Pictorial Essay
Neuroradiology/Head and Neck Imaging
January 2009

Spectrum of Choroid Plexus Lesions in Children

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.

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].
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.

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).

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].
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.
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).
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).
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.

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.

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.
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).
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).
Fig. 2 —Choroid plexus cyst in 20-week-old male fetus without any chromosomal abnormality. Transverse image of fetal brain shows choroid plexus cyst (arrow) in right lateral ventricle.
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.
Fig. 4A —Choroid plexus lipoma in 7-year-old boy. Axial unenhanced CT scan shows left choroid plexus mass with fat density (arrow).
Fig. 4B —Choroid plexus lipoma in 7-year-old boy. Coronal unenhanced FLAIR image shows same lesion with increased FLAIR signal.
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.
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).
Fig. 6 —Choroid plexus papilloma in 9-month-old boy. Axial T1-weighted contrast-enhanced MR image shows avid enhancement of cauliflower-shaped choroid plexus mass in left atrium.
Fig. 7A —Various locations of choroid plexus papillomas. Axial T2-weighted MR image in 7-month-old boy shows right atrium choroid plexus mass.
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.
Fig. 7C —Various locations of choroid plexus papillomas. Axial T1-weighted contrast-enhanced MR image in 6-year-old boy shows homogeneously enhancing frondlike mass in left temporal horn.
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.
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.
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.
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.
Fig. 9 —Choroid plexus carcinoma in 3-year-old boy. Axial unenhanced CT image shows hyperdense choroid plexus mass in right atrium, suggestive of hypercellular mass.
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.
Fig. 11A —Metastatic melanosis of choroid plexus in 1-year-old boy. Axial unenhanced CT scan shows large hyperdense mass in left lateral ventricle.
Fig. 11B —Metastatic melanosis of choroid plexus in 1-year-old boy. Axial gradient-echo MR image shows increased susceptibility in hemorrhagic choroidal plexus mass.
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.
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).
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.
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.
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).
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.
Fig. 15 —Xanthogranuloma of choroid plexus in 14-year-old boy. Coronal T1-weighted MR image shows enlargement of choroid plexus and isointense T1 signal in left lateral ventricle.
Fig. 16 —Bilateral choroid plexuses hemorrhage in 1-month-old premature boy. Axial gradient-echo MR image shows bilateral choroid plexuses hemorrhage (arrows).
Fig. 17A —Subacute hemorrhage in left choroid plexus and hydrocephalus in 2-day-old boy. Axial FLAIR MR image shows blood products in left choroid plexus and dilatation of lateral ventricles.
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.
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.
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.
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).
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.
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.
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).
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.

Footnotes

Address correspondence to R. M. Naeini ([email protected]).
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.

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Information & Authors

Information

Published In

American Journal of Roentgenology
Pages: 32 - 40
PubMed: 19098176

History

Submitted: April 27, 2008
Accepted: June 24, 2008

Keywords

  1. acquired disease
  2. choroid plexus
  3. congenital disease
  4. pediatric imaging

Authors

Affiliations

Ramin M. Naeini
Department of Radiology, Baylor College of Medicine, One Baylor Plaza, MailStop 360, Houston, TX 77030.
Jeong Hyun Yoo
Department of Radiology, Baylor College of Medicine, One Baylor Plaza, MailStop 360, Houston, TX 77030.
Present address: Dongdaemun Hospital, School of Medicine, Ewha Womans University, Seoul, Korea.
Jill V. Hunter
Department of Radiology, Baylor College of Medicine, One Baylor Plaza, MailStop 360, Houston, TX 77030.
Present address: Texas Children's Hospital, Houston, TX.

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