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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Time-compressed Fourier analysis of the electroencephalogram has proven to be a useful analytical procedure during anesthesia and surgery which simplifies data interpretation by presenting the EEG in a time-compressed frequency domain rather than the conventional time domain. This method of data analysis graphically accentuates the electroencephalographic correlates of ischemia-induced cerebral dysfunction and other cerebral oxygen consumption abnormalities. The ability to accentuate trends in frequency and power is derived from sequential plotting of spectra to produce a graph with three dimensional axes of frequency, time, and power. In carotid endarterectomies the system has proven more useful than the conventional EEG in assessing the need for a vascular shunt to maintain internal carotid flow during endarterectomy. In open-heart surgery time-compressed EEG spectral analysis has allowed early recognition of cerebral ischemia resulting from arterial hypotension and venous hypertension. Five cases are presented which demonstrate the ability of our system to reflect developing cerebral ischemia.
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PMID:Monitoring of cerebral perfusion during anesthesia by time-compressed Fourier analysis of the electroencephalogram. 32 37

The present paper analyses the supraspinal control of motor functions and sensorimotor integrations. Attention was paid mainly to three phenomena involved in these mechanisms: the Bereitschaftspotential, the long latency reflex responses and the short latency somatosensory evoked potentials (SEPs). The study includes the problems of long loop motor control and dyscontrol, the gating process of SEPs by movement, the role of N18 component of SEP and the analysis of supraspinal modulation of the H-reflex excitability curve in healthy subjects and in patients with some cerebral dysfunction. It was found that the amplitude of the Bereitschaftspotential increased with peripheral nerve stimulation. The experiments have shown a positive relationship between the long latency reflex latencies and the distance of the corresponding muscle from the brain. The amplitude of the long latency reflex response was found to be higher and its synchronization better in phasic movements than in a slightly sustained contraction. The short latency somatosensory evoked potentials were distinctly attenuated by movement gating. By its wide spread negativity, the N18 component probably facilitates the cortical transfer of the long latency muscle response. The H-reflex excitability curves in patients with various cerebral dysfunction exhibited a characteristic course corresponding approximately to the degree of dysfunction in focal cerebral lesions, arterial hypertension and neurasthenias.
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PMID:Some conceptual remarks about supraspinal mechanisms in the control of voluntary and reflex motor activities. 144 86

To determine whether hypertension, the predominant risk factor for stroke and vascular dementia, is associated with brain atrophy, magnetic resonance imaging (MRI) scans were performed to quantify brain volumes and cerebrospinal fluid spaces. Eighteen otherwise healthy, cognitively normal older hypertensive men (mean +/- SD age, 69 +/- 8 years, duration of hypertension 10-35 years) and 17 age-matched healthy, normotensive male control subjects were studied in a cross-sectional design. Axial proton-density image slices were analyzed using region-of-interest and segmentation analyses. The hypertensive subjects had significantly larger mean volumes of the right and left lateral ventricles (p less than 0.05, both absolute volume and volume normalized to intracranial volume) and a significantly smaller normalized mean left hemisphere brain volume (p less than 0.05) with a trend toward significance for a smaller normalized mean right hemisphere volume (p less than 0.09). Four hypertensive subjects and one healthy control subject were found to have severe periventricular hyperintensities on T2-weighted MRI images. When data for these subjects were removed from the analyses, the normalized lateral ventricle volumes remained significantly larger in the hypertensive group. Lateral ventricle enlargement was not related to age or use of diuretics in the hypertensive group nor to duration of hypertension between 10 and 24 years. Our findings suggest that long-standing hypertension results in structural changes in the brain. Longitudinal studies will determine whether MRI-associated changes are progressive and if such changes identify hypertensive subjects at increased risk for clinically apparent brain dysfunction.
Hypertension 1992 Sep
PMID:Brain atrophy in hypertension. A volumetric magnetic resonance imaging study. 151 53

The study of long latency muscle reflexes evoked by electrical stimulation of the digital nerves of the index finger and recorded from the first dorsal interosseous muscle with a mean latency of 50 ms provided some evidence on the potential existence of a transcortical loop. The method of long latency relexes can be used to advantage in electrophysiological diagnosis of disorders of the central nervous system, in stimulatory therapeutic rehabilitation and in motor reeducation. The study of supraspinal modulation of the H-reflex excitability curve by dermal and light stimuli inducing long loop reflexes yielded physiological characteristics of its course in healthy subjects and in patients with disorders of the central nervous system. The most striking abnormality of the curves was recorded in the different degree of their facilitation and in the absence of late inhibition in individual nosological units. The method served as the basis of the diagnostic test for the detection of cerebral dysfunction in arterial hypertension, focal cerebral lesions, and neurasthenias.
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PMID:[Long-loop muscle reflexes with a transcortical loop--mechanisms and practical applications]. 234 Apr 22

To ascertain the critical thresholds of intracranial pressure (ICP) and cerebral perfusion pressure (CPP) for cerebral circulation and brain function, the extra- and intracranial haemodynamics and electrical brain responses were evaluated noninvasively with Doppler ultrasonography and multimodality evoked potentials (MEP's) in 50 patients with severe head injury. Both extra- and intracranial blood flow velocities changed monotonically depending on the changes in ICP and CPP. They were decreased when ICP increased to 20-30 mmHg and when CPP decreased to 40-50 mmHg. The changes in elasticity index of the pulse wave of the common carotid artery was proportional to those of blood flow velocities. The frequency and degree of abnormalities of MEP's were proportionally increased with the rise of ICP and reduction of CPP. When ICP increased to higher than 31 mmHg, MEP's were classified as moderately or severely abnormal in more than 76% of the recordings. These results indicate that noninvasive study by use of Doppler ultrasonography and MEP's can provide valuable information on critical brain ischaemia and brain dysfunction in patients with acute intracranial hypertension.
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PMID:Noninvasive study of critical thresholds of intracranial pressure and cerebral perfusion pressure for cerebral circulation and brain function. 257 52

