A LARGE FOURTH VENTRICLE EPIDERMOID
CYSTBY
Dr.K.PRASANNAPOST GRADUATE STUDENT,
RAJAH MUTHIAH MEDICAL COLLEGE & HOSPITAL
(RMMCH),
ANNAMALAI UNIVERSITY, CHIDAMBARAM
CLINICAL HISTORY
51 year old male came with complaints of
chronic headache.
He had 3 episodes of generalized seizures.
There is weakness of all four limbs.
There is no history of fever, trauma.
Blood parameters were normal.
Patient was referred for MRI brain.
MRI
MR imaging of the brain revealed an extra-axial, lobulated ill
defined mass occupying the fourth ventricle with extension into
CP angle which is hypo intense on T1 & hyper intense on T2
insinuating the vessels around CP angle with no evidence 0f
blooming on gradient imaging with no enhancement in contrast.
The Fourth ventricle mass which is iso intense to
CSF in T1 & T2 is suppressed in FLAIR sequences.
The mass is causing mild dilatation of lateral
ventricles.
MRI
The lesion had homogeneous CSF intensity
on both T1-weighted and T2-weighted
images and remained hypo intense on
FLAIR sequences.
There is no evidence of any altered signal
intensity within the mass lesion.
EPIDERMOID CYST
Epidermoid cyst, or pearly tumour, is congenital in origin
and accounts for about 1% of intracranial tumours.
It is a benign extra cerebral intradural lesion and in about
40% of cases is located in the cerebellopontine angle.
They are believed to form between the 3rd and 5th week
of embryonic development as a result of displaced
epithelial remnants that remain after the neural tube
closes.
Although acquired epidermoid tumours may develop
as a result of trauma, this is uncommon in the brain.
Grossly, epidermoid tumors are typically well defined
lesions with an irregular nodular outer surface and a
shiny “mother of pearl” appearance.6,7
The cyst content is derived from desquamated
epithelial cells composed mainly of keratin in
concentric layers and cholesterol in a solid crystalline
state.1,4,7-9
EPIDERMOID CYST
On MR imaging, epidermoid tumours typically
have low signal intensity on T1-weighted images,
high signal intensity on T2-weighted images, and
no enhancement on gadolinium-enhanced images.
Epidermoid tumors showing unusual signal
intensity changes have been reported.1,7,10-
13
EPIDERMOID CYST
The tumour can be a so-called white epidermoid with
short T1 values and fatty attenuation on CT,
characterized surgically as being cystic and having a
high lipid content comprising mixed triglycerides
containing unsaturated fatty acid residues, and no
cholesterol. 11
It can show hyper intensity on T1- and T2-weighted
MR images, caused by a semi liquid cystic content
with high protein concentration.
EPIDERMOID CYST
The intra cystic haemorrhage can cause a high
signal intensity on both T1- and T2-weighted
images because of the paramagnetic effect of
heme iron (Fe3) in methemoglobin and other
haemoglobin breakdown products.
EPIDERMOID CYST
Differential diagnosis of EPIDERMOID CYST CSF collections, e.g. Arachnoid cyst or mega cisterna magna
Less lobulated follows CSF on all sequences, including FLAIR and DWI
Dermoid cyst
Often fat density due to sebum
Inflammatory cyst, e.g. Neurocysticercosis
Smaller, but may be multiple
May enhance peripherally
May have associated oedema
Usually no restricted disffusion
Cystic tumour, e.g. Acoustic schwannoma or craniopharyngioma
Solid enhancing component is usually identifiable
Neurenteric cyst
Epidermoid cysts typically show undulating margins and
model their shape to conform to the cerebropontine
angle.
The cyst has a tendency to insinuate itself around the
nerves and blood vessels in the cerebropontine angle.
They usually do not enhance with gadolinium and do not
bleed.
From a practical point of view, recognition of case as a
hemorrhagic epidermoid cyst is important.
References Mohanty A, Venkatrama SK, Rao BR, et al. Experience with
cerebellopontine angle epidermoids. Neurosurgery 1997;40:24–30 .Tampieri D, Melanson D, Ethier R. MR imaging of epidermoid cysts.
AJNR Am J Neuroradiol 1989;10:351–56 Gao PY, Osborn AG, Smirniotopoulos JG, et al. Radiologic-pathologic
correlation: epidermoid tumor of the cerebellopontine angle.AJNRAmJ Neuroradiol 1992;13:865–72
Salazar J, Vaquero J, Saucedo G, et al. Posterior fossa epidermoid cysts. Acta Neurichir 1987;85:34–39
de Souza CE, deSouza R, Costa SD, et al. Cerebellopontine angle epidermoid cysts: a report on 30 cases. J Neurol Neurosurg Psychiatry 1989;52:986–90
Ochi M, Hayashi K, Hayashi T, et al. Unusual CT and MR appearance of an epidermoid tumor of the cerebellopontine angle. AJNR Am J Neuroradiol 1998;19:1113–15
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