DOI:10.2214/AJR.08.1128
AJR 2009; 192:32-40
© American Roentgen Ray Society
Spectrum of Choroid Plexus Lesions in Children
Ramin M. Naeini1,
Jeong Hyun Yoo1,2 and
Jill V. Hunter1,3
1 Department of Radiology, Baylor College of Medicine, One Baylor Plaza,
MailStop 360, Houston, TX 77030.
2 Present address: Dongdaemun Hospital, School of Medicine, Ewha Womans
University, Seoul, Korea.
3 Present address: Texas Children's Hospital, Houston, TX.
Received April 27, 2008;
accepted after revision June 24, 2008.
Address correspondence to R. M. Naeini
(naeini{at}bcm.edu).
CME This article is available for CME credit. See
www.arrs.org
for more information.
FOR YOUR INFORMATION
This article is available for CME credit. See
www.arrs.org
for more information.
Abstract
OBJECTIVE. The aim of this article is to review the embryology of
the choroid plexus and the spectrum of disorders involving the choroid plexus
in children and to illustrate their radiologic features.
CONCLUSION. The choroid plexus is an important part of the CNS that
can be the primary or secondary location for many congenital abnormalities or
pathologic conditions such as neoplasms, infections, inflammatory processes,
cysts, and vascular malformations.
Keywords: acquired disease • choroid plexus • congenital disease • pediatric imaging
Introduction
The choroid plexus, a rich vascularized CNS structure, may be
involved in a wide spectrum of CNS disorders, either congenital or acquired,
as a primary organ or as an extension of disease. Although imaging patterns of
these disorders are not always diagnostic, they are useful to show the
abnormality and to narrow the differential diagnosis. Clinical information,
CSF studies, and ultimately biopsy may be necessary for a final diagnosis.
Embryology and Anatomy
The choroid plexus begins to differentiate in week 6 of gestation shortly
after closure of the neural tube and bulging of the pia mater into the
ventricular ependyma. The choroid plexus appears initially in the roof of the
fourth ventricle, then in the lateral ventricles, and finally in the third
ventricle. The adult appearance of the choroid plexus is seen by week 20 of
gestation. The ependymal cells, which line the ventricles, form a continuous
sheet around the choroid plexus. The capillaries of the choroid plexus are
fenestrated and noncontinuous, which allows free movement of small molecules.
Adjacent choroidal epithelial cells form tight junctions that prevent the
passage of most macromolecules into the CSF. The choroid plexus forms the CSF
and actively regulates the constituents in it
[1].
The choroid plexus can play an important role in extension of disease
processes either from the brain parenchyma or from the surface meninges,
including the ependyma, because of its location in the brain substance and its
continuity with the meninges
[2].
Congenital Disorders
The most common congenital abnormalities of the choroid plexus include
choroid plexus cysts, diffuse villous hyperplasia, lipoma, and Sturge-Weber
syndrome (encephalotrigeminal angiomatosis).
Choroid Cysts
Choroid plexus cysts develop when neuroepithelium lining the interlobar
clefts invaginates into the stroma with subsequent accumulation of CSF and
debris. They occur throughout the ventricular system but are most frequently
seen in the glomus of the lateral ventricles (Figs.
1A,
1B, and
2). Choroid plexus cysts are
seen in the fetus in approximately 1% of all pregnancies, usually are smaller
than 1 cm, and are located in the body of the plexus, although they may
protrude into the ventricular cavity
[3].
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Fig. 1A —Bilateral choroid plexus cysts in 2-year-old girl with Aicardi's
syndrome. Coronal contrast-enhanced T1-weighted MR image shows choroid plexus
cysts (black arrows) in lateral ventricles and arachnoid cysts in
midline (white arrows).
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Fig. 1B —Bilateral choroid plexus cysts in 2-year-old girl with Aicardi's
syndrome. Sagittal T1-weighted contrast-enhanced MR image shows agenesis of
corpus callosum and arachnoid cysts (arrows).
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These cysts are most often asymptomatic and almost all resolve
spontaneously by the 26th-28th week of gestation, but large cysts can cause
hydrocephalus [4]. Choroid
plexus cysts are more prevalent in fetuses with trisomy 18, trisomy 21, and
Aicardi's syndrome. Chromosomal abnormalities, specifically trisomy 18, should
be considered if the cysts are large (> 1 cm), bilateral, or irregular, or
if the maternal age is 32 years or older. An increased prevalence of choroid
plexus cysts has also been reported in the presence of other structural
anomalies and when the maternal serum screening markers are abnormal
[5].
Sonography may show multiple cysts of variable sizes and sometimes cysts
with double walls. On CT and MRI, choroid plexus cysts usually show CSF
density. They show high signal intensity on diffusion-weighted images;
however, the signal intensity of cystic fluid may be higher on T1- and
T2-weighted images and lower on apparent diffusion coefficient maps, which may
be partially explained by a slower water diffusion rate because of a higher
protein content.
