ORIGINAL ARTICLE

Duplicate origin and fenestration of the middle cerebral arteryon MR angiography

Akira Uchino • Naoko Saito • Yoshitaka Okada •

Reiko Nakajima

Received: 6 October 2011 / Accepted: 12 January 2012 / Published online: 24 January 2012

� Springer-Verlag 2012

Abstract

Introduction Duplicate origin of the middle cerebral

artery (MCA) is rare and has been misdiagnosed or con-

fused as fenestration of the proximal M1 segment of the

MCA. The condition is not a true fenestration and occurs

when two MCA branches arise separately from the termi-

nal segment of the internal carotid artery, and fuse to form

an arterial ring. We researched our institutional records to

determine the prevalence of such cases and investigated its

characteristic features on magnetic resonance (MR)

angiography.

Methods To isolate these cases, we retrospectively

reviewed cranial MR angiographic images of 3,491

patients obtained on either of two 1.5-tesla scanners at our

institution from April 1, 2007 through December 31, 2009.

Results We found four cases of duplicate origin of the

MCA, two cases each on the right and the left (3 men, one

woman), representing a prevalence of 0.11%. All four

arterial rings were small and mimicked fenestration of the

proximal M1 segment. During the same period, we found

three MCA fenestrations, two at the proximal M1 segment

and one at the middle M1 segment. Total prevalence of

duplicate origin and fenestration was 0.20%.

Conclusions In our institution, we observed 0.11%

prevalence of duplicate origin of the MCA on MR angi-

ography, and all were small and mimicked fenestration.

Clinically, an important difference between duplicate

origin and fenestration of the MCA is the potential col-

lateral circulation available from the inferior branch in the

case of saddle embolism occlusion of only the superior

branch when there is duplicate origin of the MCA.

Keywords Cerebral arterial variation � Duplicate origin �Fenestration � Magnetic resonance angiography � Middle

cerebral artery

Introduction

Cerebral arterial fenestrations represent fusion failure

during early gestation. Padget [6] showed that fenestration

of the basilar system are due to partial failure-of-fusion of

the paired longitudinal neural arteries of the 5–7 mm

embryo. The etiology of anterior circulation fenestration is

less well understood. Characteristically, fenestration occurs

when a single artery divides into two arterial channels that

fuse together. The fusion of two different arteries to form

an arterial ring is not fenestration but represents ‘‘dupli-

cate’’ or ‘‘double’’ origin of the fused vessel [7, 9]. How-

ever, previous papers did not differentiate duplicate origin

of the middle cerebral artery (MCA) from MCA

fenestration.

Recently developed 3-dimensional (3D) rotational

angiography has demonstrated fenestrations most fre-

quently at the anterior communicating artery (ACoA),

followed by the MCA [15]. However, because the vessel is

short, most fenestrations recognized at the ACoA may

actually represent the artery’s duplicate origin or complete

duplication. Previously reported MCA variations include

duplicated, accessory, and early bifurcated MCA as well as

fenestration [5, 11, 12]. To our knowledge, no paper

reports ‘‘duplicate origin’’ of the MCA.

A. Uchino (&) � N. Saito � Y. Okada � R. Nakajima

Department of Diagnostic Radiology,

Saitama Medical University International Medical Center,

1397-1 Yamane, Hidaka, Saitama 350-1298, Japan

e-mail: auchino@saitama-med.ac.jp

123

Surg Radiol Anat (2012) 34:401–404

DOI 10.1007/s00276-012-0936-9

Materials and methods

In accordance with the policies for exemption set by our

internal institutional review board, we retrospectively

reviewed MR angiographic images of the supraaortic

region from 5,319 such examinations performed in 3,626

patients in our institution from April 1, 2007 through

December 31, 2009. Informed consent was not obtained

because of the retrospective nature of the clinical study.

Of the 3,626 patients, we excluded 135 with unilateral or

bilateral occlusion of the internal carotid artery (ICA)-

MCA or suboptimal image quality and ultimately

reviewed, and analyzed MR angiographic images of 3,491

patients (2,066 men, 1,425 women).

