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Biomedical subjects

Y Mayanagi

Publications and source records attributed to Y Mayanagi.

At least 19 recordsLinked to original sources
PubMed2001

Psychiatric and neuropsychological problems in epilepsy surgery: analysis of 100 cases that underwent surgery.

PURPOSE: For the past 20 years (1978-1997), a series of 100 cases of uncontrolled epilepsy had surgery in our department under the stated standard for surgical indications and were followed up for 2-22 years after surgery. METHODS: We evaluated 70 cases of temporal lobectomy, 20 cases of neocortical focal resection, and 10 cases of corpus callosotomy. RESULTS: Analysis of postoperative seizure control showed that 78 cases were class 1 or 2 (no or rare seizures), 14 cases were class 3 (worthwhile improvement), and eight cases were class 4 (no improvement). As generally accepted, temporal lobectomy was the most effective operative procedure, yielding excellent or good results in 87% of the 70 cases so treated. Among the nine cases in whom various psychiatric symptoms developed after surgery, four cases showed neurotic and five cases psychotic symptoms. Patients with psychosis had delusions of various types as a core symptom, combined with other symptoms such as anxiety, irritability, aggression, and depressive state. In two patients with psychosis who had episodes of delusions in the interictal phase before surgery, the symptoms were extremely resistant. The full IQ score of the Wechsler Adult Intelligence Scale-Revised (WAIS-R) was increased after temporal lobectomy in 75% of the cases (p < 0.01; n = 44). The general MQ score in 31 cases, however, showed a 50:50 split between increase and decrease postoperatively. In correlation with the dominance of language by the Wada test, the general MQ score in the 15 cases of nondominant temporal lobe resection showed a significant increase (p < 0.05); whereas the MQ in the 16 cases of dominant-side operation did not change. CONCLUSIONS: Our new test, in which hippocampal stimulation and supraspan learning are combined, seems to be efficient for estimating the postoperative outcome of memory function.

Adolescent↗
PubMed2000

Noninvasive cerebral blood volume measurement during seizures using multichannel near infrared spectroscopic topography.

Near infrared spectroscopic topography (NIRS) is widely recognized as a noninvasive method to measure the regional cerebral blood volume (rCBV) dynamics coupled with neuronal activities. We analyzed the rCBV change in the early phase of epileptic seizures in 12 consecutive patients with medically intractable epilepsy. Seizure was induced by bemegride injection. We used eight-channel NIRS in nine cases and 24 channel in three cases. In all of the cases, rCBV increased rapidly after the seizure onset on the focus side. The increased rCBV was observed for about 30-60 s. The NIRS method can be applied to monitor the rCBV change continuously during seizures. Therefore, this method may be combined with ictal SPECT as one of the most reliable noninvasive methods of focus diagnosis.

Adult↗
PubMed1998

Non-invasive assessment of language dominance with near-infrared spectroscopic mapping.

Hemispheric dominance for language is usually assessed by means of the Wada test where amobarbital is injected into the carotid artery. Recently, positron emission tomography and functional MRI have been used as non-invasive alternatives to this method. We have applied 24-channel near-infrared spectroscopic topography (NIRS) as another non-invasive method to detect the unilateral cerebral activation during a language task. We used 11 healthy volunteers and six patients with intractable epilepsy. A word-generation task was applied for 17 s, followed by an extinction/resting period of 60 s. In healthy volunteers, the inferior frontal region was activated on the side opposite to the subject's handedness in infancy. In the epilepsy cases, the activated side agreed with the dominance determined by the Wada test. Our results demonstrate that NIRS is a feasible non-invasive alternative to the Wada test.

Adult↗
PubMed1996

Mesial temporal lobe epilepsy: clinical features and seizure mechanism.

