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Biomedical subjects

E Urasaki

Publications and source records attributed to E Urasaki.

At least 37 records · Page 2Linked to original sources
PubMed1993

Origin of subcortical somatosensory evoked potentials in response to posterior tibial nerve stimulation in humans.

To identify the origin of short latency somatosensory evoked potentials (SSEPs) to posterior tibial nerve stimulation, direct recordings were made from the cervical cord, the ventricular system and the frontal subcortex during 8 neurosurgical operations. The origin of each component of SSEPs was also studied in 7 selected patients with various lesions in the central nervous system. In addition, SSEPs to median nerve stimulation were investigated in 4 of 8 surgical cases and all 7 cases of the lesion study group. Bilateral posterior tibial nerve stimulation in 10 normal subjects showed spinal N28 on the skin of the posterior neck and far-field P30 and N33 components followed by a cortical P38 component at the scalp. Direct recordings made to the mid-brain through the medulla oblongata showed a negative potential with gradually increasing latency. The peak of the negativity in the vicinity of the dorsal column nucleus showed almost the same latency as that of the scalp far-field P30, and positivity with a stationary peak was found above the dorsal column nucleus. Above the mid-pons, there was a stationary negativity with no latency shift, showing the same peak latency as that of scalp N33. The spatiotemporal distributions of P30 and N33 to posterior tibial nerve stimulation were analogous to those of P14 and N18 by median nerve stimulation. Transesophageal and direct cervical cord recordings showed that the spinal N13 phase to median nerve stimulation was reversed between the dorsal and ventral sides of the cervical cord. No such reversal occurred for the spinal N28 potential. Clinical lesion studies showed that changes in P30 and P14, and in N33 and N18 correlated with one another: that is, 1) prolongation of latency of N33 was also observed for N18; 2) absence of P30 was paralleled by the absence of P14. These data suggest that spinal N28 originates from ascending activity such as a dorsal column volley, and scalp P30 comes from activity near the dorsal column nucleus, which is similar to the P14 component of median nerve stimulation. The origin of N33 is thought to be similar to N18 from median nerve stimulation, which originates from brainstem activity below the thalamus.

Adolescent↗
PubMed1992

Repeated intracerebral hemorrhage associated with impaired platelet aggregation--report of two cases.

The authors report two cases of hypertensive intracerebral hemorrhage (ICH) repeated at the same site within 1 or 2 days causing death in a 53-year-old male and a 48-year-old female. In both cases, platelet aggregation was significantly impaired. Acquired platelet dysfunction may be important in the expansion of hemorrhage in patients with repeated hypertensive ICH. In such cases administration of normal platelets may be required to prevent devastating hemorrhage.

Blood Platelet Disorders↗
PubMed1992

Preserved spinal dorsal horn potentials in a brain-dead patient with Lazarus' sign. Case report.

The case of a brain-dead patient with complex movements of the extremities (Lazarus' sign) is reported. This is the first description in the literature of short-latency somatosensory evoked potentials (SSEP's) following median-nerve stimulation by a noncephalic reference method. The scalp P14 wave (a far-field positivity with a peak latency around 14 msec that originates from the cervicomedullary junction) disappeared, and the spinal N13 wave (a near-field negativity with a 13-msec peak recorded on the posterior neck and generated by the cervical dorsal horn) was preserved. Respiratory-like movement was also seen in this case. The SSEP. findings support the hypothesis that both Lazarus' sign and respiratory-like movement have a spinal origin.

Aged↗
PubMed1991

Effects of hyperbaric environment on the P300 component of event-related potentials.

Hyperbaric chamber dives at 19 ATA with helium-oxygen were performed at the Japan Marine Science Technology Center, Yokosuka, from January 31 to February 2 in 1990. During simulated underwater experiments, event-related potentials were recorded in 2 divers for assessment of the cognitive function. Although the P300 amplitude of the potentials did not show any significant change, its latency was clearly prolongated and this prolongation continued to when the decompression reached to 70 m below sea level. These findings indicated that the hyperbaric environment corresponding to 180 m below sea level or less must cause some cognitive dysfunctions and that P300 is useful for early detection of those dysfunctions or HPNS.

Cognition↗
PubMed1990

Skin and epidural recording of spinal somatosensory evoked potentials following median nerve stimulation: correlation between the absence of spinal N13 and impaired pain sense.

