Intraventricular Lesions

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IMAGING MODALITIES

• 1. Plain skull radiographs–May demonstrate calcification and evidence of raised intracranial tension.

• 2. Plain and contrast enhanced CT–May help in characterization of the lesion confirming the presence of calcification. MDCT may help in better localization through its multiplanar capability with the help volumetric data acquisition.

• 3. Conventional ventriculography/CT ventriculography – It has become obsolete with the advent of MRI.

• 4. MRI – It has transformed the way we look at intracranial lesions with its exquisite resolution and multiplanar capability.

• 5. Angiography – Indicated in vascular malformations and for angioembolization

Lateral Ventricular Masses

• About half of these in adults and one-fourth in children are found in the lateral ventricles

• In children, intraventricular neoplasms occur more often in the trigone, primarily because certain tumor types that favour the trigonal region have a predilection for occurring in children

Choroid Plexus Papilloma (CPP)

• It is the most common tumor occurring in the lateral ventricles in the first decade

• In children, they occur more commonly in the atrium of the lateral ventricles in contrast to adults, where these are more frequently seen in the fourth ventricle

• On CT the tumor is seen as a well defined, frond like mass which is iso or mildly hyperdense to brain.

• There is usually homogenous and intense enhancement following contrast administration though heterogenous enhancement is seen in adults and in tumors with carcinomatous change

• Diffuse hydrocephalus involving dilatation of all the ventricles occurs which is usually attributed to the overproduction of CSF

• MR the tumor is hypo to isointense on T1WI and iso to hyperintense to T2WI.

• There is homogenousand bright enhancement after gadolinium injection though heterogenous enhancement can also be seen when tumor outgrows its blood supply

Right lateral ventricular mass centered on the choroid plexus and display hyper intense signal on T1, hyperintense signal on T2 with avid enhancement on post contrast study. There is associated unilateral transependymal CSF permeation.

Astrocytoma

• It usually arises in the tissues around the ventricle and invades the lateral ventricle secondarily

• The most common site is the thalamus where it can develop into a large mass within the lateral ventricle.

• On CT, the low grade astrocytoma is seen as a poorly marginated low density mass. There is usually minimal mass effect or edema around the lesion.

• It shows little or no contrast enhancement. • The anaplastic astrocytoma and glioblastoma

have heterogenous appearance due to areas of hemorrhage, necrosis or cyst formation

• MRI is helpful in the evalua-tion of degree of differentiation of the astrocytoma.

• The low grade astrocytoma has a signal pattern lower than normal brain parenchyma. The high grade gliomas and glioblastomas show varied signal intensity with areas of necrosis, hemorrhage and cyst formation.

Astrocytoma: contrast CT showintensely enhancing heterogenous mass with dense calcificationoccupying the frontal horn and body of right lateral ventricle

Subependymal Giant Cell Astrocytoma (SGCA)

• SGCA is a circumscribed tumor which occurs almost exclusively in patients with tuberous sclerosis (TS).

• It is a slow growing tumor and is discovered either during the course of routine studies in patients with TS or because it causes hydrocephalus

• It arises usually in the region of foramen of Monro but can occur anywhere in the ventricles

• On CT SGCA appears as a well-defined mass which is iso to hyperdense to cerebral parenchyma and enhance sharply following contrast injection.

• Foci of calcification are common. • On MRI the mass is hypointense on T1WI and

hyperintense on T2WI with prominent enhancement after IV gadolinium injection

There is an intraventricular mass in the foramem of Monro area, on the left, with contrast enhancement and irregular calcifications. Multiple subependymal calcified nodules are also seem.

Ependymoma

• This is commonly seen in children in the posterior fossa with a predilection for males and is less common than astrocytoma.

• Supratentorial ependymomas are seen in 30-40 percent cases and are usually extraventricular (75-80%). When intraventricular they usually arise in the trigone of lateral ventricle

• On CT ependymomas show cystic component (70%) and calcification (50%). The solid component is isodense to brain parenchyma with bright enhancement with contrast

• On MRI, the tumor is iso to hypointense on T1WI and hyperintense on T2WI. There is usually heterogeneity due to areas of hemorrhage, necrosis and calcification . With gadolinium administration there is usually moderate to intense enhancement.

• Although ependymoma is a benign tumor, it has a high recurrence rate and can spread through CSF pathways

Ependymoma: Axial T1 (A) and T2 (B) MR images show tumor having solid (small arrow) and cystic (large arrow) componentin the trigone of right lateral ventricle with pariventricular edema and hydrocephalus

Meningioma

• Intraventricular meningioma is an uncommon tumor and constitutes 0.5 to 3 percent of all intracranial tumors.

