Discussion Author(s): 2LT Arash K. Momeni
Dermoid cysts are believed to arise from congenital rests of epithelial cells and skin tissue that become incorporated into the intracranial cavity as a result of incomplete separation of the neuroectoderm from the cutaneous ectoderm at the time of neural tube closure. They are likely to present as midline masses (as opposed to epidermoids), mostly in the retroclival and suprasellar regions, due to an earlier inclusion of ectoderm into the neural tube. They may contain ectodermal glands such as apocrine glands and hair follicles. Teeth may also be found - altough rarely.
They are rare neoplasms as they account for less than 1% of all intracranial tumors. The slow growth rate of dermoids delays the clinical presentation until the 3rd or 4th decade of life. The clinical presentation is variable and nonspecific. Headache, seizures and dementia have been described. A ruptured cyst may present as chemical meningitis from leakage of cystic contents into the CSF. Rarely patients with ruptured dermoid cyst may be asymptomatic.
MR findings of dermoid tumors include heterogeneous mass usually at the midline. Sometimes fluid- fluid levels are observed. The lesion appears hyperintense on T1W imaging while on fat suppressed T1W imaging the mass loses signal. The dermoid tumor may be differentiated from an epidermoid. The location of epidermoids shows a much greater variation as well as a greater tendency to deviate from the midline. The most frequent site for epidermoid is the cerebellopontine angle, followed by the suprasellar region and the middle cranial fossa. Although epidermoids may present at any age, most are diagnosed during the fifth decade.
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