AJR 2001; 177:925-927
© American Roentgen Ray Society
Distinctive MR Imaging Appearance of Hemorrhagic Cerebral Aneurysms Associated with Atrial Myxoma
Bryan J. Hwang1,
Molly M. Connelly2 and
Michael H. Lev1,2
1
Harvard Medical School, 25 Shattuck St., Boston, MA 02115.
2
Department of Radiology, Massachusetts General Hospital, GRB285, P. O. Box
9657, Boston, MA 02114-9657.
Received January 8, 2001;
accepted after revision April 20, 2001.
Address correspondence to M. H. Lev.
Introduction
Intracranial involvement by atrial myxoma is a rare cause of neurologic
deficit; diagnosis depends on a high index of suspicion and an awareness of
the clinical and radiologic manifestations of this entity
[1]. When intracranial
hemorrhage is a clinical possibility, a gradient-echo MR susceptibility scan,
which is highly sensitive for detecting both the acute and chronic stages of
hemorrhage, should be performed
[2]. We present a case of
hemorrhagic cerebral aneurysms associated with atrial myxoma that shows
distinctive MR imaging features.
Case Report
A 73-year-old woman presented with speech difficulty and was admitted with
a clinical diagnosis of stroke. Initial unenhanced CT of the head showed
normal findings, but an echocardiogram showed a left atrial mass thought to be
an embolic source. The mass proved to be a myxoma on surgical resection. One
year later, the patient experienced new episodes of aphasia, right-sided
weakness, and confusion. A repeated echocardiogram failed to show evidence of
recurrent myxoma. Brain MR imaging (1.5-T Signa whole-body scanner; General
Electric Medical Systems, Waukesha, WI) revealed several lesions in the left
temporal, occipital, parietal, and parietofrontal regions. On T1-weighted
images (TR/TE, 650/16), these lesions were characterized by unusual foci of
signal dropout surrounded by hyperintense rims, similar in appearance to the
artifact produced by metallic aneurysm clips
(Fig. 1A). Similar findings
were present on proton density images (2500/16). On gradient-echo
susceptibility images (TR/TE, 500/50; flip angle, 10°), these lesions
showed a marked "blooming" pattern of signal loss
(Fig. 1B). The extent of the
signal loss was again noted to be more typical of metallic artifact than of
chronic hemorrhage. Cerebral angiography revealed multiple small distal
arterial aneurysms in the distribution of the left middle cerebral artery
(Fig. 1C).
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Fig. 1A. —73-year-old woman with aphasia, right-sided weakness, and
confusion due to hemorrhagic aneurysms associated with left atrial myxoma.
Sagittal T1-weighted MR image shows multiple unusual foci of signal dropout
surrounded by hyperintense rims (arrows), similar in appearance to
artifact produced by metallic aneurysm clips.
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Fig. 1B. —73-year-old woman with aphasia, right-sided weakness, and
confusion due to hemorrhagic aneurysms associated with left atrial myxoma.
Axial gradient-echo susceptibility image obtained through level of lateral
ventricles shows marked "blooming" pattern of signal loss
surrounding lesions.
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Fig. 1C. —73-year-old woman with aphasia, right-sided weakness, and
confusion due to hemorrhagic aneurysms associated with left atrial myxoma.
Lateral arteriogram from left internal carotid artery injection shows multiple
small distal arterial aneurysms in middle cerebral artery distribution
(arrows), including distal posterior temporal branch.
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Contrast-enhanced CT-guided stereotactic biopsy was performed. CT showed
multiple high-attenuation lesions, the most superficial of which, at the
posterior left parietal lobe, measured 162 ± 18 H
(Fig. 1D). In comparison, the
adjacent contrast-filled superior sagittal sinus was of lower density (98
± 3 H). Biopsy of this superficial lesion yielded an ovoid specimen of
friable brown—yellow tissue (Fig.
1E). No acute inflammatory cells were present on the frozen
section. A detailed histologic study revealed the presence of myxoid matrix,
hemosiderin-laden macrophages, and abundant free iron and hemosiderin, along
with fresh blood (Fig. 1E).
