Cerebral blood flow and CO2 reactivity in patients with transient ischemic attack]

To elucidate the changes in cerebral blood flow (CBF) and CO2 reactivity in patients with transient ischemic attack (TIA), 10 patients with TIA and 5 healthy adults (controls) underwent two consecutive CBF measurements (i.e. the first measurement during room air inhalation and the second measurement during 5%CO2 inhalation). Hemispheric mean CBF was determined by each CBF measurement using 133Xenon inhalation method. CO2 reactivity was evaluated by analysing delta CBF (= mean CBF during hypercapnea-mean CBF at rest) and delta CBF/delta PaCO2. The resting mean CBF values in the bilateral hemispheres (i.e. both of the affected and unaffected hemispheres) were significantly lower in TIA patients than controls (p less than 0.05). Inhalation of 5%CO2 significantly increased mean CBF in TIA patients bilaterally, however the mean CBF value during hypercapnea was again significantly lower in TIA patients than controls (p less than 0.05). CO2 reactivity in TIA patients was not significantly different from controls (p greater than 0.05). The result demonstrated that TIA patients have a chronic and global cerebral oligemia with normal CO2 reactivity. The chronic and global cerebral oligemia may develop a transient ischemic neurological symptom by being superimposed with local decrease of CBF.     

Cerebral Blood Flow and CO2 Reactivity in Transient Ischemic Attacks: Comparison between TIAs due to the ICA Occlusion and ICA Mild Stenosis

Hemispheric mean cerebral blood flow (CBF), together with its CO₂ reactivity in response to hyperventilation, was investigated in 18 patients with transient ischemic attacks (TIAs) by intraarterial ₁₃₃Xe injection method in a subacute-chronic stage of the clinical course. In 8 patients, the lesion responsible for symptoms was regarded as unilateral internal carotid artery (ICA) occlusion, and in 10 patients, it was regarded as unilateral ICA mild stenosis <50% stenosis in diameter). Resting flow values were significantly (P < 0.05) decreased in the affected hemisphere of TIA due to the ICA occlusion as compared with the unaffected hemisphere of the same patient, regarded as the relative control. It was not decreased in the affected hemisphere of TIA due to the ICA mild stenosis as compared with the control. With respect to the responsiveness of CBF to changes in Pa_CO2, it was preserved in both TIAs, due to the ICA occlusion and ICA mild stenosis. Vasoparalysis was not observed in either types of TIAs in the subacute-chronic stage. However, in the relationship of blood pressure and CO₂ reactivity, expressed as ΔCBF(%)/ΔPa_CO2, pressure-dependent CO₂ reactivity as a group was observed with significance (P < 0.05) in 8 cases of TIA due to the ICA occlusion, while no such relationship was noted in 10 cases of TIA due to the ICA mild stenosis. Moreover, clinical features were different between TIAs due to the ICA occlusion and ICA mild stenosis, i.e., more typical, repeatable TIA (6.3 ± 3.7 times) with shorter duration (<30 minutes) was observed in TIAs due to the ICA mild stenosis, while more prolonged, less repeatable TIA (2.4 ± 1.4 times) was observed in TIAs due to fixed obstruction of the ICA. From these observations, two different possible mechanisms as to the pathogenesis of TIA might be expected, e.g., TIA of microembolic origin due to the ICA mild stenosis, and TIA of hemodynamic origin due to fixed obstruction of the ICA, for whom the bypass surgery might be beneficial, i.e., all TIAs are not based on the same mechanism.     

Bi-hemispheric CBF and its CO2 reactivity of TIAs and completed strokes in ICA occlusions

Bi-hemispheric cerebral blood flow (CBF) measurements during rest and hyperventilation, with intra-arterial 133Xe injection method, were investigated in 19 cases, angiographically diagnosed as unilateral internal carotid artery (ICA) occlusion, including 8 cases with TIAs and 11 cases with completed strokes as the onset. Indices of cerebral vascular resistance and CO2 reactivity with decreasing arterial PCO2 were also investigated. A significant decrease (P less than 0.05) of hemispheric mean CBF was noted in the ischemic hemisphere, but normal flow values in the unaffected hemisphere and preserved CO2 responsiveness during hyperventilation were observed in both the affected and unaffected hemispheres in patients with TIAs. Moreover, a direct relationship between CBF and blood pressure, observed in 11 cases with completed strokes, was not recognized in 8 cases with TIAs. A degree of the abnormalities of the affected hemisphere in cerebral circulation was suggested to be somewhat different between TIAs and completed strokes in ICA occlusions, and bi-hemispheric CBF measurements would be an useful method for evaluating the various indices of the CBF in ICA occlusions.     

