Biomedical subjects

E Urasaki

Publications and source records attributed to E Urasaki.

50 records · Page 3Linked to original sources

PubMed1986

[Short latency somatosensory evoked potentials in patients with syringomyelia].

Short latency somatosensory evoked potentials (SSEPs) following median nerve and posterior tibial nerve stimulation were studied in six patients with syringomyelia. Three patients had Chiari malformations, two patients experienced fracture of the spine and one patient had a cauda equina ependymoma. SSEPs following median nerve stimulation were abnormal in all patients, of which five patients showed abnormal SSEPs only in the unilateral stimulation on the side of sensory deficits. SSEPs obtained from three out of eight upper extremities which showed no disturbance of deep sensation, were abnormal, so SSEPs were able to detect subclinical abnormality indicating dorsal column dysfunction. Abnormal patterns of SSEPs were classified in three types as follows; Type 1: disappearance of P13, N16 and N18 (3 cases), Type 2: the prolonged interpeak latency P11-P13 (2 cases), and Type 3: abnormal N16 and N18 with preserving P13 (1 case with Chiari malformation). P9 and P11 were present without prolonged latencies in all cases. SSEPs following posterior tibial nerve stimulation were abnormal in two of the three tested patients. Those two patients had disturbance of deep sensations in the lower extremities. All patients underwent surgical treatment, syringo-peritoneal shunt in four patients, foramen magnum decompression with syringo-subarachnoid shunt in one patient, and total removal of an ependymoma of the cauda equina with syringotomy in one patient. Postoperative neurological improvement were found in three patients, of which two cases also showed improvement in SSEPs. On the contrary SSEPs were unchanged in two patients with posttraumatic syringomyelia, whose postoperative neurological condition was also unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1985

[Origin of component N16 in short latency somatosensory evoked potentials (SSEP) to median nerve stimulation--correlation between component N16 and thalamus].

Short latency somatosensory evoked potentials (SSEP) to median nerve stimulation consists of four main subcortical components, namely P 9, P 11, P 13 and N 16 which appears before cortial N 18. However, the origin of component N 16 is a subject of controversy. In an attempt to learn about the generator source(s) of component N 16, SSEP was recorded from 25 patients with various focal lesions of the brain stem and/or thalamus, and abnormalities of the each potential was correlated to the clinically and radiologically defined site of the lesions. Furthermore, the effects of the different frequency in stimulation were also investigated in 6 normal subjects, because latency changes of each component might contribute to the understanding of the generation. Recordings were obtained from 13 patients with brain stem lesion which included 3 cases with pontine hemorrhage, 3 cases with pontine tumor, 3 cases with cerebello-pontine angle tumor, one case of pontine angioma, one case of chordoma, one case of tentorial tumor and one case of MLF syndrome. SSEP changes in these cases were classified into four types as follows: type 1: no response over the base line was recorded, type 2; some responses over the base line were recorded but N 16 was uncertain, type 3; component N 16 was clearly identified but its latency was significantly prolonged, type 4; component N 16 was divided into two peaks. Bilateral abnormality on SSEP with splitted combination of these four types in various degree was observed. Furthermore, these SSEP abnormalities were seen even in the some cases without sensory disturbance. On the other hand, component N 16 was clearly identified in all 12 patients with thalamic lesion which included 11 cases with thalamic hemorrhage and one case with thalamic tumor on the effected side. Comparison of latency and amplitude between normal side and affected side statistically showed no laterality of components P 9, P 11 and P 13, but a tendency of delay in latency of component N 16 on the affected side. Different stimulus repetition rate revealed some other characteristics of each component. Electrical stimuli to median nerve at the wrist were delivered at rates of 3, 6, 9, 12, 15, 18, 21, 24 and 27 Hz. Latencies of components P 9, P 11, P 13, N 16 in Fro.-Cv 7 lead and component N 18 in Par.-Erb lead were measured and all latency changes were calculated relative to the 3 Hz stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

PubMed1985

[Origin of the early components of somatosensory evoked potentials by the posterior tibial nerve stimulation--a comparative study of median nerve stimulation in clinical cases].

