Six patients with histologically proven epidermoid tumors are reported from the neurosurgical service, Brigham and Women's Hospital and Children's Hospital, Harvard Medical School, Boston, Mass. All patients were adults between 22 and 52 years of age at the time of diagnosis. Symptoms had been present for more than one to five years and the methods of presentation included seizures in two, ataxia (3), headaches (3), dysmetria (3), left-sided hearing loss (1), visual loss (1) and papilledema (1). The locations of the tumor were variable; cerebellar hemisphere in two, left temporal lobe (2), left cerebral hemisphere (1) and suprasellar cistern (1). Surgery was successful in all patients. None had symptoms related specifically to the tumor in childhood; one had been treated for bulimia for 17 years and another had meningitis at ten years of age. CT demonstrated a hypodense, smoothly contoured, extra axial paramedial mass with a lower density than cerebrospinal fluid. MRI showed an irregularly, but sharply marginated, mass with homogeneous density, variable enhancement with gadolinium, lack of edema in adjacent normal structures, extensive insinuation into cisternal and other cerebrospinal fluid spaces and a high signal intensity on proton-weighted images. Multiplanar magnetic resonance imaging was extremely helpful in showing the full extent of the lesion and its relation to other structures. 
COMMENT: Epidermoid, adamantinoma, cholesteatoma, and pearly tumor are terms used interchangeably to refer to this entity. Epidermoid tumors are congenital and arise from misplacement of ectoderm. They are usually benign and slow growing but malignant change may occur. The tumors may be very large at the time of diagnosis, with considerable mass effect but minimal edema. The MRI allows the distinction of an epidermoid from an arachnoid cyst. The MRI or CT is not diagnostic but the MRI is more likely to elucidate the extra axial-nature of the tumor and is preferred. Spinal epidermoid tumors may complicate a lumbar puncture performed 1 to 20 or more years previously. Symptoms are slowly progressive and manifested by back and leg pains progressing to gait difficulties.