To study the clinical features of mesial temporal lobe epilepsy, 24 cases were selected based on two criteria: (a) the origin of seizure was localized to the mesiotemporal region on phase 2 monitoring, and (b) a class 1 or 2 postoperative result was obtained after selective mesiotemporal resection. A history of febrile convulsion, particularly in the form of status epilepticus, seems to be a prognostic factor. As for presurgical evaluation, electroencephalography (EEG), magnetic resonance imaging (MRI), magnetoencephalography (MEG), and ictal single-photon emission-computed tomography (SPECT) are important tests. Recording of spontaneous seizures by means of intracranial electrodes is the most reliable for diagnosis. Ammon's horn sclerosis and mesial temporal sclerosis are the most frequent pathologic findings. The seizure mechanism was studied by means of depth EEG recordings and ictal SPECT. The hippocampal formation is more responsible than the amygdala for the origin of seizures. Preferential pathways for seizure spread may be the fornix and stria terminalis, amygdalofugal fibers, and uncinate fasciculus. The concept of mesial temporal lobe epilepsy is valid for selecting medically refractory but surgically remediable patients for surgical treatment.

Adolescent↗
PubMed1996

[Diffuse ventricular enlargement outlines the late outcome of diffuse axonal brain injury].

Clinical significance of ventriculomegaly after severe head trauma has not been fully explored yet. We analyzed hospital records of 53 cases of diffuse axonal injury and 7 cases of brain concussion together. The follow-up periods ranged from 6 months to 8 years (average 25 months). Four patients underwent CSF shunting without noticeable effect. We classified their outcome according to our modification of the Glasgow outcome scale: vegetated, severe, moderate, mild, fair, and good. We reviewed initial (within 12 hours after injury) CT scans and late (3 to 6 months after injury) CT scans or MRI's. We measured the ratio of the third ventricular width to the inner diameter of the skull on the axial view. We computed the lateral ventricular volume by our newly-devised method which took the partial volume phenomenon into account. Temporary extracerebral fluid accumulation was noted mostly within 3 months after injury in 25 of 39 cases in the mild level or above, and 2 of the 9 fair or good level cases. Ventriculomegaly occurred early and stabilized around the 3 month period. We found the differences between the late and the initial values of the third ventricular width (%) and the lateral ventricular volume (cc) highly correlated with our outcome scale (Spearman's correlation coefficient rs = 0.531, 0.676, respectively with p < 0.001 unanimously). We found the late values themselves of the third ventricular width and the lateral ventricular volume highly correlated with our outcome scale (rs = 0.575, 0.650, respectively with p < 0.001 unanimously). These 4 parameters were also highly correlated with the duration of the initial unconsciousness (LOC). Thus, posttraumatic diffuse ventriculomegaly affecting the third ventricle as well should outline the late outcome of diffuse axonal injury. Both the ventriculomegaly and the late outcome should be roughly predicted by the duration of the initial unconsciousness.

Adolescent↗
PubMed1995

Spatial and temporal analysis of human motor activity using noninvasive NIR topography.

The effect of motor activity on the left fronto-central region of the human brain was analyzed spatially and temporally by using noninvasive near-infrared light (NIR) topography. The changes in oxygenation states caused by motor activity were measured using intensity-modulated NIR spectroscopy at ten measurement positions on the head surface. The subject randomly performed unilateral finger opposition for 30 s as motor stimulation. When the subject performed contralateral (right) finger movement, significant increases in both oxygenated hemoglobin (oxy-Hb) and total hemoglobin (total-Hb) and decreases in deoxygenated hemoglobin (deoxy-Hb) were observed in a particular area. By mapping the static topograms of the changes of each Hb and comparing them with an anatomical image of MRI, it was found that the particular area was located on the motor cortex along the central sulcus. By mapping the dynamic topograms of the changes of total-Hb, which reflect the cerebral blood volume, and analyzing the spatiotemporal hemodynamic changes associated with the brain activity, it was found that the regional change in cerebral blood volume in the primary motor area overlaps the global change around the motor cortex. These results demonstrate that NIR topography can be used to effectively observe the human brain activity.

Adult↗
PubMed1994

Effect of head up tilt on cerebral circulation.

This study was performed to study the effect of the head up tilt (HUT) on cerebral circulation across the time course (60 degrees HUT for 15 minutes) and across the different angles of HUT (15, 30, 45, 60 degrees HUT for 15 minutes). Cerebral circulation was continuously monitored during 15 minutes of HUT by the carotid Doppler flow meter, the transcranial Doppler flow meter, and the near infra-red spectrophotometer. The results show that the cerebral blood flow decreased during HUT and that the cerebral blood volume decreased initially and then gradually increased. And the magnitude of the effect may have the relationship with the angles of the HUT.