• It is more common in adult females. Although rare, the meningiomas in children are more frequently intraventricular and malignant

• show equal incidence in both sexes and are usually associated with neurofibromatosis

• meningioma appears as a sharply defined, globular mass, iso- to hyperdense to brain parenchyma.

• Calcification is seen in 45 percent cases. • It shows diffuse intense enhancement with contrast • On MRI it is isointense (60%) or hypointense (40%) on T1WI

and isointense (50%) or hyperintense (50%) on T2WI .• There is homogenous and strong enhancement with IV

gadolinium administration .• Proton MR spectroscopy may reveal alanine peak with

reduced NAA.

Metastases

• Intraventricular metastases can be due to blood borne dissemination or by paraventricular spread.

• The blood borne metastasis most often involves the choroid plexus in the ventricles.

• The common primary tumors with intraventricular metastases are bronchogenic carcinoma, carcinoma of breast and melanoma

• On CT or MRI the choroid plexus metastasis shows expansion of choroid plexus with marked contrast enhancement

• The paraventricular spread of tumor can occur along CSF pathways to ventricular ependymal lining and leptomeninges or, infiltration in the subependymal space as a sheet of tumor cells.

• Malignant astrocytomas are the commonest tumor to show CSF spread followed by ependymomas, medulloblastomas, pineal tumors and choroid plexus papillomas

• On CT, these lesions are seen as discrete, iso to hyperdense nodule or sheet like subependymal rim surrounding a part or all of the ventricle .

• On MRI they appear hypointense on T1WI and hyperintense on T2WI. Melanoma metastasis differs in being hyperintense on T1WI and isointense on T2WI

Metastasis: CECT shows diffuse ependymal enhancement andhyperdense nodule in the left paraventricular region with edema in patientof carcinoma thyroid

Central Neurocytoma

• It is a well-differentiated benign intraventricular tumor of neuroepithelial origin

• The site of origin is usually at or near the midline at the base of the septum pellucidum and usually in close proximity to foramen of Monro. It is quite large at presentation and usually presents due to obstructive hydrocephalus.

• On CT, it appears as iso to slightly hyperdense mass with cystic changes and foci of calcification.

• Mild to moderate enhancement with contrast is seen.

• On MRI, the tumor show heterogenous pattern and there is variable enhancement following IV gadolinium administration

• The differential diagnosis is mainly ependymoma, subependymoma and oligodendrogliomas which are most often hyperintense.

• Heterotopic grey matter neither shows enhancement nor calcification.

• Meningioma is usually located posteriorly in the atrium of lateral ventricle as are choroid plexus tumors

Vascular Malformations

• AVMs and cavernous angiomas can have some part actually within the ventricle

• Lateral ventricle is the most common to be involved but they can occur in any part of the ventricular system

• On CT these lesions are seen as heterogenous areas, with or without calcifications.

• On contrast administration, abnormal vessels are seen as tortuous high density structures.

• MRI is superior to CT in demonstrating the feeding vessels the nidus and the serpiginous draining veins which appear as flow voids both on T1WI and T2WI.

• Angiography is the confirmatory study which shows all aspects of the vascular malformations

• There can occur intraventricular fluid-fluid level seen in cases of intraventricular hemorrhage

Intraventricular hemorrhage: NCCT brain shows presence ofhemorrhage in the left cerebral hemisphere extending into the ipsilaterallateral ventricle due to AVM rupture

Choroid Plexus Cysts and Xanthogranulomas

• Xanthogranulomas are usually discovered incidentally

• They are symptomatic only when they cause obstruction at foramen of Monro

• Cysts show low density on CT and show signal characteristics similar to CSF on MRI.

• They lack contrast enhancement and show diffusion restriction on DWI.

• Xanthogranulomas are dense on CT and may show flecks of calcification. The center is often of low attenuation due to fat content.

• On MRI, these are well defined partially cystic masses that appear hypo or isointense on T1WI and iso to hyperintense on T2WI and show contrast enhancement

CECT shows choroid plexsus cyst well-defined cystic lesion in thetrigone of left lateral ventricle with anteriorly displaced choroid plexus(arrow

Third Ventricular Masses

• In children, hydrocephalus is the most common feature of 3rd ventricular masses

• In adults mental and behavioral changes, particularly increasing apathy, are common. Depending on the parts of the ventricle involved these tumors can be further categorized as anterior or posterior 3rd ventricular masses

Anterior Third Ventricular MassesColloid cyst

• It arises from the roof of the 3rd ventricle at the level of foramen of Monro.

• They are round to oval lesions and vary in size from few millimeters to several centimeters in diameter

• Symptoms of intermittent obstruction are common and sudden death due to acute obstruction has been reported.

• On CT, colloid cysts are well encapsulated, homogeneously hyperdense masses which show little or no contrast enhancement .

