Cavum velum interpositum cyst causing symptomatic trapped ...

Cavum velum interpositum cyst causing symptomatic
trapped ventricle: A case report

Poster No.: R-0286
Congress: 2014 CSM
Type: Scientific Exhibit
Authors: T. Singh, S. Dupre; NAMBOUR/AU
Keywords: CNS, Neuroradiology brain, Anatomy, CT, MR, Endoscopy,
Cerebrospinal fluid
DOI: 10.1594/ranzcr2014/R-0286

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Aim

To describe the embryology, anatomy and pathology of cavum velum interpositum (CVI)
cysts, and to present a case of a CVI cyst resulting in a trapped lateral ventricle.

Methods and materials

Thorough literature search for the terms "cavum velum interpositum" together with related
search terms "cavum septum pellucidum" and "cavum vergae" was conducted, using
various search engines.

Cavum velum interpositum :

The velum interpositum space is the subarachnoid space between the connected fornix
and its respective choroid plexus, and the choroid forming the roof of the third ventricle
inferiorly. It is an anterior extension of the quadrigeminal plate cistern located superior to
the pineal gland. If this potential space is dilated, then it is known as the cavum velum
interpositum [1].
The clinical symptoms reported in patients with CVI cysts include macro- crania,
developmental delay, autism, epilepsy, seizures, and hydrocephalus. In the absence of
obstructive hydro-cephalus, the relationship of these symptoms to a CVI cyst found on
imaging is not clear [2]. Most cases of cavum velum interpositum occur in newborns [3].

The differential diagnosis of these midline cystic brain lesions includes an enlarged third
ventricle, a vein of Galen aneurysm, an interhemispheric cyst in relation to the agenesis
of the corpus callosum, and a suprasellar arachnoid cyst [3,4].

A typical axial MRI or CT scan will display a triangular-shaped CSF space between the
lateral ventricles. On sagittal images, a cavum velum interpositum appears like a slit with
collections of CSF behind the foramen of Monro, below the fornices, and above the tela
choroidea of the third ventricle [5].

Cavum septum pellucidum:

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When a septum pellucidum has a separation between its two leaflets this is termed a
cavum septum pellucidum.
The corpus callosum forms from anterior to posterior, except the rostrum, which connects
the genu and the lamina terminalis. Because of this, the leaflets of the septum pellucidum
are pulled towards the lamina terminalis, sealing the cavum from the posterior fornix to
the rostrum of the corpus callosum, due to the frontalization of fibers in the genu portion
by the seventh month [6]. When the gap is not closed, then the condition remains [1].

Cavum vergae:

First described by Verga and sometimes referred to as Verga's ventricle.
Cavum vergae is an extension of a cavum septum pellucidum posteriorly past the
columns of the fornix and foramina of Monro [1].

This condition takes place when there is a separation of the leaflets of the septum
pellucidum with posterior extension to the splenium of the corpus callosum. The anterior
columns of the fornix separate the anterior cavum septum pellucidum and the posterior
cavum vergae [1].

Results

CVI is an uncommon incidental finding on imaging studies. Cystic dilatation can occur, but
there are very few reported cases of patients with symptoms, or ventricular obstruction
attributable to the malformation. We report a case with of a symptomatic trapped ventricle
secondary to CVI cyst.

HISTORY:
A 62 year old female presented to the emergency deprtment with a 1month history of
headaches and truncal ataxia.

Non Contrast CT Head :

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Cavum Vellum Interpositum cyst measuring 5cm AP x 4.2 cm transverse x 4.6cm
craniocaudal, with mass effect resulting in a trapped lateral ventricle body, trigone and
temporal horn [Fig 2].
MRI Brain:
Marked dilation of the posterior portion of the right lateral ventricle including the posterior
horn and temporal horns. The choroid plexus is deviated anteriorly and abutts the wall of
the lateral trigone, with a septation just anterior to this.
No signal change in the surrounding parenchyma with loss of volume of the surrounding
parenchyma, consistent with a chronic insult.
SURGERY:
Right parietal burr hole, and durotomy was made. With endoscopic approach fenestration
of cyst into the left lateral ventricle and anteriorly into the right frontal horn was prformed.
POST OPERATIVE COURSE:
The patient remained symptom free, and was discharged.
None of the symptoms persisted.
A CT head was performed four years post fall which revealed persisting dilatation of the
right ventricular system (consistent with chronic dilatation and adjacent volume loss), with
no transependymal CSF spread or other signs of CSF obstruction.

Images for this section:

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Fig. 1: Axial Non Contrast Image of the brain with dilation of the lateral ventricles ( more
on the right).

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Fig. 2: Axial non-contrast images showing the margins of the CVI cyst.

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Fig. 4: Sagittal non contrast CT demonstrating dilation of both temporal and occipital
horns of the right lateral ventricle.

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Fig. 6: Coronal Non Contrast CT Demonstrates dilation of right lateral ventricle

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Fig. 3: Axial T2 image showing the CVI cyst.

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Fig. 5: Sagittal T2 image demonstrating dilation of both temporal and occipital horns of
the right lateral ventricle.

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Conclusion

Whilst Cavum Velum Interpositum is usually an asymtomatc incidental finding on imaging
in adults. Encystment can occur, which again is mostly asymptomatic.

Our case adds to the literature describing good response to fenestration surgery in
symptomatic CVI.

Personal information

Dr. Thakur Manas Singh
Radiology Registrar
Nambour Hospital
Queensland

Dr. Simon Dupre (FRANZCR)
Consultant Radioilogist
Nambour Hospital
Queensland

References

1. Tubbs RS, Krishnamurthy S, Verma K, Shoja MM, Loukas M, Mortazavi MM, Cohen-
Gadol AA: Cavum velum interpositum, cavum septum pellucidum, and cavum vergae: a
review : Childs Nerv Syst (2011) 27:1927-1930

2. Tong CKW, Singhal A, Cochrane DD: Endoscopic fenestration of cavum velum
interpositum cysts: a case study of two symptomatic patients:

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Childs Nerv Syst (2012) 28:1261-1264
3. Eisenberg VH, Zalel Y, Hoffmann C, Feldman Z, Achiron R(2003) Prenatal diagnosis
of cavum velum interpositum cysts: significance and outcome. Prenat Diagn 23:779-783
4. Vergani P, Locatelli A, Piccoli MG, Ceruti P, Patane L, Paterlini G et al (1999)
Ultrasonographic differential diagnosis of fetal intracranial
interhemispheric cysts. Am J Obstet Gynecol 180:423-428.
5. Mourgela S, Sakellaropoulos A, Gouliamos A, Anagnostopoulou S (2010) Cavum veli
interpositi: why this anatomical variant exists? Int J Anatomical Var 3:2-5
6. Larroche JC, Baudey J (1961) Cavum septi lucidi, cavum Vergae, cavum veli
interpositi: cavities of the median line. Anatomical and pneumoencephalographic study
in the neonatal period. Biol Neonat 3:193-236

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