Epidermoid tumors occur very rarely in the fourth ventricle. We report on the clinical features, MR findings, operative findings, and their correlations in 5 patients. The patients were all women and ranged in age from 29 to 62 years (mean 46 years). Unsteadiness of gait was the most common initial symptom. Whether the duration of symptoms was short, medium, or long term, they tended to progress within several months prior to admission to our institution. The presenting symptoms in all patients included medio-cerebellar syndrome. Lower cranial nerve palsies were present in 3 patients. The MR findings of each tumor were nonspecific, with prolonged T1 and T2 relaxation times. In the 3 patients with lower cranial nerve symptoms, moderate or marked deformity of the medulla oblongata was seen. Surgery was performed via the median suboccipital approach. The epidermoid tumor had completely filled the cisterna magna in all patients. Facile removal of the soft tumor contents provided a working space to dissect the tumor capsule free from the adjacent neurovascular structures, to which the capsule was occasionally densely adherent. Part of the choroid plexus in the fourth ventricle was removed due to extensive tumor involvement. The tumors adhered firmly to the floor of the fourth ventricle inferior to the stria medullares, corresponding to the structures of the hypoglossal and vagal trigones. There were more adhesions in patients with greater deformity of the medulla oblongata. Since manipulations of the adhesions to the medulla oblongata caused bradycardia or an excessive increase in blood pressure, small tufts of the capsule lining were left. Total removal of the capsule was possible in only 2 patients who had symptoms of dysequilibrium alone. Follow-up periods range from 12-60 months (average 27 months). A11 patients returned to their previous lifestyles, although 1 experiences occasional dysphagia and 3 have nystagmus. In conclusion, we stress that dense adhesions to the medulla oblongata were present in patients with lower cranial nerve symptoms, which were suggested upon MR imaging to be a sign of brain stem deformity, and small tufts of capsule lining should be allowed to remain on the medulla oblongata during surgery in such patients.

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Dynamic single photon emission computed tomography (SPECT) using ^lt;123>I-IMP (IMP) and ^<99m>Tc-HMPAO (HMPAO) was used to study 7 patients with arteriovenous malformation (AVM). In 4 of these patients, embolization was carried out, and the findings before and after embolization were studied by dynamic SPECT using IMP and HMPAO. In the super early dynamic SPECT using IMP, 10 serial scans were done with an interval of 24 seconds. In the super early dynamic SPECT using HMPAO, 12 serial scans were done with an interval of 15 seconds. AVMS are demonstrated as an area of hypoperfusion in routine static SPECT images, and in the super early dynamic SPECT images using IMP, AVMS are demonstrated as RI positive. However, a small AVM of less than 1 cm in diameter and a low perfusion AVM were not demonstrated on SPECT image by the super early dynamic SPECT using IMP. In SPECT images using HMPAO, the static rate ([AVM counts/lateral counts] on static SPECT images) as well as the dynamic rate ([AVM counts/lateral counts] on dynamic SPECT images) were higher than that using IMP, though the hypoperfusion area of static SPECT images was small. Thus, AVMS could be clearly identified when HMPAO was used. Three-dimensional SPECT (3 D-SPECT) images of AVMS Can be helpful in defining the AVMS as well as to show post-therapeutic changes. To evaluate the reduction of AVMS as a result of embolization, 3-D SPECT images using HMPAO are useful, as the overall view of the AVM can be seen as a positive image. It was useful to investigate the differences between the positive area in 3D-SPECT images of dynamic SPECT data using IMP and the RI defective areas in 3D-SPECT images of static SPECT data in order to evaluate partial differences of blood flow within AVMs.

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The balloon occlusion test is particularly useful as a preoperative evaluation procedure when it is planned to occlude a major artery temporarily or permanently. In patients with internal carotid artery stenosis, the lesion is usually located very near the bifurcation of the common carotid artery. In the conventional test occlusion using a single-balloon catheter, the balloon should be introduced and inflated at or distal to the stenotic lesion, which may cause thromboemolism and/or intimal dissection of the artery. To avoid this complication, occlusion of the internal carotid artery is performed by occluding both the external and common carotid arteries simultaneously using a double-balloon catheter. Using this method, the ballon occlusion test of the carotid artery has been successfully carried out in 43 of 44 patients with carotid endarterectomy. There were no complications related to this procedure. In 36 of the 43 patients, neurological symptoms and sings were not seen during test artery occlusion. In these patients, carotid endarterectomy was performed without intraluminal shunts. There were no ischemic complications due to temporary occlusion of the carotid arteries during surgery. In the other 7 patients in whom neurological symptoms and/or singns were seen during test occlusion of the carotid arteries, carotid endartere ctomy was performed using intraluminal shunts. Based on our experience, test occlusion of the carotid artery using a double-balloon catheter is a safe, useful examination that can avoid possible hemodynamic complications of carotid endarterectomy.