In order to determine the generation sites of short latency somatosensory evoked potentials to the posterior tibial nerve stimulation, scalp topography was performed on 10 normal subjects in the two different band-pass recordings, i.e., wide band-pass filter (5-3000 Hz) and narrow band-pass filter (100-1000 Hz). Furthermore, comparative study of the changes of evoked potentials between posterior tibial nerve stimulation and median nerve stimulation was carried out in 22 cases with well localized lesion of the central nervous system in the same wide band-pass filter setting. The early components of somatosensory evoked potentials elicited by the posterior tibial nerve stimulation were obtained as P 30, N 34, and P 38 in the wide band-pass filter, and P 29, N 32, P 36 in the narrow band-pass filter. Components P 30, N 34 and components P 29, N 32 were widely distributed on the scalp, but were disappeared on the scalp-scalp recording. These results suggested all those components were generated from the deep subcortical structures. In the case with high cervical lesion, component P 30 at the posterior tibial nerve stimulation was remarkably prolonged in latency, and component P 13 at the median nerve stimulation was disappeared. P 30-N 34 interpeak latency at the posterior tibial nerve stimulation was prolonged in the case with pontine lesion, while P 13-N 16 interpeak latency at the median nerve stimulation was also prolonged. In the cases with thalamic and internal capsular lesion, P 30 and N 34 at the posterior tibial nerve stimulation and P 13 and N 16 at the median nerve stimulation were all preserved in normal range. These results revealed that components P 30 and N 34 were almost identical to components P 13 and N 16, respectively. On the other hand, component P 38 at the posterior tibial nerve stimulation was suppressed or disappeared in the cases with well localized lesion at the midcentro parietal region, that includes the primary foot sensory area.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1984

[Origin of components P 11 and P 13 in short latency somato-sensory evoked potentials (SSEP): correlative study of SSEP and intraoperative evoked potentials].

In 15 patients with cervical or posterior fossa lesion, SSEPs were recorded between the skull and the non-cephalic reference electrodes during the surgical operation and compared with the evoked potentials directly recorded at the same time from the surface of the cervical spinal cord and the brain stem. The directly recorded evoked potential consisted of three main components appeared within about 25 ms., they were a small negative spike wave, a large positive spike wave and a subsequent slow potential. The positive spike wave of the evoked potentials recorded from the surface of the dorsal column was not only coincided in latency with component P 11 of SSEP, but also showed the greatest amplitude at the lower cervical level. Moreover, the positive spike wave gradually delayed in latency and reduced in amplitude from lower to upper cervical segments. The amplitude of the positive spike wave was greater at the surface of the dorsal column ipsilateral to the stimulated median nerve than that of contra-lateral recording. No polarity change was observed between the anterior and posterior surface of the spinal cord. Similarly, the positive spike wave of the evoked potentials, recorded from the surface of the brain stem, showed fairly same latency with P 13 and a maximal amplitude at the surface of the cuneate tuberculum ipsilateral to the median nerve stimulated, and those positive spike wave traveled to contra-lateral ventral surface of the pons, presumably from ipsilateral cuneate nucleus to the contra-lateral medial lemniscus.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1984

[A clinico-physiological study on the generators of short latency somatosensory evoked potential].