Vertebrobasilar transient ischemic attacks in internal carotid artery occlusion or tight stenosis

We studied 12 patients with internal carotid artery (ICA) occlusion or tight stenosis but without vertebrobasilar and subclavian atherosclerosis who suffered vertebrobasilar insufficiency (VBI). The patients with ICA occlusion were compared with a sex- and age-matched control group that had ICA occlusion but no VBI. Visible infarct on computed tomographic scan, greater size of visible infarct, weak collateral circulation, and bilateral atherosclerosis of the ICA significantly correlated with the occurrence of VBI. No significant difference was demonstrated for emboligenic lesions, but posterior to anterior flow through the posterior communicating arteries was demonstrated only in the patients with VBI. These facts suggested hemodynamic disturbances with "steal VBI." In ICA tight stenosis, VBI symptoms disappeared after endarterectomy but persisted in patients with more than 50% stenosis; this was also suggestive of hemodynamic VBI. Vertebrobasilar insufficiency had a prognostic significance, being associated with an increased occurrence of delayed stroke.     

SPECT study of cerebral blood flow reactivity after acetazolamide in patients with transient ischemic attacks

We investigated 15 patients with one or more transient ischemic attacks (TIAs) in the internal carotid artery territory within the month following the most recent TIA. Cerebral blood flow (CBF) was measured by single-photon emission computed tomography, using intravenous xenon-133 before and after injection of 1 g acetazolamide. Six patients had severe carotid stenosis or occlusion; the other nine patients had no significant carotid lesions. Twenty age-matched volunteers free of neurologic symptoms or history were used as controls. Mean CBF in the sylvian region was not significantly different between patients and controls. Seven patients exhibited a focal hypoperfusion at rest in the symptomatic hemisphere, and their hypoperfused areas were hyporeactive after administration of acetazolamide. Seven other patients exhibited hyporeactive areas after acetazolamide administration while their CBF tomograms at rest were normal. Thus, CBF abnormalities were detected in 14 of the 15 patients. Our findings suggest that CBF measured early after acetazolamide administration could be useful to confirm the clinical diagnosis of TIA. In the nine patients with no significant lesion of the internal carotid artery, the areas of hypoperfusion were small and were probably related to the focal ischemic event. In the six patients with severe lesions of the internal carotid artery, abnormalities were of variable size and intensity but were often large and pronounced. The discrepancy between these two subgroups of patients could be ascribed to the hemodynamic influence of the internal carotid artery lesions. Moreover, our findings may provide some insight into the pathophysiology of TIAs.     

Cerebral blood flow and cerebrovascular CO2 reactivity in stroke-age normal controls

We used the noninvasive 133-xenon inhalation technique to determine cerebral hemodynamics in 55 normal volunteers aged 18 to 88. Values for cerebral blood flow and cerebrovascular CO2 reactivity in fast-clearing tissue (flow gray) and slow-clearing tissue (flow white) were examined as functions of age and in relation to hematocrit, blood pressure, and evidence of extracranial vascular disease. Flow gray declined linearly with age, but no corresponding change was found in flow white or in CO2 reactivity. The data suggest that the progressive fall in flow gray is due to a physiologic aging process.     

Stroke or transient ischemic attacks with basilar artery stenosis or occlusion: clinical patterns and outcome

BACKGROUND: Basilar artery occlusion (BAO) is associated with a high mortality rate, although cases with spontaneous favorable outcomes have recently been reported, and basilar artery stenosis (BAS) has received little consideration until now. OBJECTIVE: To study the prognostic clinical factors by testing numerous combinations of admission status characteristics of patients with brain ischemia caused by BAO or BAS. METHODS: We conducted a retrospective review from the Lausanne Stroke Registry (group 1) of patients with stroke or transient ischemic attack caused by BAS less than 50% or BAO as diagnosed by magnetic resonance angiography who were not treated by thrombolysis. Neurologic findings on admission were correlated with outcomes. We compared clinical patterns associated with poor outcomes in group 1 with those in patients with stroke who died from BAO or BAS (confirmed at autopsy) (group 2). RESULTS: Eighty-eight patients were studied. The outcomes of patients with stroke in group 1 (35/43) was poor (severe disability or death) in 54% of cases. A statistical analysis revealed that 4 factors-dysarthria, pupillary disorders, lower cranial nerve involvement, and consciousness disorders on admission-were strongly (P<.001) associated with poor outcomes. The multivariate analysis showed that the outcome was poor in 100% of cases in which consciousness disorders or the combination of the remaining 3 factors were present, whereas in the absence of these factors, a poor outcome was reported in only 11%. In 87% of the 45 patients with stroke in group 2, the same clinical patterns were present on admission. CONCLUSIONS: The prognosis of BAS greater than 50% or BAO is diverse and certain clinical characteristics seem to predict a lower risk of poor outcome. Their presence may help to decide the most suitable therapy.     