Blood Pressure↗
PubMed1994

Individual differences of cerebrovascular responses to gravitational stress--prediction of orthostatic intolerance.

This experiment was designed to investigate the individual differences in the cerebrovascular responses to orthostatic stress. Seven male volunteers were exposed to head-up tilt (HUT) at 60 degrees for 15 min and to lower body negative pressure (LBNP) at 30 mmHg for 25 min. We measured the flow velocity of the middle cerebral artery and the quantity of the oxygenated and deoxygenated hemoglobin (oxy-Hb and deoxy-Hb) in the brain. Based upon oxy-Hb change during exposure to HUT, we classified the subjects into two groups: 1) the "good responder" group in which the oxy-Hb gradually increased from the 5th to 10th minute of HUT; 2) the "bad responder" group in which the oxy-Hb stabilized at lower levels after the initial decrease. The oxy-Hb changes between the two groups were significantly different during exposure to LBNP. During exposure to HUT and LBNP, no significant difference was observed in blood pressure and heart rate between the two groups. Our results suggest that there might be an individual difference in the cerebrovascular responses to orthostatic stress.

Adult↗
PubMed1993

Ipsilateral and bilateral EEG activity from the hippocampus.

Using scalp and depth electroencephalography (EEG), we examined the relationship between the surface EEG activity and abnormal EEG discharges in the ipsilateral hippocampus in order to study the neuronal connection between the two cerebral regions. Ictal EEG was divided into 4 groups: 1) unitempo-ipsilateral-bifrontal slow waves, 2) unitempo-ipsilateral-bilateral slow waves, 3) bilateral slow waves, and 4) bilateral slow waves with repetitive spikes. Abnormal depth EEG activity in the hippocampus was classified into paroxysmal discharges and recruiting rhythms. Ictally and interictally, repetitive sharp waves or spikes in the unilateral hippocampus were associated with sharp waves or spikes in the ipsilateral temporal region. These findings suggest that the ipsilateral projection of seizure activity originating in the unilateral hippocampus is dependent upon the function of the subiculum.

Adult↗
PubMed1993

Effect of lower body negative pressure on cerebral circulation.

This experiment was performed to study the effects of lower body negative pressure (LBNP) on cerebral circulation. Cerebral hemodynamics were monitored continuously and noninvasively in eight subjects at 30 mmHg of LBNP for 25 minutes by following items: 1) the carotid Doppler flowmeter which measures the carotid blood flow, 2) the transcranial Doppler sonography which measures the flow velocity of the middle cerebral artery, 3) the near infrared spectrophotometer which measures the oxygenated and deoxygenated hemoglobin in the brain. The mean flow velocity of the middle cerebral artery and the blood flow of the common carotid artery significantly decreased during LBNP, even though the mean arterial blood pressure was well maintained. The oxygenated hemoglobin was significantly increased during LBNP, while the deoxygenated hemoglobin was not changed significantly. Our results suggest that exposure to moderate LBNP (30 mmHg) decreased the cerebral blood flow with the vasodilation on the arterial side of the brain.

Adult↗
PubMed1993

[Identification of the central sulcus using magnetoencephalography and neuronavigator].

The brain-generated currents that produce potentials measured by the electroencephalogram also produce magnetic fields which can be measured by the magnetoencephalogram (MEG), N 20 compatible evoked field after median nerve stimulation is known to be generated in primary sensory cortex. Using MEG with 37 channel SQUIDs, a current dipole is back traced which corresponds to the sensory cortex. When the dipole is projected onto the MRI of the same patient, the primary sensory cortex is precisely identified in the MRI images. These data were used as the key images for navigator enabling a surgeon identify the central cortex in the surgical field. Seven patients with peri-central mass lesion (3 meningiomas, 1 metastatic tumors, 1 angiomas, 2 gliomas) underwent surgery under MEG-navigator method. In every case, the central sulcus and motor cortex were easily identified on the cortex and the tumor was removed as far as possible preserving the motor strip. There were no postoperative worsening of the motor paresis and no other complications were noticed. The method which combines the MEG functional mapping and navigator was considered to be a powerful tool in surgery of the pericentral mass lesions.