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A 60-year-old man presented with a subarachnoid hemorrhage from a ruptured aneurysm arising from the P2 segment of the right posterior cerebral artery (PCA). The aneurysm was located at the curvature of the PCA approximately 1.5 cm distal to the junction between the posterior communicating artery and the PCA. The temporopolar approach used in surgical treatment in this patient was useful. The mechanism of development of this type of saccular aneurysm is discussed and the surgical approach to aneurysms from the P2 segment of the PCA is described.

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A case of syringomyelia associated with tentorial meningioma is reported. A 45-year-old woman was admitted to our institution after experiencing headache and gait disturbance for I year. Neurological examination upon admission revealed bilateral papilledema and left cerebellar signs. MR imaging revealed hydrocephalus secondary to a large tentorial tumor with syringomyelia from the level of C2 to Th7 with tonsillar herniation. The syrinx was collapsed after total resection of the tumor and C1 laminectomy had been performed. We suggest that the pathogenesis of syringomyelia in this patient was interruption of cerebrospinal fluid flow at the foramen magnum following tonsillar herniation and increased intracranial pressure.

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We describe successful surgery for brain tumor, situated in the motor area, assessed by functional brain mapping. A 21-year-old female complained of a choking feeling during sleep since the age of 19. She had been diagnosed with hysteria because there were no epileptic discharges on electroencephalogram and no organic findings on brain CT scan. Her seizures developed right facial twitching with subsequent generalized tonic clonic seizures. MRI showed a tumor located in the right motor cortex. To identify the precise epileptogenic focus and recognize the relationship between the tumor and the clinical manifestation (globus hystericus), we implanted a subdural grid electrode over the lateral cotrtex of the frontal and parietal areas. Subdural grid recordings identified an epileptogenic cortex just behind the tumor, and functional braln mapping demonstrated that the throat areas were widely recognized around the tumor and that electrical stimulation of throat areas elicited clinical symptoms similar to globus hystericus. The tumor was completely resected, i.e. lesionectomy. Histologically, meningioangiomatosis was confirmed. The patient has remained seizure-free for 3 years since the surgery and has returned to work at her previous position.

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A rare case of a primary intracranial germ cell tumor which was suspected of transformation into rhabdomyosarcoma is reported. A 19-year-old man presented with diabetes insipidus, disturbance of consciousness, homonymous hemianopsia, and hemiparesis. CAT scanning and MR imaging showed a tumor with contrast enhancement in the hypothalamic area. The HCG level was elevated in both the serum and CSF. With a clinical diagnosis of germ cell tumor, radiation therapy combined with the PVB (cisplatin, vincristine, and bleomycin) chemotherapy regimen was implemented, which resulted in complete disappearance of the tumor. The HCG level was also normalized. However, a couple of weeks later, CAT scanning revealed a new lesion in the right occipital area, although there was no reelevation of the HCG level. The patient was readmitted to our institution and treated with steroids and glyceol, since radiation injury was suspected. Some improvement was seen, but then the patient gradually deteriorated, became bedridden, and developed cortical blindness and hemiparesis, followed by paraplegia, which suggested spinal dissemination. He died one and one-half years after the original admission. At autopsy, the primary site around the third ventricle failed to show any residual tumor cells. There was also no sign of tumor invasion of the occipital lobe. However, there were extensive disseminated spinal lesions involving the spinal cord below the mid-thoracic level which were histologically diagnosed as rhabdomyosarcoma.

