Search PubMed⌕ Search

Biomedical subjects

N Nakasato

Publications and source records attributed to N Nakasato.

At least 37 records · Page 2Linked to original sources
PubMed1999

Surgical treatment of intractable epilepsy originating from the primary sensory area of the hand--case report.

A 14-year-old right-handed girl presented with intractable epilepsy originating from the primary sensory area of the hand, manifesting as sensory partial seizures in the left hand with secondary generalization. Neurological examination showed no abnormal findings. Magnetic resonance imaging, magnetoencephalography, and cortical stimulation using chronic subdural electrodes demonstrated a lesion located in the primary sensory cortex of the hand, in which the ictal onset zone was identified by 24-hour intracranial electroencephalographic recording. Surgical resection of the lesion and multiple subpial transections of the adjacent cortices were performed. The histological diagnosis was dysembryoplastic neuroepithelial tumor (DNT). She was completely free of seizures without permanent sensory deficits postoperatively. DNT located in the primary sensory hand area may be resectable without causing postoperative sensory deficits, if accurate functional mapping and surgical resection are performed.

Adolescent↗
PubMed1998

Hemispheric asymmetry of the auditory evoked N100m response in relation to the crossing point between the central sulcus and Sylvian fissure.

The positions of the bilateral N100m sources of the auditory evoked magnetic fields (AEFs) were measured in relation to the central sulcus (CS) using an MRI-linked whole head magnetoencephalography system in 20 right-handed normal male subjects. The location of the N20m source of the median nerve-stimulated somatosensory evoked magnetic fields (SEFs), in the left hemisphere was 3.9+/-5.4 mm (mean+/-SD) posterior to that in the right hemisphere (P < 0.005). The crossing point (CP) between the CS and Sylvian fissure in the left hemisphere was 4.3+/-4.8 mm posterior to that in the right hemisphere (P < 0.001). The N100m sources were posterior to the CP in both hemispheres. The left hemispheric N100m source was 9.4+/-6.4 mm posterior to that on the right (P < 0.0001) in absolute position. The relative distance between CP and the N100m source was 22.7+/-8.5 mm in the left hemisphere and 17.7+/-5.3 mm in the right hemisphere (P < 0.01). Comparison of positions of the AEF sources and the CS as defined by the SEF demonstrated functional asymmetry of the human temporal lobe and possible source extension of the AEF-N100m beyond the Heschl gyrus over the planum temporale.

Adult↗
PubMed1998

Somatosensory evoked magnetic fields elicited by dorsal penile, posterior tibial and median nerve stimulation.

The aim of this study is to localize the primary sensory cortex of urogenital organs in the human brain. Using a newly developed MRI-linked magnetoencephalography system, we measured somatosensory evoked magnetic fields (SEFs) for unilateral stimuli on the dorsal penile nerve (DPN), posterior tibial nerve (PTN) and median nerve (MN). In five healthy male subjects, SEFs were clearly observed. Peak latency of the first cortical components were 63.8 +/- 9.2 ms for DPN, 39.8 +/- 3.0 ms for PTN and 20.7 +/- 0.7 ms for MN stimuli. Peak amplitude of the first cortical components were 63.1 +/- 10.8 fT for DPN, 160.2 +/- 50.1 fT for PTN and 335.2 +/- 70.3 fT for MN stimuli. Isofield map for the peak latencies indicated a single dipolar pattern for DPN as well as for PTN and MN stimuli. Using a single current dipole model, all SEF sources were localized on the contralateral central sulcus to the stimuli, indicating the primary sensory cortex. The DPN sources were localized on the interhemispheric surfaces, corresponding to previous speculations by direct cerebral stimulation. This non-invasive SEF technique promises further brain functional mapping for the urogenital organs.

Adult↗
PubMed1998

Hyperthyroid Graves' disease and primary hypothyroidism caused by TSH receptor antibodies in monozygotic twins: case reports.

A 33-year-old woman with signs and symptoms of hypothyroidism, including increased thyroid stimulating blocking antibody (TSBAb) activity, was referred for treatment by her local physician. Her monozygote twin was treated for hyperthyroid Graves' disease 10 years earlier. This case of hyperthyroidism and hypothyroidism in identical twins suggests the involvement of environmental factors in the pathogenesis of autoimmune thyroid diseases.

Adult↗
PubMed1998

Two-staged resection of a left frontal astrocytoma involving the operculum and insula using intraoperative neurophysiological monitoring--case report.

