Biomedical subjects

Motohiro Takayama

Publications and source records attributed to Motohiro Takayama.

12 recordsLinked to original sources

PubMed2005

Electric cortical stimulation suppresses epileptic and background activities in neocortical epilepsy and mesial temporal lobe epilepsy.

OBJECTIVE: To evaluate the suppressive effect of electric cortical stimulation upon the seizure onset zone and the non-epileptic cortex covered by subdural electrodes in patients with neocortical epilepsy and mesial temporal lobe epilepsy (MTLE). METHODS: Four patients with medically intractable focal epilepsy had implanted subdural electrodes for preoperative evaluation. Cortical functional mapping was performed by intermittently repeating bursts of electric stimulation, which consisted of 50 Hz alternating square pulse of 0.3 ms duration, 1-15 mA, within 5 s. The effect of this stimulation on the seizure onset zones and on the non-epileptic areas was evaluated by comparing spike frequency and electrocorticogram (ECoG) power spectra before and after stimulation. A similar comparison was performed in stimulation of 0.9 Hz of the seizure onset zones for 15 min. RESULTS: When the seizure onset zone was stimulated with high frequency, spike frequency decreased by 24.7%. Logarithmic ECoG power spectra recorded at stimulated electrode significantly decreased in 10-32 Hz band by high frequency stimulation of the seizure onset zone, and in 14-32 Hz band by high frequency stimulation of the non-epileptic area. Low frequency stimulation of the seizure onset zone produced 18.5% spike reduction and slight power decrease in 12-14 Hz. CONCLUSIONS: Both high and low frequency electric cortical stimulation of the seizure onset zone have a suppressive effect on epileptogenicity. Reduction of ECoG fast activities after electric cortical stimulation suggests the augmentation of inhibitory mechanisms in human cortex.

Adult↗

PubMed2005

Processing of Japanese morphogram and syllabogram in the left basal temporal area: electrical cortical stimulation studies.

Language functions in the left basal temporal area (LBTA) were investigated using electrical cortical stimulation during functional mapping in six Japanese patients with refractory epilepsy. This study provides the first direct evidence that kana (Japanese syllabogram) is processed in the LBTA. Electrical stimulation of some areas within LBTA induced disturbance in overt reading of kana words only in the first trials, with no errors in the subsequent trials. By contrast, stimulation of the same area caused obvious disturbance in kana non-word reading in all trials. Since a kana word carries both meaning and sound while a kana non-word carries only sounds of a letter string, the contrasting results of partial and complete disturbance imply a possibility that there are two distinct pathways for kana reading: one dealing with both phonological and semantic aspects of the words and the other dealing only with phonological aspect. Kanji words (Japanese morphogram) and objects/pictures were found to be processed in an area different from the area for the kana non-word processing. Furthermore, the present study also identified the common area for processing kanji reading and object/picture naming. There were no errors in matching pictures with kanji words, indicating that concepts of pictures and meanings of kanji words were not interfered by the electrical stimulation of that area. The new insight provides a clue for partial description of processing pathways for language-related visual information in LBTA. Three types of information (morphological, phonological, and semantic) are conveyed together at some stages and are separated into different routes at some other stages.

Acoustic Stimulation↗

PubMed2004

Multisensory convergence at human temporo-parietal junction - epicortical recording of evoked responses.

OBJECTIVE: Previous lesion studies in patients and functional imaging studies in normal subjects have led to the notion that the temporo-parietal junction (TPJ) has an integrative function for multisensory inputs. However, its electrophysiological properties such as response latencies and distributions of responses to various stimulus modalities in humans have not been fully investigated. The aim of the study is to clarify this issue. METHODS: We recorded evoked potentials to different kinds of sensory stimuli including somatosensory, auditory and visual modalities in 6 patients with intractable partial epilepsy, who underwent chronic implantation of subdural electrodes in TPJ for presurgical evaluation. RESULTS: In 5 out of 6 subjects, at least one electrode located in TPJ for each subject showed a maximum somatosensory evoked response commonly to electric, passive joint motion and pain stimuli. These electrodes showed the maximum responses also to tone stimuli in all of 4 subjects studied, and to visual motion stimuli in 3 out of 5 subjects studied. The polarity was consistent regardless of the stimulus modality within each individual subject, although the anatomical location, polarity and latency varied among subjects. CONCLUSIONS: A small area in TPJ for each individual subject receives sensory information of multiple modalities possibly coming from different receptive sites, although the electrophysiological properties of the responses may vary among subjects. SIGNIFICANCE: We confirmed the convergence of somatosensory, auditory and visual evoked responses at human TPJ.

