Somatosensory evoked high-frequency oscillations recorded directly from the human cerebral cortex.

OBJECTIVE: To elucidate the generator sources of high-frequency oscillations of somatosensory evoked potentials (SEPs), we recorded somatosensory evoked high-frequency oscillations directly from the human cerebral cortex. SUBJECTS AND METHODS: Seven patients, 6 with intractable partial epilepsy and one with a brain tumor, were studied. With chronically implanted subdural electrodes, we recorded SEPs to median nerve stimulation in all patients, and also recorded SEPs to lip and posterior tibial nerve stimulation in one. High-frequency oscillations were recorded using a restricted bandpass filter (500-2000 Hz). RESULTS: For the median nerve oscillations, all oscillation potentials were maximum at the electrodes closest to the primary hand sensorimotor area. Most oscillations were distributed similar to or more diffusely than P20/N20. Some later oscillations after the peak of P20 or N20 were present in a very restricted cortical area similar to P25. We investigated the phase change of each oscillation potential around the central sulcus. One-third of the oscillations showed phase reversal around the central sulcus, while later oscillations elicited in a restricted cortical area did not. High-frequency oscillations to posterior tibial nerve and lip stimulation were also maximum in the sensorimotor areas. Most of the lip oscillations showed phase reversal around the central sulcus, but most of the posterior tibial nerve oscillations did not. CONCLUSION: High-frequency oscillations are generated near the primary sensorimotor area. There are at least two different generator mechanisms for the median nerve high-frequency oscillations. We suspect that most oscillations are derived from the terminal segments of thalamocortical radiations or from the primary sensorimotor cortex close to the generator of P20/N20, and some later oscillations from the superficial cortex close to the generator of P25.

Subtemporal amygdalohippocampectomy for treating medically intractable temporal lobe epilepsy.

A SUBTEMPORAL AMYGDALOHIPPOCAMPECTOMY technique has been developed for mesial temporal lobe epilepsy. The conventional subtemporal approach has been modified to diminish temporal lobe retraction and the risk of damage to the temporal lobe. In the new technique, the surgeons' position has moved from above to below and the approach has been changed from anterolateral to posterolateral, thereby avoiding the voluminous and steeply inclined anterior temporal lobe. By this modified approach, it was unnecessary to remove the roof of the external auditory meatus and it was estimated that both the retraction pressure and the extent of temporal lobe retraction were reduced. To date, surgeons using this approach have operated on four patients with temporal lobe epilepsy whose epileptic foci were in the mesial temporal structure; the inferior temporal gyrus, the temporal tip, the vein of Labbé, and the ventral bridging veins were preserved. After surgery, two patients became completely free of seizures and the other two showed over 90% reduction in seizure frequency without neurological sequelae. Postoperative visual field examination revealed full visual fields without quadrantanopsia. This approach can preserve the temporal stem and lateral temporal lobe, it can be used to remove as much of the posterior hippocampus as necessary, and it can be extended to conventional lobectomy if it is indicated.

The use of an intraluminal shunt for bypass grafts of the cavernous internal carotid artery. Technical note.

The authors describe an indwelling intraluminal shunt for use during graft bypass procedures of the cavernous internal carotid artery. The clinical use of this shunt in a patient with meningioma invading the right cavernous sinus is described. This shunt has also been found applicable during carotid endarterectomy, and should prove to be a useful addition to the neurosurgical armamentarium for skull-base surgery.

Gliosarcoma associated with a huge cyst--case report.

A 55-year-old female presented with a unique case of gliosarcoma with a huge cystic component manifesting as loss of consciousness, left-sided hemiparesis, and anisocoria. Computed tomography demonstrated a large cyst in the right frontal lobe, and enhancement of the mural nodule after administration of contrast medium. Emergent operation was performed. Xanthochromic fluid was aspirated, and the tumor was resected. The histological diagnosis was gliosarcoma based on the presence of gliomatous and sarcomatous components. She underwent a second operation because of tumor regrowth 3 weeks after the first operation. The postoperative course was satisfactory during radiation therapy with 60 Gy and chemotherapy. The diagnosis of gliosarcoma was difficult to make preoperatively because of the neuroradiological findings similar to low-grade gliomas. Gliosarcoma should be included in the differential diagnosis of huge cystic tumors.