• Calcification is not a feature. • On MR, the signal characteristics of colloid cysts vary

widely. The most common appearance is a mass that is hyperintense on T1WI and hypointense on T2WI though it can be isointense on both T1 and T2 WI

• Rim enhancement following contrast can be observed. CSF flow artifacts at foramen of Monro can mimic colloid cysts (pseudotumor)

Germinoma

• The tumor that occurs solely in the 3rd ventricle is called “ectopic pinealoma” and rarely occurs in association with the posterior third ventricular germinoma.

• The tumor has the potential to spread via CSF pathways and therefore CSF analysis for tumor cells can be helpful in obtaining diagnosis in some patients

• On non-contrast CT, the germinoma appears as an iso to hyperdense mass with indistinct tumor boundaries.

• Calcification is rare.• It shows uniform enhancement on contrast

injection. • The tumor shows similar characters on MRI with

homogenous enhancement following IV gadolinium administration.

Germinoma:A large enhancing mass is centered on the pineal region. It is heterogeneous with areas of cystic change. There is marked compression of the tectum with resulting obstructive hydrocephalus. A little surrounding oedema is also present

Craniopharyngioma

• Primary third ventricular craniopharyngioma is extremely rare and is almost always an extension of the craniopharyngioma from the sellar supra sellar region.

• There are two peaks of occurrence; the first in young children less than 15 years and the second in the 5th to 6th decades.

• On CT the tumor shows solid and cystic components in majority of patients . The solid component shows contrast enhancement particularly in children

• Calcification is seen in almost all patients in childhood while it is seen in up to 50 percent of cases in adults.

Craniopharyngioma: CECT shows isolated anterior thirdventricular cystic lesion which was proven to be craniopharyngioma onsurgery. Note dystrophic parenchymal calcification (arrow)

Epidermoid and Dermoids

• These are uncommon tumors encountered in the anterior 3rd ventricle. They usually present due to obstructive hydrocephalus.

• On CT the epidermoid appears as hypodense lesion which does not enhance with contrast administration. Dermoid usually shows the presence of fat and calcification.

• On MRI, the epidermoid shows signal characters similar to CSF while the dermoid shows hyperintense foci of fat and areas of signal loss due to calcification on T1WI.

Cysticercosis

• Intraventricular cysticercosis presents with repeated attacks of meningitis in children and with hydrocephalus in adults

• It is seen in 20-25 percent of all neurocysticercosis, most commonly in 4th ventricle, foramen of Monro and lateral ventricle

• It can be difficult to diagnose on CT because it shows similar attenuation like CSF. MR is the best imaging modality and T2WI clearly shows the hyperintense cyst in the ventricular wall.

• It can be of the racemose variety at times and is not readily differentiated from a tuberculoma. Unilocular cystic forms may often show an eccentric hypointense nodule suggestive of scolex within the cyst on thin T2 weighted sequences

A well defined thin walled cystic lesion is noted within the third ventricle causing its expansion. It is hypointense on T1, hyperintense on T2 and suppressed on FLAIR images. An eccentric enhancing nodule is seen within this lesion, findings are suggestive of intraventricular cysticercosis.

Mild to moderate dilatation of bilateral lateral ventricles with periventricular ooze is noted

Posterior Third Ventricular Masses

• A variety of structures in and around the posterior third ventricle including the pineal gland can be the origin of these tumors.

• The tumors can be astrocytomas of all grades, ependymomas, germinomas, meningiomas, vascular malformations, pineal tumors, metastasis or primary lymphomas.

• Regardless of the origin, these masses cause obstructive hydrocephalus due to compression of the posterior third ventricle or aqueduct and abnormal eye movements from pressure on, or infiltration of the pretectal area

• Glial Tumors Astrocytomas comprise 25 percent of the mass lesions in the posterior third ventricle.

• Other gliomas like ependymomas, oligodendrogliomas, or glioblastomas can also occur in this area.

• There are no significant age or sex predilection. • The imaging features are similar to those

occurring in other areas of brain

Germinoma• Germinoma is more common in posterior than anterior 3rd

ventricle.• It is common in young males and causes precocious puberty• It may lead to Parinaud’s syndrome and hydrocephalus. • On CT and MRI, it appears as well demarcated, homogenous soft

tissue mass and shows uniform enhancement after IV contrast administration.

• There is no calcification within the tumor. • The tumor spreads through CSF pathway and responds to

radiotherapy. Therefore after obtaining tissue diagnosis (either by stereotactic or open biopsy) the entire neuroaxis should be irradiated.

large lobulated mass is centered on the pineal gland, engulfing the pineal calcifiation. It is somewhat hyperdense compared to adjacent brain. A further smaller mass is seen in the floor of the third ventricle. The midbrain is distorted, compressed and demonstrates low density suggestive of oedema. Obstructive hydrocephalus is present.