The purpose of this paper is to locate the generators of each wave component in the short latency somatosensory evoked potential (SSEP), by means of cumulative analysis of the SSEP obtained from various localized lesions in the upper cervical cord through brain stem and cerebral subcortical structures. Since there are considerable inconsistency of naming each component in the literature, SSEP to median nerve stimulation of 10 normal subjects were examined by two different recordings, i.e. recording from an electrode at the parietal scalp with a reference electrode on Erb's point (Par.-Erb), and the other at the frontal scalp with a reference electrode on Cv 7 (Fro.-Cv 7), and the SSEP was carefully studied. In normal subjects, the SSEP by Par.-Erb lead yielded 5 negative components (N 7, N 11, N 16, N 18 & N 26) and 4 positive components (P 9, P 13, P 22 & P 42), while by Fro.-Cv 7 5 negative components (N 7, N 10, N 12, N 16 & N 28) and 5 positive components (P 9, P 11, P 13, P 20 & P 44). Thirty three patients were subjected to analyse the influence of localized lesions to each component of the SSEP and the recording was evaluated in regard to (a) identification of each component, (b) latency of each component and inter-peak latency difference exceeding 2 SD, and (c) over 50% asymmetry and laterality of the amplitude. Cervical spondylotic myelopathy, high cervical cord tumor, tonsillar herniation, pontine infarct and hemorrhage, circumscribed thalamic lesion, and vascular lesion of centrum semiovale were carefully examined with CT scan and the findings were compared with neurological findings periodically. SSEP was taken repeatedly, especially before and after operative intervention, and alteration of the component was referred to the clinical progress of the lesion. In conclusion, results obtained from our present observation indicated that P 9 was the extramedullary projection, P 11 was intramedullary origin of the lower cervical cord, P 13 was medulla oblongata origin and P 13-N 16 was projection from medulla oblongata to thalamus. N 16-N 18 and N 26 were considered projection from thalamus to hand area of the parietal lobe with some association area and N 28 had the generator widely based on frontal projection system. These findings appeared to be quite useful for topographic diagnosis and functional evaluation of the lesions in central nervous system.

Adolescent↗

PubMed1983

[Physiologic significance of F wave in spastic paralysis in the diseases of the cerebral hemisphere].

In order to evaluate physiological significance of F-wave in the diagnosis of spasticity, 10 patients with intracranial mass lesion who did not show clinically lateralizing evidence especially in DTRs were examined and the data were compared with the results obtained from 10 other normal subjects. F-wave was recorded from thenar muscle with supramaximal stimulation to the median nerve at wrist. Latency and amplitude of F-wave failed to show any significant difference in patients compared with normal subjects both on affected sides, however, frequency of F-wave was found to be significantly higher on affected side except for 2 cases who had a mass lesion in occipital lobe in one case and the other was in the state of diaschisis due to recent hemorrhage in the parietal tumor. The site of lesion was carefully determined with CT scan and it was concluded that the F-wave could be detected quite in early stage of intracerebral mass lesion if the process had affected to internal capsule or cerebral peduncle under indirect mass effect such as cerebral edema. On the contrary, it was interesting to note that the mass with no affection to the premotor cortex likely showed higher frequency of F-wave on the ipsi-lateral side of lesion. As the conclusion, F-wave was found to have advantage in the diagnosis of spasticity in the early stage of illness and more accurate information on spasticity could be obtained compared with T or H-wave.

Brain Neoplasms↗

PubMed1983

[Evaluation of blink reflexes in cerebellopontine angle tumors].

Blink reflexes were analysed in 28 cases with cerebello-pontine angle tumors (22 cases of acoustic neurinoma and 6 cases of meningioma). In patients with acoustic neurinoma, delay or absence of R1 was found in all but two cases (91%) and abnormality of R2 was in 11 (50%). Estimating the mean latency difference of R1 on both sides it was found useful for establishing early diagnosis of small acoustic neurinomas, which had no apparent clinical signs of facial or trigeminal nerve involvement. In patient with obsolete hemorrhage (5 cases) or large cyst (6 cases) within the acoustic neurinomas, which were proven at operation, abnormality of blink reflexes was more prominent than in patient with solid tumors (11 cases). In patients with meningioma, although all were huge tumors, abnormality of R1 was less conspicuous in comparison with acoustic neurinoma. Bilateral delay of R2 was found in 3 of 6 patients. In 13 patients who underwent spinal accessory-facial anastomosis for facial palsy after removal of the tumors, R1-like response were recorded in all but one on the affected side and R2-like response was recorded in only one patient. Observing alteration of blink reflexes in patients with cerebello-pontine angle tumor was useful for establishing early diagnosis and evaluating function of trigeminal nerve, facial nerve and brainstem.

