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Epidermoid tumors strongly adhere to the brain stem or cranial nerves. Often the lining of the tumor connected to the brain stem or parts difficult to "peel" away are left behind leaving residual tumor after surgery, this can contribute to the risk of regrowth. About 40% of these cysts originate in the cerebellopontine angle. [3]
Epidermoid cyst may be classified as a sebaceous cyst, [15] although technically speaking it is not sebaceous. [16] " True" sebaceous cysts, cysts which originate from sebaceous glands and which contain sebum, are relatively rare and are known as steatocystoma simplex or, if multiple, as steatocystoma multiplex .
A sebaceous cyst is a term commonly used to refer to either: [1] Epidermoid cysts (also termed epidermal cysts, infundibular cyst) Pilar cysts (also termed trichelemmal cysts, isthmus-catagen cysts) Both of the above types of cysts contain keratin, not sebum, and neither originates from sebaceous glands.
This category of cysts takes over areas of necrotic tissue in the brain from injuries, diseases, or abnormalities, which occur due to the central nervous system's nonregenerative nature. These cysts can affect all germ layers of the CNS, but are most common in the arachnoid mater , and the ventricular space , which may block CSF pathways.
Cysts located within the ventricles of the brain can block the outflow of cerebrospinal fluid and present with symptoms of increased intracranial pressure. [14] Racemose neurocysticercosis refers to cysts in the subarachnoid space. These can occasionally grow into large lobulated masses causing pressure on surrounding structures. [15]
The major differential to consider in empty sella syndrome is intracranial hypertension, of both unknown and secondary causes, and an epidermoid cyst, which can mimic cerebrospinal fluid due to its low density on CT scans, although MRI can usually distinguish the latter diagnosis. [10]
Not all middle ear epidermal cysts are congenital, as they can be acquired either by metaplasia of the middle ear mucosa or by traumatic implantation of ear canal or tympanic membrane skin. In addition, cholesteatoma inadvertently left by a surgeon usually regrows as an epidermal cyst. Some authors have also suggested hereditary factors. [9] [10]
Cerebroretinal microangiopathy with calcifications and cysts (CRMCC) is a rare genetic disorder, which affects multiple organs. [ 1 ] [ 2 ] Its hallmarks are widespread progressive calcifications , cysts and abnormalities of the white matter of the brain, usually occurring together with abnormalities of the blood vessels of the retina .