Regional cerebral blood flow and its reactivity to acetazolamide in transient ischemic attacks. Study of 20 cases by gamma emission tomography

We have studied regional cerebral blood flow (= test) and reactivity of acetazolamide injection (= retest) in 20 patients who had presented transient ischemic attacks (TIA). The cerebral blood flow was measured by the atraumatic Xenon 133 inhalation method and single photon emission tomography using a specially dedicated tomograph (TOMOMATIC 64), allowing 3 tomographic levels (OM + 1, + 5, + 9 cm). Measurements were realized in a quiet, dark room. Acetazolamide (500 mg or 1000 mg) was injected intravenously immediately after the test, and the retest was performed 15 minutes after, in the same conditions. Results obtained from paired ROIS were analysed in terms of asymmetric index for the test, of relative reactivity for retest in regard of normal values established in a group of healthy volunteers. All patients had neurological examination, vascular explorations and CT scan. Six of the patients showed a bad reactivity (abolished or strongly decreased) which was evoked a significant hemodynamically stenosis, reflecting the loss of collateral capacity. In the other group results were diversified, and we classified these in 4 groups: "normal" (7), "luxury perfusion" (3), "limited infarction" (1), and "incomplete infarction" (3). When these groups were plotted versus duration of onset and delay between the last attack and the moment of the measurement, "incomplete infarction" clearly appears as a step between brief TIA (less of 1 hour) and "limited infarction". So rCBF and reactivity to acetazolamide are of major interest for the physiopathological classification of TIAs, but also for treatment and prognosis.     

Cerebral blood flow distribution and reactivity during the symptom-free stages of transient ischemic attacks--a 99mTc-HMPAO SPECT study]

Even during the symptom-free stages, patients with transient ischemic attacks (TIA) often show cerebral blood flow (CBF) disturbances. For evaluating the factors which cause these abnormalities, we studied CBF and CBF reactivity to acetazolamide (Diamox) using a 99mTc-hexamethylpropyleneamine oxime (HMPAO) single photon emission computed tomography (SPECT). The results from CBF-SPECT were compared with X-ray computed tomography (CT), cerebral arteriogram, clinical characteristics of TIA and cerebrovascular risk factors. The overall sensitivity rates in detecting the lesion were 68% in CBF-SPECT and 9% in CT. The size of the hypoperfused area tended to be wide in patients who had intracranial, severe stenotic or multiple arterial lesions on the ipsilateral side. No such relations were found between CBF and other examinations. Brain hypoperfusion was located in the subcortical region in eight patients; two patients showed a small hypodense lesion on CT which corresponded to the hypoperfusion on SPECT, and three patients showed no arteriographic abnormality. Hypoperfusion in the cortex was seen in seven patients; all patients showed arteriographic abnormality, but no CT abnormality. The severity rating of the vascular stenosis and hypoperfusion, and the incidence of the intracranial lesions were higher in this group than the group with subcotical hypoperfusion. Seven patients showed fixed normoperfusion before and after diamox injection. Two patients with a subcortical small infarction showed fixed hypoperfusion even after diamox injection. Twelve patients showed focal hypoperfusion before diamox with a new filling-in after diamox. Only one patient showed resting hypoperfusion and decreased CBF reactivity to diamox.(ABSTRACT TRUNCATED AT 250 WORDS)     