All patients were examined on either of two 1.5-tesla

scanners (Achieva Nova Dual, Philips Medical Systems,

Best, the Netherlands, or Magnetom Avanto, Siemens

Medical Systems, Erlangen, Germany). The standard 3D

time-of-flight (TOF) MR angiographic protocol was repe-

tition time (TR), 20 ms; echo time (TE), 6.0 ms; flip angle,

16�; field of view (FOV), 20 9 20 cm; and slice thickness,

0.65 mm for Achieva Nova Dual (acquisition time; 5 min

30 s). For Magnetom Avanto, parameters were TR, 22 ms;

TE, 7.0 ms; flip angle, 18�; FOV, 22 9 22 cm; and slice

thickness, 0.7 mm, with acquisition time of 7 min 34 s.

The first author, an experienced neuroradiologist, ret-

rospectively reviewed all MR angiographic images with

special attention to the proximal segment of the MCA.

Results

We found four cases of duplicate origin of the MCA (3

men, one woman), which represented a prevalence of

0.11%. Two cases were on the right and two on the left. All

were small and mimicked MCA fenestration of the proxi-

mal M1 segment (Figs. 1, 2).

We also found three MCA fenestrations, two at the

proximal M1 segment of the right MCA and one at the

middle M1 segment of the right MCA. In these seven

patients (total prevalence, 0.20%), we found one aneurysm,

but it was located outside the fenestration, at the ipsilateral

ACA-ACoA junction (Fig. 3).

Neither computed tomography angiography nor catheter

angiography was performed in these seven cases to eval-

uate the anomaly in more detail.

Discussion

The MCA has several variations [5, 11, 12]. The duplicated

MCA is a small artery arising from the terminal segment of

the ICA that supplies a part of the temporal branches of the

MCA. The accessory MCA arises from the A1 segment of

the anterior cerebral artery (ACA) and supplies a part of the

frontal branches of the MCA. A MCA which undergoes

Fig. 1 Case 2. A 54-year-old man with speech disturbance. Anter-

oposterior maximum intensity projection (MIP) image of magnetic

resonance (MR) angiography shows two arterial branches of the right

middle cerebral artery (MCA) that arise separately from the terminal

segment of the internal carotid artery (ICA) and fuse early to form an

arterial ring, indicative of duplicate origin of the MCA

Fig. 2 Case 4. A 23-year-old woman with transient ischemic attack.

Anteroposterior MIP image of MR angiography shows two arterial

branches of the left MCA that arise separately from the terminal

segment of the ICA and fuse early. The early branching temporopolar

artery (arrow) arises from the inferior branch

402 Surg Radiol Anat (2012) 34:401–404

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major branching 0.5 mm or less from its origin is regarded

as an early bifurcated MCA [11]. These MCA variations,

including duplicated origin and fenestration, may be a

result of residual anastomoses between the primitive vas-

cular network formed between the anterior and middle

cerebral arteries in the 4–5 mm embryo [8]. Various sites

and length of fusion failure cause many types of arterial

variation.

MCA fenestration is rare. Crompton [2] found only one

fenestration in 347 MCAs examined at autopsy, a preva-

lence of 0.28%. Selective cerebral angiographic prevalence

has been reported to be 0.17–0.43% [3, 4, 8]. Bharatha

et al. [1] found two MCA fenestrations among 504 patients

(0.4%) using CT angiography. Extremely high prevalence

(12/208 = 5.8%) of MCA fenestration was recently

reported using 3D rotational angiography [15], but we

doubt this high rate because the gold standard for exam-

ining arterial variation is autopsy, and MR angiographic

study of MCA fenestration is still sparse [13]. Using a

3-tesla scanner, Vuillier and colleagues [16] reported 3

MCA fenestrations among 50 patients, but one of their

cases (represented in their Fig. 1) may instead be the

superimposition of distal arterial branches that have been

misdiagnosed as fenestration. Our MR angiographic series

revealed four duplicate origins and three fenestrations

among 3,491 patients, a total prevalence of 0.20% and

consistent with previously reported prevalence established

by autopsy and conventional angiography.

