-quarter of the patients. It can also mimic microadenoma as in prior reported cases as well as in one of our cases.

CONCLUSION

ICA agenesis with type D collateral is a rare anomaly but clinically relevant due to the increased risk of an aneurysm or mimic microadenoma or false alarm for occlusion of ICA but knowledge of this rare variant can help in better management of these patients.

Cerebrovascular disorders associated with agenesis of the internal carotid artery: Findings on digital subtraction angiography

Objective

Agenesis of the internal carotid artery (ICA) is a rare vascular condition that is complicated by intracranial aneurysms and rete mirabile. The altered hemodynamics caused by this distinctive cerebrovascular angioarchitecture can cause ischemic or hemorrhagic accidents. Data on clinical and radiographic features have been limited to describing this vascular pattern. We present five cases of agenesis of the internal carotid artery confirmed by digital subtraction angiography (DSA) and further investigate the influence of altered angioarchitecture on the integrity of intracranial morphology.

Methods

Cases of ICA anomalies were screened from the patients who underwent DSA in two hospitals. Clinical manifestation, radiographic features, management, and outcomes were retrospectively reviewed.

Results

Five patients [mean age 44 years (range, 30–65 years)] were included. Two patients presented with subarachnoid hemorrhage, one with cognitive impairment, one with dizziness, and one with intermittent headache. DSA demonstrated that three cases were complicated by intracranial aneurysms, one by dural arteriovenous fistula, and one by rete aneurysm. Three patients underwent endovascular treatment and one underwent bypass surgery. No patient died or experienced cerebrovascular accident during short-term follow-up.

Conclusions

ICA agenesis can be complicated by disorders such as intracranial aneurysm, rete aneurysm, and dural arteriovenous fistula. This suggests that ICA agenesis is associated with a tendency towards disrupted cerebrovascular homeostasis resulting from altered hemodynamics.

Agenesis of the right internal carotid artery and aqueductal stenosis in a child with hydrocephalus, the role of endoscopic third ventriculostomy: a case report

Agenesis of the internal carotid artery (aICA) is a rare congenital vascular condition that can affect one or both sides of the patient. Most patients remain asymptomatic, but ischemic/hemorrhagic stroke, intracranial aneurysm, and other neurologic findings can occur. CT scan can demonstrate the absence of the bony carotid canal and helps to differentiate a complete aICA from aplasia or hypoplasia. The association of aICA and aqueductal stenosis (AS) has never been reported in the literature. We report the case of a 9-year-old with agenesis of the right ICA associated with AS and hydrocephalus, which was treated successfully with an endoscopic third ventriculostomy (ETV). We review the literature looking for the association of the clinical findings and the evolution of the patient.

Congenital unilateral absence of the internal carotid artery associated with aneurysms of different arteries: a review

There are four hundred and sixty- six cases of absent unilateral (398) and bilateral (68) internal carotid artery (ICA) published in online books, abstracts and original articles from 2020. to 2021. Of the 398 cases of absent unilateral ICA, 95 were associated with aneurysm. The analysis of these cases includes age, nationality and gender, location of aneurysm(s), description, and scheme of carotid-vertebrobasilar angioarchitecture mode in the brain base, as well as hypothesis on embryonic background of accompanying vascular variations and abnormalities. Calculated ratio between number of absent unilateral ICA cases and number of absent bilateral ICA cases is 5.8:1. The ratio between the total number of cases of absent unilateral ICA and those associated with aneurysms is 4.2:1. The association between the posterior communicating-middle cerebral anastomosis and intercavernous (trans-sellar or intercarotid) channel with absence of both anterior cerebral and anterior communicating arteries is common. More than half of the cases with aneurysms are located at the anterior segment vessels of the cerebral arterial circle. This review is based on the description and explanation of embryology and morphology of absent unilateral ICA with aneurysms, which would be significant contribution to published literature on this topic, especially due to the fact that nothing similar has been published since 1957.

