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The invisible cyst: triventriculomegaly due to third ventricular ependymal cyst. , 4–8 September, 2016.

Authors:
Case Report
We describe an ependymal cyst
of the posterior third ventricle in
a13-year old child who presented
with tinnitus, delayed puberty and
tri-ventricular hydrocephalus
identified on conventional MRI
sequences. On examination, the
patient was neurologically intact
with no typical symptoms or signs
of raised intracranial pressure.
The cyst was only clearly visible
once high resolution mid-sagittal
(CISS) MRI was performed. The
child underwent endoscopic
resection with resolution of the
tinnitus and improved radiological
appearances post-operatively.
Imaging:
All images were acquired using a
3T scanner. T2-weighted: slice
thickness = 5mm, TR 5100ms, TE
98.6ms; T2 ventriculostomy: slice
thickness = 1.5mm, TR 3500ms,
TE 82.1ms. T2 ISO cube: slice
thickness = 1mm, TR 4000ms, TE
126ms. CISS (constant
interference steady state): slice
thickness = 0.7mm, TR 5.53ms, TE
2.5ms.
T1, T2w-FLAIR, DTI and ADC
sequences were also performed.
Background
Ependymal cysts are neuro-
epithelial cysts with histological
similarities to choroid plexus
cysts. They rarely occur in the
third ventricle1and, even more
rarely, cause obstructive
hydrocephalus in this location2.
Imran M, Pandit A, Kalyal N, Tailor J, Jarosz J, Gontsarova A, Bodi I, King A, Bassi S, Chandler C and Zebian B
Department of Neurosurgery, King’s College Hospital, Denmark Hill, London
The ‘Invisible Cyst’: Tri-ventriculomegaly Due To Third Ventricular Ependymal Cyst
And The Importance Of High Resolution Magnetic Resonance Imaging
1.Din F et al. Ependymal Cyst of Third Ventricle
Presenting as Intermittent Ataxia in a 2 Year
Old Child. Journal of Neurology and
Neuroscience.2016;7(61).
2.Ormond R et al. Obstructive hydrocephalus
due to a third ventricular neuroepithelial cyst.
Journal of Neurosurgery: Pediatrics.
2008;1(6):481-484.
References
Discussion
Ependymal cysts causing obstructive
hydrocephalus are extremely rare.
They can easily be missed if the
patient is not imaged using high
resolution MR possibly accounting
for their rarity. We have found that,
whereas T2-vent and -cube
sequences are excellent at
demonstrating flow, the CISS
sequence is superior at delineating
more subtle aspects of anatomy. In
the present case, this sequence
allowed us to identify a previously
invisible cyst and alter our operative
approach accordingly. In addition, we
have shown the safety and efficacy
of the endoscopic approach. What is
of further interest in our case is the
patient’s presentation with tinnitus
in the absence of headache and the
resolution of symptoms post-
operatively. We believe that the
combination of T2-cube and CISS
sequences are essential in the
diagnostic phase of patients with
hydrocephalus especially where the
cause is not easily identified and if
clinical urgency allows. We also
believe that endoscopic resection of
symptomatic ependymal cysts
should be attempted when deemed
safe to do so, rather than a
ventriculostomy only or a shunt.
BD
CISS
C
A
T2 T2-vent T2-cube
Results
A right frontal burr hole was
performed. A disposable neuro-
endoscope was then advanced into
right lateral ventricle. The dome of
the cyst was visible through the right
foramen of Monro (1). The cyst was
then cauterised (2), removed
piecemeal using biopsy forceps (3)
allowing visualisation of the Aqueduct
of Sylvius (4). Tissue samples from the
cyst were sent. A ventriculostomy
was performed in the floor of the
third ventricle in case adhesions
formed at the level of the aqueduct
(5).
1
2
45
3
ab
The cyst was lined by flattened cuboidal and cylindrical
epithelium (a). There was no evidence of colloid nor
fibrous tissue. The biopsy reacted positively to GFAP (b)
and negatively to PAS-D. Given these features, the
histopathological diagnosis of an ependymal cyst was
made.
T2 MRI (A) demonstrated triventriculomegaly but with
no cause identifiable. T2-vent (B) and T2-cube (C)
demonstrated flow through the anterior part of the 3rd
ventricle but not through the aqueduct. On high-
resolution, mid-sagittal CISS sequence (D), a cyst was
identified in the posterior third ventricle blocking the
aqueduct.
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