MCA fenestration is usually small and located at the

proximal M1 segment [13]. Among previously reported

MCA fenestrations, we found some cases of duplicate

origin of the MCA [8, 13]. These two MCA variations have

been confused and reported together but should be differ-

entiated, as should duplicated MCA and accessory MCA.

We speculate that duplicate origin of the MCA is formed

by distal fusion of the duplicated MCA or accessory MCA

(Fig. 4). Duplicate or double origin of the cerebral artery

has been reported in the vertebral artery [9] and in the

posterior inferior cerebellar artery [7]. As noted, we pro-

pose using the term ‘‘duplicate origin’’ of the MCA rather

than fenestration to describe two separately originating

MCA branches that fuse early to form an arterial ring at the

proximal M1 segment.

Gailloud and associates [3] reported a high frequency of

associated early branching of the temporopolar artery from

the inferior limb of the fenestrated segment of the MCA

fenestration and hypothesized that MCA fenestration

results when the early branching temporopolar artery cau-

ses fusion failure of the primitive arterial network of the

MCA. We found this association in only one MCA of

duplicate origin in our series (Fig. 2). Any of the MCA

variations may form by fusion failure of the primitive

arterial network of the MCA, and if failure is complete,

duplicated or accessory MCA may form. On the other

hand, segmental fusion failure may result in formation of

early bifurcated MCA, MCA fenestration, or MCA of

duplicate origin.

Fenestration of the cerebral artery itself usually has no

clinical significance. Extremely rarely, an aneurysm can

arise at the proximal end of the fenestration [8, 14]; we

found no such aneurysm. As well, aneurysms may occur at

the duplicate origin of the MCA but rarely arise at the

junction between the ICA and duplicated MCA [10]. Fre-

quently, saddle embolism at the terminal ICA occludes the

proximal M1 segment of the MCA. In such case, when

there is duplicate origin of the MCA, the inferior branch

may provide important collateral circulation if only the

superior branch is occluded. However, such collateral cir-

culation cannot develop in the case of MCA fenestration.

Fig. 3 Case 6. A 64-year-old man with an aneurysm. Anteroposterior

MIP image of MR angiography shows a tiny fenestration of the right

MCA at its proximal M1 segment. Arrow indicates ipsilateral ACA-

ACoA junction aneurysm

(a) (b) (c)

ICA

ACAMCA

Fig. 4 Schematic illustrations of duplicate origin and fenestration of

the right middle cerebral artery (MCA). Arrows indicate anomalous

arteries. a Duplicate origin formed by fusion of the duplicated MCA.

ICA: internal carotid artery, ACA: anterior cerebral artery. b Dupli-

cate origin formed by fusion of the accessory MCA. c Fenestration of

the proximal M1 segment of the MCA

Surg Radiol Anat (2012) 34:401–404 403

123

Clinically, these may be the important differences between

fenestration and duplicate origin of the MCA.

Our study is limited because it is a retrospective clinical

study, only one neuroradiologist analyzed the MR angio-

graphic images, and only 1.5-tesla and not 3.0-tesla MR

scanners were used. Thus, there may be some selection bias

in our materials; results may have overlooked small varia-

tions, and some tiny variations may have been undetectable.

Conclusions

We propose using the term ‘‘duplicate origin’’ rather than

fenestration of the MCA to identify two separately origi-

nating MCA branches that fuse early to form an arterial

ring at the proximal M1 segment. We found MR angio-

graphic prevalence of this rare MCA variation to be 0.11%.

Clinically, an important difference between duplicate ori-

gin and fenestration of the MCA is the potential collateral

circulation available from the inferior branch in the case of

saddle embolism occlusion of only the superior branch

when there is duplicate origin of the vessel.

Acknowledgments We thank Rosalyn Uhrig, M.A., for editorial

assistance in the preparation of this manuscript.

Conflict of interest We declare that we have no conflict of interest.

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