Parasellar epidermoid and dermoid tumors are rare tumors in the whole intracranial tumors. Most of the tumors occur in the posterior fossa, especially as a C-P angle tumor. Those tumors are also seen in parasellar region. Clinical and imaging features of parasellar epidermoid and dermoid tumors are different from in the posterior fossa. Most of epidermoid tumors in the parasellar region are associated with peritumoral cyst, dermoid cyst. On the other hands, dermoid tumor in the parasellar region is mostly solid without peritumoral cyst. MRI shows wide-spreading cisternal fatty deposits in the sulci, especially in the interhemispheric fissure, due to spontaneous rupture of the tumors, which are characteristic findings to diagnose that those tumors are epidermoid or dermoid tumors. Comparing with the capsule of dermoid tumor, that of epidermoid tumor is very thin, resulting in difficult total removal of the capsule. Once the tumor capsule is remained, the tumor is possible to recur, and careful follow-up using MRI is necessary.

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The stereotactic radiosurgery(SRS)concept was created by the great Professor Lars Leksell(1907-1986). He was the successor of one the world's pioneering neurosurgeons, Professor Herbert Olivecrona(1891-1980)who was the first chairman of the Neurosurgical Department at Karolinska Hospital. One of his themes in neurosurgical practice was to minimize invasiveness. Professor Leksell succeeded in taking this theme to its pinnacle. He devised a treatment which, instead of stereotactic surgery in which infection and/or hemorrhage inevitably occurred at certain incidences, cross-fired ionizing beams from multiple directions to produce a small lesion in deep brain structures, e.g., the thalamus, basal ganglia and so on, with no risk of such complications. Following 17 years of dedicated labor, the prototype of the gamma knife became available in 1968. Nevertheless, the usefulness of gamma knife SRS only came to be widely recognized in the 1990s. The author describes the more the 60-year history of the gamma knife since its inception in 1951. Some of these stories are already known but others are hidden episodes. This article focuses on why such a prolonged incubation period, from 1951 to 1968, was necessary as well as the lag from 1968 until the 1990s in the recognizing the enormous utility of the gamma knife.

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Surgical instruments are important to conduct safe and accurate removal of the brain tumors. Various instruments are used for tumor dissection depending on the tumor pathology and resection procedures. Variety of surgical instruments have been recently developed. Among them, ultrasonic aspirator with bone curette, pulse-jet dissector and photodynamic therapy with its device are introduced.

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Primary central nervous system(CNS)angiosarcoma is extremely rare. Thirty three patients with primary CNS angiosarcoma have been reported. Here we report a 69-year-old man with a subcortical hematoma in the left temporal lobe. Magnetic resonance imaging(MRI)showed an enhanced nodule in the hematoma cavity. We performed an initial operation to evacuate the hematoma and the nodule; however, 3 hours later hematoma volume increased and intraventricular hemorrhage was observed. A second operation was performed to evacuate the hematoma and the residual nodule. After 3 weeks, a computed tomography(CT)scan showed an asymptomatic lesion, specifically oozing hematoma in the cavity; therefore we selected conservative therapy.Microscopically, the tumor cells showed an abortive vascular structure, and positive immunohistochemical staining for cluster of differentiation(CD)31, CD34, and p53. Systematic screening by CT examination did not detect any mass lesion except the brain tumor. Finally we diagnosed primary CNS angiosarcoma, and adjuvant radiation therapy was performed.We suggest the en-bloc removal of primary CNS angiosarcoma to prevent rebleeding.

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The toxoplasmosis is intracellular protozoan infection and becomes symptomatic under immunocompromised condition such as AIDS. But when a past history is not clear, correct diagnosis for toxoplasmosis becomes difficult.A 54 years old man presented with convulsive attack and left hemiparesis. Contrast enhanced T1 weighted image showed multiple ring enhancing lesions. Definitive diagnosis could not be obtained despite tumor biopsy performed for histological examination. Patient’s condition turned worse rapidly and passed away within 12days after second admission.We confirmed intracellular bradyzoites by thorough examination of pathological specimen and definitive diagnosis was obtained after the patient’s death.We should take into consideration of immunocompromised state such as HIV infection when we encounter a patient with multiple ring enhancing brain lesion.

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