A 29-year-old right-handed male with a 12-year education presented with a 2-month history of generalized epileptic activity. Neuroradiological imaging demonstrated a large lesion in the left frontal lobe involving the insulooperculum and in the temporal tip. Neurological and neuropsychological examination revealed no abnormality. Two-staged total resection of a left frontal large astrocytoma involving the insulooperculum was achieved, with preservation of the speech and motor functions. The prefrontal area was resected en bloc under general anesthesia. To avoid vascular damage including the lenticulostriate arteries, the sylvian and the interhemispheric fissures were thoroughly opened. The tumor was apparently located in the anatomical Broca's area. Eighteen days later, the residual tumor was totally resected with no language deficit after identifying the motor-speech cortex, which was displaced from the usual location, by direct cortical stimulation under local anesthesia. The medially extended insular tumor was then resected stepwise with frequent neurological monitoring with the patient awake. Surgery for intraaxial insuloopercular lesions in the dominant hemisphere carries a high risk of speech and motor deficit. This staged operation enables maximum tumor resection of dominant-side large frontal gliomas involving the insuloopercular region, with preservation of both motor and speech functions.

Adult↗
PubMed1998

Symptomatic vessel narrowing caused by spontaneous rupture of craniopharyngioma cyst--case report.

A 36-year-old female presented with cerebral infarction due to severe vessel stenosis after spontaneous rupture of a craniopharyngioma, manifesting as aphasia and drowsiness. Neuroimaging showed the suprasellar cystic tumor with wall enhancement and cerebral infarction in the left temporoparietal region, and also enhancement of the left sylvian fissure and prepontine cistern. Angiography showed severe narrowing at the C1 portion of the left internal carotid artery (ICA) and the M1 portion of the left middle cerebral artery (MCA). The tumor was subtotally removed via a bifrontal craniotomy. There was accumulated milky-white debris around the left ICA and MCA. She became alert within a few days postoperatively. Repeat angiography 1 month after surgery demonstrated slight improvement of vessel narrowing. The neuroimaging and intraoperative findings suggested that the stenosis was due to vasospasm induced by chemical meningitis resulting from cyst rupture.

Adult↗
PubMed1998

[Interhemispheric asymmetry exists in female in the N100m source position of the auditory evoked magnetic fields].

The N100m source of the auditory evoked magnetic fields (AEFs) is located more posterior in the left than the right hemisphere in male subjects. However, whether this asymmetry exists in female subjects is controversial. The present study, analyzed the N100m source positions of the AEFs due to monaural tone stimuli using a helmet-shaped 66-channel magnetoencephalography system (CTF Systems) in 62 right-handed normal adults (24 females and 38 males). The best fit sphere was calculated for each subject from the head shape reconstructed from three-dimensional magnetic resonance images. N100m source positions were estimated using a double-dipole model. The contralateral N100m response to the stimulated ear was measured relative to the midpoint of the bilateral auricular points. Statistical analysis used a standardized head size for each subject based on the mean value of all subjects (r = 8.27 cm). In females, the N100m dipole positions were 0.00 +/- 1.02 cm anterior in the left hemisphere and 0.35 +/- 0.74 cm in the right (p < 0.02). In males, the N100m dipole positions were -0.31 +/- 0.81 cm (mean +/- standard deviation) anterior in the left hemisphere and 0.61 +/- 0.78 cm in the right (p < 0.0001). The interhemispheric difference in the N100m positions was 0.35 +/- 0.65 in females and 0.92 +/- 0.77 in males (p < 0.005). In conclusion, the left hemispheric N100m is located more posterior to the right in both genders. However, this functional asymmetry is more evident in males, like previous findings of more evident anatomical asymmetry in males.

Adult↗
PubMed1997

Auditory evoked magnetic fields in patients with right hemisphere language dominance.

Auditory evoked magnetic fields for pure-tone stimuli were measured in seven subjects with right hemisphere dominance for language using a whole-head magnetoencephalography system linked to magnetic resonance imaging. N100m responses were observed in both hemispheres in five subjects. The N100m response latency to contralateral stimulation was significantly shorter on the right than on the left in all cases. Normal right-handed subjects with left hemisphere dominance showed exactly the same responses. Therefore, the shorter N100m latency in the right hemisphere is independent of the dominant hemisphere for language.

Acoustic Stimulation↗
PubMed1997

Localizing the central sulcus by functional magnetic resonance imaging and magnetoencephalography.

To further validate the potential of functional magnetic resonance imaging (fMRI) for localization of the sensorimotor cortex, fMRI was compared with somatosensory evoked fields (SEFs) in eight normal volunteers. A conventional 1.5 T MRI scanner and an MRI-linked 66-channel whole head magnetoencephalography system were used. fMRI activated by unilateral hand squeeze movement indicated the highest activation on the central sulci that were localized by SEFs in all 16 contralateral hemispheres. This indicates that although the fMRI signal activation may originate from a vein running along the central sulcus, fMRI is reliable to detect the central sulcus. The pre-central gyrus also indicated some signal activation on fMRI implying better visualization of spatial distribution of activation. fMRI and SEFs are complementary methods for localizing the central sulcus.