Diffuse Villous Hyperplasia
Diffuse villous hyperplasia is a rare condition that usually involves the
lateral ventricles and is manifested by bilateral enlargement of the entire
choroid plexus without discrete masses, resulting in overproduction of CSF and
communicating hydrocephalus (Fig.
3). Histologically, an increased number of normal-sized cells are
seen [6]. MRI is superior to CT
in establishing the diagnosis by showing diffuse enlargement of a
homogeneously enhancing choroid plexus in a patient with communicating
hydrocephalus.
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Fig. 3 —Diffuse villous hyperplasia in 2-year-old boy with communicating
hydrocephalus. Coronal T1-weighted contrast-enhanced MR image shows
enlargement and avid enhancement of lateral ventricular choroid plexuses and
moderate to severe hydrocephalus.
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Lipoma
Intracranial lipomas are rare lesions that account for fewer than 0.1% of
all intracranial tumors. Lipomas are believed to result from the
maldifferentiation of the meninx primitive
[7]. Lipomas are usually
associated with brain malformations, especially midline deformities, although
rare cases of isolated choroid plexus lipoma have been reported. On
sonography, lipomas are well-defined hyperechoic masses. They show
characteristic fat signal on MRI (Figs.
4A, and
4B).
Sturge-Weber Syndrome
Neuroimaging in Sturge-Weber syndrome may show intraparenchymal
calcification (tram-track gyral calcifications on CT scans or radiographs),
parenchymal volume loss, engorgement of deep veins, and leptomeningeal or
choroid plexus angiomata. Although MRI is more sensitive, both CT and MRI can
reveal cerebral cortical atrophy, gyriform cerebral calcifications,
compensatory ventricular enlargement, "angiomatosis" enlargement
of the ipsilateral choroid plexus, and calvarial hemihypertrophy
[8] (Figs.
5A, and
5B).
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Fig. 5A —Sturge-Weber syndrome with bilateral choroid plexus involvement in
7-year-old boy. Axial contrast-enhanced T1-weighted MR image shows enlargement
and enhancement of bilateral choroid plexuses.
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Fig. 5B —Sturge-Weber syndrome with bilateral choroid plexus involvement in
7-year-old boy. Coronal T1-weighted contrast-enhanced image shows bilateral
enlarged choroid plexuses with peripheral enhancement (black arrows)
as well as bilateral parietal pial angiomatosis (white arrows).
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Acquired Disorders
The choroid plexus can be involved in a wide variety of acquired disease
processes such as primary or secondary neoplasms, infectious and inflammatory
processes, and hemorrhage.
Papillomas and Carcinomas
Papillomas of the choroid plexus are the most common trigonal mass in young
children, typically under the age of 5 years. Papillomas and carcinomas
constitute about 5% of supratentorial tumors in children and fewer than 1% of
all primary intracranial tumors
[9]. Papillomas are benign
lesions that arise from the epithelium of the choroid plexus, most commonly
from the lateral ventricles (Fig.
6). Five to ten percent of papillomas degenerate into carcinomas
[10]. They are most common in
the first year of life and have a marked predominance in boys. The most common
location of the tumor is at the trigone, but it may be seen anywhere along the
choroid plexus (Figs. 7A,
7B,
7C,
7D, and
7E). Choroid plexus papillomas
typically result in severe hydrocephalus, due to either overproduction of CSF
or blockage in the subarachnoid cisterns or intraventricular pathways
[11].
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Fig. 7B —Various locations of choroid plexus papillomas. Sagittal
contrast-enhanced T1-weighted MR image in 5-year-old boy shows enhancing
papillary frondlike mass in third ventricle with extensions to cerebral
aqueduct, resulting in moderate hydrocephalus.
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Fig. 7D —Various locations of choroid plexus papillomas. Axial T1-weighted
contrast-enhanced MR image in 12-year-old girl shows large, relatively
homogeneously enhancing mass in region of foramen of Luschka and
cerebellopontine angle.
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Fig. 7E —Various locations of choroid plexus papillomas. Sagittal T1-weighted
contrast-enhanced MR image in 5-year-old girl shows enhancing well-defined
mass in fourth ventricle but no evidence of obstructing hydrocephalus.
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Choroid plexus carcinomas account for up to 30-40% of choroid plexus tumors
in children; almost all occur in children 2-4 years old. Although most
patients present with hydrocephalus, focal neurologic deficits are more common
in carcinomas than in papillomas
[10]. Atypical papillomas show
some malignant histologic features but do not fulfill the criteria for
carcinoma. Both atypical papillomas and carcinomas show a marked propensity to
metastasize through the CSF and cause subarachnoid masses.
