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Biomedical subjects

A Wakayama

Publications and source records attributed to A Wakayama.

28 records · Page 2Linked to original sources
PubMed1990

Functional impairment due to white matter ischemia after middle cerebral artery occlusion in cats.

We recorded regional cerebral blood flow, somatosensory evoked potentials, and auditory evoked potentials in the thalamic relay nuclei (ventral posterior lateral nucleus and medial geniculate body) and in the somatosensory and auditory cortices during and after 1 hour of transient left middle cerebral artery occlusion in nine cats. Regional cerebral blood flow was also measured in the thalamocortical tracts of five of these cats. Additionally, the integrity of thalamocortical connections was tested by retrograde labeling of the thalamic nuclei with horseradish peroxidase in eight cats (three of which experienced no ischemia). Regional cerebral blood flow was severely reduced during middle cerebral artery occlusion in the left primary auditory cortex (8.5 ml/100 g/min) and in white matter pathways (6.4-7.6 ml/100 g/min). In contrast, regional cerebral blood flow did not change significantly in the somatosensory cortex or in either thalamic nucleus. Evoked potentials were abolished in both cortices but remained unchanged in the thalamic nuclei. Cortical somatosensory evoked potentials disappeared 5-8 minutes later than auditory evoked potentials. Recirculation after 1 hour of ischemia resulted in rapid and almost complete recovery (94%) of somatosensory evoked potentials and little recovery (18.4%) of auditory evoked potentials. We conclude that in the auditory pathway both cortical and fiber tract ischemia are (perhaps synergistically) responsible for dysfunction, while in the somatosensory cortex evoked potentials are abolished due to white matter ischemia. The delayed disappearance and better recovery of somatosensory than of auditory evoked potentials indicate that ischemic tolerance is higher in fiber tracts than in cortex.

Animals↗
PubMed1989

Ischemic flow threshold for extracellular glutamate increase in cat cortex.

Extracellular glutamate (Glu), cerebral blood flow (CBF), and auditory-evoked potentials (AEPs) were measured concurrently using microdialysis and hydrogen clearance in the auditory cortex of anesthetized cats during global ischemia of various severities. A threshold-type relationship was observed between extracellular Glu and CBF: Glu increased at CBF levels below about 20 ml/100 g/min. The Glu increase was related to the impairment of AEPs. The results suggest that Glu neurotoxicity is an important factor for ischemic neuronal injury even in penumbra.

Animals↗
PubMed1989

Deafferentation versus cortical ischemia in a rabbit model of middle cerebral artery occlusion.

A two-site middle cerebral artery occlusion model in rabbits was developed. Platinum electrodes served for simultaneous recordings of regional cerebral blood flow, auditory evoked potentials, and electroencephalogram in the left and right auditory cortex and in the left medial geniculate body. Auditory evoked potentials and regional cerebral blood flow were also recorded in the subcortical white matter, and regional cerebral blood flow was recorded in the internal capsule. Distal segment occlusion of the middle cerebral artery caused severe cortical ischemia in four of 11 rabbits (Group I), accompanied by abolition of the auditory evoked potential in the left auditory cortex and white matter and severe reduction of the left electrocorticogram. Deep subcortical regions were affected either little or not at all. In the remaining seven rabbits (Group II) with only mild disturbance of cortical perfusion after distal middle cerebral artery occlusion, additional clamping of the proximal middle cerebral artery stem reduced thalamocortical tract blood flow and abolished cortical auditory evoked potentials. Spontaneous electrocorticogram was less affected in Group II than in Group I; thalamic regional cerebral blood flow and auditory evoked potentials were not altered. Histologically, ischemic lesions predominated in the cortex of Group I and in the subcortical structures of Group II rabbits. While correlated reductions in regional cerebral blood flow and auditory evoked potentials indicate effective cortical ischemia, the impairment of auditory evoked potentials in Group II rabbits must be due to cortical deafferentation by ischemia in the afferent tract. This model permits the investigation of the effects of predominantly cortical or subcortical ischemia in one functional system.

Afferent Pathways↗
PubMed1986

[Cardiac myxoma metastatic to the brain].

