American Journal of Neuroradiology 24:1133-1135, June-July 2003
© 2003 American Society of Neuroradiology
Case Report
HEAD AND NECK
Persistent Stapedial Artery: MR Angiographic and CT Findings
Turgut Yilmaza,
Cem Bilgenb,
Recep Savasa and
Hudaver Alpera
a Department of Radiology, Ege University Hospital, Izmir, Turkey
b Department of Radiology and Ear, Nose, and Throat Surgery, Ege University Hospital, Izmir, Turkey
Address reprint requests to Turgut Yilmaz, Ege University Hospital Department of Radiology, 35100-Izmir, Turkey
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Abstract
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Summary: A 2-year-old girl was found to have a pink pulsatile
mass behind the right tympanic membrane on physical examination.
We report the high-resolution CT and MR angiographic findings
of persistent stapedial artery with hypoplasia of the A1 segment
of the right anterior cerebral artery.
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Introduction
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A persistent stapedial artery is a rare congenital vascular
anomaly that may present a technical problem during middle ear
surgery. The stapedial artery is transiently present in normal
fetal development and connecting the future external carotid
artery to the internal carotid artery (ICA). In this article,
we report the high-resolution CT and MR angiography findings
of persistent stapedial artery with hypoplasia of A1 segment
of right anterior cerebral artery.
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Case Report
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A 2-year-old girl was found to have a pink pulsatile mass behind
the right tympanic membrane during routine otoscopic examination.
Glomus tympanicum was suspected clinically. The patient did
not have any complaint. The other findings from the physical
examination and the patient’s vital signs were unremarkable.
Hearing loss was not established. The patient’s short
medical history was also normal. She was born after an uncomplicated
40-week pregnancy. The results of biochemical analysis and the
hematologic profile were normal. High-resolution temporal-bone
CT examination was performed with a Somatom Plus scanner (Siemens,
Erlangen, Germany) with section thickness of 1 mm and a pitch
of 1. The CT study showed absence of the right foramen spinosum
(
Fig 1). The left foramen spinosum was normal. The right internal
carotid artery had an aberrant course running laterally in the
middle ear cavity without an osseous canal. Soft-tissue attenuation
was seen connecting the right internal carotid artery to the
tympanic segment of the facial nerve (
Fig 2). A small vascular
structure left the carotid canal and entered the middle ear.
It continued toward the stapes and then traveled in small segment
of the facial canal. Following the facial nerve canal, the small
vascular channel reached the middle cranial fossa (
Fig 3). We
then performed multisection 3D time-of-flight MR angiography
(TR/TE, 39/7; matrix, 192
x 512; section thickness, 32 mm) with
a 1.5-T MR machine (Vision; Siemens, Erlangen, Germany). The
MR angiograms showed hypoplasia of the petrous vertical portion
of the right internal carotid artery, the aberrant course of
the right internal carotid artery in the middle ear, and the
collateral supply of the right internal carotid via inferior
tympanic and caroticotympanic anastomoses (
Fig 4). The stapedial
artery arose from the aberrant right ICA (
Fig 5), and hypoplasia
of the right A1 segment of the anterior cerebral artery was
observed (
Fig 6).
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FIG 1. Axial CT scan shows a normal left foramen spinosum (single white arrow) and an absent right foramen spinosum. The right ICA is laterally displaced into the middle ear (double white arrow). The left ICA is in a normal position (black arrow).
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FIG 2. Axial images from inferior to superior: top left, top right, bottom left, and bottom right. The facial canal (arrowhead) is enlarged in the first three images. The small vascular channel can be seen leaving the vertical aberrant segment of right ICA at the level of the stapedial crura in the last image (arrows).
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FIG 3. Axial images from inferior to superior: top left, top right, bottom left, and bottom right. Following the facial nerve canal (arrow in the first three images), the small vascular channel reaches the middle cranial fossa (arrow, last image). This represents the position of the geniculate ganglion turn of the facial nerve canal.
