Answer of September 2008

Clinical History:

24 year old young gentlemen presented with abnormal behaviour and psychosis
MRI of the brain was performed.

Diagnosis:

Frontoethmoidal encephalocele

Discussion:

There is an osseous defect between frontal bone and nasal bone at right parasagittal region of the glabella, compatible with patent fonticulus frontalis. Herniation of brain tissue from the inferior part of right frontal lobe through this osseous defect into the subcutaneous layer of the glabella region is noted.  Grey matter heterotopia at periventricular white matter next to the frontal horn of the right lateral ventricle is also noted.

Encephalocele occur in one of every 4,000 live births and are most commonly occipital in location (75% of cases); lesions are frontoethmoidal in 15% of cases and basal in 10%. There are often significant associated intracranial anomalies. Occipital encephaloceles may be associated with Chiari or Dandy-Walker malformations and callosal or neuronal migrational anomalies.

Nasal gliomas occur near the root of the nose (where the cranial portion of the nose joins the forehead), are composed of dysplastic glial tissue, and are congenital nonneoplastic lesions best categorized as heterotopia. A nasal glioma may be connected to the brain by a stalk of tissue in up to 15% of cases, but the stalk does not contain a direct fluid-filled tract that communicates with the subarachnoid spaces; therefore, a nasal glioma is distinct from an encephalocele, which does contain such a connection to the intracranial subarachnoid spaces.  Nasal gliomas are often isointense relative to normal brain at MR imaging.

Dermoid and epidermoid cysts are thought to occur as a result of the persistence of ectodermal elements at sites of suture closure, neural tube closure, and diverticulation of the cerebral hemispheres as discussed earlier.