Cerebral Aneurysms with Internal Carotid Artery Agenesis: A Unique Case Similar to Moyamoya Disease and Literature Review

Internal carotid artery (ICA) agenesis/aplasia is occasionally accompanied with cerebral aneurysms caused by hemodynamic stress. If the aneurysms are located around the circle of Willis, they are managed with clipping or coil embolization. Herein, we report a case of ICA agenesis with perforating artery aneurysms treated successfully with revascularization. Moreover, a literature review of ICA agenesis with cerebral aneurysms was performed to compare with the current case. We conducted a literature review using data from PubMed. A secondary search was also performed by reviewing the references of each article previously searched. In our case, the aneurysms shrank and disappeared after direct and indirect bypass surgeries, and indirect bypass developed as in moyamoya disease (MMD). The epidemiological and clinical features of aneurysms accompanied with ICA agenesis were identified via a literature review. Aneurysms with ICA agenesis categorized as type F based on the Lie classification system, or referred to as rete mirabile, are occasionally located in an untreatable site; hence, they cannot be treated with clipping or coil embolization. Moreover, results showed that previous studies did not use revascularization for the treatment of aneurysm. In conclusion, if an aneurysm with ICA agenesis is difficult to approach directly or via an endovascular procedure, revascularization can be a treatment option.

Unilateral absence of the internal carotid artery associated with anterior communicating artery aneurysms: Systematic review and a proposed management algorithm

Background:

Absence or hypoplasia of the internal carotid artery (ICA) is a rare congenital anomaly that is mostly unilateral and highly associated with other intracranial vascular anomalies, of which saccular aneurysm is the most common. Blood flow to the circulation of the affected side is maintained by collateral pathways, some of which include the anterior communicating artery (Acom) as part of their anatomy. Therefore, temporary clipping during microsurgery on Acom aneurysms in patients with unilateral ICA anomalies could jeopardize these collaterals and place the patient at risk of ischemic damage. In this paper, we review the literature on cases with a unilaterally absent ICA associated with Acom aneurysms and provide an illustrative case.

Methods:

We combined our experience of one case of a unilaterally absent ICA associated with an Acom aneurysm with the 33 existing publications on the same subject in the literature, for a total of 40 cases. We provide a detailed systematic literature review of this association of vascular anomalies, exploring different aspects regarding the collateral pathways and how they impact management strategies and propose a management algorithm to deal with such association.

Results:

The mean age was 48.2 ± 16.5 years. The aneurysmal rupture was the most common presentation (75%). Agenesis was observed in 70% of patients, followed by hypoplasia (20%) and, finally, aplasia (10%). Lie Type A was the most common pattern of collaterals (50%), with Types B and D being of almost equal proportions. Most aneurysms were located at the A1-Acom junction contralateral to the anomalous side (Fisher’s Exact test; P = 0.03). One case of temporary clipping was reported in the literature.

Conclusion:

Acom aneurysms in patients with unilateral ICA anomalies, given they are more commonly present contralaterally, could be of acquired etiology, warranting periodic screening in asymptomatic patients. Temporary clipping might be safe in patients with Type D collateral pattern, while those with Types A or B may require intraoperative rupture risk assessment and a tailored management plan to avoid disrupting collateral flow and causing ischemia.

A case of right internal carotid agenesis with associated transcavernous anastomosis revealed by transient ischemic attack

Agenesis of the internal carotid artery (ICA) is a rare congenital vascular disorder of the cerebral circulation. CT scan of the skull base disclosing complete absence of the bony carotid canal helps to differentiate an agenesis from aplasia or hypoplasia. Although most of the patients remain asymptomatic (thanks to the sufficient collateral circulation provided by the circle of Willis) cerebral infarcts, transient ischemic attacks or intracranial aneurysms have been rarely described in association with agenesis of the ICA. Most often, the vascular territory of the involved ICA is supplied by the contralateral carotid artery and from the vertebrobasilar circulation through the anterior and posterior communicating arteries, respectively. However, collateral supply can also be provided thanks to a transcavernous anastomosis, an aberrant vascular communication between the cavernous portions of the ICAs coursing through the sella turcica. We report here the case of a 55-year-old man with right carotid agenesis and associated transcavernous anastomosis revealed by transient ischemic attack. Embryogenesis, imaging findings, possibilities of collateral circulation and potential complications have also been discussed.