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FIG 4. Coronal 3D time-of-flight MR angiogram shows hypoplasia of the petrous vertical portion of the right ICA, the normal left internal carotid artery (double arrow), and the collateral supply of the right ICA.
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FIG 6. Axial MIP MR angiogram shows hypoplasia of the right A1 segment of the anterior cerebral artery.
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Discussion
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A persistent stapedial artery is a rare vascular anomaly, with
a histopathologic incidence of two in 1400 specimens (
1).This
rare congenital vascular anomaly can be appear as a reddish
pulsatile mass on otoscopic examination, or it can be incidentally
found during middle ear surgery. Inadvertent damage to a large
persistent stapedial artery results in profuse bleeding, and
it can be confused with other middle ear masses (
2). For these
reasons, the preoperative diagnosis of a persistent stapedial
artery is important. The differential diagnosis of a persistent
stapedial artery can be made on the basis of CT, conventional
angiography, or MR angiography findings.
The embryologic development of the branchial system produces six paired aortic arches and corresponding arteries. The six arches develop in numerical order and are not all present at the same time. The first arch gives rise to the mandibular artery, which later regresses. Embryologically, the primitive second aortic arch gives rise to the hyoid artery that, in turn, gives rise to the stapedial artery near its origin from the internal carotid in the 40th or 50th week of the fetal life. The stapedial artery pierces the stapes primordium, leaving its imprint as the obturator foramen and producing its annular shape. In an embryo with a diameter of 12–15 mm, the stapedial artery divides into a dorsal branch (future meningeal artery) and a ventral division (maxillary and mandibular arteries). Finally, branches from the stapedial artery link with the branches developing from the external carotid artery. While this annexation is taking place, the hyoid artery and stem of the stapedial artery disappears during the third fetal month (3).
When a stapedial artery persists in postnatal life, the middle meningeal artery arises from it. The foramen spinosum is absent; it normally contains the middle meningeal artery. A persistent stapedial artery arises from the petrous ICA, entering the hypotympanium in an osseous canal. It goes upward between the crura of the stapes. Then, it enters the facial canal and extends a short distance, together with facial nerve. Two millimeters behind the geniculate ganglion, it leaves the facial canal and then travels anteriorly and cephalad in the extradural space of the middle cranial fossa (3–5).
A persistent stapedial artery may be isolated anomaly, or it may occur with an aberrant ICA. In the latter case, the vertical portion of the ICA is absent. The proximal and distal segments of the ICA connect via inferior tympanic and caroticotympanic anastomoses (4, 5). In our case, the persistent stapedial artery was associated with an aberrant ICA. The other vascular anomaly was hypoplasia of the right A1 segment of the anterior cerebral artery. To our knowledge, this association has not been reported in literature. This is such a common variation that it is not likely to be related to the persistent stapedial artery.
A persistent stapedial artery can cause conductive hearing loss and pulsatile tinnitus, but most patients reported in literature were asymptomatic (6). If a persistent stapedial artery is symptomatic and if ligation is considered, an arteriogram is obtained to ensure that the artery does not represent an end artery or that it does not provide a substantial supply to sensitive tissue. In the present case, the patient did not have any complaint, and the persistent stapedial artery was diagnosed incidentally. Ligation of the persistent stapedial artery can be performed in symptomatic patients.
When a pulsatile mass is present behind the tympanic membrane, the differential diagnosis includes a glomus tympanicum tumor and an aberrant carotid artery or jugular bulb. The diagnosis can be suggested by absence of the foramen spinosum on the CT scans; however, this finding is nonspecific and may be seen when the middle meningeal artery takes its origin from the ophthalmic artery.
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Conclusion
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The persistent stapedial artery is a rare vascular anomaly.
When a pulsatile mass is present behind the tympanic membrane
or when a persistent stapedial artery is suspected, the differential
diagnosis can be made by means of CT, MR angiography, or conventional
angiography to prevent complications with internal ear surgery.
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References
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Received August 23, 2002;
accepted after revision October 21, 2002.
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Abstract
Introduction