A case of cardiac myxoma presenting as metastatic brain tumor are reported. The patient was a 44-year-old man. One year prior to this admission, he had suffered stroke, which was characterized by right hemiparesis and dysarthria. The computed tomographic (= CT) scan of the head at that time showed a low density on the left basal ganglia and the echocardiogram suggested a left atrial myxoma. At surgery, a polypoid myxoma attached to the atrial septum was totally removed. Right hemiparesis was improved and the patient was discharged. A few months later, the patient was evaluated for multiple cutaneous masses and diagnosed by biopsy as metastatic myxoma. The patient's condition remained unchanged until this admission. In March 1985, the patient had a tonic-clonic convulsion marching from right hand and developed right hemiplegia with drowsy. An echocardiogram failed to reveal recurrence of the cardiac myxoma. A CT scan revealed a 5-cm, relatively circumscribed, low density mass in the left fronto-parietal lobe, ring mottled enhancement after contrast administration and more enhancement in the delayed scanning of 45 min. Craniotomy showed a tender, friable tumor with a yellowish cyst fluid, but apparently not invading the brain parenchyma. After complete excision of the mass, there was rapid lessing in the hemiplegia and improvement in the level of consciousness. A contrast-enhancement CT scan performed 2 weeks after craniotomy revealed no evidence of residual tumor. Pathohistological examination showed spindle-shaped and stellate cells which formed clusters and contained large amounts of acid polysaccharides as demonstrated by the alcian blue method.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Biphasic occurrence of delayed ischemia after early aneurysm surgery. Case report.

An unusual case of delayed ischemia following rupture of an aneurysm of the left internal carotid artery is reported. Symptoms occurred twice after clipping the aneurysm and removing most of the subarachnoid blood on the left side the day after subarachnoid hemorrhage (SAH). Initial ischemia due to vasospasm occurred on the left side of the brain on the 8th day after SAH and responded favorably to induced hypervolemia. After complete recovery, a second episode due to vasospasm occurred on the 16th day after SAH on the right side of the brain from which the subarachnoid blood had not been removed. This caused a massive lesion and permanent severe neurological deficits. This case suggests that removal of subarachnoid blood may affect the severity and time course of vasospasm, and emphasizes the necessity of extensive removal of subarachnoid blood for prevention of severe delayed ischemic symptoms.

Carotid Artery Diseases↗
PubMed1982

Cerebellar infarction with obstructive hydrocephalus.

The authors review 15 patients with acute cerebellar infarction accompanied by obstructive hydrocephalus. These patients were among 1700 consecutive patients with acute cerebrovascular disease who were examined by angiography and also, except for the initial 320 cases. by computerized tomography (CT) scan. The CT scans were helpful in diagnosis and management of the patients. It demonstrated cerebellar mass lesions as being low density, isodense, or high density, according to the amount of hemorrhage into the infarcted area. Such cerebellar mass lesions caused acute compression of the posterior fossa. The clinical picture was determined mainly by the extent of the initially infarcted area in the vertebrobasilar territory and the speed of enlargement of the subsequently developing cerebellar mass lesion. Suboccipital decompressive surgery was performed in 10 patients and was generally beneficial. The postoperative prognosis depended mainly on the presence or absence of coexisting brain-stem infarction. Five patients who were managed conservatively died during the acute stage. Prompt and correct diagnosis of this illness is required to ensure adequate therapy.

Adult↗
PubMedDate not supplied

Serial IMP-SPECT and EEG studies in an infant with hemimegalencephaly.

An 8-month-old girl of hypomelanosis of Ito associated with hemimegalencephaly had frequent seizures beginning 44 h after birth. The seizures were secondarily generalized or unilateral initially, followed by infantile spasms at about 1.5 months of age. Frequent partial seizures appeared at 4 months of age. [123I]N-Isopropyl-p-iodoamphetamine (IMP) single photon emission computed tomography (SPECT) was performed serially during an interictal period at 1, 3 and 7 months of age. At 1 and 3 months, IMP-SPECT showed a marked increase of IMP uptake in the pathological left hemisphere and electroencephalography (EEG) revealed left-sided dominant hypsarrhythmia. At 7 months of age, a reversal was seen, there being decreased uptake on SPECT in the pathological hemisphere and abundant high amplitude background activity mingled with epileptic discharges on EEG in the non-pathological hemisphere. These serial changes of IMP uptake on SPECT seemed to reflect either changes in epileptic activity or maturational changes in cerebral perfusion in hemimegalencephaly.

Age Factors↗