Absence of sleep spindles in human medial and basal temporal lobes

All-night recordings from subdural electrocorticographic (ECoG) electrodes on the human medial and basal temporal lobes were analysed to examine spindling activities during sleep. Subjects were three males and three females who were candidates for neurosurgical treatments of partial epilepsy. Subdural electrodes were attached to the medial and basal temporal lobe cortices, allowing ECoG and electroencephalogram from the scalp vertex (Cz EEG) to be recorded simultaneously during all night sleep. In one case, subdural electrodes were attached also on the parietal lobe. Fast Fourier transformation (FFT) analyses were performed on the ECoG and Cz EEG signals. No organized sleep spindles or sigma band (12-16 Hz) peaks in FFT power spectra were observed from the medial or basal temporal lobes of the non-epileptogenic hemispheres during non-rapid eye movement (NREM) sleep. In a case with parietal electrodes, organized spindle bursts were observed in parietal signals synchronized with Cz spindles. Although delta band (0.3-3 Hz) power from both the medial and basal temporal lobes fluctuated across each night as expected, sigma activity changed little. However, 14 Hz oscillatory bursts were observed in the medial basal temporal lobe of epileptogenic hemisphere in two cases and bilaterally in one case during not only NREM sleep but rapid eye movement (REM) sleep and wakefulness. From the present study we conclude that sleep spindle activities are absent in the medial and basal temporal lobes. Fourteen Hz oscillatory bursts observed from the medial or basal temporal lobe in some cases were not considered to be sleep spindles since they also appeared during REM sleep and wakefulness. These waveforms could have originated due to epileptic pathology, since they frequently appeared in epileptic regions.

Comparison of99mTc-tetrofosmin uptakes on planar images with those in excised rats organs with those in excised rats organs

The radioactivity in the organs adjacent to the heart causes interference with the quantitative assessment of myocardial uptake of tracer on scintigraphy. In order to investigate how much the functions of these organs affect myocardial uptake seen in imaging, we compared the myocardial uptake measured by means of a gamma camera with the actual activity in the excised organs.

METHODS

Thirty-three rats were imaged at 5, 10, 15, 30, 45, 60, 90 and 120 min after the administration of 99mTc-tetrofosmin, and % injected dose per pixel (%ID/pixel) for each organ was assessed on planar images (PI measurement). Percent injected dose per gram of tissue (%ID/g) in the heart as well as lungs, liver, gastrointestines and blood was measured by means of a well scintillation counter (WC measurement). Comparison between PI and WC measurements was performed with % uptake, the PI-to-WC ratio and heart-to-organ ratios.

RESULTS

Our WC measurement showed an increase in cardiac uptake until 30 min (1.67 +/- 0.31%) postinjection and subsequent gradual decrease, whereas PI measurement showed maximum activity of 1.81 +/- 0.52% at 15 min postinjection. There was a prominent difference between the two measurements, particularly at 10 min, with a PI/WC ratio of about 1.6 times. Our WC measurement showed maximum pulmonary uptake at 15 min (0.87 +/- 0.31%) and a gradual decrease over 15 min, whereas PI measurement showed maximum uptake at 10 min (1.14 +/- 0.38%). There was hardly any variation in activity observed later than at 10 min. Our WC measurement showed hardly any variance in hepatic activity from 5 min (0.77 +/- 0.19%) to 30 min (0.69 +/- 0.27%) with a subsequent gradual decrease. The percent uptake in PI measurement was generally greater than that in WC measurement, and high values were found at 10 min and 15 min with PI/WC ratios of about 3.3 times and 2.3 times, respectively.

CONCLUSION

Percent uptakes in PI measurement were greater than those in WC measurement. The difference between the two measurements was prominent in the early phases. The cardiac uptake in PI measurement was significantly greater than that in WC measurement at 10 min. It was considered that this discrepancy between the two measurements was caused by the Compton scatter from the organs adjacent to the heart.

Surgical outcome of corpus callosotomy in patients with drop attacks

PURPOSE

We examined presurgical factors that independently influence surgical outcome after corpus callosotomy. For adequate measurement of the surgical outcome, we analyzed seizure outcome of drop attacks, postoperative overall daily function, and family satisfaction.

METHODS

At least 2 years after callosotomy (mean, 40.0 months), we retrospectively investigated 52 patients with drop attacks. As presurgical factors, we analyzed the age at surgery, age at seizure onset, age at drop attack onset, sex, hemiparesis, severe mental retardation, EEG abnormality, MRI abnormality, and extent of callosal section (total or partial callosotomy). Stepwise logistic regression was used for analysis.

RESULTS

Satisfactory outcome (seizure cessation or >90% seizure reduction) was achieved in 85% of patients with drop attacks, 32% of those with generalized tonic seizures, and 31% of those with generalized tonic-clonic seizures. The families assessed the overall daily function as improved in 62% of patients, unchanged in 23%, and impaired in 15%. Family satisfaction with callosotomy was achieved in 83% of patients (definitely satisfied, 39%, somewhat satisfied, 44%). Total callosotomy is independently predictive of satisfactory reduction of drop attacks (p = 0.013). A younger age is independently predictive of improvement of overall daily function (impaired and improved: p = 0.004) and family satisfaction (unsatisfied and somewhat satisfied, p = 0.018; unsatisfied and definitely satisfied, p = 0.0006).

CONCLUSIONS

In the present study, we found that total callosotomy is more effective for treatment of drop attacks than partial callosotomy and that children receive more benefit than adults after callosotomy.

Cortical dysplasia with ossification

We present the first case of cortical dysplasia with extensive intracerebral ossification. An eight-year-old epilepsy patient with a calcified lesion was successfully treated by surgical intervention. Pathological examination revealed a number of bizarre dysplastic cells in the whole lesion, which consisted of an epileptogenic cerebral cortex and a nonepileptogenic hamartomatous lesion with adipose tissue, vascular tissue, calcification, and ossification. The patient was diagnosed as having cortical dysplasia with ossification. Our findings support the notion that cortical dysplasia has a multipotentiality of cellular differentiation, including various hamartomatous tissues. We suggest that cortical dysplasia should be considered as a potential cause for epileptogenicity of a hamartomatous lesion even when magnetic resonance imaging (MRI) fails to disclose cortical dysplasia.