Teratoma

• Mature teratomata are well-differentiated benign tumors with a malignant potential.

• They are well encapsulated and show no evidence of infiltration of surrounding structures.

• On CT teratomas show areas of fat attenuation and calcification/ossification.

• The solid portion can show some degree of contrast enhancement.

• OnT1WI the fat in the teratoma appears hyperintense. Signal loss due to calcific foci can be seen on both T1WI and T2W.

Pineoblastoma

• It resembles other PNETs (e.g. Medulloblastoma) histologically.

• It is an infiltrative tumor and presents with obstructive hydrocephalus or Parinauds’ syndrome.

• On CT, it appears hyderdense and enhances homogenously and brightly following IV contrast injection .

• On MRI, it is hypo or iso intense on T1WI and hyperintense on T2WI. Small areas of necrosis, hemorrhage, cyst formation or calcification can be seen.

• There is typically brilliant enhancement on gadolinium injection.

• It also shows spread along CSF pathways like germinoma and therefore the entire craniospinal axis should be imaged in such patients

A large mass ( * ) centred on the pineal region elvates, splays and partially engulfs the internal cerebral veins (blue arrows). Pineal calcifications (red arrows) are best seen on CT and are located at the periphery of the mass.

Enhancing soft tissue is also seen filling the floor of the third ventricle (green arrows) and in the lateral ventricles (best seen in the left forntal horn - yellow arrow)

Fourth Ventricular Masses

• Primary fourth ventricular neoplasms are common in children but rare in adults. The pediatric tumors are cerebellar astrocytoma, medulloblastoma, ependymoma and choroid plexus papilloma.

• In adults, metastases are the most common fourth ventricular neoplasm. Other tumors such as choroid plexus papilloma, epidermoid, dermoid are rare

• masses like arachnoid cysts, vascular malformation, cysticercosis,minflammatory cysts are occasionally seen within the fourth ventricle

Cerebellar astrocytoma

• It is the most common posterior fossa neoplasm and constitutes 25 percent of all fourth ventricular neoplasms in children.29 Histologically majority of the tumors are of pilocytic type

• It usually originates from the vermis and extends anteriorly into the fourth ventricle. Rarely, the tumor arises primarily within the ventricle itself.

• On CT, the tumor appears as a large lesion with solid (40%) or cystic (60%) components. The cystic mass shows a mural nodule. The nodule is always solitary and isodense with cerebellum on non contrast scans. The nodule may or may not be calcified.

• On contrast administration the nodule shows intense, homogenous enhancement which does not extent beyond the contor of the cyst

• On MRI, the appearance is similar with cystic component being hypo- to isointense on T1WI and hyperintense on T2WI. The

• mural nodule shows intense enhancement with IV gadolinium

Pilocytic Astrocytoma: MRI brain showing a large posterior fossa cystic mass with enhancing mural nodule

Medulloblastoma

• This primitive neuro-ectodermal tumor (PNET) is the second most common posterior fossa tumor constituting one-fourth of all posterior fossa tumors in children

• The tumor shows dissemination along the CSF pathways

• Spinal cord metastases are also common (12- 40%). Dorsal and lumbosacral region is seeded most commonly and the deposits are often multiple

• On CT medulloblastoma is usually seen as a large, mildly hyperdense, midline solid mass arising from the inferior vermis.

• The tumor bulges anteriorly into the fourth ventricle and may extend into adjacent cisterns.

• Rarely, calcification, hemorrhage and necrosis are seen.

• On contrast, it shows moderate degree of homogenous enhancement.

• On MR, the typical medulloblastoma fills the fourth ventricle and extends inferiorly through foramen of Magendie into the cistern magna.

• It appears hypointense on T1WI and shows variable signal pattern on T2WI.

• Moderate enhancement is typical after IV gadolinium injection . Due to high tumor cellularity it may show diffusion restriction with low ADC values.

• Other fourth ventricular tumors like ependymoma and astrocytomas can often be differentiated from it on MRI based on this findings

Ependymoma

• It is the third most common fourth ventricular tumor in children. Nearly 50 percent of posterior fossa ependymomas are located in the fourth ventricle

• On CT, the mass is midline and situated within an expanded fourth ventricle and often shows calcification (50%). There is usually moderate enhancement on contrast administration

• The mass typically extends outwards into cerebellopontine cisterns or into the cisterna magna through the fourth ventricular exit foramina (Figs 19.19 B and C).

• Hydrocephalus is nearly always seen. The tumor exhibits similar morphology on MRI as hypo to isointense signal on T1WI and intermediate to hyperintense signal on T2WI with heterogenous post contrast enhancement

Ependymoma: CECT (A) showing an illdefined heterogeneously enhancing fourth ventricular tumor with presence of calcification.

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