PubMed Health⌕ Search

Biomedical subjects

W Taki

Publications and source records attributed to W Taki.

At least 37 records · Page 2Linked to original sources
PubMed2000

Electrocorticogram-electromyogram coherence during isometric contraction of hand muscle in human.

OBJECTIVE: To clarify how the primary sensorimotor and supplementary motor areas are involved in the generation of the rhythmicity of electromyogram (EMG) activity during continuous muscle contraction. METHOD: We analyzed the coherence between subdurally recorded cortical electroencephalograms (EEG) and EMGs of the contralateral wrist extensor muscle during continuous isometric contraction in 8 patients with medically intractable epilepsy. RESULTS: In all subjects, a significant coherence between the primary motor area (M1) and EMG was observed at the peak frequency of 15+/-3 Hz (means+/-SD). In the primary somatosensory area (S1) of 7 subjects and the supplementary motor area proper (SMA proper) of 4 subjects, significant coherence with EMG was observed at 12+/-5 and 15+/-4 Hz, respectively. The time lags revealed by cross-correlogram were 10+/-3, 7+/-1 and 22+/-8 ms in the M1, S1 and SMA proper, respectively, with the EMG lagging in all areas. CONCLUSION: These findings suggest that the rhythmic activity in the SMA proper, as well as in the S1 and M1, is related to the generation of the rhythmicity of EMG activity.

Electromyography↗
PubMed2000

Movement-related change of electrocorticographic activity in human supplementary motor area proper.

We investigated movement-related change in the cortical EEG signal by simultaneous recording from the primary sensorimotor area (S1-M1) and the supplementary motor area proper (SMA proper) in four patients with intractable partial epilepsy. By the use of temporal spectral evolution (TSE) analysis, the change in background cortical activity in relation to self-paced finger/wrist extension was compared among the SMA proper, S1 and M1. All three areas showed a decrease in the amount of activity for the frequency range between 10 and 40 Hz before the onset of movement [event-related desynchronization (ERD)]. The SMA proper showed earlier onset of ERD for 18-22 Hz activity (-3.4 +/- 0.5 s, mean +/- standard deviation) than M1 (-1.7 +/- 0.7 s) and S1 (-1.4 +/- 0.5 s). The degree of ERD in S1 was greatest for 10-14 Hz and that in M1 for 18-22 Hz, whereas in the SMA proper ERD was observed throughout the frequency bands from 10 to 40 Hz. Neither the degree nor the onset time of ERD in the SMA proper was lateralized to either the ipsilateral or the contralateral side with respect to the movement. A transient increase in activity after movement [event-related synchronization (ERS)] was observed in all three areas. In the SMA proper, two out of four subjects showed ERS for frequency bands below 40 Hz with both ipsilateral and contralateral movements. By contrast, in S1 and M1, ERS was recorded for frequency bands between 20 and 90 Hz, and was predominantly associated with the contralateral movement. The present study suggests that the background cortical activity in the SMA proper has a specific temporal pattern with respect to self-paced movement, and that the SMA proper is involved in motor preparation earlier than S1-M1 in a bilaterally organized manner.

Adult↗
PubMed2000

Role of primary sensorimotor cortices in generating inhibitory motor response in humans.

To clarify the mechanism by which inhibitory motor responses such as cortical negative myoclonus are generated in humans, three patients with medically intractable partial epilepsy (two with frontal lobe epilepsy and one with parietal lobe epilepsy) were studied by means of direct cortical stimulation with a single electric pulse through subdural electrodes. All underwent chronic long-term video/EEG monitoring, cortical mapping by 50 Hz electric cortical stimulation and recording of cortical somatosensory evoked potentials with chronically implanted subdural grid electrodes (3 mm in diameter and centre-to-centre distance of 1 cm) to map both epileptogenic and functional zones. After these clinical evaluations, cortical stimulation by single electric pulse (0.3 ms duration, 1 Hz) was carried out through pairs of subdural electrodes located at the primary sensorimotor area (MI-SI), pre-supplementary motor area (pre-SMA) and lateral negative motor area (lateral NMA), while surface EMG was recorded from the muscles of the contralateral hand. The results showed that (i) in all subjects, single pulse stimulation of MI-SI elicited a motor evoked potential (MEP) followed by a silent period (SP) in the contralateral distal hand muscles, the latter lasting 300 ms after the stimulus. The duration of SP was proportional to the size of the preceding MEP. In one subject, SP without any preceding MEP was elicited, and, in another subject, there was a short SP immediately before MEP in the contralateral thenar muscle. (ii) Following the stimulation of either pre-SMA or lateral NMA, no SP was observed. It is concluded that the inhibitory mechanism within the MI-SI, but probably not in the non-primary motor areas, either closely linked to or completely independent of excitation, most likely plays an important role in eliciting brief negative motor phenomena such as cortical negative myoclonus or SP.