Presence of human herpesvirus 6 and herpes simplex virus detected by polymerase chain reaction in surgical tissue from temporal lobe epileptic patients

We investigated the presence of human herpesvirus 6 (HHV-6) and herpes simplex virus (HSV) in surgical tissue from temporal lobe epileptic patients. A total of 17 cases were studied, including eight males and nine females. The mean age was 24.9 +/- 11.1 years and the mean age of onset was 11.1 +/- 5.4 years. Five patients were diagnosed as encephalitis/meningitis and another three had a history of suspected encephalitis/meningitis, but no patient showed any obvious neurological symptom or mental handicap. Mesial and lateral temporal tissues were examined by polymerase chain reaction. Among six patients positive for HHV-6 (35%), the mesial temporal lobe was positive in four and the lateral temporal lobe was positive in three. Herpes simplex virus was positive in only one patient. Three of the six patients positive for HHV-6 did not show any apparent causes. Mild encephalitis/meningitis induced by HHV-6, a condition sometimes not recognized as encephalitis/meningitis, may be one of the most frequent causes of temporal lobe epilepsy.

Enhanced motor cortical excitability in the unaffected hemisphere after hemispherectomy

We evaluated motor cortical excitability of the unaffected hemisphere in three patients with intractable epilepsy who underwent hemispherectomy, using transcranial magnetic stimulation (TMS) and PET. TMS of the unaffected hemisphere evoked motor responses not only in the contralateral muscles but also in the ipsilateral ones in all the patients. A PET study in one patient showed activation of the unaffected motor cortex by movement of either arm. All of these responses were enhanced after the hemispherectomy, probably due to motor cortical disinhibition by transection of the corpus callosum. The PET study also showed postoperative activation of the premotor area of the unaffected hemisphere. These phenomena indicate posthemispherectomy neuroplastic reorganization leading to preservation of the motor function after the operation.

[Functional hemispherectomy for children aged 2 years or less for the treatment of intractable epilepsy caused by cortical dysgenesis]

Thirteen children aged 2 years or less who had intractable epilepsy caused by cortical dysgenesis underwent functional hemispherectomy. The cerebral malformations were hemimegalencephaly in 8 cases and focal cortical dysplasia in 5 cases. Among 11 children who were followed for at least 6 months after the operation (6 to 54 months with a median of 26 months), 5 were seizure-free, 4 achieved > 90% seizure reduction, and 2 achieved 50-90% reduction. Ventriculo-peritoneal shunt was placed in 3 children with hemimegalencephaly. After hemispherectomy, all the children showed improvement in psychomotor development. Development was accelerated in 3 seizure-free children. In children with cortical dysgenesis, functional hemispherectomy may result in remarkable seizure reduction and steady developmental progress.

Modification of peri-insular hemispherotomy and surgical results

OBJECTIVE

We modified the peri-insular hemispherotomy technique devised by Villemure and Mascott. Our modified technique and the surgical results obtained with this method are presented.

METHODS

The frontoparietal operculum is resected, and the resection cavity is connected with the lateral ventricle. Through this cavity, a transventricular corpus callosotomy and resection of the medial temporal structures are performed.

RESULTS

This technique was used for 34 patients, with satisfactory surgical results. Cerebrospinal fluid shunt placement was necessary for five patients, and incomplete callosal sectioning was postoperatively detected in three cases.

CONCLUSION

Our modification of the peri-insular hemispherotomy can be safely and effectively used to treat epilepsy caused by hemispheric lesions, even in cases without ventricular dilation.

Vacuum assisted cardiopulmonary bypass in minimally invasive cardiac surgery: its feasibility and effects on hemolysis

The present study describes a cardiopulmonary bypass (CPB) technique that incorporates vacuum assisted venous drainage and arterial return using a centrifugal pump in minimally invasive cardiac surgery (MICS). The technique was performed on 40 patients scheduled to undergo MICS. The proposed CPB technique enables a good operative field to be obtained even through a limited incision through the use of peripheral cannulation using small cannulae. Vacuum pressure was applied to the venous reservoir (-43 +/- 14 mm Hg) to maintain adequate CPB flow (>2.4 L x min-1 x M-2). The effects of CPB on hemolysis were subsequently compared between patients who underwent the proposed procedure (MICS group; n = 6) and a control group who underwent coronary arterial bypass grafting (CABG group; n = 6) with conventional CPB. Plasma free hemoglobin (FHb) increased and plasma haptoglobin (Hp) decreased during CPB in both groups, with no significant difference between the groups. By the next day, FHb had returned to pre-CPB levels whereas Hp remained lower in both groups. Again, these values did not differ significantly between groups. Thus, we conclude that the proposed CPB technique is useful in MICS with acceptable effects on hemolysis.

Multiple myeloma presenting high fever and high serum levels of lactic dehydrogenase, CRP, and interleukin-6

Two myeloma patients presented high fever with no signs or data indicating infection at diagnosis or relapse. Both patients had plasmablastic myeloma, and serum levels of lactic dehydrogenase (LDH) and CRP were extremely high. Plasmablastic morphology, high LDH, and CRP were recognized as poor prognostic factors, indicating a fulminant phase of multiple myeloma. Interleukin-6 (IL-6) was only high in measured cytokines. We proposed that IL-6 caused high fever and induced the fulminant phase in these 2 cases.

[Endovascular neurointervention for cerebral aneurysm]

Embolization would have an advantage in the treatment of cerebral aneurysms by eliminating the need for craniotomy. The recent protocol of endovascular treatment for cerebral aneurysm is classified into two main categories; is parent artery occlusion and intra-aneurysmal embolization. For aneurysms with a broad neck and large sac, it is recommended to consider proximal arterial occlusion if tolerance is confirmed by cerebral blood flow study at the time of balloon Matas' test. Parent artery occlusion is a classical technique, but still mandatory and effective clinically. In patients who have aneurysms with a has well-defined neck and who are not good candidates for craniotomy, intra-aneurysmal embolization would be recommended as an alternative means of treatment. Care should be taken to prevent problems and complications, including careful catheter and guidewire manipulation. Careful selection of cases and appropriate pre-, intra-, and post-procedure patient management is essential. Since the clinical application of Gugliemi's detachable coil (GDC) started, the potential of endovascular treatment for cerebral aneurysm has changed considerably. Preliminary results of embolization using GDC suggest that endovascular treatment would offer marked improvement in the management of patients harboring cerebral aneurysms.

