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KEY FACTS

Terminology
- Intraventricular obstructive hydrocephalus (IVOH) = obstruction proximal to foramina of Luschka, Magendie - Acute IVOH (aIVOH) - Chronic compensated IVOH (cIVOH)
Imaging
- aIVOH = ballooned ventricles plus indistinct (blurred) margins - "Fingers" of CSF extend into periventricular WM - Most striking around ventricular horns (periventricular halos) - After decompression, corpus callosum may show hyperintensity
- cIVOH = ballooned ventricles without periventricular halo
Top Differential Diagnoses
- Ventricular enlargement secondary to parenchymal loss
- Normal-pressure hydrocephalus
- Extraventricular obstructive hydrocephalus
- Choroid plexus papilloma
Pathology
- Intraventricular obstruction to CSF flow - CSF production continues, ventricular pressure ↑
- Ventricles expand, compress adjacent parenchyma
- Periventricular interstitial fluid ↑ - Leads to myelin vacuolization, destruction
- Pathology varies depending on obstruction etiology
Clinical Issues
- Varies with acuity, severity
- Headache, papilledema (aIVOH)
- Nausea, vomiting, diplopia (6th nerve palsy)
Diagnostic Checklist
- Size of ventricles generally correlates poorly with intracranial pressure

TERMINOLOGY

Abbreviations
- Intraventricular obstructive hydrocephalus (IVOH) - Acute IVOH (aIVOH) - Chronic compensated IVOH (cIVOH)
Synonyms
- Noncommunicating hydrocephalus
Definitions
- Enlarged ventricles caused by physical obstruction at or proximal to 4th ventricular outflow foramina (of Luschka, Magendie)

IMAGING

General Features

Best diagnostic clue

- aIVOH
        - Ballooned ventricles with indistinct (blurred) margins
- cIVOH
        - Ballooned ventricles without periventricular halo

Size

- Bifrontal horn:intracranial diameter ratio > 0.3
- Temporal horn width > 3 mm

Morphology

- Varies with site, duration of blockage
- Global/focally enlarged ventricle(s) ± ↑ intracranial pressure (ICP)
- Ventricles proximal to obstruction enlarge, appear more rounded
- Look for enlarged anterior recesses of 3rd ventricle

CT Findings

NECT

- Large ventricles proximal to obstruction
        - aIVOH
                  - Ballooned ventricles with periventricular low-density halo
        - cIVOH
                  - Ballooned ventricles without thick periventricular halo
- Basal cisterns, sulci compressed/obliterated

MR Findings

T1WI

- Lateral ventricles enlarged
- Corpus callosum (CC) thinned, stretched upward
        - May be impinged against falx
        - Impaction may cause pressure necrosis
- Fornix, internal cerebral veins (ICV) displaced downward
- Enlarged 3rd ventricle often herniated into expanded sella
- Funnel-shaped aqueduct of Sylvius in aqueductal stenosis

T2WI

- aIVOH
        - "Fingers" of CSF-like hyperintensity extend into periventricular white matter (WM), most striking around ventricular horns (periventricular halos)
        - Disturbed/turbulent CSF flow
        - Absent aqueductal flow void common
        - CC may appear hyperintense
- cIVOH
        - Large ventricles, normal CSF pressure
        - No periventricular halo
        - CC may show hyperintensity after decompression (15% of shunted IVOH cases)
- Thin-section T2WI, FIESTA, or CISS sequences
        - Exquisitely delineate CSF spaces
        - May demonstrate subtle abnormalities not detected on standard images

FLAIR

- Fluid in periventricular halo does not suppress

T1WI C+

- Neoplasm causing IVOH may enhance
- aIVOH may cause leptomeningeal vascular stasis, enhancement
        - Can mimic meningitis, metastases

MRS

- Small lactate resonances can be detected in up to 20% of CSF spaces, even if no hydrocephalus

Other Modality Findings
- Contrast-enhanced ventriculography - MR/CT used to identify site of obstruction, status of 3rd ventriculostomies - MR can be used for assessing CSF flow
- Cardiac gated-phase contrast MR - May show absent aqueductal CSF flow

