Diagnosis of pericardial cysts using diffusion weighted magnetic resonance imaging: A case series.

Abstract

Congenital pericardial cysts are benign lesions that arise from the pericardium during embryonic development. The diagnosis is based on typical imaging features, but atypical locations and signal magnetic resonance imaging sequences make it difficult to exclude other lesions. Diffusion-weighted magnetic resonance imaging is a novel method that can be used to differentiate tissues based on their restriction to proton diffusion. Its use in differentiating pericardial cysts from other pericardial lesions has not yet been described.
We present three cases (a 51-year-old Caucasian woman, a 66-year-old Caucasian woman and a 77-year-old Caucasian woman) with pericardial cysts evaluated with diffusion-weighted imaging using cardiac magnetic resonance imaging. Each lesion demonstrated a high apparent diffusion coefficient similar to that of free water.
This case series is the first attempt to investigate the utility of diffusion-weighted magnetic resonance imaging in the assessment of pericardial cysts. Diffusion-weighted imaging may be a useful noninvasive diagnostic tool for pericardial cysts when conventional imaging findings are inconclusive.

Full text

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CASE REPORTOpen Access
Diagnosis of pericardial cysts using diffusion
weighted magnetic resonance imaging: A case
series
Asam Raja1, Jonathon R Walker2, Maneesh Sud2, Joe Du2, Matthew Zeglinski2, Andrew Czarnecki1,
Negareh Mousavi4, Davinder S Jassal1,2,3*and Iain DC Kirkpatrick1
Abstract
Introduction: Congenital pericardial cysts are benign lesions that arise from the pericardium during embryonic
development. The diagnosis is based on typical imaging features, but atypical locations and signal magnetic
resonance imaging sequences make it difficult to exclude other lesions. Diffusion-weighted magnetic resonance
imaging is a novel method that can be used to differentiate tissues based on their restriction to proton diffusion.
Its use in differentiating pericardial cysts from other pericardial lesions has not yet been described.
Case presentation: We present three cases (a 51-year-old Caucasian woman, a 66-year-old Caucasian woman and
a 77-year-old Caucasian woman) with pericardial cysts evaluated with diffusion-weighted imaging using cardiac
magnetic resonance imaging. Each lesion demonstrated a high apparent diffusion coefficient similar to that of free
water.
Conclusion: This case series is the first attempt to investigate the utility of diffusion-weighted magnetic resonance
imaging in the assessment of pericardial cysts. Diffusion-weighted imaging may be a useful noninvasive diagnostic
tool for pericardial cysts when conventional imaging findings are inconclusive.
Introduction
Congenital pericardial cysts arise when a portion of the
pericardium pinches off during embryonic development
[1,2]. The majority of pericardial cysts are found in the
right anterior cardiophrenic angle. They often lack inter-
nal septations and fail to enhance with contrast [3].
Pericardial cysts typically contain a simple fluid whose
attenuation on computed tomography (CT) is similar to
water. Their contents are usually hyperintense on T2-
weighted magnetic resonance images (MRI) images and
hypointense on T1-weighted signals [3].
The diagnosis of pericardial cysts is not always
straightforward since they may present in atypical loca-
tions [3]. Moreover, their elevated protein content may
increase their density on CT images, decrease their T2-
weighted MRI signals and increase their T1-weighted
signals [3]. As a result, differentiating these lesions from
hematomas or neoplasms can be quite challenging. The
lack of internal architecture may differentiate a cystic
lesion when findings on CT and conventional MRI
sequences are equivocal. However, this method is not
always reliable [3].
Diffusion-weighted imaging (DWI) using MRI is able
to differentiate the diffusion restriction of protons
within a tissue by calculating the apparent diffusion
coefficient (ADC) [4]. The diffusion of protons within a
simple cyst is less restricted when compared to a variety
of more complex and particularly malignant lesions [4].
Simple cysts, as a result, display larger ADC values [4]
which can be utilized as a diagnostic tool in order to
differentiate a pericardial cyst from other pericardial
lesions.
Case Series
Case 1
A 51-year-old Caucasian woman was referred for assess-
ment of chest pain and dyspnea. Her past history was
significant for cervical dysplasia. A physical examination
* Correspondence: djassal@sbgh.mb.ca
1Department of Radiology, University of Manitoba, Winnipeg, Manitoba,
Canada
Full list of author information is available at the end of the article
Raja et al. Journal of Medical Case Reports 2011, 5:479
http://www.jmedicalcasereports.com/content/5/1/479
JOURNAL OF MEDICAL
CASE REPORTS
© 2011 Raja et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.

