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DEMOGRAPHICS/CLINICAL
HISTORY
The patient is an 18-month-old boy with developmental delay.
DISCUSSION
Definition and Background
Cephaloceles (encephaloceles) encompass all neural tube defects
that result in abnormal herniation of intracranial structures through mesodermal
defects. They can be divided into meningoceles and meningoencephaloceles, depending
on whether there is a neural component within the herniation. The herniating
brain is often abnormal.Encephaloceles can be divided into the anterior (sincipital),
basal, and posterior (occipital) types. Sincipital (also called frontoethmoidal
type) encephaloceles represent herniation towards the soft tissues of the
forehead, external nose, and orbit. These are particularly common in Southeast
Asia, and are further classified as nasofrontal, nasoethmoidal, and nasoorbital
(anterior and posterior orbital), named according to the bones at the superior
and inferior margins of the defect.Basal encephaloceles protrude through
defects in the basal skull bones (anterior and central skull base) and can be
subdivided into the transethmoidal, sphenoethmoidal, sphenomaxillary,
spheno-orbital, and transsphenoidal subtypes.Posterior encephaloceles are
occipital or craniocervical in location, with defects located in the occipital
bone, and posterior arch of atlas. These are often associated with a hindbrain
abnormality.Rare varieties include the convexity encephaloceles, including the
atretic cephaloceles.
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Characteristic
Clinical Features:
Most anterior (frontoethmoidal) and posterior (occipital)
encephaloceles are usually diagnosed at birth, if not diagnosed antenatally. These often
present as a skin-covered mass, although some atretic cephaloceles over the
convexity may not be diagnosed till much later in life. If the encephalocele is
not skin-covered, it is treated as a neurosurgical emergency at birth.Basal
cephaloceles may present as an intranasal or nasopharyngeal mass with nasal obstruction,
or with symptoms of complications such
as CSF leaks (CSF rhinorrhea) or recurrent
meningitis, or epilepsy. Nasal meningoencephaloceles may change in size in response
to the Valsalva maneuver and will transillumi-nate. Hydrocephalus may occur.Posterior
encephaloceles are associated with higher risk of hydrocephalus and seizures,
the determinants of overall prognosis.
Characteristic
Radiologic Findings
In general, encephaloceles are associated with defects in the
cranium or the skull base that may be best defined by CT, further enhanced with
3D rendering. Evaluation of the contents of the herniation and the brain parenchyma,
and any associated anomalies, is best performed with MRI.
It is useful to remember that the structures of the anterior
skull base including the cribriform plate may be partially or incompletely
ossified till about 2 years of age.Posterior encephaloceles may be associated
with Chiari and Dandy-Walker malformations.
Primary Differential
Diagnoses
1-Nasal Dermoid
2-Nasal Glioma
Discussion of
Differential Diagnoses
Nasal Dermoid: The most common nasal abnormalities, presenting
as a midline mass without or with a sinus tract. External opening may show a
tuft of hair.
Nasal Glioma: Midline, firm, nasal or nasopharyngeal mass
consisting of glial tissue that could be considered a variant of an
encephalocele, although no skull base defect may be demonstrable.
  
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Labels: Brain