[Endovascular neurointervention for intracranial dural arteriovenous fistula]

Dural arteriovenous fistula(DAVF) is an abnormal shunt within the dura matter or near the venous sinuses. Various congenital and idiopathic causes have been suggested, including such as venous sinus occlusion, trauma, surgery, and changes in hormone levels, but the exact etiology of the disease is unknown. The pattern of venous drainage seen on angiography was used as the basis for a classification of DAVF by Djindjian. Recent classification suggests that lesions that drain into the venous sinus or meningeal vein will behave only in a benign manner, whereas those that have subarachnoid venous drainage or alone or in addition will behave aggressively. Selection of treatment can be made from observation, carotid manual compression, transarterial or transvenous embolization, radiotherapy, or surgical intervention. The goal of treatment and consequently the techniques used, depends on the intensity of symptoms or the neurologic and, in particular, hemorrhagic risk posed by the type of venous drainage. The therapeutic decision depends also on the patient's general clinical status. Embolization can create a reduction of flow, which results in disappearance in symptoms and sometimes complete cure as seen at angiography. Complex DAVF must be treated with combined endovascular techniques plus neurosurgery or radiotherapy.

Usefulness of cerebral blood flow (CBF) measurements to predict the functional outcome for rehabilitation in patients with cerebrovascular disease (CVD)

PURPOSE

The objectives of this study were to (1) elucidate the relationship between the mean CBF in the whole brain (Av.mCBF) before rehabilitation of CVD patients and the BI score before and after rehabilitation, (2) determine whether the efficacy of rehabilitation can be predicted by measurement of the Av.mCBF, and (3) investigate what part of the brain was most important to improving the BI score.

MATERIALS AND METHODS

The Av.mCBFs in 160 patients with CVD were calculated by Patlak plots with 99mTc-HMPAO before rehabilitation, and we determined the BI score before and after rehabilitation. Based on the BI scores before and after rehabilitation, patients were divided into four groups: Group A, BI = 100; Group B, 80 < or = BI < or = 99; Group C, 60 < or = BI < or = 79; Group D, 0 < or = BI < or = 59. We evaluated the relationship between the Av.mCBF and BI score before and after rehabilitation.

RESULTS

The Av.mCBF before rehabilitation showed a tendency to be more correlated with the BI score after rehabilitation (r = 0.414, p < 0.0001) than before rehabilitation (r = 0.272, p = 0.0006). After rehabilitation, there was a tendency for the Av.mCBF value to increase in direct proportion to the BI score of the group: it was highest in Group A and lowest in Group D. The strongest correlation was found between the frontal lobe regional CBF before rehabilitation and the BI score after rehabilitation (r = 0.343, p < 0.0001).

CONCLUSIONS

Measurement of the Av.mCBF before rehabilitation of CVD patients will permit prediction of the efficacy of rehabilitation. Also the regional CBF of the frontal lobe is most important for improving the BI score.

Suppression of gamma activity in the human medial temporal lobe by sevoflurane anesthesia

We have reported the presence of continuous gamma (30-150 Hz) activity in the human medial temporal lobe (MTL). Since the MTL is involved in learning and memory, we speculated that MTL gamma activity is related to such higher brain functions. It is thus of interest to learn how this activity changes during different states of consciousness. In this study, we recorded electrocorticographic (ECoG) activity directly from the surface of the MTL after various doses of sevoflurane anesthesia. Five epileptic patients underwent electrode placement operations in which electrodes were attached to the surfaces of the MTL and the basal temporal lobe (BTL). Immediately following the operation ECoG was recorded from each patient under four concentrations of sevoflurane anesthesia (1.5, 2.0, 2.5 and 3.0%). Fast Fourier Transform (FFT) analysis was performed on the MTL ECoGs. Under the lowest sevoflurane concentration, MTL gamma activity was observed in all patients. However, gamma activity was progressively suppressed by increased concentrations of sevoflurane, in a dose-dependent manner. Sevoflurane has been known to reduce neuronal excitability in the rat hippocampus in vitro, probably by changing GABAergic inhibition. The reduction of MTL gamma in the present study may be the result of such a mechanism. Although memory function was not tested in this study, the amount of MTL gamma activity may be related to residual memory function during anesthesia.

[Thoracoscopic lobectomy (non rib-spreading method): versus a video assisted lobectomy and a conventional thoracotomy]

We analyzed 33 thoracoscopic lobectomy (non rib-spreading method: NR) cases and 33 video assisted lobectomy (VA) cases and 49 posterolateral thoracotomy (PL) cases, regarding post-operative changes in the serum enzyme levels, operative bleeding, required analgesic treatments, changes in the respiratory function and other factors. Regarding the post/pre-operative ratio of creatinin phosphokinase, bleeding and analgesic treatment NR was showed significantly lower levels than the other two methods. Regarding the post/pre-operative ratio of vital capacity of the lung NR was significantly less than PL for every six months after the operation. With NR the mean number of dissected mediastinal nodes was 14.2 +/- 7.4 which was not significantly different from VA and PL. We thus concluded that NR caused less thoracotomic damage and especially far less restrictive damage to the respiratory function than both PL and VA. NR may also result in a better quality of life than VA and PL. The node dissection required for NR is also not considered to be inferior to that for PL because the number of dissected nodes for NR was not significantly different from that for PL. Therefore, in cases presenting with clinical stage I primary lung cancer NR is thus considered to be indicated in order to obtain an improved post-operative quality of life.

MR images of ovarian carcinosarcoma

The MR imaging of an ovarian carcinosarcoma is described. The tumor was heterogeneous and showed very high-intensity on T2-weighted images and iso-intensity on T1-weighted images, with visible enhancement. Even though signal intensities were somewhat different from those of ovarian adenocarcinoma, the preoperative diagnosis of ovarian carcinosarcoma is still difficult.

Beta-1 (10-20 Hz) cortical oscillations observed in the human medial temporal lobe

During wakefulness, signals from subdural electrodes attached to the basal and medial temporal lobes of adult human epilepsy patients revealed a rhythmic oscillation in the beta-1 frequency range (10-20 Hz). This activity was more prominent in the medial than in the basal temporal cortex. We also observed simultaneous oscillations in alpha frequency activity in the medial and the basal temporal cortices. In an eyes-open condition, the alpha oscillation was attenuated, while the beta-1 oscillation in the medial temporal lobe was not. This is the first report that the beta-1 oscillation is present in the human medial temporal lobe. Since we recorded this activity from within the limbic system, beta-1 activity may be an analog of the hippocampal rhythmic slow activity observed in some animals.

Diffusion-weighted MR imaging in multiple sclerosis: comparison with contrast-enhanced study

OBJECTIVE

To assess the utility of cerebral diffusion-weighted MR imaging in the diagnosis of multiple sclerosis (MS) in comparison with contrast-enhanced T1-weighted imaging.