Although ICH continues to decline as a cause of stroke, ICH must be considered in every patient with acute onset of focal cerebral dysfunction even if headache is absent. A variety of diseases leads to the occurrence of ICH, with hypertension continuing to head the list. The prognosis for recovery depends on the cause of the hemorrhage, the site and size of the lesion, and the patient's neurologic status. Each case must be treated individually. Both medical and surgical therapies are important in the management of these difficult problems. As more information is obtained on the natural history of ICH, treatment strategies will continue to evolve.
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PMID:Diagnosis and treatment of spontaneous intracerebral hemorrhage. 331 94

Disturbance of the hemispheric cerebral circulation and brain dysfunction in acute intracranial hypertension were evaluated noninvasively by ultrasonic Doppler technique and multimodality evoked potentials consisting of auditory evoked brain-stem response (ABR), cortical somatosensory evoked potential (SEP) and visual evoked potential (VEP) in 36 patients with severe head injury and cerebrovascular disease. Glasgow coma scale score was less than 8 in all cases and the age ranged from 17 to 75 years (mean of 46 years). Intracranial pressure (ICP) was measured from the extradural space using Gaeltec transducer and systemic blood pressure was simultaneously recorded. Common carotid blood flow velocity (CBFV) was recorded on both sides and mean velocity (M), diastolic mean velocity (Md) and mean blood flow were calculated. The abnormalities on MEPs were graded into 4 categories. M and Md values on CBFV were significantly (p less than 0.05 and p less than 0.01) lowered on affected side (main lesion side) even when ICP was staying less than 20 mmHg comparing with control value obtained from the normal subjects (M: 19.48 +/- 3.52, Md: 15.98 +/- 2.01 cm/sec). With the increase of ICP more than 21 mmHg, CBFV on the contralateral side was also decreased and M as well as Md values were maintained at the lowered level during 21 to 60 mmHg of ICP. A significant rapid decrease of CBFV was observed at extreme intracranial hypertension more than 61 mmHg. Lowered CBFV was also noted when cerebral perfusion pressure was reduced less than 50 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Noninvasive evaluation of hemispheric cerebral circulation and brain function in acute intracranial hypertension]. 373 Jan 95

A series of 12 patients with cerebellar infarcts diagnosed by computerized tomography are reviewed. The clinical features of cerebellar infarctions cover a wide spectrum, mimicking symptoms and signs from an acute labyrinthitis to a rapidly expanding posterior fossa mass lesion with brain stem and cerebral dysfunction. Two patients were asymptomatic and three showed signs of cerebellar dysfunction only. Three patients had evidence of brain stem dysfunction with cranial nerve palsies accompanying the cerebellar deficit. Two presented a pseudovestibular form with sudden onset of nausea, vomiting, rotary dizziness and ataxia. A pseudotumoral form with intracranial hypertension was found in two cases, in which softening tissue acts as a rapidly expanding posterior foss mass lesion. It is difficult to identify the exact artery involved in a cerebellar infarct because of the collateral circulation and connections between the three major arteries. Atherosclerosis and general decrease in blood flow can be regarded as the most likely factors precipitating focal cerebellar infarction. Surveillance is necessary during the first days with anti-edematous therapy. Rapid deterioration of consciousness should be considered a sign of increasing intracranial pressure progressing with the development of hydrocephalus. If necessary, surgical decompression by external drainage or by direct access to the posterior fossa can be carried out.
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PMID:[Cerebellar infarct. Clinical presentation and x-ray computed tomography of the brain]. 394 88

In a consecutive series of 160 patients in Hunt and Hess Neurological Grades I to III who were operated upon for a ruptured supratentorial aneurysm within 3 days after the hemorrhage, 42 patients (26%) had an unfavorable outcome. Delayed ischemic cerebral dysfunction with permanent deficit accounted for the unfavorable outcome in 18 patients (43% of all unfavorable results or 11% of the total series), whereas the unfavorable outcome was due to deficit ascribed to surgical trauma in 11 patients (26% of all unfavorable results or 7% of the total series) and to the initial hemorrhage in 7 patients (17% of all unfavorable results or 4% of the total series). Impaired outflow of cerebrospinal fluid with shunt dependency occurred in 3% of the total series. Of the patients with an unfavorable outcome, 17 (40%) had had arterial hypertension before the hemorrhage. The incidence of unfavorable outcome in good grade patients (Grades I and II) was not influenced by timing of operation (Day 1, 2, or 3 after hemorrhage). The results favor the opinion that it is principally the patient's condition during the acute stage that determines the outcome. (Neurosurgery 13:629-633, 1983).
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PMID:Causes of unfavorable outcome after early aneurysm operation. 665 14

Somatosensory evoked potentials (SEP) were recorded in 9 patients with vasospasm caused by subarachnoid haemorrhage. There was a correlation between SEP changes and clinical outcome evaluated one month after onset. And, evaluation of SEP changes under induced hypertension or infusion of dehydrates was available to study the nature of ischaemic brain dysfunction caused by vasospasm. Furthermore, this study suggests that the available period of induced hypertension may be short in cases with severe clinical outcomes.
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PMID:Brain dysfunction following vasospasm evaluated by somatosensory evoked potentials. 710 27


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