Multiple intracranial vessel fenestrations: A report of two cases from a tertiary care center

Amlan Kusum Datta; Subhadeep Gupta

doi:10.4103/jasi.jasi_167_21

CASE REPORT

Year : 2022 | Volume : 71 | Issue : 3 | Page : 248-250

Multiple intracranial vessel fenestrations: A report of two cases from a tertiary care center

Amlan Kusum Datta, Subhadeep Gupta
Department of Neurology, Bangur Institute of Neurosciences, Institute of Post Graduate Medical Education and Research, Kolkata, West Bengal, India

Date of Submission	30-Sep-2021
Date of Decision	17-Apr-2022
Date of Acceptance	09-Jun-2022
Date of Web Publication	20-Sep-2022

Correspondence Address:
Dr. Amlan Kusum Datta
Department of Neurology, Bangur Institute of Neurosciences, Institute of Post Graduate Medical Education and Research, 52 1/A Sambhu Nath Pandit Street, Bhowanipore, Kolkata - 700 020, West Bengal
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jasi.jasi_167_21

Abstract

Intracranial vascular fenestrations are unique anatomical anomalies, consequential to developmental perturbations in vessel embryology. The importance of identification rests on its frequent association with disturbed cerebral flow dynamics and intracranial pathologies. Herein, we report two cases from the same institute of such an association. One presented with an isolated intraventricular hemorrhage, found to have basilar artery fenestrations, whereas the other presented with subarachnoid hemorrhage, with fenestrations involving both the anterior and posterior circulations. Neither of the two patients had any evidence of aneurysms, arteriovenous malformations, or dissections and were managed conservatively. Being acquainted with the anatomy and pathophysiology of these vascular aberrations are paramount in achieving optimal patient outcomes in certain vascular catastrophes.

Keywords: Angiography, embryology, fenestrations, neuroanatomy, subarachnoid hemorrhage

How to cite this article:
Datta AK, Gupta S. Multiple intracranial vessel fenestrations: A report of two cases from a tertiary care center. J Anat Soc India 2022;71:248-50

How to cite this URL:
Datta AK, Gupta S. Multiple intracranial vessel fenestrations: A report of two cases from a tertiary care center. J Anat Soc India [serial online] 2022 [cited 2023 Mar 24];71:248-50. Available from: https://www.jasi.org.in/text.asp?2022/71/3/248/356491

Introduction

A “fenestration” refers to an anatomical aberration, wherein a vessel segregates into two or more vascular channels, which fuse into a single lumen along its distal course. The high degree of variability in the reported prevalence of intracerebral arterial fenestrations, with rates ranging from <1% up to as high as 60%,^[1] may be attributed to the lack of uniformity among the nature of imaging modalities, ranging from noninvasive angiograms to more advanced high-resolution three-dimensional digital subtraction angiography (DSA) techniques. Apart from the intriguing embryological aspect, interest in fenestrations stem from their propensity to be associated with intracranial pathologies such as subarachnoid hemorrhages (SAH), strokes, and dissections.^[2] Albeit controversial, it is sumptuous to assume arterial fenestrations to be a marker of neurovascular pathologies owing to their supposed ability to alter microvascular flow dynamics. Herein, the authors report two cases of isolated intracranial vascular events associated with intracranial arterial fenestrations, without any other identifiable bleeding sources.

Case Report

Patient 1

A 40-year-old male, without known vascular risk factors, presented with a thunderclap headache. Neurological examination revealed the presence of neck stiffness without any other focal deficits. Computed tomography (CT) scan, which was done at our institute approximately a week after the initial event, revealed an intraventricular hemorrhage in the fourth ventricle, with the presence of hydrocephalus [Figure 1]. Magnetic resonance angiography (MRA), using a 3 Tesla magnetic resonance imaging scanner, Time of flight sequence of intracranial vessels revealed two fenestrations of the basilar artery [Figure 1b] with the presence of bilateral fetal posterior cerebral arteries (fPCAs). No other pathologies such as aneurysms, dissection, or arteriovenous malformations were noted. In absence of any therapeutic scope, the patient was managed conservatively, and an invasive angiographic study was not performed. He was discharged in hemodynamically stable condition and followed up for 1 year, till which he has remained asymptomatic.