METHODS AND MATERIALS

We reviewed T2-weighted spin-echo (SE), fluid-attenuated inversion-recovery (FLAIR), contrast-enhanced T1-weighted SE and echo-planar diffusion-weighted images (DWIs) obtained in seven patients with definite MS on nine occasions.

RESULTS

In total, 94 plaques were demonstrated on T2-weighted SE and/or FLAIR images. A total of 13 of these plaques showed enhancement on contrast-enhanced T1-weighted images and hyperintensity on DWIs, and five non-enhancing plaques showed hyperintensity on DWIs.

CONCLUSION

Diffusion-weighted imaging, which provides information based on pathophysiology different from contrast-enhanced imaging, is a potential supplementary technique for characterizing MS plaques.

Interictal hyperperfusion observed in infants with cortical dysgenesis

We investigated increases of interictal regional cerebral blood flow (rCBF) in patients with intractable epilepsy caused by cortical dysgenesis. Using single photon emission computed tomography, we measured interictal rCBF of epileptic foci in 24 patients with cortical dysgenesis who achieved Engel Class I or II outcomes at least 1 year after surgical intervention. The patients included 14 males and ten females, ranging in age from 2 months to 34 years (mean 6 years and 5 months). In the interictal period, dysplastic areas showed hyperperfusion in four patients (17%), hypoperfusion in 15 (62%), and isoperfusion patterns in five (21%). Interictal hyperperfusion was found in four infants aged 3-4 months; three with focal cortical dysplasia and one with hemimegalencephaly. Our results suggest that interictal hyperperfusion may indicate the presence of an active epileptic focus in infants with cortical dysgenesis, but not in older children or adults with the same disorder. Given the risk of misinterpreting the normal side as hypoperfused, the phenomenon of interictal hyperperfusion in the epileptogenic area should be taken into account when diagnosing pediatric epilepsy caused by cortical dysgenesis.

Stereotactic radiosurgery for brain metastases using a linac system: evaluation of initial local response by imaging

PURPOSE

We analyzed the efficacy of initial local response of MBT by imaging obtained within two months after treatment, to determine if there are factors that may be important for the initial local response of the disease. If an earlier local tumor response can be expected from SRS, patients with a poor prognosis should be treated with this modality.

METHODS

Thirty-six patients with 59 lesions were treated by linac radiosurgery. The primary tumor, peripheral dose, tumor volume, and CT enhancement pattern of the tumor before treatment (homogeneous or ring-enhancing) were chosen as factors related to local tumor response and were used in the statistical analysis.

RESULTS

1) The initial local response of radiation-resistant tumors to conventional EBRT was worse than that of other tumors. The initial local responses of MBT from breast carcinoma, colon carcinoma, and pulmonary carcinoma were good. 2) Excluding radioresistant tumors, the cases irradiated at 25 Gy or more tended to show good local control. 3) No statistically significant differences were found between local response and factors such as the enhancement pattern and tumor volume in the analysis of MBT.

Rhabdomyosarcoma in a patient with mosaic Klinefelter syndrome and transformation of immature teratoma

A 27-year-old man was found to have a mediastinal tumour and the histological diagnosis was immature teratoma. Remission was achieved by chemotherapy and total resection. However, he developed anaemia and leukoerythroblastosis after 2 years of remission, and was referred to our hospital. Rhabdomyosarcoma cells were detected in the bone marrow and pleural effusion. Moreover, karyotype analysis of peripheral blood and bone marrow cells revealed mosaic-type Klinefelter syndrome. We diagnosed the case as transformation of teratoma into rhabdomyosarcoma in Klinefelter syndrome. Although intensive chemotherapy was performed, the patient died with meningeal infiltration.

Successful surgical treatment of a dural arteriovenous fistula at the craniocervical junction with reference to pre- and postoperative MRI

We report a 62-year-old woman who presented with a myelopathy at the lower thoracic level. Left vertebral angiography revealed a dural arteriovenous fistula (DAVF) at the craniocervical junction, draining into an anterior spinal vein. Below the T7 level, the spinal cord gave high signal on T2-weighted images and enhanced with Gd-DTPA. The patient was successfully treated by simple clipping of vein draining the DAVF. The abnormal signal intensity and contrast enhancement rapidly regressed, except in the conus medullaris. Regression of the parenchymal abnormality on serial MRI following treatment corresponded closely with postoperative improvement of neurological function.

A new MRI technique for demonstrating the surface of the brain together with the cortical veins

We assessed combining of surface-anatomy scanning (SAS) MRI and MR venography (MRV). We obtained SAS images with a half-Fourier single-shot fast spin-echo sequence, then MRV of the identical section with a two-dimensional phase-contrast technique. We then added the two sets of images. The combined images, which were obtained within 10 min, provided information about the surface anatomy and cortical veins. This simple technique is useful for demonstrating brain surface structures, especially in patients from whom one plans to excise a lesion.

Minimally invasive port-access coronary artery bypass grafting

The Port-Access endovascular cardiopulmonary bypass system (Heartport, Inc., Redwood City, CA, USA), a recent technological innovation in minimally invasive cardiac surgery, was conducted successfully in coronary artery bypass grafting on a 69-year-old woman. The left internal thoracic artery was harvested through a limited left anterior thoracotomy and anastomosed to the left anterior descending coronary artery on a protected and arrested heart. Intraoperative coronary angiography confirmed good graft patency. The patient was discharged from the hospital in good condition 7 days after the operation. This was the first successful minimally invasive Port-Access coronary artery bypass grafting in Japan.

Enhanced gamma (30-150 Hz) frequency in the human medial temporal lobe

We performed fast Fourier transformation power spectral analysis of the electrocorticogram in human medial temporal lobe during wakeful rest in six epileptic subjects. Compared with the electrocorticogram wave in the basal temporal lobe, which showed monotonic decline of spectral power across the frequency axis, the electrocorticogram wave in the parahippocampal gyrus was enhanced (or did not decline) in the gamma frequency range (30-150 Hz) in all subjects. Although it has been suggested that electrical oscillations of the hippocampus have functional roles in higher brain functions, namely learning and memory, the knowledge of hippocampal oscillations is largely limited to animal studies. The present results demonstrate that fast frequency oscillation is also present in the human medial temporal lobe, which has been reported in animal hippocampi. They also demonstrate the importance of recording very fast field potentials in human electrocorticograms. This fast oscillation is likely to play important functional roles related to learning and memory, possibly to induce long-term potentiation in the human medial temporal lobe.