Adult↗
PubMed2000

Gradual tilting of crystallographic orientation and configuration of dislocations in GaN selectively grown by vapour phase epitaxy methods

Cross-sectional transmission electron microscope (TEM) observation was performed for selectively grown gallium nitride (GaN) in order to examine the dependence of GaN microstructure on the growth conditions. The GaN films were grown by hydride vapour phase epitaxy (HVPE) or metalorganic vapour phase epitaxy (MOVPE) on GaN covered with a patterned mask. Thin foil specimens for TEM observation were prepared with focused ion beam (FIB) machining apparatus. It was demonstrated that the c-axis of GaN grown over the terrace of the mask tilts towards the centre of the terrace when the GaN is grown in a carrier gas of N2. The wider terrace results in a larger tilting angle if other growth conditions are identical. The tilting is attributed to 'horizontal dislocations' (HDs) generated during the overgrowth of GaN on the mask terrace. The HDs in HVPE-GaN have a semi-loop shape and are tangled with one another, while those in MOVPE-GaN are straight and lined up to form low-angle grain boundaries.

Journal Article↗
PubMed2000

Posttreatment sequelae of palliatively treated cerebral arteriovenous malformations.

OBJECTIVE: Posttreatment sequelae of palliatively treated cerebral arteriovenous malformations (AVMs) were studied to evaluate the significance of these nonradical treatments. METHODS: Between 1987 and 1997, 46 patients with cerebral AVMs were managed with treatments such as partial embolization, radiosurgery, subtotal resection, or feeder ligation alone. Their AVMs were not radically resected because of difficulties in radical treatment, hesitance to treat eloquent area lesions, or residual nidi after subtotal obliteration. The patients' posttreatment sequelae were evaluated. The duration of follow-up ranged from 0.5 to 169 months (mean, 49.4+/-39.8 mo). RESULTS: Twenty-six bleeding episodes from AVMs were documented in 18 patients. The annual risk of bleeding in this palliatively treated group was 14.6%. Persistent progressive neurological deficit was observed in one patient. Major neurological deficits occurred in 10 patients (23.3%), and the mortality rate was 9.3%. CONCLUSION: Palliative treatments cannot prevent bleeding and may even worsen the posttreatment course compared with the natural history of cerebral AVMs. A more conservative indication is required in recommending palliative treatment alone.

Carotid Arteries↗
PubMed2000

Use of cavernous sinus EEG in the detection of seizure onset and spread in mesial temporal lobe epilepsy.

PURPOSE: The study goal was to evaluate the clinical usefulness of intravenous EEG recording by placing wire electrodes in the cavernous sinus (CS) and the superior petrosal sinus (SPS) in patients with intractable temporal lobe epilepsy (TLE), with special emphasis on the ictal recording. METHODS: We placed Seeker Lite-10 guide wire as electrodes in the bilateral CS, SPS, or both to simultaneously record both ictal and interictal EEGs with the scalp EEG in five patients with TLE. In addition, in one patient, we averaged interictal scalp and intravascular EEG time-locked to the epileptiform discharge recorded from the CS/SPS-EEG to further delineate the relationship of the spikes between scalp and intravenous recording. RESULTS: In four of five patients, clinically useful recording was obtained to determine ictal focus. We recorded habitual seizures in three patients, and the detailed characteristics of ictal epileptiform discharges were shown. The averaged waveform of interictal epileptiform discharges clarified the spike distribution in the scalp EEGs, which was otherwise undetectable in the single trace. All of the patients completed the intravenous EEG monitoring without any neurological or psychological problems. CONCLUSIONS: The CS/SPS-EEG is a relatively noninvasive method that is useful for the detection of ictal focus and its spreading pattern and thus for the selection of surgical candidate among patients with intractable TLE. Although the number of seizures detected during the short monitoring period may be limited, due to the advantages of its safety and simplicity, it is worth trying for potential surgical candidates before more invasive examinations are applied. A further study with a larger number of patients is needed to estimate its practical risk.

