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06-84
Sincipital Encephalocele With Corpus Callosum Agenesis
And Intracranial Lipoma: A Case Report
V UPADHYAYA, DN UPADHYAYA, S SARKAR
Ind J Radiol Imag 2005 15:4:507-510
Key words : - Encephalocele, Intracranial, Agenesis
INTRODUCTION
Encephaloceles are extracranial herniations of intracranial
structures through defects in the skull and dura.
Meningoceles are herniations of meninges alone and
meningoencephaloceles are herniations of brain tissue
and meninges. If part of a ventricle is also included, it is
called hydroencephalomeningocele. In most cases, these
are detected prenatally by obstetric ultrasound or at birth
by clinical presentation of a subcutaneous mass.
Encephaloceles may be isolated anomalies, or they may
be seen in conjunction with other anomalies, or may be a
part of a syndrome. Agenesis or hypogenesis of the corpus
callosum is a commonly associated finding.
We report one such case of sincipital encephalocele with
agenesis of corpus callosum and intracranial lipoma.
Fig. 2 Axial T2-weighted image
Fig. 1 Axial T1-weighted image
Fig. 3 Sagittal T1-weighted image
From the Sarkar Diagnostic Centre, Mahanagar, Lucknow - 226006
Request for Reprints: Vaishali Upadhyaya, Sarkar Diagnostic Centre, C-1093, Sector A, mahanagar, Lucknow - 226006
Received 1 June 2005; Accepted 10 November 2005
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508 V Upadhyaya et al
CASE REPORT
A two year old boy presented with a large soft swelling on
the forehead since birth. There was no history of delayed
milestones. Local examination revealed a soft fluctuant
swelling in the middle of forehead with a well defined defect
in the subjacent cranium. The swelling was not
transilluminant but had an expansile impulse on crying.
The intercanthal distance was increased. The child had
no apparent sensory motor deficit and was actively moving
all limbs.
An MR study of the brain was done (Figs. 1, 2 & 3) which
revealed a large sincipital encephalocele containing brain
tissue and meninges. No dysplastic changes were seen
in the herniated brain tissue. Corpus callosum was not
seen on sagittal images and lateral ventricles were widely
separated suggestive of callosal agenesis. There was an
anterior interhemispheric mass of high signal intensity
on T-1 weighted images and low signal intensity on T-2
weighted images suggestive of lipoma. Vessels were seen
as signal void structures passing through the lipoma. There
was distortion of brain stem and cerebellum. A large
cisterna magna was also seen. CT was done (Figs. 4 &
5) for better delineation of the bony defect. There was a
large frontal defect of about eight cms through which there
was herniation of the brain and the meninges. Findings
suggestive of callosal agenesis were also seen. On CT,
the lipoma showed characteristic fat attenuation and
peripheral small calcific foci were noted.
Fig. 4 Axial CT section
IJRI, 15:4, November 2005
Fig. 5 Axial CT section (Bone window)
Surgical planning was done by a team of neurosurgeons
and plastic surgeons and the priorities defined as below-
1. Both extracranial and intracranial approach was to
be used.
2. Excision of the sac along with the abnormal dura and
excision/invagination of the brain tissue followed by
repair of the normal dura.
3. Skeletal reconstruction along with proper wound cover.
Pre-operative preparations were made but the surgery
had to be shelved due to the refusal of the attendants
to give high-risk consent.
Prognosis was explained and the patient discharged on
request.
DISCUSSION
Encepahloceles occur due to failure of surface ectoderm
to separate from the neuroectoderm which results in a
bony defect in the skull table, which allows herniation of
meninges or brain tissue. Ingraham and Matson divided
encephaloceles into threee categories: occipital, sincipital
and basal [1]. Suwanwela and Suwanwela have subdivided
the sincipital group further into frontoethmoidal
encephaloceles, interfrontal encephaloceles and those
encephaloceles associated with craniofacial clefts [2].
The frontoethmoidal group is subdivided further into
nasofrontal, nasoethmoidal and naso-orbital types.
