Occult Encephalocele
Findings:
Multiple MR images demonstrate a small protrusion of the right cerebellum into the inner table of the right occipital calvarium.
Differential Diagnosis:
Occult encephalocele, arachnoid granulation, leptomeningeal cyst related to previous skull fracture, postop encephalocele. While arachnoid granulations may cause scalloping of the inner table and may be a component of this case, arachnoid granulations are not typically associated with a protrusion of brain. There has been no history of trauma or surgery to the region.
Discussion:
Occult occipital encephaloceles that only extend into the inner table are extremely rare with only a few reported cases. The reported cases largely represent a herniation of brain into a remote skull fracture plane. When an occult encephalocele involves the temporal lobe, a relation to complex seizures has been reported and the herniated brain may be dysplastic.