Adult↗
PubMed2000

Posterior fossa arteriovenous malformation associated with persistent primitive trigeminal artery--case report.

A 21-year-old female presented with an unusual case of posterior fossa arteriovenous malformation (AVM) associated with ipsilateral persistent primitive trigeminal artery (PPTA), manifesting as intraparenchymal hemorrhage involving both the brain stem and the left cerebellar hemisphere. The presenting symptoms were compatible with Wallenberg's syndrome and Foville's syndrome on the left side. She was initially treated conservatively, and subsequently with transarterial embolization followed by stereotactic radiosurgery. This case combined the rare association of posterior fossa AVM and PPTA, with the clinical presentation of intraparenchymal hemorrhage causing both Wallenberg's syndrome and Foville's syndrome.

Adult↗
PubMed2000

Cerebrospinal fluid rhinorrhea associated with untreated prolactinoma--case report.

An 80-year-old female presented with non-traumatic cerebrospinal fluid (CSF) rhinorrhea due to untreated prolactinoma, with simultaneous development of bilateral leg pains and gait disturbance due to lumbar canal stenosis. Neuroimaging showed an intrasellar mass extending into the sphenoid sinus, right cavernous sinus, and suprasellar cistern. Computed tomography cisternography clearly showed the CSF pathway through the tumor. Subtotal removal of the tumor and reconstruction of the sellar floor via a transsphenoidal approach resulted in resolution of the CSF rhinorrhea. Both the invasive features and/or spontaneous shrinkage of the tumor might have created the abnormal CSF pathway. The clinical manifestation of lumbar canal stenosis might be triggered by such profound CSF leakage.

Aged↗
PubMed2000

Preoperative embolization of upper cervical cord hemangioblastoma concomitant with venous congestion--case report.

A 16-year-old male presented with a large, solid hemangioblastoma located in the upper cervical cord manifesting as hyperactive reflexes, subtle weakness, and diminished position sense in all extremities. Neuroimaging studies indicated venous congestion due to arteriovenous shunt through the tumor. Preoperative embolization was accomplished without morbidity, and resulted in marked devascularization of the tumor and elimination of an early filling vein. Four days after embolization, the tumor was totally excised without excessive intraoperative bleeding. His neurological deficits gradually improved after surgery. Preoperative embolization is a valuable adjunct to surgical excision of large intramedullary hemangioblastomas, especially those associated with arteriovenous shunt, as cord dysfunction related to venous congestion and the risk of torrential intraoperative bleeding are reduced.

Adolescent↗
PubMed2000

Endovascular treatment for a ruptured persistent trigeminal artery variant aneurysm on the distal portion--case report.

A 71-year-old female presented with a rare case of ruptured aneurysm on the distal persistent trigeminal artery (PTA) variant trunk. The endovascular approach was used to successfully occlude the proximal PTA variant, as direct catheter approach to the PTA variant aneurysm on the distal portion was prevented by the tortuous course of the vessel. She was discharged without neurological deficit.

Aged↗
PubMed2000

Selective transvenous liquid embolization of a Type 1 dural arteriovenous fistula at the junction of the transverse and sigmoid sinuses. Case report.

The authors describe the case of a 51-year-old man with a Type 1 dural arteriovenous fistula (AVF) located at the junction of the transverse and sigmoid sinuses. The dural AVF developed after the patient underwent a craniotomy for an acute extradural hematoma. The patient suffered pulsatile tinnitus 3 months after surgery. After several attempts at transarterial embolization (TAE), the venous channel located close to the skull fracture was accessed via a transfemoral-transvenous approach and was embolized by administering a liquid nonadhesive agent. Successful embolization of the dural AVF was achieved both clinically and radiologically without causing considerable hemodynamic alterations. This procedure, either alone or combined with TAE, would seem to be an alternative treatment for dural AVFs in this location, without causing compromise of flow within the affected sinuses, when selective venous access is available.