Surgical treatment of a case of early infantile epileptic encephalopathy with suppression-bursts associated with focal cortical dysplasia

We report a surgically treated case of early infantile epileptic encephalopathy (EIEE) with suppression-bursts associated with focal cortical dysplasia. Tonic-clonic seizures followed by a series of spasms occurred about a hundred times a day at a few days of age. Interictal electroencephalogram (EEG) revealed a suppression-burst pattern that was predominant in the left hemisphere. Magnetic resonance imaging (MRI) suggested focal cortical dysplasia in the left prefrontal area. Combination therapies with antiepileptic treatments showed only partial efficacy. The patient underwent lesionectomy at age 4 months, after which he gradually showed psychomotor development and a decrease of spasms to 0-2 series daily. In cases of EIEE with focal cortical dysplasia, surgical treatment may have beneficial effects on both psychomotor development and seizure control.

Clinical outcome in three patients with myelodysplastic syndrome showing polyclonal hematopoiesis

The clinical outcome of 3 myelodysplastic syndrome (MDS) patients with polyclonal hematopoiesis is reported. All patients were heterozygous for the phosphoglycerate kinase (PGK) gene. The presence of polyclonal hematopoiesis was determined by the X-chromosome-linked restriction fragment length polymorphism-methylation method using the PGK gene as a marker. The patients were initially diagnosed as having refractory anemia (RA), RA with ring sideroblasts (RARS), and RA with an excess of blasts (RAEB), respectively. Their pancytopenia persisted during the follow-up period of 11.4 years for the RA patient, 19.5 years for the RARS patient and 0.8 years for the RAEB patient. Although the RARS patient continues to be in good health, leukemic transformation occurred in the other 2 patients. A karyotype change from 46,XX to 45,XX,t(3;21),-7 was observed at the time of disease progression in the RA patient. The coexistence of a monoclonal MDS clone and normal bone marrow cells is thought to be the most probable reason for the polyclonal hematopoiesis of these patients.

Myelodysplastic syndromes with nephrotic syndrome

It is sometimes reported that the immunological abnormalities in myelodysplastic syndromes (MDS) induce autoimmune disease (i.e., acute systemic vasculitic syndrome, chronic cutaneous vasculitis, polyneuropathy, relapsing polychondritis, and steroid-responsive pulmonary disorders). We investigated the clinical features of patients with MDS accompanied by nephrotic syndrome. We enrolled 125 patients with MDS who were admitted between January 1979 and May 1996 in this study. The renal function was assessed based on the laboratory data and the findings at the physical examination. The diagnoses of nephrotic syndrome and glomerular disease were established when 24-hr urinary excretion was more than 3.5 g and serum total protein was less than 6.0 g/dl, and when the 24-hr protein excretion was more than 1.5 g. Five patients (4%) had glomerular disease, and three (2.4%) had nephrotic syndrome. Of the five patients with glomerular disease, two had refractory anemia (RA), and three had chronic myelomonocytic leukemia (CMMOL). Three of the total 11 patients with CMMOL were diagnosed as having nephrotic syndrome. Among the CMMOL patients, those with nephrotic syndrome showed higher absolute monocyte numbers than did those without nephrotic syndrome (8830 +/- 4677/microl vs. 3061 +/- 2887/microl, P = 0.03). One CMMOL patient was treated with VP-16 and hydroxyurea. As the white blood cell count in this patient decreased, the 24-hr urine protein excretion and the serum tumor necrosis factor alpha level decreased. The relationship between nephrotic syndrome and CMMOL was not clear. High monocyte count and the serum cytokines in MDS patients may play a partial role in the evolution of glomerulonephritis, and CMMOL may be closely related to nephrotic syndrome.

Functional magnetic resonance imaging of auditory cortex: with special reference to the side of aural stimulation

PURPOSE

To determine whether left- or right-side uniaural stimulation produces different fMRI activation patterns.

METHODS

Subjects were 12 volunteers (8 right-handed, 4 left-handed) with normal hearing. Functional imaging using FE-type multishot echo planar imaging was obtained in the axial plane during pure-tone and pseudoword tasks. Auditory stimuli were presented to each ear individually. In pure-tone tasks, subjects heard clustered sequences at 2000 Hz. In pseudoword tasks, subjects heard spoken Japanese syllables. The numbers of activated pixels in the auditory cortex were counted and compared for pure-tone and pseudoword tasks, as was activation according to the side of aural stimulation.

RESULTS

In right-handed subjects, prominent activation in pure-tone tasks was noted in the dominant hemisphere in 100% of cases and was unrelated to the side of the stimulation. In pseudoword tasks, prominent activation was noted on the side contralateral to the stimulus in 62.5-100% of cases. In left-handed subjects, prominent activation was noted on the side contralateral to the stimulus in both pure-tone and pseudoword tasks.

CONCLUSION

Left- and right-side stimulation produced differences in fMRI responses, especially between pure-tone and pseudoword tasks. Moreover, right-handedness and left-handedness affected results. This type of auditory fMRI may be a noninvasive indicator of language lateralization.

Brain tumors in surgical neuropathology of intractable epilepsies, with special reference to cerebral dysplasias

Surgical specimens from 30 patients (13 males and 17 females) with intractable epilepsy with brain tumors and allied lesions were histopathologically examined: 4 of nonneurogenic origin (1 angiolipoma with cortical dysplasia and 3 cavernous hemangiomas), 2 low-grade fibrillary astrocytomas, 1 pleomorphic xanthoastrocytoma, 3 pilocytic astrocytomas with nuclear polymorphism, 1 oligoastrocytoma, 9 gangliogliomas, 3 gangliogliomatous lesions combined with tuberous sclerosis-like dysplastic changes, and 7 undetermined lesions suspected of being mixed glioma, dysembryoplastic neuroectodermal tumor (DNT), or dysplasia. They were all located supratentorially: in the temporal lobe in 21, frontal lobe in 6, and parietooccipital lobe in 3. The age of onset was under 20 years in most patients. Some kinds of dysplasias, such as focal cortical dysplasia, glioneuronal heterotopia, and clustered neurons in the hippocampus and amygdaloid nucleus, were combined in 11 cases, especially those with age of onset under 10 years. Pilocytic astrocytoma-like features were seen in 5 of the gangliogliomas and 3 of the undetermined lesions, and DNT-like features in 2 of the former and 3 of the latter. Gangliogliomas, pilocytic astrocytomas, mixed gliomas, DNTs, and dysplasias may be closely inter-related in the development of intractable epilepsies of young patients.