短暂性脑缺血发作间期局部脑血流及脑细胞功能状态

目的 通过对短暂性脑缺血发作(TIA)患者发作间期局部脑血流及脑细胞功能状态的研究，探讨TIA的有效治疗依据。方法 41例处于发作间期的TIA患者与55名做对照的健康成人均行单光子发射电子计算机断层显像(single-photon emission computed tomography，SPECT)、CT灌注成像(computed tomography perfusion imaging，CTPI)和正电子发射体层摄影术(positron-emission tomography，PET)等检查，对检查结果进行相关分析。结果 SPECT显示放射稀疏和(或)缺损39例，检出率为95．1％。CTPI显示灌注异常26例，检出率为63．4％，提示TIA发作间期仍有半数以上存在相应区域局部脑血流动力异常。而对于CTPI显示脑血流正常者，SPECT仍显示有放射稀疏和(或)缺损，考虑为局部脑细胞功能减低所致，PET检测结果亦显示细胞代谢异常。结论 TIA发作间期患者虽无临床症状及体征，但脑细胞功能未完全恢复正常，部分患者仍处于脑血流异常状态。提示临床医师应重视TIA患者的治疗，防止TIA复发，预防脑梗死的发生。     

Bi-hemispheric CBF and Its CO2 Reactivity of TIAs and Completed Strokes in ICA Occlusions

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Bi-hemispheric cerebral blood flow (CBF) measurements during rest and hyperventilation, with intra-arteria1 ¹³³Xe injection method, were investigated in 19 cases, angiographically diagnosed as unilateral internal carotid artery (ICA) occlusion, including 8 cases with TIAs and 11 cases with completed strokes as the onset. Indices of cerebral vascular resistance and CO₂ reactivity with decreasing arterial\PCO₂ were also investigated.

A significant decrease (P < 0.05) of hemispheric mean CBF was noted in the ischemic hemisphere, but normal flow values in the unaffected hemisphere and preserved CO₂ responsiveness during hyperventilation were observed in both the affected and unaffected hemispheres in patients with TIAs. Moreover, a direct relationship between CBF and blood pressure, observed in 11 cases with completed strokes, was not recognized in 8 cases with TIAs.

A degree of the abnormalities of the affected hemisphere in cerebral circulation was suggested to be somewhat different between TIAs and completed strokes in ICA occlusions, and bi-hemispheric CBF measurements would be an useful method for evaluating the various indices of the CBF in ICA occlusions.     

Treatment after transient ischemic attacks: a comparison between anticoagulant drug and inhibition of platelet aggregation

Treatment with an anticoagulant (AC) or acetylsalicylic acid (ASA), chosen at random, was given to 241 patients with symptoms of carotid transient attacks of ischemia, some of whom recovered completely within 24 hours (TIA) while the others had slight residual symptoms (TIA-IR). Cerebral infarction was recorded in 4 patients in each of these treatment groups during a mean follow-up period of 20 months. The incidences of TIA and TIA-IR were also similar in the two groups. Severe hemorrhage occurred more often in the AC group, whereas other side reactions, including gastrointestinal disorders, were more common in the ASA group. Recurrent cerebral ischemic events were significantly more common among the patients that had had greater than or equal to 2 TIAs in the 14 days immediately preceding randomization, and in those with a history of CVS symptoms more than 14 days before randomization, or those with a carotid bruits. In the group experiencing greater than or equal to 2 TIAs in the 14 days prior to randomization the incidence of recurrent cerebral ischemic events was the same for the two types of treatment.     

Cognitive impairment in patients with carotid artery occlusion and ipsilateral transient ischemic attacks

Abstract. Although transient ischemic attacks (TIAs) by definition do not cause lasting neurological deficits, cognitive impairment has been suggested in patients with carotid artery disease who have suffered from a TIA. The purpose of our study was to assess whether patients with carotid artery disease and TIAs are cognitively impaired, to describe the frequency, nature and severity of this impairment, and to search for associated patient characteristics.Thirty-nine consecutive patients with carotid occlusion and ipsilateral cerebral or retinal TIAs, and 46 healthy controls underwent extensive neuropsychological assessment. Performances were compared group-wise with analysis of variance. In addition, the presence of cognitive impairment in the individual patient was determined. Associations between illness characteristics and cognitive impairment were explored with regression analysis.Fifty-four percent of patients were cognitively impaired. Cognitive deficits were non-specific in nature and mild in severity. Impairment occurred also in patients with isolated retinal symptoms and in those without visible ischemic brain lesions on MRI. Neither the presence of any vascular risk factor, the side of the symptomatic carotid occlusion, the uni- or bilaterality of carotid occlusion, nor the number of cerebral ischemic lesions were predictors of cognitive impairment.We conclude that about half of the patients with carotid artery occlusion and ipsilateral TIAs are cognitively impaired. The presence of cognitive deficits in patients with isolated retinal symptoms and in those without cerebral ischemic lesions on MRI argues against an exclusive role for structural brain damage in the pathogenesis of these deficits.