A clinical lesion study and intraoperative epidural recordings were made to test the origin and clinical significance of the spinal N13 and P13 of somatosensory evoked potentials (SEP) that follow median nerve stimulation. Intraoperatively, the respective peak latencies of spinal P13 and N13 coincided with those of the N1 component of the dorsal cord potential and its phase reversed positivity. On both the ventral and dorsal sides of the cervical epidural space, maximal amplitude was at the C5 vertebral level to which nerve input from the C6 dermatome is the main contributor. The modality of sensory impairment in the hand dermatome was examined in selected patients with cervical lesions, who showed such normal conventional SEP components as Erb N9, far-field P9, P11, P14, N18 and cortical N20, with or without loss of spinal N13. Statistically, the loss of spinal N13 was associated with decrease of pain sensation in the C6 dermatome. This was interpreted as being due to damage to the central grey matter of the cord, including the dorsal horn. Our results suggest the spinal N13 and P13 originate from the same source in the C6 spinal cord segment and that they are good indicators for the detection of centromedullary cervical cord damage.

Adult↗
PubMed1989

Choroidal epithelial cyst in the cerebellopontine angle associated with trigeminal neuralgia--case report.

The authors describe the case of a 37-year-old female with a symptomatic epithelial cyst in the cerebellopontine angle, which is extremely rare. The cyst caused trigeminal neuralgia, which completely disappeared following its removal. The histological diagnosis was choroidal epithelial fluid-filled cyst. The wall of the cyst consisted of a single layer of epithelial cells with microvilli and a basement membrane.

Adult↗
PubMed1989

[Association of asymptomatic syringomyelia with tentorial meningioma].

A case of asymptomatic syringomyelia associated with tentorial meningioma is reported. A 53-year-old female was admitted to our hospital with the complaints of headache, decrease of bilateral visual acuity and gait disturbance. Neurological examination revealed no abnormality except for bilateral papilledema and left cerebellar sign. Motor and sensory systems were also intact. CT and MRI scans showed a left tentorial mass lesion, cervical syringomyelia and left tonsillar herniation. A relationship between the fourth ventricle and syringomyelia was not clearly identified. The tumor was totally removed and a histological diagnosis of fibroblastic meningioma was made. Postoperative radiological examination showed a diminishing of syringomyelia with the improved tonsillar herniation. Association of syringomyelia with brain tumor was reviewed, and its pathogenesis was discussed.

Cerebellar Neoplasms↗
PubMed1988

Quantitative analysis of reversible dysfunction of brain-stem midline structures caused by disturbance of basilar artery blood flow with the auditory brain-stem responses.

To clarify the effects of disturbances in basilar artery blood flow, basilar artery angiospasm was induced in 2 cats and 4 guinea pigs and auditory brain-stem responses (ABRs) were continuously recorded preceding, during and following the angiospasm. The angiospasm caused specific ABR changes in that waves II (P2-N2) and III (P3-N3) were attenuated without any corresponding amplitude reduction of P4. Those changes were equivalent following stimulation of either ear. Moreover, the ABR changes gradually recovered within 5 h. On the basis of the animal experiments, 52 patients with subarachnoid hemorrhage, supratentorial tumor showing increased intracranial pressure or hydrocephalus were selected for repeated ABR examinations. ABR abnormalities similar to those observed in the animal experiment were obtained especially from the patients exhibiting grade 3 or 4 symptomatology with subarachnoid hemorrhage. In these cases, the wave III to wave IV-V amplitude ratio was significantly decreased. In some cases the ABR abnormalities and the wave III to wave IV-V amplitude ratio recovered as the clinical course improved. These results support the conclusion that specific ABR changes (wave III to wave IV-V amplitude ratio) reflect transient ischemic dysfunction of the midline portion of the brain-stem caused by disturbances of basilar artery blood flow.

Adolescent↗
PubMed1988

[A case of neurofibromatosis with spinal dural ectasia and vertebral body scalloping: a case report].

A 41-year-old man noticed colorless cutaneous nodules all over his body at the age of 24. Recently the nodules increased markedly in number and several large nodules were removed at the dermatological clinic of our hospital. The histological diagnosis of the nodules was neurofibroma. He was then referred to our neurosurgical clinic for neurological examinations to rule out involvement of the central nervous system. He showed no abnormality in neurological examination except for hyper-reflexia of the left patellar tendon reflex and occasional right leg weakness. Cranial CT scan and EEG were normal. Mental examination and routine laboratory studies were also normal. Vertebral scoliosis from C6 to T3 level, enlargement of the bilateral vertebral foramen at the level of T2 to T4, vertebral dysplasia of the C6 and T3, and the scalloping of the vertebral posterior margin of the T2 to T4 were seen in the plain X-ray films and tomography of the upper thoracic and cervical spine. The myelography and metrizamide CT scan showed multiple diverticular dilation of CSF space at the level of T1 to T4. This extended through the enlarged vertebral foramina to the chest cavity forming a dumb-bell shape. Spinal cord was normal and there was no tumor in the spinal canal. Dural ectasia and vertebral body scalloping were more clearly shown by magnetic resonance imaging (M.R.I). Dural ectasia accompanying von Recklinghausen's disease is rare and no MRI findings have been reported. Therefore, we reported this case and mainly discussed roentgenological findings and MRI of dural ectasia and other spinal abnormalities.