[Basic approaches in minimally invasive cardiac surgery (MICS) and its selection]

Recently, minimally invasive cardiac surgery (MICS) has been developed and popularized as a less stressful and less invasive technique in the field of cardiac surgery. There are eight currently available MICS approaches for open heart surgery. The optimum approach should be selected for each patient based on the results of preoperative examination including chest X-ray, computed tomography, and angiography. Between December 1996, when we first introduced MICS for mitral repair, and the end of November 1998, we performed MICS in 67 patients [excluding cases of MIDCAB]. These included 11 patients who received the Port-Access (Heartport, Inc.) system. Although no patients died in hospital stay, one died of cerebrovascular bleeding eight months later. All patients were evaluated in the outpatient department as being NYHA class I. In view of future technological progress, we expect that MICS will gradually become more widespread in cardiac surgery.

Differential effects of wortmannin on the release of substance P and amino acids from the isolated spinal cord of the neonatal rat

1. Effects of wortmannin, an inhibitor of myosin light chain kinase, on the release of substance P and amino acids, GABA and glutamate, were investigated in the isolated spinal cord preparation of the neonatal rat. 2. Wortmannin at 0.5 - 10 microM depressed the release of substance P evoked by high-K+ (90 mM) medium from the spinal cord (IC50 = 1.1 microM). Wortmannin also depressed the high-K+ (70 mM)-evoked release of substance P from cultured dorsal root ganglion neurons of neonatal rats. In contrast, the high-K+ (90 mM)-evoked release of GABA and glutamate from the spinal cord was not affected by wortmannin (0.1 - 10 microM). 3. Upon stimulation of a dorsal root, a monosynaptic reflex and a subsequent slow ventral root depolarization were evoked in the ipsilateral ventral root of the same segment in the isolated spinal cord preparation. The magnitude of the slow ventral root depolarization was depressed gradually to about 70% of the control during the course of 30 min under wortmannin (1 microM). In contrast, the monosynaptic reflex was unaffected by wortmannin. 4. Immunofluorescent staining revealed that immunoreactivities of substance P and myosin II were colocalized at presynaptic terminals in the dorsal horn of the neonatal rat spinal cord. 5. The present results suggest that myosin phosphorylation by myosin light chain kinase may play a crucial role in the release of substance P, but not in the release of GABA and glutamate in the neonatal rat spinal cord. This may reflect a difference in the exocytic mechanisms of substance P-containing large dense core vesicles and amino acid-containing small clear vesicles.

[Evaluation of an ultrasonic cutting and coagulating system (harmonic scalpel) for performing a segmental and wedge resection of the lung]

In order to prevent the local recurrence of malignant tumors, it is important for surgeon to maintain a sufficient margin between the tumor and the edge at resection. For this reason we do not use an auto-suturing device, but instead use the ultrasonic cutting and coagulating system (HARMONIC SCALPEL, ETHICON ENDO-SURGERY Cincinnati, Ohio) whenever we perform either a segmental resection or a wedge resection of the lung. The subjects investigated consisted of 24 cases of lung tumors (15 metastatic tumors, 5 cases with primary lung cancer, 3 inflammatory tumors; and one benign tumor). The type of operation included 10 segmental resections and 14 wedge resections, with 21 open thoracotomies and 3 instances of thoracoscopic surgery, while 15 were single resections and 9 were multiple resections. Little bleeding was seen at the resection of the parenchyma and the vessels of the lung. However prolonged air leakage was observed in some cases that needed pleurodesis. The mean duration time of the surgery was 266 minutes, and the mean blood loss was 173 ml. The operative duration was a little longer than normal, because many cases were not first thoracotomies and some cases had multiple tumors. Nevertheless the amount of blood loss was slight. The longest post-operative period was two years and six months, no local recurrence has yet been seen in any of malignant cases. We consider this system to be very effective for performing a resection of the lung parenchyma because of the reduced blood loss and the apparent increased prevention of recurrence.

Combination of surface anatomy MRI and MR venography to demonstrate cerebral cortex and cortical veins on one image

We assessed in 12 patients the value of MR images in which a surface anatomy scanning (SAS) image and an MR venogram are added. We obtained SAS images using the half-Fourier technique and MR venograms with the 2D phase-contrast technique. The added images provided sufficient information concerning brain surface as well as cortical veins. Their findings correlated with those at surgery in six patients who underwent scalp incision marking. This technique provides valuable anatomical information preoperatively.

Endobronchial hamartoma treated by an Nd-YAG laser: report of a case

Endobronchial hamartomas are only rarely encountered. They cause irreversible lung damage due to bronchial obstruction if not diagnosed early and treated properly. Among the various treatments for this rare disease, a surgical resection remains the most popular. We herein report a case of a 53-year-old man presenting with an endobronchial hamartoma which was successfully excised by laser irradiation via a rigid bronchoscope, along with a review of 113 patients with this disease reported in the literature.

[Results of resection of T3 primary lung cancer]

Primary resection for lung cancer was performed in 711 patients. Extensive surgery was performed in 99 T3 lung cancer (13.7%). Overall 5-year survival rate was 31.7%. Overall hospital mortality was 7.5%. Mean 5-year survival was 34.9% for patients with complete resection, 0% for patients with incomplete resection (p < 0.05). In patients with complete resection, mean 5-year survival was greater in patients with N0 (39.1%) than in patients with N1 (23.5%) or N2 (27.7%), but there was no statistically significant difference. There was also no statistically significant difference between adenocarcinoma and squamous cell carcinoma. Mean 5-year survival rate for patients with invasion of chest wall was 34.1%, with invasion of mediastinal pleura was 37.5%, with invasion of main bronchus was 58.3%, with interlobular invasion was 18.7%. Complete resection of T3 lung cancer may yield long time survival.

3D-CT angiography of cerebral arteriovenous malformations

We studied 76 patients with cerebral arteriovenous malformations (AVMs) using dynamic-CT with intravenous injection of contrast material and reconstructed three-dimensional images (3D-CT angiography). All patients received stereotactic radiotherapy (gamma-knife). We compared 3D-CT angiography with conventional angiography to determine the usefulness of this technique. 3D-CT angiography could be performed in conjunction with usual axial high-resolution CT without any additional scanning time and within 10-30 minutes for the overall study. Most niduses and drainers of AVMs were clearly visualized by 3D-CT angiography. 3D-reconstruction was very helpful in demonstrating the niduses, drainers, and three-dimensional structure of AVMs. Demonstrations of feeders were not remarkable. Dynamic CT was very helpful in dose planning for gamma-knife radiosurgery, because gamma-knife angiograms were limited in terms of angles, magnification, and establishing precise localizations using a head frame. 3D-CT added information on trails of drainers and was useful in reducing the volume of irradiation. 3D-CT angiography of cerebral AVMs could be performed routinely, and three-dimensional imaging was helpful in demonstrating the complex anatomy of cerebral AVMs. This technique was very helpful in planning gamma-knife radiosurgery.