Retrolabyrinthine presigmoid transpetrosal approach for selective subtemporal amygdalohippocampectomy.

The retrolabyrinthine presigmoid transpetrosal approach is a modification of the subtemporal approach which is suitable for complete amygdalectomy. By drilling away the retrolabyrinthine presigmoid petrosal bone, at least 1 cm more space below and 1 cm more space medially is obtained than in the subtemporal approach, and temporal retraction pressure is diminished when approaching from below. Operative results according to the Engel's classification of seizure control, and pre- and postoperative Wechsler Adult Intelligence Scale (WAIS), revised WAIS, and Wechsler Intelligence Scale for Children scores were measured in 16 patients treated by normal or modified subtemporal amygdalohippocampectomy. Postoperative follow-up ranged from 8 to 79 months. There has been no morbidity or mortality among these 16 patients, and postoperative seizure frequency has been diminished to less than 10% of the preoperative level in 15 of the 16. In eight patients, seizures have been eliminated totally. Subtemporal amygdalohippocampectomy achieved significantly increased performance and full scale intelligence quotient within 2 months after surgery, compared to preoperative levels. Subtemporal amygdalohippocampectomy is an alternative to the transsylvian approach, but is less invasive.

[Multiple myeloma presenting with a solitary cranial tumor with subdural extension: a case report].

We report a case of multiple myeloma presenting with a solitary cranial tumor in the frontal region, extending from subcutaneous tissue to subdural space. To our knowledge, invasion of a tumor beyond the dura mater has never been described in case of multiple myeloma presenting with a solitary calvarial tumor. In the present case, the subdural extension was clearly visualized by several diagnostic means. A 53-year-old female patient visited the clinic of our University Hospital, complaining of a left frontal mass in May 1991. The mass grew rapidly, and she was hospitalized in June. On admission, neurological examination showed nothing abnormal. Laboratory studies showed normocytic normochromic anemia. Protein electrophoresis disclosed hypergammaglobulinemia with S-spike, and serum paraprotein was specific to IgA with lambda light chains by immunoelectrophoresis. Urinary Bence-Jones protein was not detected. An osteolytic lesion visualized in the frontal bone on plain skull radiographs showed destruction of the frontal bone, and an enhanced mass extending from the epidural to subcutaneous space was shown by computed tomography. The mass had compressed the frontal lobe. T1-weighted magnetic resonance images of the area showed isointensity signals, homogeneously enhanced with gadolinium-diethylenetriamide pentaacetic acid. Subdural extension in the deep area of the tumor was suggested. At operation, we confirmed infiltration of the tumor from the dura mater into the subdural space. Postoperative biopsy of bone marrow of the iliac bone demonstrated myeloma cells. The tumor was histologically diagnosed as plasmacytoma. The patient was highly resistant to postoperative combined therapy, and started on a fatal course leading to respiratory insufficiency caused by interstitial pneumonia in April 1992.(ABSTRACT TRUNCATED AT 250 WORDS)

[Use of cortical somatosensory evoked potentials in surgical treatment of AVMs in and around the central sulcus].