Evidence of prior vascular occlusion with partial recanalization was also
found. Neither calcification nor myxoma cells were identified in the processed
sections. Together with the histologic results, findings on MR imaging, CT,
and arteriographic imaging of multiple, hyperdense, high susceptibility
lesions in the left middle cerebral artery distribution in a myxoma patient
who 1 year earlier had CT of the head with normal findings suggested an
embolic origin for the lesions. The final diagnosis, based on the available
clinical, radiographic, and pathologic data, was of multiple hemorrhagic
aneurysms arising at sites of prior myxoma-related embolization.
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Fig. 1D. —73-year-old woman with aphasia, right-sided weakness, and
confusion due to hemorrhagic aneurysms associated with left atrial myxoma.
Axial contrast-enhanced CT scan obtained in stereotactic frame shows multiple
high-density lesions. High Hounsfield attenuation of these lesions (162
± 18 H) is more suggestive of calcium than of hemorrhage or enhancement
(adjacent sagittal sinus and arteries are of lower density, approximately 98
± 3 H). Biopsy of posterior left parietal lesion (arrow) was
without evidence of calcification
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Fig. 1E. —73-year-old woman with aphasia, right-sided weakness, and
confusion due to hemorrhagic aneurysms associated with left atrial myxoma.
Photomicrograph of histopathologic specimen from posterior parietal lesion
shows abundant hemosiderin and hemosiderin-laden macrophages (brown cellular
material), moderate myxoid matrix, and minimal RBCs. Neither calcification nor
myxoma cells were present in sample.
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Discussion
Initial clinical presentation with focal neurologic deficits, despite an
absence of cardiac symptoms, may lead to the diagnosis of left atrial myxoma.
Conversely, in patients with a known history of cardiac myxoma, neurologic
sequelae may not become clinically apparent until long after resection of the
cardiac mass. A wide range of neurologic manifestations, including embolic
infarction and metastases, have been reported in 25-45% of patients presenting
with left atrial myxoma [3,
4]. Hemorrhagic aneurysms,
typically characterized by chronic recurrent bleeding, may be partially
thrombosed and therefore contain blood-breakdown products; such aneurysms have
been reported in 38% of myxoma patients
[3]. The pathogenesis of these
aneurysms is related to hematogenous dissemination and peripheral lodging of
emboli arising from either the cardiac tumor itself, or from thrombus formed
on its surface.
The typical angiographic features of myxoma-associated aneurysms are well
described [3]. This patient's
case illustrates the usefulness of MR imaging in the identification of such
lesions, which display marked magnetic susceptibility effects to a greater
extent than would be expected from more common sources of intraparenchymal
hemorrhage. The pathologic basis for the unique MR imaging appearance of these
lesions, which are notable for their conspicuity on both T1-weighted and
susceptibility-weighted images, might be attributed to the unusually dense
accumulation of iron and hemosiderin from chronic recurrent hemorrhage
[5,
6]. Our patient's case supports
this contention. A similar phenomenon has been described for cavernous
hemangiomas [7]. Unlike
hemorrhagic aneurysms associated with myxoma, cavernous hemangiomas (also
called cavernous angiomas or cavernous malformations) are typically
angiographically silent. Despite their blooming on gradientecho MR imaging
susceptibility images, they do not show the striking T1 abnormality revealed
by our patient [8].
We hypothesize that the distinctive MR imaging appearance we have described
may be a result of the combined effects of either the dense deposits of
hemosiderin and iron breakdown products within the hemorrhagic aneurysms or
the composition of the myxoid matrix itself. The accumulation of myxoid matrix
may also help to explain the hyperdense appearance of the lesions on CT,
despite the absence of calcification. The high attenuation (162 H) of the
posterior left temporal lesion is greater than would be expected from either
recent intraparenchymal hemorrhage or, given the lower (98 H) attenuation
value of the adjacent venous sinus, from contrast enhancement alone. On the
basis of the data available to us, however, the precise mechanism underlying
the unusual imaging appearance of these lesions cannot be definitively
determined.
Although atrial myxoma is a well-described cardiac tumor, its diagnosis is
often overlooked in cases in which the initial clinical presentation is almost
exclusively neurologic. In patients with known cardiac myxoma, however, the
onset of neurologic deficits may be significantly delayed—sometimes
manifesting long after the primary mass has been resected. In patients with
strokelike symptoms, the multiplicity, distribution, and distinctive CT and MR
imaging characteristics of new cerebral lesions should raise suspicion for an
underlying cardiac source if more common causes for embolism are not
evident.
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