Cerebral infarction with transient signs (CITS): do TIAs correspond to small deep infarcts in internal carotid artery occlusion?

Stroke

Stroke is the second most common cause of death and major cause of disability worldwide. Because of the ageing population, the burden will increase greatly during the next 20 years, especially in developing countries. Advances have occurred in the prevention and treatment of stroke during the past decade. For patients with acute stroke, management in a stroke care unit, intravenous tissue plasminogen activator within 3 h or aspirin within 48 h of stroke onset, and decompressive surgery for supratentorial malignant hemispheric cerebral infarction are interventions of proven benefit; several other interventions are being assessed. Proven secondary prevention strategies are warfarin for patients with atrial fibrillation, endarterectomy for symptomatic carotid stenosis, antiplatelet agents, and cholesterol reduction. The most important intervention is the management of patients in stroke care units because these provide a framework within which further study might be undertaken. These advances have exposed a worldwide shortage of stroke health-care workers, especially in developing countries.

The role of carotid stenosis in vascular cognitive impairment

As the contribution of carotid stenosis to cognitive impairment still remains unclear, neuropsychological function and soft neurological signs were examined in patients aged 65 and over. Twenty-five patients with symptomatic carotid stenosis (CS) of 75% or more were compared with 25 patients with first anterior circulation stroke, 25 with peripheral vascular disease and 25 healthy controls. All patients were assessed using CAMCOG (Cambridge Cognitive Examination), tests examining frontal lobe function (Behavioural Dyscontrol Scale [BDYS], Trail-Making Tests A and B, Controlled Word Association Test) and a scale for primitive reflexes (Frontal Release Signs Scale). Patients with symptomatic CS showed greater global impairment on CAMCOG and more severe impairment in frontal lobe function than controls. Those patients scoring less than 15 on the BDYS were more likely to have experienced transient ischemic attacks (TIA) for 5 or more years. Frontal lobe dysfunction, suicidal thinking and age were all independent predictors of global cognitive impairment. Mean number of frontal release signs was higher in patients with CS than in controls, with a higher proportion of patients showing all release signs except glabellar, paratonia and snout reflexes. The study is limited by small numbers and the absence of brain imaging, but provides some evidence for an association between severe carotid stenosis and neuropsychological impairment. The presence of clinically 'silent' cerebrovascular disease affecting frontal lobe function may be missed in routine clinical practice.

Factors causing prolonged hypoperfusion after transient ischemic attack

Even during the symptom-free stages, patients with a TIA often experience cerebral blood flow disturbances. In order to evaluate the factors which cause this abnormality, we studied the cerebral blood flow disturbance, anatomy and clinical status in 21 patients after TIAs. The results of 99mTc-hexamethyl-propylene-amine oxime SPECT were compared with CT, cerebral angiogram, cerebrovascular risk factors and clinical findings to determine which factor is most responsible for the hypoperfusion of brain after TIA. The overall sensitivity rates in detecting a lesion were 67% in SPECT and 19% in CT. The hypoperfused area tended to be large in patients who had intracranial, severe stenotic, multiple, or hemodynamically significant arterial lesions on the ipsilateral side. No such relationships were found between other examinations. We conclude that hypoperfusion after TIA essentially reflects a continuous cerebral blood flow disturbance that can be attributed to atherosclerosis of the cerebral arteries, with subsequent embolic and/or hemodynamic cerebral ischemia, although there may be a variety of processes.

Large vessel disease in Chinese patients with capsular infarcts and prior ipsilateral transient ischaemia

Carotid angiography was carried out in 21 Chinese patients with acute capsular infarcts; all had had a previous ipsilateral transient ischaemic attack (TIA) or reversible ischaemic neurological deficit (RIND) during the preceding 6 months. Sixteen (group 1) showed lacunar capsular infarcts, and 5 (group 2) either "giant lacunae" or "striatocapsular infarcts". Angiography showed that 81% of group 1 and all group 2 patients had ipsilateral severe stenosis or occlusion of either the M1 segment of the middle cerebral artery or the internal carotid artery. Ten group 1 patients and 3 group 2 patients also had contralateral intra- or extracranial carotid artery stenosis. Apart from hypertension, other risk factors such as hyperfibrinogenaemia, polycythaemia, and low HDL-cholesterol level seem to play a role. Haemorheological abnormalities in the presence of atherostenosis at the orifice of lenticulostriate arteries and/or artery-to-artery embolism might be the cause of infarcts in the majority of the patients. A fifth of patients had recurrent large ipsilateral infarcts. Thus capsular lacunar syndromes with prior ipsilateral TIA or RIND are not as benign as previously thought, and they should indicate more intensive studies including cerebral angiography, and more vigorous therapy.