Encephaloceles occur approximately 1 to 3 times in
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IJRI, 15:4, November 2005
10,000 live births. The incidence of sincipital
encephalocele is substantially greater in the tropical
latitudes, particularly in parts of Asia and Africa. Occipital
encephaloceles are more common in Western
Hemisphere.
With encephaloceles, there is a reasonably high
incidence of associated facial anomalies in the form of
midline clefts and associated brain malformations, such
as agenesis of the corpus callosum, Arnold-Chiari
malformation, Dandy-Walker malformation and brain
migrational anomalies.
Most encephaloceles are diagnosed on routine antenatal
US scanning. Postnatally, infants may present with CSF
rhinorrhea and recurrent meningitis. Postnatal
presentation also depends on the associated
malformations and the size and contents of the defect.
The prognosis and treatment depend on the site, size
and the contents of the encephalocele.
The prognosis for the anterior encephalocele patient is
generally good and is usually associated with normal
intelligence and motor development. However, mental
retardation, epilepsy and ocular problems have been
described in this group [3]. Poor prognostic indicators
include a large or posterior encephalocele and systemic
anomalies.
Postnatally, the aim of the radiologist is to precisely define
the size of the encephalocele, delineate the contents and
identify associated anomalies. MR is the modality of
choice. CSF spaces and brain parenchyma are directly
visualized. Although bony defects are poorly shown by
MR, the MR studies in patients with encephaloceles are
valuable because tissues within these defects produce a
signal. On T-1 weighted images, brain tissue protrudes
through the defect and contrasts with the surrounding
low-intensity signal of CSF and the signal void of bone.
On T-2 weighted images, CSF produces a signal that
can be seen in contrast to the bony edges. The
relationships of the encephalocele and its contents to
the extracranial soft tissues are clearly shown. Large
arteries and veins associated with the brain parenchyma
are also well shown [4]. MR also demonstrates associated
intracranial anomalies. CT can provide excellent depiction
of the bony defect but it cannot resolve the exact nature
of the herniated contents. Like MR, it can identify
associated intracranial anomalies.
The most commonly associated finding is agenesis or
hypogenesis of the corpus callosum. Corpus callosum is
Sincipital Encephalocele 509
the largest cerebral commissure connecting neocortical
areas and develops between 12 to 20 weeks of gestation.
The development results from neocortical commissural
axon fasciculation and reflects the inter-hemispheric
circuitry and successive steps of synaptogenesis [5].
Development occurs from front to back with the exception
of the rostrum, which develops after the splenium. Callosal
agenesis can be partial or complete. Imaging by CT and
MR in complete callosal agenesis reveals widely
separated and nonconverging lateral ventricles,
disproportionately enlarged occipital horns (colpocephaly)
and an elevated third ventricle which is continuous
superiorly with the interhemispheric fissure. In sagittal
MR studies, corpus callosum, cingulate gyrus and sulcus
are not seen. Gyri on the medial hemispheric surface
radiate outward from the high-riding third ventricle. In partial
agenesis of corpus callosum, the splenium and rostrum
are absent.
Intracranial lipomas represent rare development
malformations of the nervous system. They result from
lipomatous differentiation of the persistent meninx
primitiva, the mesenchymal derivative of the embryonic
neural crest which envelops the developing embryo.
Interhemispheric lipomas constitute 40% to 50% of
intracranial lipomas and are frequently associated with a
dysgenetic corpus callosum [6]. Callosal lipomas are of
two types: an anterior bulky tubulonodular variety which
is associated with forebrain and rostral callosal anomalies
and a more posterior ribbon-like curvilinear lipoma which
is seen with a normal or nearly normal corpus callosum.
CT scan shows findings of callosal agenesis with a fatty
density mass that is variably calcified. On MR, the lipoma
shows high signal on T-1 weighted studies and low signal
on T-2 weighted studies. Prominent vessels often course
directly through the more bulky anterior callosal lipomas
[7].
Our patient had a sincipital encephalocele with corpus
callosum agenesis and an anterior tubulonodular type of
interhemispheric lipoma.
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