Primary cardiac leiomyosarcoma growing rapidly and causing right ventricular outflow obstruction

Leiomyosarcomas are extremely rare primary cardiac tumors. We report a rapidly growing primary leiomyosarcoma of the right ventricle, which obstructed the right ventricular outflow tract within one month after symptom onset in a 68-year-old man. Two-dimensional echocardiography was useful in diagnosing the extent and progression of the tumor. The tumor was surgically resected on an emergency basis, and the right ventricle and pulmonary artery were successfully reconstructed. Recurrence of the tumor on the right ventricle was observed, and the patient was overcome by sudden dyspnea and died three months after surgery.

MRI findings of multiple malignant gliomas: differentiation from multiple metastatic brain tumors

Multiple malignant gliomas are relatively uncommon, but are sometimes difficult to differentiate from multiple metastatic brain tumors. We analyzed the MR findings of four cases of multiple gliomas, comparing them with 12 cases of multiple metastatic brain tumors. All tumors were pathologically proven by surgical operation or autopsy. Gliomas were located in the deep white matter of the cerebrum, with none found in the posterior fossa. Tumors were relatively large, and irregular, thick, ring-like enhancement was noted after the administration of Gd-DTPA. Intratumoral hemorrhage was noted in only one case. High signal intensity on T2WI around the tumor suggested that edema was greater and more extensive than in metastatic tumors and was seen even in the corpus callosum. One autopsied case that showed this high intensity presented not only edema but also tumor infiltration. Metastatic tumors were located mainly in the corticomedullary junction of the brain. They were relatively small, and eight of 12 tumors showed, nodular or smooth ring-like enhancement. Intratumoral hemorrhage was noted in four cases. Edema was noted mainly around the tumor. We conclude that differential diagnosis between gliomas and metastases is possible to some extent by MRI.

[Relationship between imaging and pathological features and clinical factors in surgical cases of temporal lobe epilepsy]

The relationships between imaging, pathology and presumed causes in surgical cases of temporal lobe epilepsy (TLE) was studied. The subject was 62 patients (33 males and 29 females) who had had no attacks for more than one year after surgery. Average age at surgery was 28.2 +/- 9.9 years. Obvious neurological abnormalities were not found in these cases. MRI, PET and SPECT were performed. Hematoxylin and eosin was used for pathological judgement. Their medical charts were used to investigate their clinical factors. Although patients suspected of having encephalitis/meningitis had been hospitalized for 2 days to three months during childhood due to disturbance of consciousness with high fever and convulsion for several days; they were not diagnosed with encephalitis/meningitis at that time, and they suffered almost no handicaps other than epilepsy for several years following their comatose episodes. [Result] (1) On MRI, mesial temporal sclerosis (MTS) was detected in 48 of 52 patients (92%); 32 (62%) had high-signal intensity on T 2-weighted images; 31 (60%) had atrophy ¿23 (44%) had high-signal intensity on T 2 + atrophy¿; 5 (10%) had calcified lesions; and 2 (4%) had cystic lesions. On PET and SPECT, abnormal cerebral blood flow was noted in 33 of 36 (92%). (2) On pathological findings (61 cases), Ammon's horn sclerosis (AHS), tumors, gliosis in lateral temporal and meningeal inflammatory finding were detected in 42 (69%), 10 (23%) and 8 (13%) cases, respectively, whereas 2 showed no abnormalities. The 2 patients with normal pathology showed both high-signal intensity and atrophy on MRI. (3) The presumed causes of TLE were encephalitis/meningitis and/or suspected of these diseases in 15 patients (24%), injuries at birth in 5 (8%), and none in 42 (68%). The presumed causes in the 43 patients with AHS were encephalitis/meningitis in 11, injuries at birth in 3, and none in 29. Of the 15 patients in whom encephalitis/meningitis was estimated as the causes of TLE, only 6 (40%) had pathological evidence of meningeal inflammatory finding. Of the 42 patients in whom cause could not be determined, 2 had pathological evidence of meningeal inflammatory finding.

A case of malignant peritoneal mesothelioma showed complete remission with chemotherapy

A 71-year-old woman presented with an abdominal mass and ascites and was subsequently admitted to our hospital in June 1995. Further examination revealed that the mass was malignant and, as a result, surgery was indicated. However, the mass demonstrated widespread peritoneal dissemination, which therefore could not be resected, and pathological findings suggested a malignant peritoneal mesothelioma. The patient showed a remarkable response to combined chemotherapy with an accompanying intraperitoneal injection of cisplatin and etoposide and an intravenous injection of caffeine. However, owing to side effects, this regimen was discontinued. The patient was administered a combination drug of uracil and tegafur (UFT) in addition to intraperitoneal injection of cisplatin as an outpatient. By the 223rd day after surgery, the tumor mass and ascites had completely disappeared according to the CT. Hence chemotherapy was judged to have resulted in complete remission. Such a marked response to chemotherapy is rare in an advanced malignant peritoneal mesothelioma such as the present case. Eight months later, the tumor recurred in the pleura. Another regimen of chemotherapy with cisplatin and CPT-11 was performed. However, this treatment proved ineffective. The patient subsequently died of respiratory failure in January 1997 due to the mesothelioma. This is a case report of complete remission of malignant peritoneal mesothelioma by combined chemotherapy.

Surgical treatment of epilepsy from schizencephaly with fused lips

BACKGROUND

Surgical treatment of schizencephaly with fused lips has been reported in few cases. In all of the previously reported cases, temporal lobectomy was selected as a major surgical treatment, except for one case with cortical resection. We present a case of direct resection of dysplastic walls of the schizencephalic cleft and the surrounding epileptic area.

CASE

This 20-year-old college student with medication-resistant epilepsy was surgically treated by subpial cortical resection of the epileptogenic area around a schizencephalic cleft. Magnetic resonance imaging showed an unilateral schizencephalic cleft with fused lips in the right parietal lobe. Pathologic examination demonstrated dysplastic neurons in the epileptogenic cortex. Intraoperative electrocorticography clearly detected epileptiform discharges around the cleft, and the epileptogenic lesion was completely resected. He has been seizure-free for 1 year since the operation and he has no neurologic deficits.

