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PubMedDate not supplied

Blood flow through cerebral collateral vessels one month after middle cerebral artery occlusion.

Acute occlusion of a middle cerebral artery (MCA) reduces cerebral blood flow in normotensive Wistar-Kyoto rats (WKY) and in stroke-prone spontaneously hypertensive rats (SHRSP). The goal of this study was to determine whether MCA occlusion produces a sustained reduction in cerebral blood flow or whether collateral vessels restore blood flow to normal levels. We measured blood flow through cerebral collateral vessels to the territory of the occluded MCA and to homologous tissue of the other hemisphere in WKY 1 month after occlusion of the MCA. Cerebral blood flow, measured with microspheres, was restored to normal levels under control conditions in the territory of the occluded MCA. During vasodilatation produced by seizures, blood flow and vascular conductance were increased to similar levels in tissue distal to the site of MCA occlusion and in the homologous tissue of the other hemisphere. MCA occlusion did not produce infarction in any of the WKY. In contrast, 1 month after MCA occlusion in SHRSP, a large atrophic infarct was invariably present in the territory of the occluded MCA. The number of collateral vessels to the territory of the MCA do not differ in SHRSP and WKY. Internal diameter and orientation of the anastomotic vessels differ in SHRSP and WKY. We conclude that, after 1 month of MCA occlusion, changes in the collateral vessels supplying the territory of the occluded MCA in WKY were sufficient to restore blood flow to normal under control conditions and to virtually normal levels during vasodilatation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Short-term prognosis of stroke due to occlusion of internal carotid artery based on transcranial Doppler ultrasonography.

BACKGROUND AND PURPOSE: The clinical course of stroke due to occlusion of the internal carotid artery is influenced by amount of collateral flow. We measured mean frequency shifts in the middle cerebral artery by transcranial Doppler ultrasonography to determine its prognostic value. METHODS: Patients with proven extracranial occlusion of the internal carotid artery and ipsilateral hemispheral stroke were enrolled in our study. We performed transcranial Doppler ultrasonography on 31 patients within 48 hours after the stroke onset and followed up 25 patients in 28 days. At the same time, neurological examination with quantification of neurological deficit was done. We correlated values of flow frequency shifts on the side of stroke with degree of neurological deficit at the onset and at 28 days as well as the degree of clinical improvement and the value of frequency shifts. RESULTS: We found a negative correlation between blood flow frequency shifts in the middle cerebral artery and degree of neurological deficit at the onset (Spearman rank correlation coefficient, -0.567; p less than 0.001). We also found a positive correlation between the change of the neurological deficit during follow-up and frequency shifts at the onset (Spearman rank coefficient, 0.548; p less than 0.05). CONCLUSIONS: Diminished blood flow velocity (mean frequency shift) in the area of stroke is a negative prognostic factor for the degree of neurological deficit at the onset and a negative prognostic factor for possible improvement. Knowledge of hemodynamic conditions in the stroke area may help to improve therapeutic decisions.

Adult↗
PubMed1994

Course of cerebrovascular reactivity in patients with carotid artery occlusions.

BACKGROUND AND PURPOSE: Patients with internal carotid artery occlusions and highly impaired cerebrovascular reactivity have been identified as having an increased risk of stroke. It is still unclear, however, whether cerebral hemodynamics may be restored in the course of time by the development of collaterals. METHODS: During a 5-year period we assessed cerebrovascular reactivity in 452 carotid occlusions by transcranial Doppler CO2 testing. Ninety-eight patients could be reinvestigated at least once after 2 to 58 months (mean follow-up time, 26 months). RESULTS: On admission, patients with recent transient ischemic attack or stroke (< or = 3 months) as well as patients with contralateral carotid stenoses of 80% diameter reduction or greater and occlusions revealed a significantly higher incidence of impaired CO2 reactivity (P < .0001 and P < .01, respectively). During follow-up, 64% of the patients with no or minor contralateral carotid stenoses, but only 22% of the patients with bilateral carotid occlusions, showed a spontaneous improvement in cerebrovascular reactivity (P < .001), mainly during the first few months. In six of eight patients cerebral hemodynamics on the occluded side improved after endarterectomy of a contralateral high-grade carotid stenosis. Five of the patients who did not undergo surgery developed a stroke during follow-up, with three of them occurring in patients with permanently exhausted cerebrovascular reactivity. CONCLUSIONS: In the majority of patients with carotid occlusions an initially impaired cerebrovascular reactivity improves spontaneously with time. This could influence therapeutic decisions: During the first few months antihypertensive treatment may be avoided in such cases until a reestablished reactivity can be demonstrated. If cerebral hemodynamics remain depleted, extracranial-intracranial bypass surgery or endarterectomy of an asymptomatic contralateral high-grade carotid stenosis could be helpful.

Aged↗
PubMed1995

Spontaneous middle cerebral artery reperfusion in ischemic stroke. A follow-up study with transcranial Doppler.

BACKGROUND AND PURPOSE: The aim of this study was to investigate by means of transcranial Doppler (TCD) ultrasonography how many spontaneous reperfusions of the middle cerebral artery (MCA) occurred during the first week after onset of acute ischemic stroke in the carotid territory. METHODS: TCD examination, computed tomographic scan, and arterial digital angiography were performed in 56 patients with acute ischemic stroke within 6 hours of the onset of symptoms. The TCD examination was repeated within 24 hours, 48 hours, and 7 days after stroke; a further TCD examination was performed within 3 to 9 months in 27 patients. RESULTS: At 6 hours, 33 patients presented abnormal TCD findings in the symptomatic MCA (16 "no flows" and 17 asymmetries). Of these, 4 patients (3 no flows and 1 asymmetry) died before the 7-day follow-up was completed, whereas of the 29 remaining patients undergoing all the TCD control examinations, only 14 presented permanently abnormal TCD findings (7 asymmetries and 7 no flows). These data are consistent with an MCA reperfusion occurring at any level of the MCA, although most frequently in the distal part, and in the majority of cases during the first 48 hours. One patient who showed MCA asymmetrical flow velocity at the day-7 TCD examination was normal at the TCD follow-up at 3 to 9 months. CONCLUSIONS: TCD examination offers an easy and reliable way of monitoring MCA reopening and might be useful to identify subgroups of patients who may benefit most from pharmacological reperfusion.

Acute Disease↗
PubMed1996

Hemodynamic parameter assessment with dynamic susceptibility contrast magnetic resonance imaging in unilateral symptomatic internal carotid artery occlusion.

BACKGROUND AND PURPOSE: Hemodynamic parameters such as regional cerebral blood volume (rCBV), mean transit time (MTT), and regional cerebral blood flow (rCBF) can be assessed by dynamic susceptibility contrast MRI. The aim of the present study was to apply this method in patients who had symptomatic unilateral internal carotid artery occlusion. METHODS: Relative hemodynamic parameters (rCBV, MTT, and rCBF) were evaluated on the occluded side and thus compared with contralateral hemispheric values. We also attempted to detect any relationship between collateral flow and the hemodynamic parameters. RESULTS: Although rCBV was clearly increased in five patients over the whole hemisphere, we did not observe a statistically significant difference regarding the whole sample between sides (mean rCBV, 14.1 +/- 4.58 on the occluded side versus 11.8 +/- 2.99 on the contralateral side, P>.10). MTT was clearly increased on the occluded side (mean MTT, 4.29 +/- 0.83 on the lesion side versus 3.14 +/- 0.81 on the contralateral side, P<.010). A statistically significant decrease of rCBF on the occluded side was observed (mean rCBF, 3.27 +/- 0.73 versus 3.93 +/- 1.03 on the contralateral side; P<.01). CONCLUSIONS: A significant hemodynamic compromise in patients who had unilateral symptomatic carotid occlusion was observed according to CBF and MTT values. This approach might be promising in the understanding of cerebral hemodynamics in patients with vascular disorders.

Aged↗
PubMed1996

Aspirin in ischemic cerebrovascular disease. How strong is the case for a different dosing regimen?

BACKGROUND: A vast consensus exists in defining a narrow range of recommended daily doses of aspirin, ie, 75 to 160 mg, for the prevention of myocardial infarction, stroke, and vascular death in patients with different manifestations of coronary hearth disease. In contrast, for patients with cerebrovascular disease, a much larger degree of uncertainty still exists, with recommendations ranging from 30 to 1300 mg daily. SUMMARY OF COMMENT: The contention that higher doses of aspirin (650 to 1300 mg) are more effective than lower doses in stroke prevention is based on indirect and selective comparisons of different trial data, mini-meta-analyses, or subgroup analyses of individual trials. In the absence of definitive evidence from direct randomized comparisons of low-dose versus high-dose aspirin in trials of adequate size to detect a moderate difference between the two, the biological hypotheses that underpin the suggestion of greater efficacy of higher aspirin doses in cerebrovascular disease patients are reviewed and disputed. Practical implications of the use of higher doses of aspirin are also assessed on the basis of theoretical calculations of absolute benefits and risks. CONCLUSIONS: Until additional information from ongoing trials is available, good clinical practice should dictate the use of the lowest dose of aspirin shown effective in the prevention of stroke and death in patients with ischemic cerebrovascular disease, ie, 75 mg daily.

Aspirin↗
PubMed1999

Lack of correlation between pattern of collateralization and misery perfusion in patients with carotid occlusion.

BACKGROUND AND PURPOSE: Misery perfusion, identified by increased oxygen extraction fraction (OEF), predicts subsequent stroke in patients with carotid occlusion. The purpose of this investigation was to determine the relationship of angiographic findings to increased OEF in these patients. METHODS: Forty-seven patients with carotid occlusion were studied with cerebral angiography and positron emission tomography (PET). The following angiographic data were collected blind to PET results: (1) pial collateralization, defined as retrograde filling of the MCA branches to the level of the insula; (2) presence of border zone shift; (3) presence of delayed venous phase; and (4) measurement of posterior communicating artery size. Patients were divided into 2 groups based on the PET measurement of normal or increased OEF. RESULTS: Seventeen of 47 patients had increased OEF distal to the occluded carotid artery. No significant relationship between increased OEF and any angiographic finding was found. Pial collateralization was present in only 2 patients, both with increased OEF (P=0.105). Border zone shift was equally distributed between the 2 groups (12 of 30 with normal OEF and 6 of 15 with increased OEF). Delayed venous phase was present in 4 patients, 3 of whom had increased OEF (P=0.073). The relationship between the size of the posterior communicating artery and OEF was not significant by linear regression analysis (P=0.242). CONCLUSIONS: With the possible but infrequent exceptions of delayed venous phase and pial collateralization, anatomic findings made on routine angiographic studies of patients with carotid occlusion do not correlate with increased OEF.

Adult↗
PubMed1975

Regional cerebral blood flow studies following superficial temporal-middle cerebral artery anastomosis.

Regional cerebral blood flow (rCBF) studies were performed during the postoperative period on 16 patients with internal carotid occlusions and inaccessible stenoses, and middle cerebral artery occlusion and stenoses, who underwent superficial temporal artery-middle cerebral artery (STA-MCA) anastomoses. The intra-arterial xenon method with selective application of the xenon bolus through the internal carotid and the newly established superficial temporal channel has allowed comparison of the flow provided by the pathological input with flow through the new input. The results show that initial rCBF (rCBF1) was globally reduced in all patients to a mean of 28.4 +/- 11.9 ml/100 gm/min at a mean pCO2 of 29.6 +/- 9.55 mm Hg. Patients with transient ischemic attacks (TIA) and minor strokes with minimal residua (RIND) had a mean rCBF1 of 30.4 +/- 11.6 ml/100 gm/min at a mean pCO2 of 30 +/- 10 mm Hg, while patients with completed strokes had a mean rCBF1 of 25.0 +/- 12.4 ml/100 gm/min at a mean pCO2 of 29.1 +/- 8.8 mm Hg. There was no significant difference between these two groups. This finding suggests that in this small group of patients with TIA's and RIND's, the cause of the stroke is probably related more to decreased perfusion than embolus, and may explain why these patients' symptoms improve after STA-MCA anastomosis. The results of this study suggest that in addition to an inaccessible lesion, global or focal decreased rCBF is a necessary criterion in the definition of indications for intracranial revascularization procedures.

Cerebral Angiography↗
PubMed2000

[Postoperative evaluation of EC/IC bypass surgery--long-term follow up study by donor artery compression test].

Focal cerebral vascular dependency of donor arteries was evaluated in 45 patients who had undergone EC/IC bypass surgery. During EEG recording, digital compression was applied to the anastomosed donor superficial temporal artery (STA) at the preauricular region. The appearance of slow waves on the EEG recording suggests hypofunction of the local brain. In cases showing positive response to the STA compression test, we suggest that the blood supply via STA is an essential collateral route to the ischemic brain. The test was periodically repeated in the postoperative follow-up period for a mean of seven years. Eleven cases (24%) showed positive results in the STA compression test during the long-term postoperative follow-up period.

Adult↗