Electric potentials named N1, P2 are recorded from electrodes on the primary sensory cortex when the contralateral median nerve is electrically stimulated transcutaneously at the wrist. N1 is negative wave about 20 msec in peak latency, derived from cortex area 3b, and P2 is positive wave about 24 msec in peak latency, elicited from area 1 and 2. These components will show phase reversals between two responses recorded from precentral and postcentral electrodes pairs. In this report, we attempted to recognize central fissure in 4 cases of arteriovenous malformation in sensorimotor cortex with the benefit of the intraoperative cortical SEPs. We obtained successful recording of phase reversal and identified central fissure in all cases, to whom several anesthetic agents which were said to affect SEP in latency and amplitude were administered continuously during operation. Electrophysiologically recognized central fissures did not coincide with central sulcus arteries those identified by angiographic measurements of two patients. Avoiding injury to the motor cortex, 3 AVMs were completely resected without causing additional neurological deficits. One case whose nidus was hidden into the motor cortex was given up for its resection. In this case the clipping of feeding vessels was chosen for the treatment. Direct monitoring of SEP gives us many additional informations to radiological landmarks concerning the place of sensorimotor cortex and the selection of the surgical approach to the paracentral lesion.

Microanatomy of medial temporal area and subtemporal amygdalohippocampectomy.

For seizure control in temporal lobe epilepsy, the head of the hippocampus to the choroidal point, parahippocampal gyrus, entorhinal area, uncus, and at least the basolateral nucleus of the amygdala should be completely removed. The subtemporal approach should be selected for removal of these structures, and it does not interrupt the temporal stem and optic radiation. Pre- and postoperative neuropsychological examinations revealed that there is no significant decline of scores of various examinations including WAIS, WMS, Randt memory, and verbal associates learning tests, even if the resection were performed on the language dominant side. Seizure control for the 20 non-lesional patients operated with this approach is 60% (Class I and II), without definite permanent complications.

Malignant nerve sheath tumor of the jugular foramen followed by meningeal dissemination in a patient with neurofibromatosis.

A 20-year-old female with von Recklinghausen's disease became aware of hoarseness and dysphagia with a right neck mass, and received subtotal resection of a jugular foramen neurofibroma. One year later the jugular foramen tumor recurred and pathologic examination at excision showed a malignant transformation. Despite postoperative chemotherapy and radiotherapy, it recurred soon and followed the metastatic cerebral tumor by meningeal dissemination. Malignant nerve sheath tumors of the jugular foramen are very rare and the clinical course and pathological pictures of this tumor are reviewed.

Germinoma originating in the basal ganglia. Report of a case showing unusual appearance on MRI.

A case of germinoma originating in the basal ganglia is presented. Preoperative MRI showed an area of a reticulated core of mixed signal intensity with a surrounding rim of low signal intensity in the right basal ganglia on T2-weighted image. This finding was reported to be characteristic of cavernous angioma, but the tumor was histopathologically identified to be a germinoma with old hemorrhage. The pitfall of MRI in diagnosing brain tumors is discussed.

Twenty-kilodalton human growth hormone (20K hGH) secretion from growth hormone-secreting pituitary adenoma cells in vitro.

Circulating human growth hormone (GH) consists of several molecular isoforms. Increased proportion of circulating non-22K hGH and 20K hGH was reported in active acromegaly. In this study, we studied the release of 20K and 22K hGH from cultured GH-producing human pituitary adenoma cells in vitro. Pituitary adenoma cells obtained from 6 acromegalic patients were cultured and submitted to perifusion experiments. Concentrations of 20K and 22K hGH in the serum and the perifusion effluent were determined by specific enzyme-linked immunosorbent assays recently developed. The %20K value varied in a wide range from 3.58 to 8.72% in vitro and was lower than in the serum (mean+/-SD: 6.57+/-1.88% vs 9.08+/-2.12%, P<0.05). There was no correlation between the %20K values in vitro and in vivo (r=0.31, P>0.05). The in vitro secretions of 20K and 22K hGH were in parallel and strongly correlated (r=0.953, P<0.001). These findings suggest that different GH-producing pituitary adenoma cells secrete 20K hGH in variable amounts and that the proportion of 20K hGH in the serum might be affected by metabolic clearance of hGH isoforms. It was also suggested that 20K and 22K hGH might be secreted in toto from GH-producing human pituitary adenoma cells.