Adolescent↗

PubMed2004

Electric stimulation on human cortex suppresses fast cortical activity and epileptic spikes.

PURPOSE: To investigate underlying mechanisms and adequate parameters for electric cortical stimulation to inhibit epileptic focus in humans. METHODS: A patient with intractable partial epilepsy had subdural electrodes implanted for preoperative evaluation. Cortical functional mapping was performed by using 50-Hz alternating square pulse of 0.3-ms duration, 1 to 7 mA, within 5 s. Spike frequency and electrocorticogram (ECoG) power spectra were compared before and after the stimulation when epileptic focus and distant area were stimulated. A similar comparison also was performed in low-frequency stimulation of 0.9 Hz applied for 15 min. RESULTS: Interictal spikes were reduced after electric cortical stimulation of the epileptic area at a frequency of 50 Hz as well as 0.9 Hz, with concomitant decrease in the electrographic fast activities at 50-Hz stimulation. CONCLUSIONS: These data suggest that electric cortical stimulation at both high and low frequency has a suppressive effect on epileptic activities in human cortex, possibly through distinct mechanisms.

Adult↗

PubMed2004

A combined subtemporal and transventricular/transchoroidal fissure approach to medial temporal lesions.

OBJECTIVE: To minimize therapeutic morbidity such as cognitive function disturbance and vascular injury to perforating arteries, preoperative functional mapping of the basal temporal lobe functions was performed and the medial temporal lesions were resected via a combined subtemporal and transventricular/transchoroidal fissure approach. METHODS: Twenty-one patients with medial temporal lesions including tumors, arteriovenous malformations, and medial temporal lobe epilepsy underwent operation. The neurovascular structures in the ambient cistern were first dissected free from the medial temporal lobe with a conventional subtemporal approach. Then, the temporal horn was opened through the basal surface of the temporal lobe. Finally, the ambient cistern was accessed from the temporal horn through the choroidal fissure. In five patients whose lesions were revealed to be located on the dominant side by preoperative intracarotid amytal administration test (Wada test), functional mapping of the basal temporal lobe language cortex was monitored for 1 week by use of a subdural electrocorticogram grid before the extirpation surgery. The entrance point from the temporal base to the temporal horn was determined by the result of the functional mapping. RESULTS: The lesions were resected safely and completely in all cases. Language and cognitive functions were preserved even in patients with the basal language area on the dominant side. CONCLUSION: Surgeons can confirm the important neurovascular structures from the subtemporal route and from the transtemporal horn route by a combined subtemporal and transventricular/transchoroidal fissure approach. This approach is especially effective for avoiding ischemic complications by allowing direct confirmation of the anterior choroidal and thalamoperforating arteries.

Adult↗

PubMed2003

Distinct cortical areas for motor preparation and execution in human identified by Bereitschaftspotential recording and ECoG-EMG coherence analysis.

OBJECTIVE: To clarify the cortical areas involved in motor preparation and execution by investigating Bereitschaftspotentials (BPs) and electrocorticogram-electromyogram (ECoG-EMG) coherence from subdural electrodes placed around the rolandic area. METHODS: BPs and ECoG-EMG coherence were investigated for presurgical evaluation in a patient with cavernoma in the left frontal lobe. BPs were recorded in association with the tongue, right hand and right foot movements. ECoG-EMG coherence was calculated in association with weak muscle contraction of the right hand. RESULTS: Two cortical areas related to voluntary motor control were identified; one in the primary hand motor area, which generated surface-negative BPs with hand movements and showed significant coherence of ECoG with EMG of the contralateral hand muscle, and the other in the ventral rolandic area posterior to the central sulcus, which generated surface-positive BPs with voluntary movements of multiple sites (hand, tongue and foot) but did not show any ECoG-EMG coherence. CONCLUSIONS: It is postulated that the former area represents the primary motor area involved in both motor preparation and execution, and the latter area represents the non-primary motor area involved in motor preparation. SIGNIFICANCE: BP recording combined with ECoG-EMG coherence analysis could reveal the functional roles of motor cortices and the reorganization induced by structural brain lesion.