Adult↗
PubMed1997

Striate cortical generators of the N75, P100 and N145 components localized by pattern reversal visual evoked magnetic fields.

Magnetic fields evoked by checkerboard pattern reversal visual stimulation to the monocular left or right half-field were recorded over the whole head using a helmet-shaped 64 channel magnetoencephalography system in fourteen normal subjects. The sources of the triphasic N75m-P100m-N145m responses were located using a single current dipole model. Relative locations and orientations of the N75m and N145m dipoles to the P100m dipole were calculated for each subject to reduce errors due to 'anatomical variability and then averaged for all subjects under the same stimulus conditions. These averaged parameters showed that N75m and N145m originated from the same location in the striate cortex as P100m and reversed their orientations successively by 180 degrees during the time course.

Adult↗
PubMed1997

Neuromagnetic evaluation of cortical auditory function in patients with temporal lobe tumors.

The N100m wave response of the auditory evoked magnetic field originates in the posterior part of the bilateral superior temporal planes for either contra- or ipsilateral ear stimulus. Cortical auditory function was evaluated in 14 patients with temporal lobe tumors using a magnetic resonance (MR) imaging-linked whole-head magnetoencephalography (MEG) system. Before surgery, seven patients had normal N100m latency (within the range of the mean +/- 2 standard deviations of 37 normal volunteers) in both normal hemispheres and in those with lesions, and MR imaging indicated no tumor invasion or edema in the posterior one-third of the superior temporal planes, even when the sylvian fissure was shifted upward due to the mass effect. Seven patients had prolonged N100m latency or absence of N100m in the hemisphere containing the lesion, and the posterior portion of the superior temporal plane was involved by the tumor or perifocal edema. Prolonged N100m latency recovered to the normal range after removal of tumors in two of four patients investigated postoperatively. The MEG system can be used to evaluate cortical auditory function noninvasively before and after surgical treatment of temporal lobe tumors.

Adult↗
PubMed1997

[Evaluation of various somatosensory stimulations for functional MRI].

The aim of this functional magnetic resonance imaging (fMRI) study was to test detectability of activated area using various somatosensory stimulations. The following stimulations were performed in normal volunteers: regular or irregular electrical median nerve stimulation (n = 5, each), tactile stimulation to the palm and fingers (n = 8), pain stimulation to the index finger (n = 5) or to the palm and fingers (n = 5). fMRI was acquired with a spoiled gradient echo sequence at 1.5 T. Detectability of activated area was the highest when the pain stimulation was applied to the palm and fingers (80%). A successful rate for the tactile stimulation was 25%, and the other stimulations failed to demonstrate any activation. When successful, the highest signal activation on fMRI was seen on a sulcus, which presumably arose from a vein. The sulcus was defined as the central sulcus by somatosensory evoked field using a median nerve stimulation. Our study indicates that the pain stimulation to the palm and fingers may be a choice for the sensory fMRI.

Adult↗
PubMed1997

[Postoperative normalization of prolonged P100m latency in the visual evoked magnetic field in a patient with occipital meningioma].

A 49-year-old female with a left occipital parasagittal meningioma was found to have prolonged P100m latency of the pattern reversal visual evoked magnetic field only in the hemisphere containing the lesion. After total removal of the tumor, the P100m latency was normalized in the affected hemisphere. Based on current dipole models, all the P100m dipoles were localized at the lateral bottom of the calcarine fissures bilaterally, as indicated by our previous study with normal subjects. Since the tumor was located near the parietoocipital sulcus and distant from the primary visual cortex, disturbance of the higher visual cortex probably affected the P100m latency.

Brain Mapping↗
PubMed1997

["Associative" visual agnosia for objects, pictures, faces and letters with altitudinal hemianopia].