Imaging Recommendations

Best imaging tool

- MR with contrast to evaluate cause of CSF obstruction

Protocol advice

- 3D FEISTA/CISS
        - ↓ CSF flow artifact
        - Allows better delineation of ventricular contour, septa
- Sagittal high-resolution T2-weighted images

DIFFERENTIAL DIAGNOSIS

Ventricular Enlargement Secondary to Parenchymal Loss
- Old term: Ex vacuo hydrocephalus (not used)
- Age related (ventricular volume ↑ 1.2-1.4 mL after 60 years) - Ischemia/infarction, trauma, infection, toxic
- Obtuse frontal angle (> 110°)
- Diffuse/focal enlargement of sulci, cisterns
- Normal lateral ventricles can be asymmetric (related to handedness, not sex)
- May correlate with some psychiatric disorders (e.g., schizophrenia)
Normal-Pressure Hydrocephalus
- Progressive dementia, gait disturbance, incontinence
- Ventricular dilation with normal CSF pressure
- Sulci normal/minimally enlarged
- ↑ CSF displacement through aqueduct
- MRS shows lactate peak
Extraventricular Obstructive Hydrocephalus
- Dilated ventricles due to mismatch between CSF formation, absorption
- ↓ CSF absorption through arachnoid villi
- Subarachnoid hemorrhage most common cause - Others: Meningitis, carcinomatosis, granulomatous disease
Choroid Plexus Papilloma
- Accounts for 2-5% of childhood intracranial tumors
- Child < 5 years with ↑ ICP
- Most common lateral ventricle trigone
- May overproduce CSF
- Hemorrhage, tumor spread may cause IVOH
Longstanding Overt Ventriculomegaly in Adults
- Early childhood onset or longstanding progression of hydrocephalus into adulthood
- Markedly enlarged ventricles, high ICP
Benign Enlargement of Subarachnoid Spaces and Ventricles
- Seen in association with macrocephaly in infants
- Not associated with developmental delay

PATHOLOGY

General Features

Etiology

- Normal CSF production = ~ 0.4 mL/min, 500-600 mL/24 hrs
        - Total volume of CSF in adult = 125-150 mL
- Intraventricular obstruction to CSF flow; as CSF production continues, ventricular fluid pressure ↑
- Ventricles expand, compress adjacent parenchyma; stretching may rupture/open ependymal cell junctions
- Periventricular interstitial fluid ↑ → myelin destruction
- Etiology depends on site
        - Foramen of Monro
                  - Colloid cyst
                  - Subependymal nodule, tuberous sclerosis complex
                  - Subependymal giant cell astrocytoma
        - 3rd ventricle
                  - Pituitary macroadenoma
                  - Craniopharyngioma
        - Aqueduct of Sylvius
                  - Aqueductal stenosis
                  - Tectal glioma
                  - Pineal region tumors
        - 4th ventricle
                  - Medulloblastoma, ependymoma
                  - Glioma, pilocytic astrocytoma, hemangioblastoma
                  - Cerebellar infarct
                  - Congenital anomalies (Chiari malformations, Dandy-Walker malformations, rhombencephalosynapsis)
        - Metastasis, neurocysticercosis, or meningioma can occur at multiple intraventricular locations

Genetics

- Cell adhesion molecule L1 (*L1CAM*) only gene recognized to cause congenital hydrocephalus
        - Located on X chromosome (Xq28)

Complications of hydrocephalus - CC impingement syndrome - Medial atrial diverticula

Gross Pathologic & Surgical Features
- Focal/generalized ventricular enlargement
- Ependyma, adjacent WM are secondarily injured
- Variable pathology depending on causative factor
Microscopic Features
- ↑ periventricular extracellular space
- Ependymal lining damaged or lost; surrounding WM becomes pale and rarefied

CLINICAL ISSUES

Presentation

Most common signs/symptoms

- Varies with acuity, severity
- Headache, papilledema (aIVOH)
- Nausea, vomiting, diplopia (6th nerve palsy)