Choroid plexus papillomas typically appear as lobulated, intraventricular
masses that are iso- or mildly hyperdense on unenhanced CT and homogeneously
enhancing after the injection of contrast material. Calcifications are seen in
about 25% of cases. Aggressive papillomas (Figs.
8A, and
8B) have more irregular
margins and occasionally grow into the adjacent white matter, causing edema.
On MRI, papillomas present as homogeneous intraventricular masses on
T1-weighted sequences. Characteristically, the central portions of the
papilloma are hypointense compared with gray matter on T2-weighted images.
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Fig. 8A —Atypical choroid plexus papilloma in 1-year-old girl. Sagittal
unenhanced T2-weighted MR image shows a cauliflower-like heterogeneous
intraventricular mass resulting in ventricular enlargement and increased T2
signal in periventricular white matter secondary to transependymal flow.
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Fig. 8B —Atypical choroid plexus papilloma in 1-year-old girl. Coronal
contrast-enhanced T1-weighted MR image shows avid enhancement of right choroid
plexus mass and enlargement of lateral ventricles and third ventricle.
Histologic examination was consistent with atypical choroid plexus
papilloma.
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Choroid plexus carcinomas may be hyperdense on CT because of their
increased cellularity (Fig.
9). Carcinomas almost always grow into the brain through the
ventricular wall and cause vasogenic edema
[11]. Carcinomas usually show
areas of high and low intensity on both T1- and T2-weighted images because of
hemorrhage and cyst formation (Fig.
10).
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Fig. 10 —Choroid plexus carcinoma in 2-year-old boy. Axial T2-weighted
unenhanced MR image shows massive aggressive-appearing right temporoparietal
mass with heterogeneous T2 signal intensity containing multiple cysts
obstructing right temporal horn and causing midline shift and compression of
brainstem structures.
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Despite these differences, the differentiation between papillomas and
carcinomas can be difficult on imaging in the absence of metastasis, and
diagnosis depends on the histology. Extensive parenchymal invasion and
peritumoral vasogenic edema are suggestive of malignant lesions. Other choroid
plexus neoplasms such as meningioma or lymphoma, either primary or secondary,
are rare but have been reported in the literature
[5,
12].
Metastatic Lesions
Metastatic neoplasms involving the choroid plexus in children are rare.
They commonly originate from aggressive tumors such as neuroblastoma,
retinoblastoma, Wilms' tumor, or melanoma. The imaging pattern is nonspecific
and depends on the primary tumor characteristics (Figs.
11A, and
11B).
Choroid Plexitis
The choroid plexus is highly vascular and may serve as a main portal for
hematogenously borne pathogens into the CNS. Lack of a blood-brain barrier and
the strategic location of the choroid plexus make it an important site for the
initial dissemination of various pathogens such as Mycobacterium
tuberculosis and Cryptococcus, Cytomegalovirus, Nocardia, and
Toxoplasma organisms and other bacteria and parasites. Granulomatous
diseases such as Langerhans cell histiocytosis can also involve the choroid
plexus (Figs. 12A, and
12B).
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Fig. 12A —Langerhans cell histiocytosis involving bilateral choroid plexuses
in 4-year-old boy. Axial T2-weighted MR image shows enlargement of bilateral
choroid plexuses in lateral ventricles and heterogeneous T2 signal
intensity.
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Fig. 12B —Langerhans cell histiocytosis involving bilateral choroid plexuses
in 4-year-old boy. Coronal contrast-enhanced T1-weighted image shows avid
enhancement of bilateral choroid plexuses (dashed arrows) as well as
dural-based lesions involving tentorium bilaterally (solid
arrows).
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CT and MRI in choroid plexitis may show enlargement of the choroid plexus
with avid enhancement. Edema of the adjacent periventricular white matter and
abnormal ependymal enhancement may also be seen
[2,
13] (Figs.
13A, and
13B). Interpretations should
be correlated with appropriate clinical history; final diagnosis usually
depends on CSF studies or blood cultures.
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Fig. 13A —Choroid plexitis and ventriculitis in 1-year-old girl with
meningitis caused by Serratia organism. Axial unenhanced CT scan
shows bilateral encephalomalacia and hyperdense ependymal lining of bodies of
lateral ventricles.
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Fig. 13B —Choroid plexitis and ventriculitis in 1-year-old girl with
meningitis caused by Serratia organism. Axial contrast-enhanced CT
scan shows abnormal enhancement of right-sided choroid plexus and enhancement
of ependyma of bodies of both lateral ventricles.
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Infantile Myofibromatosis
The involvement of the CNS in infantile myofibromatosis is rare and
generally occurs in the dura with invasion to the calvaria. Although it is
extremely rare, multicentric infantile myofibromatosis can involve the choroid
plexus [14] (Figs.