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A case of multiple intracerebral hematoma representing a transitional form to chronic encapsulated hematoma was diagnosed by MR imaging and analyzed microscopically. A 26-year-old man complained of lower left quadrantic hemianopsia on June 1/~, 1996. MR imaging on June 19 revealed a hypointense nodule surrounded by an hyperintense zone on both T1-weighted and T2-weighted images of the right occipital lobe and a small hyperintense lesion on T2-weighted images of the left frontal lobe. The patient experienced a bronchial asthma attack on June 23, followed by sensory disturbance of the right upper limb. CT scanning demonstrated a hematoma in the left frontal lobe. Follow-up MR imaging on July 2 showed the left frontal hematoma as an iso- to hypointense area surrounded by a hyperintense zone on T1-weighted images and as a hypointense area on T2-weighted images. On July 4, the patient suddenly complained of dysarthria. CT scanning showed that the left frontal hematoma had increased in size, and an emergency craniotomy was performed. A tough membrane was found at the bottom of the hematoma cavity. On July 18, craniotomy for the right occipital hematoma was performed. A thick capsule surrounded clots in various stages of organization. Histological examination of the 2 lesions revealed occult vascular malformation within the collagenous tissue. The patient was discharged without any neurological deficit on July 27. To the authors' knowledge, no case of multiple chronic encapsulated hematoma has been reported previously. The pathogenesis and MR imaging findings of chronic encapsulated intracerebral hematoma are discussed.

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We report a rare case of an intracranial endodermal cyst arising from the ventral surface of the medulla oblongata. A 22-year-old woman was admitted to our institution with a lesion on the ventral surface of the medulla oblongata as visualized on MR imaging. The mass was seen as a hyperdense lesion on CT scanning, as a hyperintense mass on T1-weighted MR imaging, and as a hypointense mass on T2-weighted imaging. Since the lesion was suspected to be an epidermoid cyst, surgery was performed via the retromastoid suboccipital approach, and the tumor was easily and totally resected. Biochemical assay of the resected cyst contents revealed a cholesterol level of 82 mg/dl. Histologically, the cyst wall was composed of a monolayer of stratified or pseudostratified epithelial cells. Most of the cells were ciliated, and a few goblet cells were also seen. Immunohistochemical examination revealed that the cells were positive for EMA, cytokeratin, CEA, and PAS, and therefore the diagnosis of endodermal cyst was made. Intracranial endodermal cysts arising from the ventral surface of the medulla oblongata are rare. To the authors' knowledge, only 4 cases have previously been reported in the literature. The origin, clinical and neuroradiological features, and differential diagnosis of endodermal cysts are discussed.

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We report a rare case of cervical syringomyelia caused by a Chiari malformation type I combined with Noonan syndrome in a 33-year-old woman. After experiencing dissociated hypoesthesia of the right upper and lower extremities for approximately 6 months, the patient was seen at our institution. MR imaging revealed syringomyelia associated with a Chiari type I malformation. In addition to fever and pain anesthesia in the right upper and lower extremities, she was underweight, had hypertelorism, a down-salting palpebral fissure, ptosis of the eyelids, depressed nasal root, webbing in the skin of the neck, and arterioventricular septal defect, and had been late in walking unsupported. Since a genetic condition was suspected, chromosomal analysis was carried out. A diagnosis of Noonan syndrome was made. Decompressive occipital craniectomy and C1 and C2 laminectomy were performed to treat the syringomyelia, which gradually alleviated the anesthesia. Patients with Noonan syndrome tend to have mental retardation and therefore they may not notice abnormal physical sensations. Even syringomyelia may remain undiagnosed in such patients.

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A 55-year-old female presented with skull metastasis from breast cancer manifesting as acute epidural hematoma due to minor head trauma. She bumped her forehead against a steel pipe. Her consciousness became somnolent and left hemiparesis appeared. Skull X-ray films showed a large skull defect in the right frontal area. There was no evidence of skull fracture. Computed tomographic scans showed acute epidural hematoma bordering on large skull tumor. The right external carotid angiogram showed the tumor stain. It was assumed that direct injury of the vulnerable feeding artery of the tumor caused the hemorrhage. Removal of the tumor and hematoma was performed with no sequela. Skull metastasis associated with acute epidural hematoma after minor head trauma is a unique occurrence.

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This is a case of a dumbbell type neurinoma for which a posterolateral approach to surgery was adopted, resulting in the total removal of the neurinoma with a single surgical procedure. The patient is a 61-year-old woman with a solid mass in her neck, which was incidentally found. Magnetic resonance images suggested a dumbbell neurinoma with a large extraspinal part extending laterally through the C2-3 neural foramen. She was operated on with the successful removal of the mass using a posterolateral approach through the posterior margin of the sternocleidomastoid muscle. This approach provided excellent access, not only to the extraspinal portion of the tumor. but also to the intraspinal portion of the tumor through partial laminectomy without removing any part of the vertebral bodies and facet joints.

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