Acute Disease↗
PubMed1999

Somesthetic function of supplementary motor area during voluntary movements.

To clarify the somesthetic functions of the supplementary motor area (SMA), we recorded the cortical potentials following the median nerve electric stimulation directly from the SMA and investigated the modulation caused by voluntary movements in two patients with intractable SMA seizures. The evoked potentials over the SMA consisted of positive (61.5ms) and negative (100.0 ms) peaks, which were enlarged by voluntary movements of the stimulated hand. The present finding is in strong contrast with the attenuation (gating) of the response at the primary sensorimotor area (SM1) and suggests that the voluntary movements differently modulate the somatosensory functions of SMA and SM1.

Adult↗
PubMed1999

Endovascular treatment of aneurysms on the feeding arteries of intracranial arteriovenous malformations.

The association between intracranial aneurysms and arteriovenous malformations (AVMs) is well documented. Recent advances in the understanding of the haemodynamics of this association encourage an aggressive approach to these aneurysms. However, the pathophysiology of these aneurysms is not fully understood and a strategy for their management has not been established. We describe seven patients, with eight aneurysms, on the feeding arteries of AVMs. The aneurysms could be divided into those located 1. proximally on the superficial feeding artery (type I; 4 aneurysms); 2. distally on the superficial feeding artery (type II; 3 aneurysms); and 3. on the deep feeding artery (type III; 1 aneurysm). All aneurysms were treated by the endovascular procedure prior to, or simultaneously with, treatment of the AVM, using detachable coils or liquid embolic material. All aneurysms were obliterated successfully, with no adverse events. Each patient further received treatment of the AVM. None of the patients suffered intracranial haemorrhage after treatment for the aneurysms. Based on our experiences, we discuss the indications for this approach for each type of aneurysm. We believe endovascular treatment could be an important alternative for treatment of aneurysms associated with AVMs, thus reducing the risk of haemorrhage.

Adult↗
PubMed1999

Ectopic expression of the bHLH gene Math1 disturbs neural development.

The basic helix-loop-helix gene Math1, a positive regulator of neuronal differentiation, is specifically expressed in the dorsal part of the developing nervous system. To determine the effects of ectopic expression of Math1, we generated two transgenic mouse lines; One carried the Cre recombinase gene under the control of the nestin promoter and enhancer, which direct expression in neural precursor cells, and the other carried the Math1 gene, the expression of which was regulated by the cytomegalovirus (CMV) promoter but interrupted by the stop cassette flanked by loxP sites. In F1 embryos that carried the two transgenes, the stop cassette was removed by Cre recombinase in the developing nervous system, and Math1 expression was ectopically directed from the CMV promoter. We found that these embryos exhibited abnormal morphology of the brain and extensive cell death in the nervous system. These results suggest that ectopic expression of Math1 is toxic to neurons and leads to apoptosis.

Animals↗
PubMed1999

The role of the hippocampus in auditory processing studied by event-related electric potentials and magnetic fields in epilepsy patients before and after temporal lobectomy.

To clarify the relationship between the hippocampus and the event-related responses in auditory information processing, we recorded event-related potentials (ERPs) and event-related magnetic fields (ERFs) associated with the auditory oddball paradigm in 12 patients with temporal lobe epilepsy before and after surgical treatment, and in eight age-matched healthy volunteers. Lesions in the patients were hippocampal sclerosis (8), cyst (2), cavernoma (1) and calcified arteriovenous malformation (1), all in the unilateral temporal lobe. Standard temporal lobectomy (8), selective amygdalohippocampectomy (2), selective hippocampectomy (1) and inferior lateral temporal resection (1) were carried out. ERPs were recorded in nine patients before surgery, in all 12 patients after surgery, and in all normal subjects. P300 was maximal at Pz in the patients both before and after surgery, and in normal subjects. The peak latency and amplitude of P300 measured at Pz in the patients either before or after surgery did not differ significantly from those in normal subjects. After surgery, only the amplitude of P300 over the anterior and mid-temporal area on the resected side was attenuated, while it was symmetric before surgery regardless of the side of epileptogenic focus. ERFs were recorded in three patients before surgery and in six normal subjects by using a whole-head neuromagnetometer. ERFs in response to the target stimuli at a latency of approximately 400 ms were recognized at the anterior, middle and posterior lateral channels on each hemisphere (M400). The latency and dipole moments for M400 did not differ significantly between the patients before surgery and the normal subjects. As a result of analysis using the time-varying multidipole model, three dipoles for M400 were estimated in two patients in whom ERFs were available before surgery for the analysis, and in normal subjects: mesial temporal area, superior temporal area and inferior parietal area on each hemisphere. After surgery, in four out of six patients in whom ERFs were recordable, M400 at the anterior temporal channels on the resected side disappeared, and the activity in the affected mesial temporal area was lost. In one patient who underwent inferior lateral temporal resection, M400 waveforms and its sources were preserved in all regions. There were no significant differences in the latency and dipole moments of the unaffected source of M400 before versus after surgery. These results suggest that the hippocampus contributes to the scalp-recorded P300 only at the corresponding anterior temporal region, and does not influence its general waveform and predominant distribution over the scalp.