14A, and
14B). Typically, infantile
myofibromatosis is a benign process with early rapid growth, stabilization,
and regression of the lesion. The multicentric form with visceral involvement
generally has a poorer prognosis.
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Fig. 14A —Infantile myofibromatosis involving choroid plexus in 14-day-old
girl with family history of infantile myofibromatosis. Infant had multiple
other lesions, including hard palate mass (not shown) that was biopsied and
was consistent with infantile myofibromatosis. Axial T1-weighted MR image
shows hyperintense mass in body of left lateral ventricle
(arrow).
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Fig. 14B —Infantile myofibromatosis involving choroid plexus in 14-day-old
girl with family history of infantile myofibromatosis. Infant had multiple
other lesions, including hard palate mass (not shown) that was biopsied and
was consistent with infantile myofibromatosis. Follow-up axial T1-weighted MR
image at 6 months shows spontaneous significant decrease in size of choroid
plexus mass.
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Xanthogranuloma
Xanthogranulomas are benign tumors composed of xanthoma cells
(macrophages), cholesterol clefts, chronic inflammatory cellular reaction, and
hemosiderin. They have been found incidentally in 1.6-7% of cases in an
autopsy series [15]. These
lesions are most commonly seen bilaterally in the lateral ventricles; they are
asymptomatic because they are too small to obstruct the ventricles. However,
those occurring in the third ventricle are more likely to present with
noncommunicating hydrocephalus.
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Fig. 17B —Subacute hemorrhage in left choroid plexus and hydrocephalus in
2-day-old boy. Diffusion-weighted image (B) and apparent diffusion
coefficient map (C) show areas of restricted diffusion corresponding to
areas of left-sided choroid plexus hemorrhage.
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Fig. 17C —Subacute hemorrhage in left choroid plexus and hydrocephalus in
2-day-old boy. Diffusion-weighted image (B) and apparent diffusion
coefficient map (C) show areas of restricted diffusion corresponding to
areas of left-sided choroid plexus hemorrhage.
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Fig. 18A —Choroid plexus hemorrhage in 7-year-old boy with history of external
ventricular drainage catheter. Axial unenhanced CT image shows right frontal
approach external ventricular catheter with tip in body of right lateral
ventricle.
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Fig. 18B —Choroid plexus hemorrhage in 7-year-old boy with history of external
ventricular drainage catheter. Axial T2-weighted unenhanced MR image after 1
week shows small amount of hemorrhage in choroid plexus in right atrium
(arrow).
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Fig. 19A —25-week-premature boy with intraventricular hemorrhages rated grade
IV on left and grade III on right. Axial and coronal T2-weighted MR images
show adherent hemorrhagic choroid plexuses causing narrowing of midportion of
bodies of both lateral ventricles and severe distention and entrapment of
occipital horns.
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Fig. 19B —25-week-premature boy with intraventricular hemorrhages rated grade
IV on left and grade III on right. Axial and coronal T2-weighted MR images
show adherent hemorrhagic choroid plexuses causing narrowing of midportion of
bodies of both lateral ventricles and severe distention and entrapment of
occipital horns.
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Fig. 20 —Choroid plexus hemorrhage and intraventricular hemorrhage in
7-day-old premature boy. Axial T2-weighted gradient-echo MR image shows small
residual right choroid plexus hemorrhage (white arrow) and
intraventricular hemorrhage (black arrows) in occipital horns,
resulting in unilateral right-sided obstructive hydrocephalus (entrapped
ventricle).
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On CT scans, xanthogranulomas usually are oval-shaped and have a smooth
wall similar to colloid cysts. On MRI, they are iso- to hyperintense on
T1-weighted images and hyperintense on T2-weighted, likely because of high
lipid content with variable enhancement
(Fig. 15).
Choroid Plexus Hemorrhage
The choroid plexus is a frequent site of intracranial hemorrhage in
neonates. Prematurity, trauma during shunt placement, head injury, or
hemorrhage secondary to anticoagulation therapy during bypass or vascular
malformation
[16-18]
are the most common causes of choroid plexus hemorrhage. CT or MRI shows a
hematoma with or without intraventricular or subarachnoid hemorrhage.
Complications of choroid plexus hemorrhage include ventriculomegaly,
hydrocephalus, and adhesion of the choroid plexus to the ventricular wall or
to a tethered choroid plexus (Figs.
16,
17A,
17B,
17C,
18A,
18B,
19A,
19B, and
20).
Conclusion
A wide range of disorders in children can involve the choroid plexus, which
is often over-looked as a source of symptoms. An understanding of the
embryology and radiographic features of these lesions may help radiologists to
improve their diagnostic accuracy.
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Abstract
Introduction
