AJR 2000; 175:893-894
© American Roentgen Ray Society
Neuroradiology Case of the Day |
Case 3
Frontoethmoidal Encephalocele
Gregory A. Christoforidis,
Melissa Baujan and
Eric C. Bourekas
Axial unenhanced CT scans (Figs.
3A,3B,3C,3D)
of the brain and skull base show a defect along the right half of the
cribriform plate and a mass obliterating most of the visualized right upper
nasal cavity contiguous with the brain above. This mass obstructs drainage
from the right maxillary sinus. Differential considerations include a tumor
traversing the cribriform plate, granuloma, esthesioneuroblastoma, or an
encephalocele. The margins along the defect on the cribriform plate and bony
septations of the ethmoid air cells are smooth, suggesting compressive
deossification rather than destructive bony changes. This finding implicates a
less aggressive lesion such as a benign tumor or an encephalocele. The fact
that the lesion appears contiguous with the brain puts encephalocele high in
the differential diagnosis.
Multiplanar T1-weighted, T2-weighted, and gadolinium-enhanced MR images
(Figs. 3E and
3F) of the brain confirm the
presence of an anterior encephalocele and also display meningeal enhancement
suspicious for meningitis. When further questioned, the patient relayed a
prior history of cerebrospinal fluid leak after an altercation many years ago.
At that time, he refused surgical repair against medical advice.
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Fig. 3E. —46-year-old male prisoner who presented with fever and mental status
changes. Coronal T2-weighted (E) and sagittal gadolinium-enhanced
T1-weighted (F) MR images of brain confirm presence of anterior
encephalocele (arrows) and also display meningeal enhancement
suggestive of meningitis (arrowheads). Encephalocele extends to
nasopharynx and obstructs right maxillary sinus.
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Fig. 3F. —46-year-old male prisoner who presented with fever and mental status
changes. Coronal T2-weighted (E) and sagittal gadolinium-enhanced
T1-weighted (F) MR images of brain confirm presence of anterior
encephalocele (arrows) and also display meningeal enhancement
suggestive of meningitis (arrowheads). Encephalocele extends to
nasopharynx and obstructs right maxillary sinus.
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Encephalocele can be a congenital or an acquired abnormality of the brain
in which intracranial contents including meninges, cerebrospinal fluid, and
brain tissue herniate through a skull defect. Congenital encephaloceles occur
when the mesodermal layer between the neural tube and the ectoderm fails to
develop and the anterior neuropore remains open. Anterior encephaloceles can
also occur after trauma or surgery. Brain pulsations are presumed to push
brain tissue through the defect. The issue of whether the herniated brain
tissue is functional has not been resolved. Patients are prone to recurrent
episodes of meningitis. In addition, visual acuity and hypothalamic function
may be affected. Clinical presentation includes a nasopharyngeal mass, which
may enlarge with Valsalva's maneuver and which can potentially obstruct the
adjacent maxillary sinus
[1].
The other diagnoses are incorrect for various reasons. An extraaxial mass
such as a meningioma is less likely in this case because there are no signs of
extraaxial mass such as widening of the cerebrospinal fluid space at the base
of the brain adjacent to the lesion. Squamous cell carcinoma invading the
anterior cranial fossa more typically erodes the margins of the cribriform
plate when it invades the calvarium. Juvenile nasopharyngeal angiofibromas
typically involve the nasal cavity via extension through the pterygomaxillary
fissure. They can also involve the infratemporal fossal, middle cranial fossa,
and orbit but would not typically invade through the cribriform plate. More
importantly, these angiofibromas almost always occur in boys in their early
teenage years [1].
References
-
Grossman RI, Yousem DM. Neuroradiology: the
requisites. St. Louis: Mosby—Year Book,
1994: 359-376
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