[Segmental agenesis of the cervical internal carotid artery with collateral blood supply from the ascending pharyngeal artery and intercavernous anastomosis: a clinical case and literature review]

The article presents a clinical case of segmental agenesis of the cervical ICA with collateral blood supply to the ICA territory through the intercavernous anastomosis and ascending pharyngeal artery with the branching primitive stapedial artery - the aberrant ICA variant. A feature of the case is a unique combination of the intercavernous anastomosis and the aberrant ICA, which provide collateral blood flow in cervical ICA agenesis. In the world literature, there are no reports of similar combinations. The discussion provides information on the stages of circle of Willis formation and presents a literature review of cases of intercavernous anastomoses associated with ICA agenesis.

Agenesis of the Internal Carotid Artery with Transcavernous Anastomosis Associated with Anterior Communicating Artery Aneurysms

Agenesis of the internal carotid artery (ICA) is a rare congenital anomaly. Recently, several cases of ICA agenesis have been associated with cerebral aneurysms. We present the seventh case of ICA agenesis with transcavernous anastomosis associated with cerebral aneurysms. A 47-year-old man presented with transient numbness of his left hand. Magnetic resonance angiography indicated the presence of anterior communicating artery (ACoA) aneurysms. Digital subtraction angiography revealed two ACoA aneurysms, absence of the left ICA, and an anomalous collateral vessel connecting the cavernous portions of both internal carotid arteries, which was considered to be a transcavernous anastomosis. Head bone window computed tomography with contrast medium revealed the absence of the petrous carotid canal on the left suggesting the diagnosis of left ICA agenesis. The ACoA aneurysms were clipped successfully, and the postoperative course was uneventful.

Congenital absence of internal carotid artery with intercavernous anastomosis: Case report and systematic review of the literature

The absence of an internal carotid artery is a rare congenital anomaly. In the absence of the internal carotid artery, collateral circulations develop through the circle of Willis, persistent embryonic arteries or transcranial collaterals of the external carotid artery. Six pathways of collateral circulation have been described. Intercavernous anastomosis is between cavernous segments of the bilateral internal carotid arteries and is rarely seen. Patients with an absence of the internal carotid artery can be completely asymptomatic. However, these patients can present with subarachnoid hemorrhage or stroke accompanying cerebral aneurysm or abnormal collateral. We combined our case with 33 previous publications to form a retrospective series including 35 cases of unilateral internal carotid artery agenesis with intercavernous anastomosis.

Left internal carotid artery agenesis with trans-sellar collateral and a right aortic arch: Case report

We present a case of unilateral internal carotid artery (ICA) agenesis with trans-sellar anastomosis associated with a right aortic arch, and discuss the embryonic development and clinical implications of this condition. A 26-year-old woman without significant medical history was referred to our hospital complaining of tinnitus. She denied any other symptoms, and examination did not reveal any other neurological deficits. Radiological examinations showed agenesis of the right ICA with trans-sellar anastomosis, and a right aortic arch. This vascular configuration reflects the anatomical homology with avian vascular structure. Recognition of this anomaly has important implications for clinical situations, such as the planning of carotid or transsphenoidal surgery, the management of thromboembolic disease, and the surveillance and detection of associated cerebral aneurysms.

Acute infarction in a patient with agenesis of the internal carotid artery and transcavernous anastomosis

A 70-year-old man presented with left-sided weakness and dysarthria. His brain MRI and magnetic resonance angiography demonstrated acute infarctions in the bilateral middle cerebral artery territories in a setting of agenesis of the right internal carotid artery (ICA) with transcavernous anastomosis, a rare developmental anomaly. In this setting, atherosclerotic disease in the unilateral common carotid artery or ICA can induce acute infarctions in the bilateral anterior circulation.

Intercavernous connection between the internal carotid arteries

Intercavernous communication between the left and right internal carotid arteries is an uncommon entity. The authors report a case involving a pediatric patient who was found to have such a vascular anomaly. Such variations should be known by the neurosurgeon so as to avoid misdiagnosis and potential iatrogenic injury.