Adult↗
PubMed1991

Open surgery assisted by the neuronavigator, a stereotactic, articulated, sensitive arm.

A new computed tomographic-stereotactic device that translates the operating point onto preoperative computed tomographic (CT) images, the Neuronavigator, has been developed. We have applied this system to various neurosurgical procedures to examine its usefulness. The system consists of a 6-joint sensing arm and a 16-bit personal computer. It projects the location of the arm tip onto a corresponding CT slice with a cursor that guides the surgeon toward the intracranial target during open surgery. The system also projects the location of the tip onto angiograms, and when used in conjunction with echography or a transcranial Doppler (TCD) flow meter, the surgeon's ability to navigate is enhanced. Sixty-eight patients underwent operation with the Neuronavigator. The navigation system worked as the core of a multimodal three-dimensional data base that proved to be useful during surgery. The maximum detection error was 2.5 mm, which was considered sufficient for open microsurgery. It also proved useful in designing the position of a craniotomy, in targeting deep-seated mass lesions, and in tracing the tumor edge, which had been identified on a CT scan. When the angiogram was combined with the navigator, it became easy to identify key vessels within a small operating field. The system was also combined with a TCD flow meter. This combination makes it possible to translate the measuring point of the TCD directly into CT coordinates, improving the precision of location of the TCD probe. The Neuronavigator combines various diagnostic images into one database and effectively guides the surgeon during surgery.

Adolescent↗
PubMed1991

[Epilepsy surgery--advances in presurgical evaluations and operative techniques].

In 1886, Victor Horsley realized the possibility of surgical treatment of epilepsy, which had been suggested by John H. Jackson. However, it is only recently that surgery has been widely accepted as an important method of comprehensive management of epilepsies. In general, the presurgical evaluation is carried out in two phases: first phase of noninvasive studies (EEG and videomonitoring, brain imaging, psychometrics) and second phase using surgical techniques (videomonitoring with intracranial electrodes, angiography, Wada test, functional mapping). EEG-videomonitoring to record habitual seizures of patients contributed significantly. Although in about 25% of cases, phase 1 monitoring with scalp and sphenoid electrodes may be sufficient in determining surgical indication, depth electrode exploration is still necessary in the rest of cases. Among brain imaging tests, SPECT and PET showed better correlation with EEG abnormality, PET studies in ictal stage is the most reliable methods. The classical operative techniques, such as focal resection, temporal lobectomy and callosotomy are still in use. Application of microsurgical techniques enhanced the reliability of surgical outcome. The complex partial seizures of temporal origin are the most promising candidates for surgery. Careful presurgical evaluation may warrant more than a 90% postoperative improvement.

Epilepsy↗
PubMed1991

[Three dimensional CT reconstruction system on a personal computer].

A new computer system to produce three dimensional surface image from CT scan has been invented. Although many similar systems have been already developed and reported, they are too expensive to be set up in routine clinical services because most of these systems are based on high power mini-computer systems. According to the opinion that a practical 3D-CT system should be used in daily clinical activities using only a personal computer, we have transplanted the 3D program into a personal computer working in MS-DOS (16-bit, 12 MHz). We added to the program a routine which simulates surgical dissection on the surface image. The time required to produce the surface image ranges from 40 to 90 seconds. To facilitate the simulation, we connected a 3D system with the neuronavigator. The navigator gives the position of the surgical simulation when the surgeon places the navigator tip on the patient's head thus simulating the surgical excision before the real dissection.

Brain↗
PubMed1988

Posteromedial hypothalamotomy in the treatment of violent, aggressive behaviour.

Although emotion in the human is largely modified by the frontal association areas (software) and may better be called affect, it is still very much influenced by the balance of the ergotropic and the trophotropic circuits in the prosencephalon (hardware) especially in patients with organic brain lesions. Violent, aggressive, restless behaviours or rage can be regarded as an unbalanced state of these two circuits with dominance of the ergotropic circuit. In order to restore the balance of these two circuits, small stereotactic lesions were made in the ergotropic portion of the posterior hypothalamus (posteromedial hypothalamotomy) with good results in the follow-up of 10-25 years. Postoperatively there was no disturbance in endocrine activities and growth.

Aggression↗