We report a 63-year-old right-handed man with the associative visual agnosia and bilateral altitudinal hemianopia. Neurological examination revealed fair visual acuity and normal ocular movement. Other cranial-nerve, motor, sensory, and autonomic functions were normal. The brain MRI showed multiple infarction involving the right fusiform and lingual gyri extending to the adjacent white matter of the occipito-temporal lobes and posterior part of the parahippocampus, the left fusiform and lingual gyri, and multiple lacunae in bilateral basal ganglia. Cerebral angiography demonstrated occlusion at the P1 portions of bilateral posterior cerebral arteries. 123I IMP-SPECT revealed decreased perfusion in bilateral occipital lobes, worse on the right. Visual evoked fields showed normal pattern of P100 m on bilateral occipital lobes. Neuropsychologically he was alert and oriented in place. In WAIS-R, he could not perform any of performance subtests, while his VIQ was 72. His verbal and visual memory was impaired. His visual perception of forms seemed to be almost preserved. He could copy simple drawing precisely, although he could not recognize the drawing just copied. He could match pictures, letters and photographs of faces. His visual identification of forms, on the other hand, was severely disturbed. He could identify only simple geometrical figures, but not simple drawings such as an apple or the face of his daughter. Reading Kanji was impaired and he read Kana in letter-by-letter manner. Tactile identification of objects was much better than visual one. Naming objects from verbal description was well preserved. Drawing fruits or cars from memory was intact. These data suggests that the present case had fairly good visual perception as was demonstrated by good copying and matching performance, and the case could be classified into the associative type of visual agnosia if the dichotomized classification of apperceptive and associative type is employed. However, closer look at his way of copying clearly showed that he copied in piecemeal fashion, suggesting difficulty in seeing a figure as a dynamic whole. It is possible that fine and precise discrimination of shape and pattern is subserved by the bilateral ventral or occipito-temporal visual system which was compromized in the present case.

Agnosia↗
PubMed1997

[Neurophysiological monitoring during surgery for astrocytoma at the motor strip with awake craniotomy].

We present a case of a 26-year-old male with fibrillary astrocytoma at the right face motor cortex. Surgery was performed with the patient under propofol anesthesia. Stimulation mapping techniques for localization of the motor and sensory cortex were applied. The entire right face motor cortex was resected up to the hand region, resulting in a gross total removal of the tumor. Postoperatively, the patient only had transient weakness of the left lower face. For improving the prognosis of gliomas around the motor strip, it is necessary to resect the tumor as much as possible while preserving motor function. Preoperative understanding of the anatomical relationship between the tumor and the motor strip, and intraoprative neurophysiological monitoring may be necessary. In order to simulate the operative fieled preoperatively, we superimposed the superficial venous image obtained by magnetic resonance angiography (MRA) upon the surface anatomy scan (SAS). Magnetoencephalography (MEG) provided precise localization of the central sulcus, preoperatively. The methods of direct cortical stimulation to localize sensorimotor pathways with awake craniotomy enabled us to resect the tumor maximally and to minimize morbidity.

Adult↗
PubMed1997

[Reliability and factorial structure of a rating scale for persistent vegetative state].

We developed a new rating scale, Kohnan Vegetative Score, to measure severity and small clinical changes in vegetative state patients. It has 7 items corresponding to the conditions of vegetative state by Japanese Society of Neurosurgery: motor function, food ingestion, urination and defecation, eye movement, vocalization, communication, and facial expression. Each item is rated in 5 ordinal categories: slight (score = 1), mild(2), moderate(4), and extreme(5). The sum of the scores is used as the summary score, which ranges from 7 to 35, and high score means 'severe'. We examined the reliability and the factorial structure of the Kohnan Vegetative Score. The subjects were 10 patients who met the conditions of vegetative state. Four neurosurgeons rated the subjects, and then 2 of them repeated the rating after one week interval. As a measure of reliability, the (weighted) Kappa coefficient proposed Cohen (1960, 1968) was calculated for each item, and the intraclass correlation coefficient (ICC) was calculated for the summary score. To analyze the factorial structure, the factor analysis was carried out. The minimum and the maximum weighted Kappa values were 0.44 and 0.64 for intra-rater reliability, and 0.37 and 0.69 for inter-rater reliability, respectively. Concerning the factorial structure, the contribution of the first factor was 91.5% which indicated the unidimensionality of the scale. The ICC's estimate for the summary score were 0.90 (95% C.I.: 0.766-0.970). On the basis of these results, the Kohnan Vegetative Score has unidimensionality and high reliability enough for a practical use.

Aged↗
PubMed1996

Gustatory evoked magnetic fields in humans.

Magnetic fields evoked by taste stimuli of the human tongue were measured over the whole head using a helmet-shaped 64 channel magnetoencephalography system in five normal subjects. The stimuli were 10% glucose and 0.3 M NaCl solutions and distilled water. The most prominent peak (N175m) appearing over the bilateral hemispheres had a latency of 150-210 ms. The N175m sources were located using a two-dipole model in a spherical conducting medium based on the individual head dimensions and superimposed on magnetic resonance images. The N175m dipoles due to 10% glucose and 0.3 M NaCl stimuli were located at the operculum and circum-insular areas in both hemispheres, but those due to distilled water could not be located accurately.

Adult↗