Adult↗
PubMed1988

[Scalp recorded P13 and spinal recorded N13 in short latency somatosensory evoked potentials].

Using non-cephalic reference and by median nerve stimulation, P 13 component and N 13 component are recorded on the scalp (scalp P 13) and the posterior neck (spinal N 13), respectively, in the short latency somatosensory evoked potentials (SSEP). The purpose of this study is to disclose the origin, characteristics and clinical significance of these two components. Ten healthy volunteers served for normal subjects. Ten patients with pontine lesion or brain death were studied. The effect of barbiturate was also studied in additional 5 patients during anesthesia for cranioplastic surgeries. Electrical stimuli of 0.2 msec square wave pulse were used in routine examination. To confirm the effects of stimulation frequency, 3, 6, 9, 12, 15, 18, 21, 24 and 27 Hz were also used in normal subjects. Recording electrodes were placed in the following sites. (1) Scalp electrode at the Shagass' point contralateral to the stimulated side (Par.). (2) Posterior neck electrode on the spinous process of the fifth cervical vertebrae (Cv5), (3) Anterior neck electrode on the thyroidal cartilage (Ant. C). (4) Erb's electrode just above the mid-clavicular point ipsilateral to the stimulation. Erb's electrode contra-lateral side of stimulation was used as a reference. Spinal N 13 on posterior neck reversed its polarity into P 13 (spinal P 13) on the anterior cervical electrode. A study with different stimulus rates revealed that the latency of scalp P 13 significantly prolonged at 24 Hz stimulation. On the other hand, the latency of spinal N 13-P 13 easily prolonged even at 18 Hz. This suggested that spinal N 13-P 13 were generated polysynaptically.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

[Craniopharyngioma in the third ventricle].

A rare case of craniopharyngioma wholly located within the third ventricle is reported. A 55-year-old female was admitted to our hospital with the complaints of headache and fever of unknown origin. Neurological findings were normal. Computed tomography (CT) scan showed homogeneously enhanced mass lesion within the third ventricle. Axial and coronal CT scans disclosed an intact suprasellar cistern. The tumor was completely removed using an interhemispheric trans-lamina terminalis approach. Histological diagnosis was squamous cell type of craniopharyngioma. Post-operative diabetes insipidus was well controlled, and irradiation of 50 Gy was performed. Craniopharyngioma located entirely in the third ventricle was reviewed, and etiology, clinical feature and treatment were discussed.

Brain↗
PubMed1988

[Lazarus' sign and respiratory-like movement in a patient with brain death].

In the diagnosis of brain death, it is generally accepted that respiratory function has to be absent, however, spinal reflexes can be preserved. We presented a patient who showed a complex movements of upper limbs (Lazarus' sign) and respiratory like movement during the apnea test for the determination of brain death. This 72-year old female admitted to our hospital in a semicomatous state due to severe subarachnoid and ventricular hemorrhage. Her conscious level suddenly deteriorated to deep coma because of second hemorrhage on the same day. She became apnea and no brain stem reflexes elicited. Three days later, electrophysiological examination revealed a flat recording of electroencephalography, absence of auditory evoked potentials and no response of blink reflex. Short latency somatosensory evoked potentials obtained by median nerve stimulation showed the presence of Erb's N9 and spinal N13-P 13 components originating from cervical dorsal horn, however, the scalp P13 generated by cervico-medullary junction was absent. This patient fulfilled all other criteria for brain death. Four days after, an apnea test was performed. Spontaneous movements of both upper limbs were observed starting between 7 and 8 minutes after disconnecting the intubation tube from the ventilator. Both arms flexed at the elbow, abducted and elevated from the bed. Then, both hands were brought up to chest. Wrist and fingers were in a neutral position (Lazarus' sign). Simultaneously, shallow and irregular respiration like movements were recognized. These movements ceased immediately after connecting the respirator. These two types of movements were reproducible except for in the final test. Blood pressure gradually decreased, and cardiac arrest occurred one hour after.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

[Correlation between abnormal SSEP and clinicoradiological findings in cervical lesions].