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was unremarkable. A twelve-lead electrocardiogram
showed normal sinus rhythm. A subsequent exercise
treadmill test did not reveal any evidence of stress-
induced ischemia. Her left ventricular systolic function
was normal as demonstrated by transthoracic echocar-
diography (TTE). Multidetector CT (MDCT) identified
a fluid density lesion measuring 6 × 4 cm at the right
anterior cardiophrenic angle, consistent with a pericar-
dial cyst (Figure 1). Our patient underwent cardiac mag-
netic resonance imaging (CMR) for further assessment
of this lesion. DWI performed at b-values of 0s/mm2,
50s/mm2, 400s/mm2and 800s/mm2demonstrated a
steep drop in signal from the cyst contents with increas-
ing b-values corresponding to an ADC value of 3.47 ×
10-3mm2/s (Figure 2).
Case 2
A 66-year-old Caucasian woman with past history of
hypertension and diabetes mellitus presented with a
long-standing history of chest pain and shortness of
breath. Physical examination and a twelve-lead electro-
cardiogram were unremarkable. Multiple cardiac ima-
ging studies including a TTE and myocardial perfusion
study did not show any evidence of ischemia. MDCT
revealed a cyst within her anterior mediastinum measur-
ing 4.7 × 1.7 cm, representing a possible pericardial cyst
in an atypical location. CMR was performed to further
evaluate this lesion. DWI demonstrated signal character-
istics consistent with free diffusion within the cyst and
an ADC of 3.02 × 10-3mm2/s.
Case 3
A 77-year-old Caucasian woman with a past medical
history of vitamin B12 deficiency and cholecystectomy
underwent MRI for evaluation of suspected biliary colic.
An incidental finding of a 10.4 × 4.2 cm cystic lesion
along the right cardiac border was suspected to be of
pericardial origin. Our patient was referred for further
characterization of the lesion with CMR. The calculated
ADC within the cyst was 3.18 × 10-3mm2/s.
Discussion
Congenital pericardial cysts are rare, yet important,
lesions that account for 7% of all mediastinal masses [1].
The prevalence of pericardial cysts is one in 100,000 [1]
and approximately 60% of patients present between 30
and 50 years of age [2]. Pericardial cysts are commonly
located in the left (51% to 70%) and right (28% to 38%)
cardiophrenic angles. A small percentage, however, are
located in the upper mediastinum, hilus or cardiac bor-
der (8% to 11%) [5]. The classic description of a pericar-
dial cyst is a 1 cm to 5 cm unilocular, smooth-walled
cyst with an outer layer of endothelial or mesothelial
cells [6]. Their serous fluid-filled center and lack of
solidity distinguishes them from other pericardial
masses. Rare complications such as infection and
hemorrhage may, however, confound efforts to charac-
terize pericardial cysts using this description [6].
Up to one third of patients with pericardial cysts will
become symptomatic at some point [1,7]. Atypical chest
pain, persistent cough or new onset dyspnea secondary
to the cyst’s mass effect on adjacent structures are fre-
quent presenting symptoms of patients with pericardial
cysts [1,7]. In rare, yet devastating occasions, pericardial
cysts may spontaneously rupture or hemorrhage into
surrounding tissues leading to cardiac tamponade, heart
failure and sudden death [8-10]. Thus, an early and
accurate diagnosis in symptomatic individuals is neces-
sary in order to offer prompt and potentially life-saving
therapy.
Figure 1 Case 1 -Axial CT image of this patient’s thorax
demonstrates a lesion in the right anterior cardiophrenic
angle. The attenuation of the contents measured 19.6 Hounsfield
Units (HU), or near water density.
Figure 2 Case 1 -The ADC map using DWI CMR demonstrates a
high value of the cyst contents, 3.47 × 10-3mm2/s. The ADC of
cerebrospinal fluid measured in this patient was 3.1 × 10-3mm2/s.
Raja et al. Journal of Medical Case Reports 2011, 5:479
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Pericardial cysts are usually discovered incidentally as
an unexpected round mass on routine chest radiography
or TTE in asymptomatic patients [1,6]. On TTE, a peri-
