Examination reveals soft tissue mass lesions involving
the retroconic, and extraconal spaces of both orbits. Small soft tissue
lesion is seen near the posterior wall of the right maxillary sinus. Minimal
enhancement is noted on contrast examination.
Diagnosis
Frontal encephalocele
Discussion
Encephaloceles signify the herniation of neural tissue through defects
in the skull. They may contain meninges (meningocele) or brain matter
and meninges (encephalomeningocele), or they may communicate with a ventricle
(encephalomeningocystocele). Encephaloceles have an etiology similar to
that of gliomas. No familial pattern has been demonstrated with these
lesions. Association with other diseases (eg, Ehlers-Danlos syndrome,
frontonasal dysplasia), however, may suggest a genetic component.
Nasal encephaloceles can be divided into 2 types: sincipital (60%) and
basal (40%).
The sincipital form is divided into subtypes as follows:
(1) the nasofrontal (40%), which exits the cranium between the nasal and
frontal bones;
(2) the nasoethmoidal (40%), which exits between the nasal bones and nasal
cartilages; and
(3) the nasoorbital (20%), which exits through a defect in the maxilla
frontal process. Sincipital encephaloceles typically present as soft compressible
masses over the glabella.
The basal form is divided into subtypes as follows:
(1) the transethmoidal, which exits through the cribriform plate into
the superior meatus, extending medial to the middle turbinate;
(2) the sphenoethmoidal, which exits through the cribriform plate, between
the posterior ethmoid cells and sphenoid, to present in the nasopharynx;
(3) the sphenoorbital,
which enters the orbit via the superior orbital fissure and may produce
exophthalmos; and
(4) the transsphenoidal, which herniates in the nasopharynx via defects
posterior to the cribriform plate. Basal encephaloceles may remain hidden
(clinically) for years.
Biopsy is strongly contraindicated due to risk of infection and meningitis.
Treatment involves surgical excision with repair of the bony defect. Often
a craniotomy is necessary to approach the encephalocele.
Dr Sanjeev Mani, Mumbai
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