TIA, RIND, minor stroke: a continuum, or different subgroups? Dutch TIA Study Group

The results of CT were studied prospectively in 606 patients with a transient ischaemic attack (TIA), 422 patients with a reversible ischaemic neurological deficit (RIND), and 1054 patients with a minor stroke, were all entered into a multi-centre clinical trial. CT scanning showed a relevant ischaemic lesion in 13% (95% confidence interval 10-16%) of TIAs, 35% (95% confidence interval 30-40%) of RINDs, and 49% (95% confidence interval 46-52%) of minor strokes (p less than 0.000001). Even within the 24 hour margin, relevant infarcts occurred more often with longer attacks, but were still found in some patients with attacks lasting less than a minute. The type and location of the infarcts were similar in the three groups. These findings suggest that the differences between TIAs, RINDs, and minor strokes are quantitative rather than qualitative.

Transient ischemic attacks: an update

This is a review of extant concepts of transient ischemic attacks (TIAs), their definitions, prognostic significance, pathogenesis, physiology, and management. The natural history of TIAs depends upon the risk factors of the population group studied, so that therapeutic trials should be controlled and randomized and not dependent upon published natural history data. A strong association between TIAs and coronary artery disease has now been established. It may be difficult to establish the cause or pathogenesis of TIAs in any given patient in view of the relatively poor correlation between the patient's symptoms and location of arterial plaques. Recent studies have suggested mechanisms aside from impaired perfusion or embolization from carotid plaques or vertebral basilar disease. There are no proven indications for carotid endarterectomy, a procedure which has been excessively used in the United States, but presently ongoing prospective, randomized, controlled multi-center studies will likely resolve this important issue. Neither is there scientific validation for the use of long-term anticoagulants, but data support the efficacy of ASA in reducing the incidence of stroke and myocardial infarction in patients with TIAs.

Extended use of cranial CT in the evaluation of patients with stroke and transient ischaemic attacks

The hypothesis was explored that patterns of ischaemic brain damage shown by CT may be of greater value in estimating the relevance of angiographic stenosis in the carotico-vertebral arteries in some patients than presenting clinical features. Five angiographic and six CT abnormalities were defined and charted independently in a blinded manner in 312 patients whom clinical features and subsequent management were known. Charts were combined for statistical analysis. Statistically significant associations were found between two types of CT lesion and angiographic abnormalities, but these were present in only 18% of cases. The distribution of clinical features did not differ significantly within this subset compared to the whole population, from which it was concluded that the hypothesis was upheld. Furthermore significantly more patients in this subset were subjected to carotid endarterectomy, suggesting that management decisions may have been modulated by CT findings in some patients.

The role of imaging in the management of cerebral and ocular ischaemia

The last decade has seen several major technological advances in vascular neuroradiology, the most clinically significant of which have been the facility to image the brain and the extracranial carotid bifurcation noninvasively with accuracy and safety. Another major advance has been unequivocal evidence from formal statistical overviews that antiplatelet therapy, particularly aspirin, reduces the risk of serious vascular events by about 25%. These advances have changed clinical practice such that most patients presenting with symptoms suggestive of cerebral ischaemia should now have cranial CT to exclude intracerebral hemorrhage, not only because the causes and prognosis of cerebral ischaemia differ from those of intracerebral hemorrhage, but because many patients with cerebral ischaemia should be considered for antiplatelet therapy. Besides the use of long term antiplatelet therapy and control of vascular risk factors, other acute treatment options are limited with the possible exception of anticoagulation, thrombolysis, cytoprotective agents and carotid endarterectomy. If, as seems likely, the current clinical trials show that carotid endarterectomy plus medical therapy improve upon the stroke-free survival of patients treated medically, at least in symptomatic patients with severe stenosis, the number of carotid endarterectomies performed will increase considerably because carotid bifurcation disease is the most common cause of cerebral and ocular ischemic events. It will then be even more important to be able to obtain accurate anatomical and physiological information about the extracranial and intracranial circulations with utmost safety. Duplex ultrasound is currently the noninvasive screening method of choice for carotid bifurcation disease because it is available, relatively cheap, and reasonably accurate. It not only images the vessel lumen and degree of stenosis, but also the morphology of the vessel wall and associated plaque, the relevance of which is still uncertain in the pathogenesis of cerebral and ocular ischaemia. A major limitation of duplex sonography is that it cannot reliably distinguish tight stenosis from occlusion and it does not image the proximal or distal carotid circulation. The aim of newer techniques will be to distinguish tight extracranial carotid stenosis from occlusion and to provide anatomical, physiological and pathological information about the intracranial circulation and ischemic lesions (in view of potential for thrombolytic therapy of major intracranial vessel occlusion) with safety and reproducible accuracy.