Clinical profile

- Varies with etiology, severity, age of onset

Demographics

Age

- May be any age from in utero (congenital hydrocephalus) to adult

Epidemiology

- Epidemiologic data varies widely, depending upon etiology and type of hydrocephalus

Natural History & Prognosis
- Usually progressive unless treated
Treatment
- Medical management to delay surgical intervention
- CSF diversion (shunt), endoscopic intervention, and ventriculostomy
- Surgery to alleviate primary cause of obstruction
- Most common neurosurgical procedure in children = CSF shunting for hydrocephalus

DIAGNOSTIC CHECKLIST

Consider
- Longstanding aqueductal stenosis can be caused by slow-growing tectal tumor
- Rarely, hydrocephalus caused by spinal tumor
Image Interpretation Pearls
- Size of ventricles generally correlates poorly with ICP
- Pulsatile CSF may create confusing signal intensity, even mimic intraventricular mass
- Ventricular asymmetry can be normal variant
- If seen with absent septum pellucidum in fetus/neonate, look for vermis (r/o rhombencephalosynapsis)

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References

Selected References

Images

Selected Images

Axial FLAIR MR in a patient with headache and vomiting demonstrates a colloid cyst at the foramen of Monro causing intraventricular obstructive hydrocephalus (IVOH) with dilatation of both lateral ventricles . Note thin rim of periventricular hyperintensity due to interstitial edema.

Axial NECT in a patient with pineal region germinoma shows marked dilatation of the lateral ventricles and anterior 3rd ventricle with periventricular halo and diffuse effacement of the cortical sulci.

Coronal T1 C+ MR in a patient presenting with headache and ataxia demonstrates a large heterogeneously enhancing mass in the left cerebellum with mass effect and effacement of the 4th ventricle . Biopsy revealed a glioblastoma.

Axial FLAIR MR in the same patient shows marked dilatation of the lateral ventricles with extensive periventricular interstitial edema caused by compromised drainage of interstitial fluid or transependymal CSF migration.

Sagittal CISS MR in a patient with obstruction at the 4th ventricular outlet due to adhesions shows ballooning of the 4th ventricle , widening of the aqueduct of Sylvius , dilated 3rd and lateral ventricles with downward sloping of 3rd ventricular floor .

Axial FLAIR MR in a patient with tuberous sclerosis shows large subependymal giant cell astrocytoma causing obstructive hydrocephalus with mild periventricular edema . Note the subtle hyperintensity in the occipital lobe tuber .

Sagittal CISS MR in a patient with aqueductal stenosis due to a thin web causing obstructive hydrocephalus is shown. High resolution thin-section T2 MR exquisitely delineates the CSF spaces and may demonstrate subtle abnormalities not detected on standard sequences.

Axial FLAIR MR in the same patient shows marked enlarged lateral ventricles with a very thin periventricular hyperintense rim and no sulcal effacement due to chronic compensated IVOH.

Axial FLAIR MR in a patient with IVOH shows an ependymal cyst at the foramen of Monro with asymmetric dilatation of the lateral ventricles, L > R. There is marked bulging of the medial wall of the left lateral ventricle.

Sagittal T1 MR in the same patient demonstrates the large medial atrial diverticula , which herniates inferiorly through the tentorial incisura into the posterior fossa, compressing the vermis , tectal plate , aqueduct, and 4th ventricle .

Additional Images

Sagittal T1WI MR shows large mass within the 4th ventricle causing IVOH or noncommunicating hydrocephalus.

Sagittal T2WI MR in the same patient shows transependymal CSF flow, seen here as "fingers" extending into white matter around the enlarged lateral ventricle. The case was medulloblastoma with acute IVOH.

Coronal T1 C+ MR shows IVOH with a large enhancing intraventricular mass causing marked enlargement of the lateral ventricles .

Axial NECT in the same patient shows the large intraventricular mass within the 4th ventricle. Note the dilated temporal horns .

Sagittal T1WI MR shows IVOH secondary to aqueductal stenosis and distal stenosis of cerebral aqueduct . Note the enlarged lateral and 3rd ventricles.

Axial FLAIR MR shows neurosarcoidosis and IVOH secondary to diffuse meningeal disease. Periventricular white matter hyperintensities are also present, as well as choroid involvement .