Accessory Nerve↗

PubMed1983

[Acromegaly and spinal canal stenosis].

A rare case of acromegaly with radiculomyelopathy due to spinal canal stenosis is reported. A long history of acromegalic deformity was seen on this 55 years old acupuncture therapist for the last 18 years, while he had developed unusually increased appetite, profuse perspiration and gained weight. Fifteen years ago, acromegalic tendency became prominent and was accompanied by low back and knee pain. In 1974 CB-154 was administered in several occasions beside 4000 rads irradiation to the sella. After radiation therapy was completed his outlook was somewhat improved, although low back pain was aggravated and associated with atrophy of the left lower extremity. The neurological examination at admission in 1980 revealed acromegalic feature, increased DTRs on both upper and lower extremities, dysesthesia of feet and atrophy of the leg muscles in general, mainly due to diffuse atrophy. Patient bended knees due to pain and unable to walk. He had radiating pain in the postero-lateral aspect of the left lower extremity and some dysesthesia of feet, although no specific root lesion was identifiable. Spinal roentgenograms disclosed diffuse ossification of anterior and posterior longitudinal ligaments, and marked spondylotic changes. Although the low back pain was impending complaint of the patient, the hypophyseal tumor was advised to remove and transsphenoidal hypophyseal adenomectomy was performed. A good amount of softend tumor tissue was removed however, adenoma found markedly fibrotic. Low back pain and knee were decreased gradually, but intermittent claudication was evident. Acromegaly in association with spinal canal stenosis were reviewed in literature, and the relationship of growth hormone and therapeutic problems were discussed.

Acromegaly↗

PubMedDate not supplied

Absence of spinal N13-P13 and normal scalp far-field P14 in a patient with syringomyelia.

Short latency somatosensory evoked potentials to median or ulnar nerve stimulation were recorded in a patient with syringomyelia. Scalp-recorded far-field P14 was clearly preserved, but spinal N13-P13 components disappeared. Our findings support the hypothesis that spinal N13-P13 is generated by structures intrinsic to the cervical cord, most likely in the ventral central gray matter.

Adult↗

PubMedDate not supplied

Origin of scalp far-field N18 of SSEPs in response to median nerve stimulation.

To identify the origin of scalp-recorded far-field negativity of short-latency somatosensory evoked potentials to median nerve stimulation (designated N18), direct records were made from the thalamus and ventricular system during 4 stereotaxic and 3 posterior fossa operations. In the thalamus a negative potential with almost the same latency as the scalp N18 was restricted to the Vim nucleus, but there was a large positive potential in the VC nucleus and medial lemniscus. Vim negativity increased in amplitude when high frequency stimulation was given to the median nerve, indicative of a facilitation effect. In contrast, the amplitude of scalp N18 decreased at high frequency stimulus. Direct recordings made through the medulla oblongata to the mid-brain showed a negative potential with gradually increasing latency. Above the upper pons, there was stationary negativity with no latency shift. The similarity between this negative potential and N18 is shown by their having the same latency and same response to the amplitude reduction and latency prolongation produced by high frequency stimulus. Our data suggest that scalp N18 comes from brain-stem activity between the upper pons and the mid-brain rather than from the thalamus.

Adult↗

PubMedDate not supplied

Spinal intramedullary recording of human somatosensory evoked potentials.

We here report the first description of the intramedullary spatial distribution of evoked dorsal horn potentials in a human spinal cord. Somatosensory evoked potentials (SEPs) to median nerve stimulation were recorded within the cervical spinal cord of a patient with syringomyelia. Spinal intramedullary recording demonstrated a negative slow wave of the same polarity as the dorsal spinal surface response and a complex wave interpreted as the summation of its negativity and phase-reversed positivity. These two wave forms may depend on the locations at which the recording electrodes are attached to the dorsal horn.