cardial cyst appears as a homogeneous echolucent mass,
which is consistent with minor attenuation of the ultra-
sound through a low-density fluid-filled structure. There
also exists an echo-free space indicating its separation
from the cardiac chambers [6]. The differential diagnosis
is broad and includes tumors undergoing cystic degen-
eration, such as Hodgkin disease, germ cell tumors,
mediastinal carcinomas, nerve root tumors, abscesses
and pancreatic pseudocysts [1,6]. The current standard
of care mandates follow-up CT with intravenous con-
trast or CMR (T1- and T2-weighted methods) to con-
firm the diagnosis of a pericardial cyst.
Cardiac CT has proven uses for characterizing pericar-
dial masses. Its accuracy, however, suffers from similar
pitfalls as chest radiography and echocardiography. It
cannot distinguish malignant tissue from non-malignant
fluid-filled cysts with a great degree of confidence [6].
Similarly, T1- and T2-weighted MRI may also provide
inconclusive results when cysts contain proteinaceous,
non-serous fluid [6]. Thus, there is a lack of a reliable,
non-invasive imaging modality that can differentiate
pericardial cysts from other pericardial masses with
similar appearances, but substantially different prog-
noses and treatments.
Differentiating exudate from transudate on MRI has
previously been reported using DWI and ADC values.
Under optimized parameters, DWI is an effective tool
with a high sensitivity and specificity (91% and 85%
respectively) for discriminating fluids with different pro-
tein and cellular contents [11]. Moreover, DWI seems to
be a reliable tool for differentiating other benign chest-
mediastinal masses [12], focal breast lesions [13] and
bladder lesions [14] from malignant lesions. Application
of DWI’s discriminatory power to fluid-filled, pericardial
lesions is a logical next step.
The present case series illustrates three independent
patients in whom pericardial cysts displayed consistently
high ADC values. ADCs may thus prove useful in differ-
entiating symptomatic pericardial cysts from neoplastic
and infectious mediastinal lesions that are otherwise
irreconcilable by conventional CT or MRI. Future stu-
dies, with surgical confirmation, are warranted to evalu-
ate the utility of diffusion weighted MRI as the first test
of choice for the noninvasive assessment of pericardial
cysts.
Conclusion
This report presents three cases of pericardial cysts that
were evaluated with DWI using CMR. The ADC maps
consistently demonstrated high ADC values, indicating
free diffusion of protons within the pericardial cysts.
This study is a first attempt to investigate the utility of
DWI in the assessment of pericardial cysts. Further
study into the diagnostic utility of DWI when CT and
MRI are equivocal in patients with a pericardial mass is
warranted.
Consent
Written informed consent was obtained from the
patients for publication of this case series and its
accompanying images. A copy of the written consent is
available for review by the Editor-in-Chief of this
journal.
Author details
1Department of Radiology, University of Manitoba, Winnipeg, Manitoba,
Canada.2Institute of Cardiovascular Sciences, St Boniface General Hospital,
University of Manitoba, Winnipeg, Manitoba, Canada.3Section of Internal
Medicine, Department of Internal Medicine, University of Manitoba,
Winnipeg, Manitoba, Canada.4Section of Cardiology, Department of Internal
Medicine, Bergen Cardiac Care Centre, St Boniface General Hospital,
University of Manitoba, Winnipeg, Manitoba, Canada.
Authors’ contributions
All authors contributed to the writing of the manuscript. All authors read
and approved the final manuscript.
Competing interests
The authors declare that they have no competing interests.
Received: 8 March 2011 Accepted: 24 September 2011
Published: 24 September 2011
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doi:10.1186/1752-1947-5-479
Cite this article as: Raja et al.: Diagnosis of pericardial cysts using
diffusion weighted magnetic resonance imaging: A case series. Journal
of Medical Case Reports 2011 5:479.
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