Cavum veli interpositi
A cavum veli interpositi (CVI), often incorrectly termed a cavum velum interpositum, is an anatomic variation where there is a dilatation of the normal cistern of the velum interpositum. When larger than 1 cm in axial transverse measurement, with outwardly bowed margins and positive mass effect, the term cyst of the velum interpositum or cavum veli interpositi cyst should be used.
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Clinical presentation
This variation is often detected incidentally and individuals are usually asymptomatic. Sometimes this space is not only visible but expanded as a cystic space, in which case patients may have symptoms relating to altered CSF flow (obstructive hydrocephalus leading to a headache).
Unlike the cavum septi pellucidi and cavum vergae, a cavum veli interpositi has not been associated with neuropsychiatric disorders 1.
Gross anatomy
The cavum veli interpositi extends below the splenium of the corpus callosum and the column of the fornix and above the internal cerebral veins. It is triangular in shape, the apex pointing anteriorly reaching as far forward as the foramen of Monro 1,4-5.
Epidemiology
A cavum veli interpositi is a relatively frequent finding on imaging of infants and young children, seen in ~25% (range 18-34%) of infants younger than 2 years of age 1. In most cases, this space closes as the individual ages.
Radiographic features
Neonatal ultrasound
May be seen as a cystic space in the pineal region and is more common in this age group than either pineal cysts or arachnoid cysts 1. The internal cerebral veins (best seen on color Doppler) can be seen below the cystic space 1.
CT/MRI
Classically seen as an enlarged CSF space situated between the atria/trigones of the lateral ventricles, behind the foramen of Monro, beneath the columns of the fornices and above the tela choroidea of the 3rd ventricle.
On axial images may have a triangular configuration pointing anteriorly, its anterior extent never extending further than the foramen of Monro 5.
On coronal imaging, the fornices are elevated and splayed 5.
Treatment and prognosis
In the vast majority of cases, patients are asymptomatic. In cases where cystic dilatation is present with positive mass effect and obstruction to normal CSF flow, surgical (endoscopic) fenestration may be curative 1.
Differential diagnosis
-
cavum septi pellucidi
- located anterior to the foramen of Monro, between the frontal horns of the lateral ventricles
- also triangular, but with the apex pointing posteriorly
-
cavum vergae
- rectangular in cross-section (parallel wall)
- located superior to the columns of the fornices, which are displaced inferiorly
-
pineal cyst
- ovoid or spherical
- located below the internal cerebral veins
- abutting the colliculi
-
arachnoid cyst of the quadrigeminal cistern
- usually eccentric, and not triangular in cross section
- located below the cerebral veins
- abutting the colliculi
Related Radiopaedia articles
Pineal region masses
The pineal region is anatomically complex and plays host to a number of unique masses and tumors as well as potentially affected by many entities seen more frequently elsewhere in the brain.
General reading
Pathology
- cystic non-neoplastic lesions
- pineal parenchymal tumors
- germ cell tumors
- tumors also encountered in the pineal region
- pineal gland metastases
- vascular lesions
Anatomy: Brain
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brain
- grey matter
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cerebrum
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cerebral hemisphere (telencephalon)
- cerebral lobes and gyri
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occipital lobe
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- lingual gyrus
- fusiform gyrus (Brodmann area 37)
- calcarine (visual) cortex
- cuneus
- temporal lobe
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cerebral sulci and fissures (A-Z)
- calcarine fissure
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- olfactory sulcus
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- posterior parolfactory sulcus
- precentral sulcus
- preoccipital notch
- postcentral sulcus
- rhinal sulcus
- rostral sulcus
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- superior frontal sulcus
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- superior temporal sulcus
- cortical histology
- cerebral lobes and gyri
- white matter tracts
- deep grey matter
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pituitary gland
- posterior pituitary and stalk (part of diencephalon)
- anterior pituitary
- inferior hypophyseal arterial circle
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cerebral hemisphere (telencephalon)
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brainstem
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grey matter
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cranial nerve nuclei
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cerebellum (part of metencephalon)
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cranial nerves (mnemonic)
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- facial nerve (CN VII) (segments mnemonic | branches mnemonic)
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vestibulocochlear nerve (CN VIII)
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circle of Willis
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normal variants
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cerebral veins
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superficial veins of the brain
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superficial veins of the brain
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- normal variants
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dural venous sinuses
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