Brain Mapping↗

PubMed2003

Conversion of semantic information into phonological representation: a function in left posterior basal temporal area.

A unique feature of Japanese language is that its written sentences consist of both morphograms (kanji) and syllabograms (kana). Despite extensive research by PET, functional MRI and magnetoencephalography, the issues of the difference (or the similarities) between the processing of kanji and kana, and between word reading and object/picture naming have not been resolved as yet. This study investigated the function of the posterior basal temporal area in the language dominant hemisphere in auditory and visual language processing, with special emphasis on semantic and phonological recognition. Subdural electrode grids were placed on the left temporal area of a right-handed woman with intractable temporal lobe epilepsy as part of a pre-surgical evaluation. Her dominant hemisphere for language was shown to be the left on the Wada test. Electric stimulation of 50 Hz was applied to the electrodes during the tasks related to language. Our results showed a clear distinction in the responses and/or performance of the subject depending on the type of characters presented and the tasks employed. Electric stimulation of a localized area in the posterior basal temporal lobe caused neither comprehensive nor productive deficit in the tasks using auditory stimuli. In the tasks using visual stimuli, in contrast, impairments were observed in (i) reading of kanji words and (ii) naming of objects/pictures and geometric designs, but not in (iii) reading of kana, (iv) copying of kanji, kana and geometric designs, and (v) using tools. The subject maintained full comprehension of spoken language, suggesting that the auditory tasks are not processed in the posterior basal temporal area. The fact that the impairment of kanji reading and disturbance of object/picture naming were elicited by electric stimulation of the same area indicates that there is at least one anatomical area that is used commonly for kanji (but not kana) and object processing. The conceptual entity of the test items supposedly was recognized correctly, but the concept failed to be matched to correct phonological representation. The left posterior basal temporal area, therefore, has an important function of connecting visual semantic information into phonological representation.

Adult↗

PubMed2003

Large vertebral arteriovenous fistula treated with stent-grafts--case report.

A 24-year-old woman presented with neck bruit and thrill. Neurological examination revealed no focal abnormality. Angiography and magnetic resonance imaging showed an arteriovenous fistula (AVF) at the C4-5 levels of the right vertebral artery (VA). The fistula had a single orifice that drained into the epidural veins via the C4-5 intervertebral foramen. A stent-graft was made of a 3.9 cm balloon-expandable stent and an expandable polytetrafluoroethylene graft sutured outside the stent. The stent-graft was advanced through the femoral artery up to the VA but did not pass far enough distally to seal the entire fistula because of the high friction between the bulky device and the small vessel. Another 2 cm stent-graft was delivered and successfully positioned across the fistula. The AVF completely disappeared and the right VA was well preserved. Follow-up angiography at 3 weeks and 5 months after the treatment showed no fistula and no stenosis inside the stent-grafts. Stent-grafts are useful to treat AVF with a large orifice. The stent-graft is a promising technology to treat neurovascular diseases, although improvement is required for use in smaller vessels.

Adult↗

PubMed2002

"Supplementary motor area (SMA) seizure" rather than "SMA epilepsy" in optimal surgical candidates: a document of subdural mapping.

PURPOSE: To clarify the relationship between epileptogenic zone and supplementary motor area (SMA) in patients who were regarded as the optimal surgical candidates for their intractable SMA seizures. METHODS: We analyzed the epileptogenic zone at/or adjacent to the SMA in four patients with clinical SMA seizures. All four patients had noninvasive presurgical evaluations (long-term video/EEG monitoring, MRI, and neuroimaging with radioisotopes), which provided convergent results between ictal semiology and the epileptogenic area, and thus, they had chronically implanted subdural electrodes, and finally had focus resection with a follow-up period of more than 2 years. RESULTS: Three patients had lesions shown by MRI outside the SMA, and one patient had a lesion within the SMA. Interictal epileptiform discharges were seen at/or outside the SMA. Ictal EEG pattern originated from the SMA in one patient, from the high lateral frontal area in two patients, and from the precuneus in one patient. In the latter three patients, the ictal EEG pattern immediately spread to the SMA. Those ictal onset zones were consistently localized within/or just adjacent to the lesions revealed by MRI. Only one patient had SMA resection, and three had the resection of epileptogenic zone by preserving the SMA. No neurological deficits developed and good seizure control was achieved. CONCLUSION: Among surgical candidates for intractable SMA seizures, frontal cortex other than SMA or even parietal cortex can be epileptogenic, and thus, the SMA itself may not necessarily have to be resected. This notion is clinically important when selecting surgical candidates as well as when planning presurgical invasive evaluation in patients with intractable SMA seizures.

