Journal of Neuroimaging Vol 12 No 1 January 2002
Ionita et al: Paradoxical Embolism

Paradoxical Brain Embolism From
Thrombus Associated With Vena
Caval Filter in a Patient With Cancer

Catalina Ionita, MD
Pierre Giglio, MD
Eugene Isayev, MD
Ronald Alberico, MD
Patrick Pullicino, MD, PhD

ABSTRACT
A 71-year-old man experienced sudden onset of hemiparesis and aphasia. He had a 4-month history of gallbladder cholangiocarcinoma, complicated with a postoperative deep-vein thrombosis (DVT) that necessitated a vena caval filter placement. Diffusion-weighted magnetic
resonance imaging of the brain showed multiple hyperintense foci. Magnetic resonance spectroscopy was compatible with cerebral infarction.
Abdominal computed tomography showed a thrombus in the inferior
vena cava extending through the filters. A transcranial Doppler bubble
study revealed the presence of a right-to-left shunt. Paradoxical cerebral embolism must be considered in patients with DVT who have new
onset neurologic deficits even in the presence of a caval filter.
Key words: Cancer, intracaval filter, right-to-left shunt, paradoxical
emboli, transcranial Doppler, bubble study.
Ionita C, Giglio P, Isayev E, Alberico R, Pullicino P.
Paradoxical brain embolism from thrombus associated
with vena caval filter in a patient with cancer.
J Neuroimaging 2002;12:69–71.

Case Presentation
A 71-year-old right-handed white man was admitted to the
hospital with lightheadedness and vague abdominal pain. He
had a gallbladder cholangiocarcinoma with liver metastases
surgically resected 3 months previously, followed by 4 cycles
of chemotherapy. He subsequently developed recurrent intraabdominal abscesses, which were drained under computed
tomography (CT) guidance. During the chemotherapy, he developed a left ileofemoral vein thrombosis. Two Simon Nitinol
filters were placed in the inferior vena cava, and the patient
was started on a full anticoagulation dose of subcutaneous
enoxaparin sodium, 1 mg/kg twice a day, as an outpatient.
Enoxaparin was discontinued on admission because of the
possibility of intra-abdominal hemorrhage. Twelve hours later,

the patient started to have intermittent speech difficulty and
generalized tremors. The next day, he developed sudden
right-sided weakness with language difficulty. Neurologic examination revealed an awake and alert patient, with decreased fluency of spontaneous speech, frequent naming
errors, and difficulties in performing cross-body commands,
but with comprehension and repetition preserved. He had a
right homonymous hemianopsia, normal fundi, and
extraocular movements. He had a severe right facial droop.
He had a hypotonic right hemiparesis more prominent in the
arm and distally, with a right Babinski sign. Finger-nose test
showed bilateral dysmetria. Laboratory investigations
3
showed a white cell count of 23.5 × 10 /L, hemoglobin of 10.7
3
g/dL, and platelet count of 428 × 10 /L. The chemistry was
initially normal, but 2 days later the patient developed acute
renal failure with a blood urea nitrogen of 80 mg/dL, creatinine
of 4.3 mg/dL, potassium of 5.7 mEq/L, and proteinuria > 300
mg/L. Blood and urine cultures were negative. Coagulation
tests showed a prothrombin time of 17.6 seconds, activated
partial thromboplastin time of 39 seconds, fibrinogen of 229
mg/dL, antithrombin III level of 59% (normal 80-120), protein
C level of 32% (normal 65-129), free protein S level of 32%
(normal 57-120), and D-dimer positive. A transthoracic
echocardiogram was normal.
A CT scan of the abdomen and pelvis was negative for
abscesses or fluid. A sagittal reformat revealed an inferior
vena cava thrombus extending caudal and cephalad to both
filters, with persisting thrombus in the iliac veins bilaterally and
in the femoral vein on the right (Fig 1). Diffusion-weighted and

Received March 19, 2001, and in revised form June 11, 2001.
Accepted for publication July 9, 2001.
From the Department of Neurology, Buffalo General Hospital,
Buffalo, New York (CI, PG, EI, PP); and the Department of Radiology, Roswell Park Cancer Institute, Buffalo, New York (RA).
Address correspondence to Dr Pullicino, Neuroscience Department, UMDNJ, 185 South Orange Avenue, Newark, NJ
07103. E-mail: pullic@umdnj.edu.