CONCLUSION

Subpial resection of the dysplastic cortex surrounding the cleft under the guide of electrocorticography is an effective and minimally invasive procedure for the treatment of schizencephaly.

[Minimally invasive approach for mitral valve, aortic valve, and atrial septal defect surgery]

We successfully introduced minimally invasive cardiac surgery (MICS) to japan by performing thoracoscopic clipping of a patent ductus arteriosus in July 1992. MICS via a small right parasternal incision (Cosgrove procedure) was applied for one patients with severe rheumatic mitral stenosis, one with severe aortic regurgitation, and one with atrial septal defect (ASD). Mitral valve replacement (MVR), aortic valve replacement (AVR), and direct closure of the ASD were performed successfully by MICS for the the first time in Japan. All three patients required no blood transfusion and had no complications postoperatively, being discharged from hospital at 15, 13, and 9 days after their operations. MICS was satisfactory for mitral valve and ASD operations, but AVR by this approach took much longer than by standard midline sternotomy due to the poor surgical field obtained via the small right parasternal incision. A minimally invasive approach for surgery on the aortic valve and ascending aorta may require transection of the sternum or some other method. MICS has several advantages, including less trauma and pain, faster patient recovery, shorter ICU and hospital stays, a lower cost, and a better cosmetic outcome. Therefore, it is better for the patient when it is feasible. MICS should develop and be applied to more patients with cardiovascular disease in the future. Some of the standard cardiovascular operations may soon be replaced by MICS.

Three-dimensional imaging of cortical structure, function and glioma for tumor resection

A three-dimensional brain imaging protocol with PET and MRI was used to visualize the cortical structure in relation to brain function and glioma infiltration to determine tumor resectability.

METHODS

Sixteen patients with glioma had a PET scan with 11C-methionine to visualize tumor infiltration. The PET images were co-registered to the patients' own MRI reconstructed to the three-dimensional brain surface images to indicate the gyral structure and the extent of tumor infiltration. Thirteen patients, who bore tumors adjacent to the language or motor cortex, had H2 15O activation study to locate the eloquent cortex. The area of tumor infiltration was superimposed on the brain surface images together with the language and/or motor cortex.

RESULTS

When a tumor was located within a single gyrus without influencing surface cortical gyrus pattern, the motor and language areas were identified morphologically by three-dimensional surface image alone. However, when the tumor caused swelling and deformation of cortical structure, functional mapping with H2(15)O activation technique was essential in locating them correctly. In such cases, the combined mapping of the facial motor area with oral movement and the language area with word repetition was the most useful method to identify the parasylvian structure in the dominant hemisphere. Total or near total resection of low-grade glioma in eight patients and the effective decompression of the active part of the malignant glioma in four patients was completed without causing functional neurological deterioration.

CONCLUSION

The three-dimensional expression of cortical structure and function combined with PET glioma imaging with 11C-methionine is useful for radical resection of cerebral glioma.

Coexistence of ganglioglioma and cortical dysplasia in a patient with intractable epilepsy--case report

An 8-year-old girl presented with coexistence of ganglioglioma and cortical dysplasia manifesting as intractable epilepsy. Preoperative computed tomography demonstrated a small calcified lesion in the left frontal lobe which was not diagnosed as ganglioglioma. Magnetic resonance imaging also failed to demonstrate positive evidence of ganglioglioma or cortical dysplasia. A calcified tumor and the surrounding epileptogenic areas were resected under electrocorticography (ECoG) guidance. Histological examination revealed coexistence of ganglioglioma and cortical dysplasia. The patient became seizure-free after surgery. Resection of the ganglioglioma together with the adjacent epileptogenic area under intraoperative ECoG guidance is important to achieve a successful surgical result in patients with ganglioglioma.

A monoclonal antibody that recognizes ganglioside GD1b in the rat central nervous system

A monoclonal antibody (MAb), generated by immunizing BALB/c mice with homogenized bovine retinal tissue, was specific to ganglioside GD1b incorporated into liposome membranes. The antibody (MAb-5G6), classified as IgM, immunostained intensely the perikaryon and processes of motoneurons in the cranial motor nuclei and spinal cord. Spinal and trigeminal ganglion cells were also immunopositive to the MAb. Some fiber tract systems, such as the spinal and mesencephalic trigeminal tracts, the solitary tract and the posterior funiculus, were also immunoreactive to the MAb. These findings suggest that MAb-5G6 labeled specifically neurons with axons extending outside of the central nervous system as a peripheral nerve. The immunoreactive substances were visualized under electron microscopy just beneath the postsynaptic membrane and just inside the plasmalemma of the thick dendrites. No axon terminal was immunolabeled by the MAb. In the rat embryos, immunoreactivity to MAb-5G6 was found in the dorsal and ventral root fibers on the 15th embryonic day (E15). However, cell bodies of the spinal ganglion cells and motoneurons were immunostained by MAb-5G6 at a later stage (E20). The ventral commissure fibers in the floor plate of the spinal cord were transiently immunolabeled during E13-15.

High prevalence of hantavirus infection in a group of Chinese patients with acute hepatitis of unknown aetiology

In southwestern China, small but substantial numbers of patients with acute hepatitis were found without known hepatropic viral infections (hepatitis A, B, C, D or E, cytomegalovirus, Epstein-Barr virus) and were receiving no hepatotoxic drugs. Prevalence of antibodies, both neutralizing and specific immunoglobulin (Ig)M and IgG, to Hantaan virus were evaluated in a cohort of 136 such patients: 83 were of unknown aetiology, 53 had known viral hepatitis and 59 healthy subjects acted as controls. The results showed that the incidence of neutralizing antibody to Hantaan virus in acute hepatitis patients with non-hepatitis A-E virus infections (13 of 83) was significantly higher than in those with A-E infections (0 of 53, P<0.01). Furthermore, the incidence of specific IgM antibody to Hantaan virus in acute hepatitis patients with non-hepatitis A-E virus infections (6 of 83) was significantly higher than in those with A-E infections (0 of 53, P<0.05) and in healthy subjects (0 of 59, P < 0.05). These findings suggest that Hantaan virus may be an important agent, contributing, at least in southwestern China, to a significant number of the cases of acute hepatitis of unknown aetiology. This hantavirus infection resulted in an acute hepatitis, differing from the typical diseases: haemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS).