Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Collateral sensitivity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,225 records · Page 68Linked to original sources
PubMed2006

Collateral nerve fibers in human spinal cord: visualization with magnetic resonance diffusion tensor imaging.

Diffusion tensor magnetic resonance imaging provides structural information about nerve fiber tissue. The first eigenvector of the diffusion tensor is aligned with the nerve fibers, i.e., longitudinally in the spinal cord. The underlying hypothesis of this study is that the presence of collateral nerve fibers running orthogonal to the longitudinal fibers results in an orderly arrangement of the second eigenvectors. Magnetic resonance diffusion tensor scans were performed with line scan diffusion imaging on a clinical MR scanner. Axial sections were scanned in a human cervical spinal cord specimen at 625 microm resolution and the cervical spinal cord of four normal volunteers at 1250 microm resolution. The spinal cord specimen was fixed and stained for later light microscopy of the collateral fiber architecture at 0.53 microm resolution. Diffusion measured by MR was found to be anisotropic for both white and gray matter areas of the spinal cord specimen; the average fractional anisotropy (FA) was 0.63 +/- 0.09 (diffusion eigenvalues lambda1 0.38 +/- 0.05 micros/mm2, lambda2 0.14 +/- 0.03 micros/mm2, lambda3 0.10 +/- 0.03 micros/mm2) in white matter and 0.27 +/- 0.04 (lambda1 0.36 +/- 0.04 micros/mm2, lambda2 0.28 +/- 0.03 micros/mm2, lambda3 0.21 +/- 0.04 micros/mm2 in gray matter. The normal-volunteer FA values were similar, i.e., 0.66 +/- 0.04 (lambda1 1.66 +/- 0.14 micros/mm2, lambda2 0.55 +/- 0.02 micros/mm2, lambda3 0.40 +/- 0.01 micros/mm2) in white matter and 0.35 +/- 0.03 (lambda1 1.14 +/- 0.07 micros/mm2, lambda2 0.70 +/- 0.03 micros/mm2, lambda3 0.58 +/- 0.02 micros/mm2) in gray matter. The first eigenvector pointed, as expected, in the longitudinal direction. The second eigenvector directions exhibited a striking arrangement, consistent with the distribution of interconnecting collateral nerve fibers discerned on the histology section. This finding was confirmed for the specimen by quantitative pixel-wise comparison of second eigenvector directions and collateral fiber directions assessed on light microscopy image data. Diffusion tensor MRI can reveal non-invasively and in great detail the intricate fiber architecture of the human spinal cord.

Adult↗
PubMed2001

TCD and the Diamox test for testing vasomotor reactivity: clinical significance.

Transcranial Doppler sonography has become widely used in assessing cerebral vasomotor reactivity which provides information regarding cerebral autoregulation and collateral circulation. Cerebral vasomotor reactivity is defined as a shift between cerebral blood flow or cerebral blood velocity before and after administration of a potent vasodilatory stimulus test. Three such tests are currently used for this purpose: the apnea test, CO2 inhalation and the Diamox test (i.v. acetazolamide), all of which are based on the dilatatory response of cerebral blood flow to hypercapnia. Certain advantages of the Diamox test were described, but each of the three tests has its strong and weak points, and this will be the topic under discussion. There are several practical applications of the combined TCD and the vasodilatory tests in assessing of cerebral vasomotor reactivity: 1. To evaluate the intracranial hemodynamic status in patients with carotid occlusive disease with the intent of predicting the occurrence of ischemic brain events. 2. To compare intracranial hemodynamics before and after carotid endarterectomy. 3. To compare autoregulation and collateral circulation in the different parts of the circle of Willis. 4. To predict dementia after stroke. In summary, the potential clinical usefulness of combined TCD and provocative vasodilatory tests has been clearly shown. Further large scale studies are needed in order to augment the applications of cerebral vasomotor reactivity assessment in the clinical setting.

Acetazolamide↗
PubMed1990

N-methyl-D-aspartate-evoked release of acetylcholine from the medial septum/diagonal band of rat brain.

N-Methyl-D-aspartate (NMDA)-evoked release of [3H]acetylcholine (ACh) from slices of rat brain medial septum/vertical limb of the diagonal band (ms/vdB) was examined. NMDA increased the release of tritium in a concentration-dependent manner and the specific non-competitive NMDA antagonist, MK-801, and the competitive NMDA antagonist kynurenic acid inhibited this release. Tetrodotoxin inhibited the NMDA-evoked release suggesting the [3H]ACh released arises from collaterals of the cholinergic septohippocampal neurons. Basal release of tritium was significantly increased by glycine alone and strychnine inhibited this response while having no effect on NMDA-evoked release. However, glycine, although not affecting the NMDA-evoked release, did enhance release of tritium in the presence of NMDA and blocking concentrations of Kynurenic acid. Together, these findings suggest that under the conditions of these experiments sufficient concentrations of glycine permit the full expression of NMDA-evoked modulation of [3H]ACh release, and that the predominant actions of glycine were mediated by a specific, strychnine-sensitive receptor.

Acetylcholine↗
PubMed2006

Leptin facilitates learning and memory performance and enhances hippocampal CA1 long-term potentiation and CaMK II phosphorylation in rats.

Leptin, an adipocytokine encoded by an obesity gene and expressed in adipose tissue, affects feeding behavior, thermogenesis, and neuroendocrine status via leptin receptors distributed in the brain, especially in the hypothalamus. Leptin may also modulate the synaptic plasticity and behavioral performance related to learning and memory since: leptin receptors are found in the hippocampus, and both leptin and its receptor share structural and functional similarities with the interleukin-6 family of cytokines that modulate long-term potentiation (LTP) in the hippocampus. We therefore examined the effect of leptin on (1) behavioral performance in emotional and spatial learning tasks, (2) LTP at Schaffer collateral-CA1 synapses, (3) presynaptic and postsynaptic activities in hippocampal CA1 neurons, (4) the intracellular Ca(2+) concentration ([Ca(2+)](i)) in CA1 neurons, and (5) the activity of Ca(2+)/calmodulin protein kinase II (CaMK II) in the hippocampal CA1 tissue that exhibits LTP. Intravenous injection of 5 and/or 50mug/kg, but not of 500mug/kg leptin, facilitated behavioral performance in passive avoidance and Morris water-maze tasks. Bath application of 10(-12)M leptin in slice experiments enhanced LTP and increased the presynaptic transmitter release, whereas 10(-10)M leptin suppressed LTP and reduced the postsynaptic receptor sensitivity to N-methyl-d-aspartic acid. The increase in the [Ca(2+)](i) induced by 10(-10)M leptin was two times greater than that induced by 10(-12)M leptin. In addition, the facilitation (10(-12)M) and suppression (10(-10)M) of LTP by leptin was closely associated with an increase and decrease in Ca(2+)-independent activity of CaMK II. Our results show that leptin not only affects hypothalamic functions (such as feeding, thermogenesis, and neuroendocrine status), but also modulates higher nervous functions, such as the behavioral performance related to learning and memory and hippocampal synaptic plasticity.

Animals↗
PubMed1996

ST segment deviation during myocardial ischemia: are there gender differences?

UNLABELLED: Prior research indicates that women have greater ST segment shifts at the time of percutaneous transluminal coronary angioplasty (PTCA) balloon inflation than men. However, ST deviation in men and women has not been compared during balloon occlusion of the same coronary vessel. METHODS: To determine whether there is a gender difference in degree of ST deviation, 12-lead electrocardiographic (ECG) recordings were made in 45 subjects undergoing PTCA (25 men, 20 women). A total ST score was obtained by summing absolute deviations across all 12 leads. All patients had single vessel coronary artery lesions in the proximal half of one of the major epicardial arteries without evidence of collateral circulation. RESULTS: There were no differences between men and women in terms of age, left ventricular hypertrophy, ejection fraction, or the Norris Coronary Prognostic Index, which combines age, history of infarction, and evidence of heart failure on chest X-ray. When comparing mean ST segment deviation in men and women, vessel to vessel, no gender differences were found. CONCLUSION: When matched for coronary vessel, men and women have comparable ST deviation patterns during coronary occlusion with PTCA balloon inflation. Therefore, detection of myocardial ischemia related to coronary occlusion with continuous ST segment monitoring should be equally sensitive in men and women.

Adult↗
PubMed1990

The effects of strain rate on the properties of the medial collateral ligament in skeletally immature and mature rabbits: a biomechanical and histological study.

The effects of strain rate on the structural properties of the femur-medial collateral ligament-tibia complex (FMTC) and on the mechanical (material) properties of the medial collateral ligament (MCL) of skeletally immature and skeletally mature rabbits were studied. The FMTCs were tested in tension to failure, at five extension rates (0.008 mm/s-113 mm/s). For the FMTCs from the skeletally immature animals, values of load, elongation, and energy absorbed at failure increased substantially with extension rates. Such increases also existed for skeletally mature animals, but they were much less in magnitude. All samples from the skeletally immature animals failed by tibial avulsion, whereas samples from the skeletally mature animals failed within the ligament substance. The mechanical properties of the ligament substance were minimally strain-rate sensitive for both groups. Histological sections of the ligament substance and insertion sites from the failed samples were examined, and these observations were correlated with the biomechanical findings. For the rabbit model used in this study, we conclude that skeletal maturity has more influence on the biomechanical properties of the MCL than does strain rate.

Aging↗
PubMed1993

Interstitial PCO2 and pH in rat hippocampal slices measured by means of a novel fast CO2/H(+)-sensitive microelectrode based on a PVC-gelled membrane.

We describe here the construction and properties of a double-barrelled microelectrode (tip diameter 4-10 microns) which permits simultaneous measurements of PCO2 and pH, and which has a 90% response time of only one or a few seconds for a step change in PCO2. The fast response of the CO2-sensitive barrel is due to (i) the use of a PVC-gelled (tridodecylamine-containing) membrane solution which enables the construction of extremely short (> or = 4 microns), yet mechanically stable, membrane columns, and (ii) the presence of carbonic anhydrase in the filling solution. Recordings made in the pyramidal layer of area CA1 in rat hippocampal slices showed that the deviation in the acid direction of the basal interstitial pH (pH0) from that of the perfusion solution was attributable to a higher PCO2 level within the tissue. Most of the late acid shift evoked by stimulation of the Schaffer collaterals (5- to 20-s trains at 10 Hz) could also be explained on the basis of an accumulation of interstitial CO2 at a constant HCO3- concentration. This conclusion was supported by the finding that inhibition of extracellular carbonic anhydrase activity by 10 microM benzolamide completely abolished the activity-induced fall in pH0, but not the increase in PCO2. The initial stimulus-induced alkalosis was accompanied by a slight decrease in PCO2 only, implying a parallel increase in the interstitial HCO3- concentration. Benzolamide produced a dramatic enhancement of the early alkaline shift as well as of the simultaneous fall in PCO2. The latter effect of the drug unmasks a cellular CO2 sink that is induced by neuronal activity.

Animals↗
PubMed1993

Diagnostic value of 123I-phenylpentadecanoic acid (IPPA) metabolic and thallium 201 perfusion imaging in stable coronary artery disease.

The diagnostic value of 123I-phenylpentadecanoic acid (IPPA) metabolic cardiac imaging was studied in a group (n = 29) of patients with angiographically confirmed CAD using single photon emission computed tomography (SPECT). A symptom-limited exercise test was first done with IPPA, and 2 days later with thallium. Medications were not withheld during testing. Fourteen healthy control subjects participated in parallel IPPA and 15 in thallium tests. Data acquisition and output were comparable in the two imaging modalities. By testing various relatively simple criteria for abnormality we found that the semiquantitative interpretation was more accurate than the visual readings. The best compromise of accuracy with the scored criteria consisted of a sensitivity of 86% and a specificity of 86%, obtained with IPPA polar tomograms (mild exercise defect) and a sensitivity of 86% and a specificity of 80% obtained with thallium (regionally decreased washout). With visual interpretation alone, a sensitivity of 83% and a specificity of 71% was detected with IPPA (mild exercise defect) and 72% and 73%, respectively, with thallium (partial reversibility). The sensitivity of the exercise ECG alone was 62%. The results of this study imply that IPPA imaging could be a rational, uncomplicated clinical method for non-invasive diagnosis of CAD. The diagnostic ability of IPPA is at least as good as that of thallium, and it is possible to use them in succession.

Adult↗
PubMed1975

[Respective value of labelled fibrinogen and rheography in the detection of phlebitis].

The authors have studied in 212 patients the diagnostic value of radio-active fibrinogen and rheography in deep venous thrombosis of the leg by comparing the results from these two methods with phlebography. Radio-active fibrinogen seems the better means of diagnosis in early distal phlebitis. However, the method is expansive, the radio-active substance can only be manipulated in certain specialized centers, and is useless in the presence of hematoma. Rheography is less expansive, more easily manipulated, yet less sensitive as only proximal phlebitis can be detected-especially when completely occlusive. In addition, active patient cooperation is necessary. The time needed to realize the two methods is a major obstacle; however, they can be fruitful if integrated into a specialized department for the diagnosis and treatment of thrombo embolic disease.

Collateral Circulation↗
PubMed1987

Cytoarchitecture of the avian ventral lateral geniculate nucleus.

The avian thalamic ventral lateral geniculate nucleus (GLv) was studied by light microscopic techniques in order to understand its anatomy, neuronal composition, and the nature of its retinal and tectal afferents. The avian GLv is of considerable interest because physiological experiments show that it is the brain structure with the highest percentage of color-opponent responses (Maturana and Varela, '82). We used adult pigeons and quail for the present study. With Nissl techniques a predominance of medium-size neurons (58%) constitute the GLv. The shape, size, and orientation of the different neurons is highly variable throughout the GLv. With the Golgi methods, 5 classes of neurons are distinguished: I and IV (large), II (medium-size), III and V (small). Some class IV large neurons have bifurcated axons; no axons were distinguished on the small neurons. Optic fibers penetrating the GLv are often collateral branches of retinal axons that continue elsewhere. Fink-Heimer methods show that retinal axon terminals end around large and medium-size neurons and also reach the internal lamina of the GLv. HRP tracing shows that the large and medium-size neurons of the GLv project to the optic tectum. On the basis of comparisons between the cytoarchitecture of the GLv described here and the physiological findings previously reported (Maturana and Varela, '82; Pateromichelakis, '79), we suggest that: (1) large GLv neurons are the color-opponent units, (2) medium-size neurons are the movement-sensitive units, and (3) small neurons are either interneurons (local circuit neurons), or they might project to the area pretectalis or to some other GLv projection region not yet described.

Animals↗
PubMed1988

Dissociation of muscle action potentials and spinal somatosensory evoked potentials after ischemic damage of spinal cord.

In patients undergoing spinal fusion and Cotrel-Dubousset instrumentation we recorded compound muscle action potentials (CMAP) from the lower limb and spinal somatosensory evoked potentials (SSEP) from the caudal epidural space after direct stimulation of rostral spinal cord via epidural electrodes. In three of 30 patients tested, the derotation maneuver altered CMAP but not SSEP. In ten dogs, we observed similar dissociation with decrease or disappearance of CMAP amplitude and unchanged SSEP after ligation of the thoracoabdominal aorta or intercostal arteries at each level. In contrast, both CMAP and SSEP were unchanged by clamping the artery at the lumbar level. This is likely due to the lack of collateral vascular flow at the thoracic cord level, the anterior cord in particular, which is mainly supplied by a single large radicular artery (Adamkiewicz artery). These findings support that the CMAP and SSEP are mediated through two independent pathways located in the anterior and posterior spinal cord, respectively. We postulate that the dissociate alteration of CMAP and SSEP by derotation maneuver is due to greater vulnerability of the anterior cord or motor tract to ischemia caused by the displacement of anterior spinal or radiculomedullary artery. Therefore, the patients requiring major derotation procedure would benefit from CMAP monitoring, which provides more sensitive measure of anterior cord function that the conventional SSEP monitoring.

Action Potentials↗
PubMed2003

Detection of myocardial viability by contrast echocardiography in acute infarction predicts recovery of resting function and contractile reserve.

OBJECTIVES: We sought to determine whether myocardial contrast echocardiography (MCE) performed before and early after primary coronary stenting (PCS) in patients with acute myocardial infarction (AMI) could predict recovery of resting left ventricular systolic function and contractile reserve. BACKGROUND: Myocardial contrast echocardiography can be used to assess perfusion within the risk area before PCS and the extent of necrosis soon after PCS. METHODS: In 30 patients with AMI, MCE and two-dimensional echocardiography were performed before PCS and 3 to 5 days and 4 weeks after PCS. Contractile reserve was assessed by dobutamine echocardiography at four weeks in patients with persistent severe wall-motion abnormalities. RESULTS: Of segments without perfusion at 3 to 5 days, 95% had severe hypokinesis to akinesis at 4 weeks. Of segments with normal perfusion at 3 to 5 days, 90% had normal wall motion or mild hypokinesis at 4 weeks, whereas those with partial perfusion at 3 to 5 days were evenly divided between normal wall motion, hypokinesis, and akinesis. In segments with persistent severe wall-motion abnormalities at four weeks, contractile reserve was found in >80% of segments with perfusion, compared with only 10% of segments without detectable perfusion (p < 0.01). The presence of myocardial perfusion by MCE before PCS was associated with maintained or improved perfusion at 3 to 5 days and eventual recovery of resting wall motion. CONCLUSIONS: Myocardial contrast echocardiography performed early after PCS provides information on the extent of infarction, and hence the likelihood for recovery of resting systolic function or contractile reserve. The presence of perfusion before PCS, from either collateral or antegrade flow, predicts the maintenance of perfusion and recovery of systolic function.

Aged↗
PubMed1999

Use of contrast-enhanced ultrasound in follow-up after endovascular aortic aneurysm repair.

PURPOSE: To investigate the use of contrast-enhanced ultrasound in the detection of endoleak after endovascular repair of abdominal aortic aneurysm. MATERIALS AND METHODS: Eighteen patients underwent follow-up on 20 occasions after endovascular aortic aneurysm repair by arterial-phase contrast-enhanced spiral computed tomography (CT). All patients had unenhanced color Doppler ultrasound and Levovist-enhanced ultrasound on the same day. The ultrasound examinations were reported in a manner that was blind to the CT results. CT was regarded as the gold standard for the purposes of the study. RESULTS: There were three endoleaks shown by CT. Unenhanced ultrasound detected only one endoleak (sensitivity, 33%). Levovist-enhanced ultrasound detected all three endoleaks (sensitivity, 100%). Levovist-enhanced ultrasound indicated an additional six endoleaks that were not confirmed by CT (specificity, 67%; positive predictive value, 33%). In one of these six cases, the aneurysm increased in size, which indicates a likelihood of endoleak. Two of the remaining false-positive results occurred in patients known to have a distal implantation leak at completion angiography. CONCLUSION: In this small group of patients, contrast-enhanced ultrasound appears to be a reliable screening test for endoleak. The false-positive results with enhanced ultrasound may be due to the failure of CT to detect slow flow collateral pathways. Although the number of patients in this study is small, enhanced ultrasound may be more reliable than CT in detecting endoleak.

Aged↗
PubMed1989

Role of excitatory amino acid receptors in synaptic transmission in area CA1 of rat hippocampus.

The new antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), which blocks responses to kainate and quisqualate, has been used in conjunction with D-2-amino-5-phosphonovalerate (APV), which blocks selectively responses to N-methyl-D-aspartate (NMDA), to determine the role of excitatory amino acid receptors in synaptic transmission. An excitatory postsynaptic potential (EPSP)-inhibitory postsynaptic potential (IPSP) sequence was evoked in CA1 neurons by stimulation of the Schaffer collateral-commissural pathway in rat hippocampal slices. CNQX (10 microM) substantially reduced the EPSP without having any effect on input resistance or membrane potential. The IPSP was also reduced provided that the stimulating electrode was place approximately 1 mm from the recording electrode. The EPSP that remained in the presence of CNQX had characteristics of an NMDA receptor-mediated potential; it had a slow timecourse, summated at high frequencies, was blocked reversibly by APV, increased greatly in size in Mg2+-free medium, and showed an anomalous voltage dependence in Mg2+-containing medium. In the presence of CNQX, an APV-sensitive polysynaptic GABAergic IPSP could be evoked, indicating that NMDA receptors can mediate suprathreshold EPSPS in inhibitory interneurons. It is suggested that either NMDA or non-NMDA receptors can, under different circumstances, mediate the synaptic excitation of pyramidal neurons and inhibitory interneurons in area CA1 of the hippocampus.

2-Amino-5-phosphonovalerate↗
PubMed1993

Relationship of severity of myocardial stunning to ATP dependent potassium channel modulation.

Pharmacological modulation of ATP sensitive potassium channels (K+ATP channels) in vivo may influence ischemia and reperfusion injury of myocardium. The purpose of this investigation was to ascertain the actions of multiple K+ATP channel openers and interactions with a K+ATP channel antagonist in a model of stunned myocardium in anesthetized and conscious dogs. The results indicate that the K+ATP channel openers, aprikalim and nicorandil, enhance recovery of regional contractile function of stunned myocardium. This action was blocked by the selective K+ATP antagonist, glyburide. The beneficial effects of K+ATP channel openers were not related to changes in systemic hemodynamics or coronary collateral perfusion, but instead may be a manifestation of direct cardioprotective actions of these compounds.

Adenosine Triphosphate↗
PubMed1994

[Diagnostic value of heart-liver nuclein ratio in cirrhotic portal hypertension].

A new method for evaluating portal systemic collaterals with administering 99mTc-MIBI per rectum was described in 80 cases. The heart to liver uptake ratio (H/L) in 15 healthy subjects was 0.267 +/- 0.1, slightly increased (0.455 +/- 0.13) in 8 patients with viral hepatitis and significantly increased in 68 cirrhotics. There was a good correlation between H/L ratio and the Child-Pugh classification with the ratio in Child A group of 0.57 +/- 0.12, in Child B group of 1.0 +/- 0.19, and in Child C group of 1.19 +/- 0.25 respectively (P < 0.01). For the diagnosis of portal hypertension, tentatively taking the ratio of > or = 0.62 as positive the sensitivity was 96%, specificity 89%, and accuracy 94%. The authors believe that 99mTc-MIBI imaging is a noninvasive method very useful in evaluating porta-systemic shunts.

Gamma Cameras↗
PubMed1988

Scanning electron microscope, freeze etching and glycosaminoglycan cytochemical studies of the cerebellar climbing fiber system.

Mouse and teleost fish cerebelli were processed by the freeze-fracture methods for scanning and transmission electron microscopy in order to study the three-dimensional morphology and intramembrane features of climbing fiber-Purkinje spine synapses. In addition, Alcian Blue and ruthenium chloride stainings were applied to mouse cerebellar tissue to investigate the polyanion composition of these excitatory synapses under the transmission electron microscope. In the granular layer, tendril and glomerular collaterals of climbing fibers were observed. In the molecular layer climbing fibers exhibited a characteristic crossing-over or arborescence pattern type of bifurcation, Scheibel's collaterals and multiple thorn synapses with Purkinje spiny dendrites. At the synaptic active zones of climbing fiber-Purkinje spine synapses the freeze-etching replicas showed focal aggregates of intramembrane particles at the E and P faces of the pre- and post-synaptic membranes. Membrane protuberances and pits were also observed at the pre-synaptic membrane. Ultracytochemical study of the climbing fiber synaptic varicosities revealed an Alcian Blue and ruthenium chloride positive material which appeared at the axoplasm surrounding the synaptic vesicles, at the pre- and post-synaptic densities and in the synaptic cleft. The axoplasmic material was sensitive to testicular hyaluronidase, therefore it would correspond to glycosaminoglycans (hyaluronic acid and/or chondroitin sulphates), which have been earlier reported in other cerebellar excitatory systems as those of mossy fiber-granule cell and parallel fiber-Purkinje dendritic spine.

Animals↗
PubMed1985

[Transcranial sonographic monitoring of the blood flow of the middle cerebral artery in recanalizing operations of the extracranial internal carotid artery].

During endarterectomy of the internal carotid artery (ICA) blood flow velocity of the ipsilateral medial cerebral artery (MCA) was continuously monitored in twelve patients with the help of a new transcranial pulsed Doppler system. Additionally, the basal cerebral arteries where examined pre- und postoperatively in order to evaluate criteria for selective intraoperative shunting and to document flow improvement following ICA reconstruction. All patients had symptoms, either of TIA or of minor stroke. Five of them had in addition a contralateral ICA occlusion. During intraoperative carotid cross-clamping on the patients with unilateral ICA lesions, MCA blood flow dropped to zero in only one of them. In the other cases, a 20 to 60% flow reduction occurred indicating cross-filling or/and collateral blood supply via the posterior circulation. More severe MCA flow reductions were found in patients with contralateral ICA occlusion, with the occurrence of a no-flow state in two of them. All patients were operated on with an indwelling shunt. Its effect on MCA blood flow varied considerably. Apparently, the shunt was necessary in some patients but was superfluous in the majority of them. Transcranial Doppler meets the basic criteria of an examination technique to be recommended for monitoring. The method is noninvasive. The parameter, i.e. MCA flow velocity, can be evaluated on-line. It is representative and highly sensitive for cerebral circulatory disturbances and impending ischemia in the carotid territory. Transcranial MCA flow monitoring does not affect the course of the operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