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Intraventricular Obstructive Hydrocephalus


KEY FACTS

Terminology

  • Intraventricular obstructive hydrocephalus (IVOH) = obstruction proximal to foramina of Luschka, Magendie

    • Acute (aIVOH)

    • Chronic “compensated” (cIVOH)

Imaging

  • aIVOH = “ballooned” ventricles plus indistinct (“blurred”) margins

    • “Fingers” of CSF extend into periventricular white matter

    • 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

  • Longstanding overt ventriculomegaly in adults

Pathology

  • Intraventricular obstruction to CSF flow

    • CSF production continues, ventricular pressure ↑

  • Ventricles expand, compress adjacent parenchyma

  • Periventricular interstitial fluid increases

    • Leads to myelin vacuolization, destruction

  • Pathology varies depending on obstruction etiology

Clinical Issues

  • Headache, papilledema (aIVOH)

  • Nausea, vomiting, diplopia (6th nerve palsy)

Diagnostic Checklist

  • Size of ventricles generally correlates poorly with intracranial pressure

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

Axial FLAIR 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
.

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

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 WM
.

(Courtesy S. Candy, MD.)

TERMINOLOGY

Abbreviations

  • Intraventricular obstructive hydrocephalus (IVOH)

    • Acute IVOH (aIVOH)

    • Chronic “compensated” IVOH (cIVOH)

Synonyms

  • “Noncommunicating” hydrocephalus

Definitions

  • Enlarged ventricles caused by obstruction proximal to 4th ventricular outflow foramina (of Luschka, Magendie)

IMAGING

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