The purpose of this paper is to evaluate the short latency somatosensory evoked potentials (SSEP) in the diagnosis of cervical lesions. Recordings were obtained from 59 patients with cervical lesions which included 24 cases of cervical spondylosis, 4 cases of disc herniation, 14 cases of OPLL, 4 cases of intramedullary tumor, 7 cases of extramedullary tumor and 6 cases of syringomyelia. SSEP changes in these cases were classified into three major types as follows: type I; normal SSEP, type II; prolongation of interpeak latency, and type III; absence of the component of SSEP. Types II and III were subdivided into two subgroups, respectively, as follows: type IIa; prolongation of interpeak latency between P9 and P11, type IIb; prolongation of P11-P13, type IIIa; no responses after P11 and type IIIb; no responses after P13. Type I was detected in 25 cases (42%), type II in 16 cases (27%), and type III in 18 cases (31%). These SSEP findings were compared with clinicoradiological findings. In type I, the locations of the lesions confirmed by the radiological findings were variable, and there was no definite tendency in the localizations. 80% of type I showed only numbness of extremities or disturbance of the superficial sensations. The cervical lesion was located just under the C5 vertebral level in type IIa and IIIa, while the lesion was extended above the C4 vertebral level in type IIb and IIIb. These results were explained by the generation sites of P11 and P13 (P11 originated from the lower dorsal column, and P13 from nearby the dorsal column nucleus).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

[Blink reflexes in hemifacial spasm with special reference to the synkinetic responses].

Blink reflexes were studied in 20 patients with hemifacial spasm. The latencies of R1 on the affected side was not different from that on the unaffected side in 10 patients who had no previous facial nerve block, but increased in 10 patients with experience of facial nerve block. Synkinetic responses (SR 1, SR 2 and SR 2 c) were observed by the simultaneous recording from the orbicularis oris muscle on the affected side. SR 1 were obtained in all patients (100%), but SR 2 in 18 patients (90%) and SR 2 c in 19 patients (95%). The mean latency of SR 1 was slightly longer than the mean latency of R 1. When the site of stimulation was moved along the eyebrow from the supraorbital nerve approaching to the stylomastoid foramen, the latencies of R 1 and SR 1 became shorter, but R 2 and SR 2 were suppressed with increased latency. Following local anesthesia (xylocaine) to the temporal branch of the facial nerve, SR 1 was abolished with preserved R 1, R 2 and SR 2. On the other hand, R 2 and SR 2 were abolished with preserved R 1 and SR 1 following xylocaine block to the supraorbital nerve. The result suggested that the afferent pathway of SR 1 is the facial nerve (antidromic conduction) and that of SR 2 is the trigeminal nerve. Ephaptic transmission of those antidromic and orthodromic impulses forming a reverberating circuit should be one of the etiological factors in hemifacial spasm.

Adult↗
PubMed1987

[Primary brain tumor complicating subdural hematoma].

A case of sphenoidal ridge meningioma complicating chronic subdural hematoma and a case of malignant astrocytoma producing not only intracerebral hematoma but also acute subdural hematoma were reported, and the mechanism of subdural hematoma formation was discussed according to the literature. Malignant glioma often produces intracranial hemorrhage, but scarcely produces subdural hematoma. On the other hand, meningioma scarcely produces intracranial hematomas, but among of them subdural hematoma is not unusual. The reason for it is probably due to the difference of the place where each tumor grows originally. Rupture of the bridging veins or the intratumoral abnormal vessels due to twisting of the brain from trivial head trauma or without trauma might produce subdural hematoma.

Aged↗
PubMed1986

[Frontal SEPs and parietal SEPs following median nerve stimulation--clinical correlation and consideration of their generation sites].

In order to know the characteristics of frontal and parietal SEP components following median nerve stimulation, 25 patients with unilateral cerebral lesions above the thalamus were examined, and their SSEPs were carefully compared with the clinical and radiological findings. In 10 normal subjects, there were three cortical components of the frontal SEPs (P 20-N 28-P 44) and four those components of the parietal SEPs (N 18-P 22-N 26-P 42). In patient's group, central conduction times (CCTs) between components P 13 and each cortical component were measured and the latency differences between normal side and affected side were calculated. When the latency differences increased over 3 S.D. from the mean of the control values or the some cortical components disappeared, they were regarded as abnormal. According to the combination of the abnormalities in frontal and parietal SEPs, three groups were classified as follows: group 1; frontal and parietal SEPs were normal (n = 10), group 2; frontal and parietal SEPs were both affected (n = 10), group 3; parietal SEPs were affected but frontal components were preserved in normal range (n = 5). CT scan showed that the region from internal capsule to cortex around the central sulcus remained intact in the patients of group 1, while this region was involved in various degrees in all cases of the group 2. In patients of group 3, frontal or parietal regions were variously affected. Both the motor and sensory functions were mainly intact in group 1, and disturbed in group 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