Fig 1. Computed tomography scan of the abdomen-sagittal reformat showing the 2 filters (triangles) and the intracaval thrombus
hypodensity (arrows) extending caudal and cephalad to both filters.

Copyright © 2002 by the American Society of Neuroimaging

69

B

A

C

D

Fig 2.

Diffusion-weighted magnetic resonance imaging of the brain showing multiple hyperintense foci, in multiple vascular territories, consistent with multiple embolic infarcts.

flair magnetic resonance imaging of the brain showed multiple
foci of acute infarction, in multiple vascular territories, consistent with embolic infarctions (Fig 2). The magnetic resonance
spectroscopy (STEAM, TR = 1500 ms, TE = 35 ms) showed a
small doublet peak at 1.33 ppm consistent with lactate. The
glutamine/glutamate peak was slightly increased. The spectrum was consistent with early ischemia and not suggestive of
abscess or tumor (Fig 3). Insonation of the right middle cerebral artery following injection of microbubbles into a forearm
vein revealed multiple microembolic signals about 10 seconds
after injection on 2 separate occasions, which indicated the
presence of a right-left shunt.

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Journal of Neuroimaging Vol 12 No 1 January 2002

Discussion
The most likely source of the multiple cerebral emboli in this
patient was the vena caval thrombus because the patient had
a right-to-left shunt and thrombus was detected cephalad to
both vena caval filters. Intracaval filters do not provide full protection against further embolic events; the open architecture
of both Greenfield and Simon Nitinol filters provides patency at
the expense of allowing the passage of emboli up to 3 mm in
diameter. In the presence of a right-to-left shunt, small emboli
that could lodge asymptomatically in the lungs may go to the
1–4
brain and cause infarctions. The Simon Nitinol filter is

vena caval filter should suggest the possibility of paradoxical
embolism and trigger a search for a patent foramen ovale.
We recommend CT of the abdomen and either trans5,6
esophageal echocardiography or transcranial Doppler bub7
ble study in any patient with an open type of intracaval filter
who develops new neurologic symptoms. Cancer patients,
particularly those with gastrointestinal adenocarcinoma, may
have a hypercoagulable state and may be especially prone to
this complication. These patients should probably also be
screened for a right-to-left shunt presence, even if they do not
have neurological symptoms, and especially if they have a
deep-vein thrombosis or evidence of thrombosis. In our case,
the presence of an extensive vena caval thrombus suggested
that this thrombus was actually progressing, in spite of
anticoagulation. Although the neurological symptoms developed 12 hours after the enoxaparin was stopped, since the
biological effect of 1 mg/kg dose of enoxaparin lasts 3 to 5
days, and the therapeutic anticoagulant level lasts 12 to 16
hours, stopping of enoxaparin was unlikely to have been the
cause of the thrombus. The hypercoagulable state associated
with cancer is frequently resistant to anticoagulation and
recurrent embolism, pulmonary or cerebral, is still possible,
even with a vena caval filter placement. Vena caval ligation
8,9
may be indicated to prevent recurrent emboli.

References

Fig 3. Magnetic resonance spectroscopy of the brain showing a
small doublet lactate peak (arrows) and the prominent glutamine/
glutamate peak (triangles). N-acetyl aspartate/creatine and choline/
creatine levels are near normal. This spectrum supports the diagnosis
of acute stroke.

a larger filter than the Greenfield filter and is often used for patients with a vena cava diameter greater than 8 mm.
There is increasing evidence that open architecture caval
filters cannot be totally relied on for protection from pulmonary
embolism, and our case demonstrates this is also true for
stroke. Neurologists should be aware of this. In a patient with
unexplained acute neurological symptoms, the presence of a

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