Adult↗
PubMed1999

Focal ictal direct current shifts in human epilepsy as studied by subdural and scalp recording.

In order to clarify further the characteristics of ictal direct current (DC) shifts in human epilepsy, we investigated them by subdural and scalp recording in six and three patients, respectively, both having mainly neocortical lobe epilepsy (five with frontal lobe epilepsy, two with parietal lobe epilepsy and two with temporal lobe epilepsy). By using subdural electrodes made of platinum, ictal DC shifts were observed in 85% of all the recorded seizures (89 seizures) among the six patients, and they were localized to just one or two electrodes at which the conventional initial ictal EEG change was also observed. They were closely accompanied by the electrodecremental pattern in all patients except for one in whom 1 Hz rhythmic activity was superimposed on clear negative slow shifts. Seizure control after resection of the cortex, including the area showing DC shifts, was favourable irrespective of histological diagnosis. Scalp-recorded ictal slow shifts were observed in 23% of all the recorded seizures (60 seizures) among the three patients. They were, like the subdurally recorded ones, mainly surface-negative in polarity, closely related to the electrodecremental pattern and consistent in their location. It seems that scalp-recorded DC shifts were detected particularly when seizures were clinically intense, while no slow shifts were observed in small seizures. It is concluded that at least subdurally recorded ictal slow shifts are clinically useful before epilepsy surgery to delineate more specifically an epileptogenic area as well as to further confirm the conventional initial ictal EEG change, and that scalp-recorded ictal slow shifts also have high specificity although their low sensitivity is to be taken into account.

Adolescent↗
PubMed1999

Cognitive motor control in human pre-supplementary motor area studied by subdural recording of discrimination/selection-related potentials.

To clarify the functional role of human pre-supplementary motor area (pre-SMA) in 'cognitive' motor control as compared with other non-primary motor cortices (SMA-proper and lateral premotor areas) and prefrontal area, we recorded epicortical field potentials by using subdural electrodes in five epileptic patients during presurgical evaluation, whose pre-SMA, SMA-proper, prefrontal and lateral premotor areas were defined by electric cortical stimulation and recent anatomical orientations according to the bicommissural plane and callosal grid system. An S1-Go/NoGo choice and delayed reaction task (S1-choice paradigm) and a warned choice Go/NoGo reaction task (S2-choice paradigm) with inter-stimulus intervals of 2 s were employed. The results showed (i) transient potentials with onset and peak latencies of about 200 and 600 ms, respectively, after S1 in the S1-choice paradigm mainly at pre-SMA and to a lesser degree at the prefrontal and lateral premotor areas, but not in the S2-choice paradigm. At SMA-proper, a similar but much smaller potential was seen after S1 in both S1- and S2-choice paradigms and (ii) slow sustained potentials between S1 and S2 in both S1- and S2-choice paradigms in all of the non-primary motor areas investigated (pre-SMA, SMA-proper and lateral premotor areas) and prefrontal area. It is concluded that pre-SMA plays a more important role in cognitive motor control which involves sensory discrimination and decision making or motor selection for the action after stimuli, whereas SMA-proper is one of the main generators of Bereitschaftspotential preceding self-paced, voluntary movements. In the more general anticipation of and attention to the forthcoming stimuli, non-primary motor cortices including pre-SMA, SMA-proper and lateral premotor area, and the prefrontal area are commonly involved.

Adult↗