Adult↗

PubMedDate not supplied

Amplitude abnormalities in the scalp far-field N18 of SSEPs to median nerve stimulation in patients with midbrain-pontine lesion.

Various amplitude ratios were measured in 20 normal controls and 36 patients with midbrain-pontine, thalamic or putaminal lesions in order to evaluate the amplitude abnormalities in scalp far-field N18 following median nerve stimulation. A study of normal controls showed that the distributions of P9/N18, P14/N18 and N18/P14 + N18 resembled a gaussian distribution and could be used as criteria for determining the decrease in N18 amplitude in each patient. There was a decrease in N18 amplitude, or the absence of N18, in patients with midbrain-pontine lesions, but not in those with thalamic or putaminal lesions. Nine amplitude ratios (P11/P9, P14/P9, N18/P9, P9/P11, P9/P14, P9/N18, N18/P14, P14/N18 and N18/P14 + N18) were compared statistically for normal controls and 3 groups of patients based on non-parametric, Wilcoxon's non-pairs and signed-rank tests. A decrease in N18 amplitude in midbrain-pontine lesion was shown by significant changes in N18/P9, P9/N18, N18/P14, P14/N18 and N18/P14 + N18, no amplitude decreases in P11 and P14 being found from the amplitude ratios of P11/P9, P9/P11, P14/P9 and P9/P14. No significant changes were seen in any of the 9 amplitude ratios when the normal controls and patients with thalamic and putaminal lesions were compared. The amplitude ratios of N18 can be used to detect a decrease in N18 amplitude in patients with midbrain-pontine lesions. The data obtained support the hypothesis that N18 originates in the midbrain-pontine region and that neither the thalamus nor thalamocortical radiation make major contributions to the formation of the N18 peak.

Adult↗

PubMedDate not supplied

P30 and N33 of posterior tibial nerve SSEPs are analogous to P14 and N18 of median nerve SSEPs.

Generator sources of far-field P30 and N33 components produced by posterior tibial nerve stimulation were compared with those of the P14 and N18 components of median nerve stimulated somatosensory evoked potentials. Intracranial spatio-temporal distributions of P30 and N33 were similar to those of the P14 and N18 obtained by median nerve stimulation. In clinical cases, the changes in P30 and N33 were correlated with those in P14 and N18, indicative that P30 and N33 are derived from activities similar to those that produce P14 and N18.

Adult↗

PubMedDate not supplied

Short latency somatosensory evoked potentials recorded around the human upper brain-stem.

We analyzed the intracranial spatiotemporal distributions of the N18 component of short latency median nerve somatosensory evoked potentials (SSEPs) in 3 patients with epilepsy. In these patients, depth electrodes were implanted bilaterally into the frontal and temporal lobes, with targets including the amygdala and hippocampus; the latter two targets are close to the upper pons and midbrain. In this study N18 was divided into the initial negative peak (N18a) and the following prolonged negativity (N18b). Mapping around the upper pons and midbrain showed that: (1) the amplitude of the first negativity, which coincided with scalp N18a, was larger contralateral to the side of stimulation, but showed no polarity change around the upper brain-stem; and (2) the second negativity, which was similar to scalp N18b, did show an amplitude difference or a polarity change. This wave appeared to reflect a positive-negative dipole directed in a dorso-ventral as well as dorso-lateral direction from the midbrain, where positivity arises from the dorsum of the midbrain, contralateral to the side of the stimulation. Recordings from depth electrode derivations oriented in a caudo-rostral direction suggest that N18a and N18b may in part reflect neural activity originating from the upper pons to midbrain region which projects to the rostral subcortical white matter of the frontal lobe as stationary peaks.

Adult↗