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[edit] Discussion

  • Epidermoids (AKA epidermoid inclusion cysts) are benign congenital lesions.
  • Account for approximately 1% of all intracranial tumors.
  • Patients are usually not symptomatic until they are aged 20-40 years.
  • Epidermoids should be distinguished from dermoids, which also are a result of congenital ectodermal inclusion.
  • Dermoids also result from ectodermal inclusions, but they have a lining that has further differentiated to include dermal appendage structures such as hair follicles, sebaceous glands, and sweat glands.
  • Central nervous system dermoids should be distinguished from abdominal (ovarian) dermoids that are actually well-differentiated teratomas.
  • Epidermoids rarely rupture. Dermoids more commonly rupture (spillage of the contents of dermoids into the subarachnoid space may cause chemical meningitis).
  • Epidermoids occur with equal frequency in men and women.
  • Although the vast majority of epidermoids are intradural, they can be extradural.
  • The most common locations are within the cerebellopontine angle (CP), parasellar region, and middle cranial fossa.
    • The CP angle is the most common site for epidermoids.
    • Of all CP angle masses, epidermoids are the third most common after vestibular schwannomas and meningiomas.
    • Occurrences within the ventricular system, brain parenchyma, and even the spinal cord, have been reported.

  • Total removal is the goal of surgery.
  • Aggressive resection might not be undertaken when lesions are adherent to vital structures such as the cranial nerves or brainstem.

[edit] Imaging Findings

  • At diagnosis, epidermoids usually insinuate within the sulci and cisterns, and they may engulf cranial nerves and blood vessels.
  • Preferred Examination: CT and MRI are both helpful in diagnosing epidermoids. Although CT findings may be nonspecific, MRI findings are reliable in diagnosis.

[edit] CT

  • Epidermoids usually have the same attenuation as that of cerebrospinal fluid; this characteristic makes their differentiation from arachnoid cysts difficult. Enhancement is rare, but can sometimes be seen around the margin of the tumor. Calcification occurs in only 15-20% of cases.

[edit] MRI

  • On T1-weighted images these lesions are generally slightly hyperintense or isointense relative to gray matter.
  • The lesions are usually isointense relative to CSF on T2-weighted images, but they may be slightly hyperintense.
  • Enhancement of portions of the rim may be seen after the administration of contrast material. The remainder of the lesion does not enhance.
  • Fluid-attenuated inversion recovery (FLAIR) images demonstrate epidermoids as being hyperintense relative to CSF.
  • Diffusion-weighted imaging can be used to differentiate from arachnoid cysts, because epidermoids have markedly restricted diffusion and, therefore, high signal intensity on the diffusion-weighted trace images.

[edit] Images

Patient #1

[edit] See Also

[edit] External Links

[edit] References