Figure 1: Upper panel: Noncontrast CT Brain (a) blood in the fourth ventricle (black arrowhead) and dilatation of temporal horn of lateral ventricle suggestive of hydrocephalous. Time of flight MR angiography, (b and c) left VA terminating as a left posterior inferior cerebellar artery, two fenestrations in the basilar artery (white arrow), bilateral fetal PCA originating from ICA (white arrowhead), and hypoplastic A1 segment of right ACA. Lower panel: Noncontrast CT Brain, (d) blood in Sylvian fissure (black arrowhead). 3D DSA after right ICA injection, (e) reveals fenestration of M1 segment of the right middle cerebral artery (white arrowhead). DSA after left VA injection, and (f) large distal left vertebral artery fenestration (black arrow). CT: Computed tomography, MR: Magnetic resonance, VA: Vertebral Artery, PCA: Posterior Cerebral artery, ICA: Internal carotid artery, ACA: Anterior cerebral artery, DSA: Digital subtraction angiography

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Patient 2

A 35-year-old nonhypertensive male, presented with “thunderclap headache,” followed by transient loss of consciousness, without any focal neurological deficit. Noncontrast CT brain showed the presence of subarachnoid hemorrhage involving the right Sylvian fissure [Figure 1]d. Since MRA was unremarkable, DSA of intracranial vessels was conducted, after obtaining prior informed patient consent. Although no aneurysms could be detected, following injection of contrast into the left vertebral artery, a fenestration was noted in the same vessel. Another fenestration was seen involving the proximal right middle cerebral artery (MCA), following injection into the right internal carotid artery (ICA). Like the previous patient, he too was managed conservatively and made an uneventful recovery. He is into the 9^th month of follow-up and his course has been uneventful to date.

Discussion

Recent advances in angiographic techniques, particularly with the development of three-dimensional DSA techniques, have enabled the better demonstration of thin fenestration channels, which previously remained occult on traditional angiographic methods despite evidence of their more frequent existence from postmortem and surgical series^[3],[4],[5]

Fenestrations may arise due to either failure of fusion of paired embryological vessels or from a failure of complete obliteration of a primitive vascular anastomotic network.^[6] Naturally, the duplicated vascular channels comprise distinct endothelial and muscular layers, occasionally sharing a common adventitia.^[6] As with other morphological variations, fenestrations too are located frequently at or near the midline, with the anterior communicating and basilar arteries (BA) being most involved.^[1] BA fenestrations, believed to be the result of a failure of fusion of paired longitudinal neural arteries, can occur anywhere along its course, with the vertebral-basilar junction being the favored location^[2],[6] [Figure 2]a. The presence of bilateral fPCAs as noted in the first case [Figure 1]c, perhaps represent an attempt to compensate for the perturbed basilar artery flow.

Figure 2: (a) DSA image depicting basilar artery fenestration with corresponding. (b) Line diagram showing a fenestration of the BA, adjacent to the site of origin of the AICA, proximal to origins of SCA and PCA, distal to the origin of PICA. (c) Line of normal embryologic fusion along midline of two longitudinal neural arteries to form the basilar artery. DSA: Digital subtraction angiogram, BA: Basilar artery, AICA: Anterior inferior cerebellar artery, SCA: superior cerebellar artery, PCA: Posterior cerebral artery, PICA: Posterior inferior cerebellar artery

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The primitive ICA divides into a cranial and caudal division, the latter of which gives rise to the primitive anterior choroidal artery (ACho). Numerous arterial twigs develop distal to the ACho, which subsequently form the MCA. Errors in the regression of one or more of these vascular channels result in the origin of MCA fenestrations^[7] [Figure 3]. The coexistence of multiple fenestrations, that too, arising from posterior and anterior circulations, is an extremely unlikely event.^[1] Double fenestrations of BA, as in the first case, involving its proximodistal segments represent fusion anomalies of both the caudal rami of ICA and paired longitudinal arteries [Figure 2].^[6] Therefore, although the adult morphological predisposition mimics an isolated posterior circulation developmental aberration, it might actually represent a fusional defect of both the anterior and posterior circulation.

Figure 3: (a) Digital subtraction angiography image depicting fenestration of MCA with corresponding. (b) Line diagram showing fenestration of proximal right MCA (M1). (c) normal fetal development of the MCA from arterial twigs arising from the ICA, distal to the ACA. MCA: Middle cerebral artery, ICA: Internal carotid artery, ACA: Anterior cerebral artery

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The frequent association of fenestrations with intracranial pathologies may be attributed to altered microvascular flow dynamics and histopathological aberrations of fenestrated vessels.^[8] Although generally believed to be caused by aneurysmal rupture, in 5%–15% of cases of SAH, no bleeding source can be delineated.^[9] Hudák et al.^[8] had previously reported a high incidence of arterial fenestrations in cases of angiographically negative SAH. Even though autopsy studies have revealed the presence of muscular defects in walls of arteries affected by fenestrations,^[10] definite evidence implicating fenestrations as a cause of SAH is lacking.

The presence of an unexplained intracranial vascular pathology might be a compelling reason to thoroughly search for intracranial fenestration anomalies using high-resolution invasive angiography techniques if need be. However, larger population-based studies are needed before assuming that these defects may prospectively give rise to de novo intracranial bleeding or other pathologies.

Consent

Informed consent obtained.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Acknowledgment

Our sincere gratitude to the patients and their kin for their kind cooperation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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