Coronal T1 C+ MR shows neurocysticercosis involvement within the 3rd ventricle and aqueduct , causing IVOH. The lateral ventricles are dilated.

Axial FLAIR MR shows neurocysticercosis resulting in IVOH. Large intraventricular cysts are present in the lateral vents , obstructing the foramina of Monro.

Axial T1WI MR shows a well-defined, hyperintense lesion at the foramen of Monro in a patient with headaches, most consistent with a colloid cyst. Note the enlargement of the lateral ventricles due to obstruction at the foramen of Monro.

Sagittal T1WI C+ MR shows a homogeneously enhancing mass in the posterior 3rd ventricle , which causes obstruction and dilatation of the lateral and 3rd ventricles. On pathology, this was an astrocytoma.

Coronal T2WI MR shows a pilocytic astrocytoma centered in the right thalamus causing severe mass effect on the 3rd ventricle and resultant obstructive hydrocephalus .

Axial T2WI MR demonstrates a well-defined CSF intensity cyst with the left temporal horn most consistent with an ependymal cyst . Note the dilated and trapped left temporal horn .

Sagittal T1WI C+ MR shows an enhancing mass in the pineal region causing mass effect on the tectal plate and aqueductal obstruction. Note the extensive leptomeningeal enhancement due to CSF spread of tumor. CSF cytology showed a primitive neuroectodermal tumor.

Axial T2WI MR in a patient with corpus callosum impingement syndrome, after shunting for severe IVOH, shows a shunt tube , bilateral subdural fluid collections, and striated hyperintensity in the corpus callosum with somewhat less striking changes in the periventricular white matter . (Courtesy S. Candy, MD.)

Axial NECT in a patient with headache demonstrates a classic colloid cyst at the foramen of Monro causing IVOH with dilatation of both lateral ventricles . Note the periventricular hypodensities due to transependymal leakage of CSF.

Axial CECT demonstrates a subacute left posterior inferior cerebellar infarct causing mass effect on the 4th ventricle and resulting in obstructive hydrocephalus .

Axial FLAIR MR shows massive enlargement of the 3rd and lateral ventricles by a CSF-like mass within the 3rd ventricle . There is periventricular interstitial edema . At surgery, an ependymal cyst of the 3rd ventricle was found and fenestrated.

Sagittal T1 MR shows a large arachnoid cyst in the superior cerebellar cistern causing severe mass effect on the tectal plate and aqueduct .There is dilatation of the 3rd and lateral ventricles with thinning of the corpus callosum .

Sagittal T1WI C+ MR shows a cyst with an enhancing mural nodule of hemangioblastoma in the vermis, causing severe effacement of the 4th ventricle and obstructive hydrocephalus.

Sagittal T2 MR demonstrates an enlarged T2 hyperintense tectal plate glioma , which causes obstruction at the aqueduct and dilatation of the lateral and 3rd ventricles .

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KEY FACTS

Terminology

Imaging

Top Differential Diagnoses

Pathology

Clinical Issues

Diagnostic Checklist

TERMINOLOGY

Abbreviations

Synonyms

Definitions

IMAGING

General Features

Best diagnostic clue

Size

Morphology

CT Findings

NECT

MR Findings

T1WI

T2WI

FLAIR

T1WI C+

MRS

Other Modality Findings

Imaging Recommendations

Best imaging tool

Protocol advice

DIFFERENTIAL DIAGNOSIS

Ventricular Enlargement Secondary to Parenchymal Loss

Longstanding Overt Ventriculomegaly in Adults

Benign Enlargement of Subarachnoid Spaces and Ventricles

PATHOLOGY

General Features

Etiology

Genetics

Gross Pathologic & Surgical Features

Microscopic Features

CLINICAL ISSUES

Presentation

Most common signs/symptoms

Clinical profile

Demographics

Age

Epidemiology

Natural History & Prognosis

Treatment

DIAGNOSTIC CHECKLIST

Consider

Image Interpretation Pearls

References

Selected References

Images

Selected Images

Additional Images

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