Adolescent↗

PubMed2002

Low-frequency electric cortical stimulation has an inhibitory effect on epileptic focus in mesial temporal lobe epilepsy.

PURPOSE: This study was conducted to investigate the effect of low-frequency electric cortical stimulation on epileptic focus in humans. METHODS: We stimulated the epileptic focus in a patient with medically intractable mesial temporal lobe epilepsy (MTLE) by means of subdural electrodes and evaluated the change in the number of interictal epileptiform discharges. We used biphasic electric current of 0.3-ms duration presented at 0.9-Hz frequency for 250 s, comparing stimulus intensity of 7.5, 2, and 0.5 mA. RESULTS: Interictal epileptiform discharges at the ictal focus occurred less frequently after the stimulation with the intensity of 0.5 mA. With the intensity of 7.5 mA and 2.0 mA, however, habitual auras were elicited by the stimulation, and afterdischarges were seen on the cortical EEG. CONCLUSIONS: Low-frequency, low-intensity electric cortical stimulation could produce inhibitory effects on epileptic activity. At the same time, however, a caution for possible induction of EEG seizures is needed, even when applying low-frequency electric stimulation.

Adolescent↗

PubMed2002

Partial epilepsy manifesting atonic seizure: report of two cases.

PURPOSE: Atonic seizures are commonly seen in patients with generalized epilepsy but only infrequently in patients with partial epilepsy. Clinically generalized atonic seizures as a partial epilepsy have not been studied in detail with video/EEG monitoring. Here we describe the clinical and physiologic characteristics of atonic seizures due to partial epilepsy and discuss the underlying mechanism. METHODS: Two patients with partial epilepsy manifesting atonic seizures, one with frontal lobe epilepsy (FLE) and the other with parietal lobe epilepsy (PLE), were reported. The long-term video/EEG monitoring, magnetic resonance imaging (MRI), and interictal fluorodeoxyglucose-positron emission tomography (FDG-PET) were investigated in each patient. RESULTS: Paroxysmal diminution of muscle tone mainly involved the axial muscles in both patients. In contrast with the abrupt falls seen in patients with Lennox-Gastaut syndrome, the falls in these patients were slow, taking 2-5 s to fall down. Ictal EEG records showed low-voltage fast activity in the frontocentral area followed by repetitive spikes at the midline frontocentral area in the patient with FLE, and rhythmic spikes in the left central area in the patient with PLE. Interictal FDG-PET disclosed hypometabolic regions consistent with the clinical and EEG findings. CONCLUSIONS: Slow falls might be a feature of atonic seizures in partial epilepsy. Long-lasting atonia in partial epilepsy could be due to either one of the following two possible mechanisms: (a) epileptic activities arising from the negative motor area, of which 50-Hz electric stimulation causes motor inhibition, or (b) sustained atonia with successive electromyogram (EMG) silent periods caused by epileptic discharges arising from the inhibitory area of the primary sensorimotor area.

Adult↗

PubMed2002

Clinical application of a new bioabsorbable artificial dura mater.

OBJECT: In their pursuit of a better substitute for dura mater in neurosurgical procedures, the authors review their experience with GM972. METHODS: A newly developed synthetic dural substitute composed of bioabsorbable polymers (GM972) was placed in 53 patients during neurosurgical procedures. The handling properties of the material, surgical wound features. and findings of hematological, computerized tomography, and/or magnetic resonance imaging examinations were evaluated. The average follow-up period was 35.5 months. The handling properties and biocompatibility of this new dural substitute were highly satisfactory, and no significant complication was observed. In patients who underwent a second surgery performed more than 18 months after the initial operation, this new dural substitute was found to have been replaced by autologous collagenous tissue. Because of its bioabsorbability, chronic foreign body reactions to this synthetic dural substitute were negligible. CONCLUSIONS: In this report the authors support the effectiveness and safety of this bioabsorbable artificial dural substitute that provides a reduced risk of transmission of latent infection.

Absorbable Implants↗