Computed tomography in patients with transient ischaemic attacks: when is a transient ischaemic attack not a transient ischaemic attack but a stroke?

In a prospective community-based study, 184 patients with transient ischaemic attacks (TIAs) were identified from a study population of about 105,000 between 1981 and 1986. Computed tomography (CT) was attempted in all those with cerebral ischaemic attacks (n = 152, 83%); patients with amaurosis fugax only (n = 32, 27%) were not scanned routinely. Scans were obtained in 120 (79%) of those with cerebral attacks and 12 (38%) of those with amaurosis fugax. The scans were reported by a neuroradiologist who was blinded to the patients' clinical features. Of 120 (27%:95% confidence interval 19-35) scans in patients with cerebral attacks, 32 showed a focal area of hypodensity or cortical loss, but in only 14 (12%:95% confidence interval 6-18) was this in an area of the brain appropriate to the patients' symptoms. There were no significant differences in the clinical features, the duration of attacks or the prognosis (i.e., risk of death, stroke or myocardial infarction) of patients with and without ischaemic lesions on CT. It is concluded that patients with clinically definite TIAs who have a presumed ischaemic and appropriately sited lesion on CT should not be re-classified as having had a stroke.

Cerebral infarction in patients with transient ischemic attacks

Cranial computed tomography of 284 patients with transient ischemic attacks (TIAs) and without previous stroke was evaluated. The sample population included patients with carotid and/or vertebrobasilar TIAs. Computed tomography revealed cerebral infarction in 34 patients, including 5 with multiple infarctions. The lesion location was consistent with TIA symptoms in 16 patients. In another 16 patients, however, the lesion location did not correspond to the TIA symptoms; these lesions were attributed to previous silent infarctions. Two patients with multiple infarctions had both symptomatic and asymptomatic lesions. Age and carotid stenosis were each significantly related to an increased chance of detecting cerebral infarction (either symptomatic or asymptomatic). No significant relationship between race, gender, hypertension, diabetes, cardiac disease, or smoking and the incidence of infarction was found by either univariate or multivariate analyses.

The role of cranial computed tomography in carotid surgery

In patients who present with TIA, RIND, or CVA, the cranial CT scan can rule out other etiologies for neurologic symptoms. In addition to the clinical presentation, the CT scan allows further stratification of patients being considered for carotid endarterectomy. We propose that patients be classified as TIA (+), TIA (-), RIND (+), or CVA (-). The CT scan has defined a new subgroup of patients, TIA (+) and RIND (+)--the Silent Cerebral Infarction. Patients who are categorized as TIA (+), RIND (+), and CVA (+) (cerebral infarction on CT or by history) are at increased risk for intraoperative ischemia and postoperative neurologic deficit. As such, they should be selectively shunted based on intraoperative EEG monitoring or routinely shunted. There is a strong association between ulcerative plaque at the carotid bifurcation and cerebral infarction on CT. The CT scan is a critical diagnostic procedure in evaluating the patient with an acute neurologic event. Patients with negative CT scans are candidates for early operation. Carotid endarterectomy should generally be delayed for 4 to 6 weeks in patients with positive CT scans.

The possible significance of symmetry and asymmetry of the mean hemispheric CBF in patients with one-sided cerebral ischemia

The difference in mean hemispheric CBF was compared in two groups of patients suffering from one-sided cerebral ischemia. One group without significant arteriographic abnormalities and a group with a one-sided internal carotid artery occlusion. The Xenon inhalation method (ISI) was used. It seems to be difficult to draw any conclusions from the differences between mean hemispheric ISI values, especially for patients with fairly severe clinical symptoms. In far the most patients without significant arteriographic abnormalities, no significant difference was found. A great difference (high ISI ratio) for patients with no or only slight symptoms may indicate a disturbed blood flow to the hemisphere with the lower ISI. Such high ratios were only found in patients suffering from a one-sided occlusion of the internal carotid artery. This rather simple and harmless method of blood flow measurement may prove to be a valuable contribution toward insight into the pathophysiology of blood flow in patients, especially those suffering from one-sided internal carotid artery occlusion.

X-ray computed tomography (CT) study of small, deep and recent infarcts (SDRIs) of the cerebral hemispheres in adults. Preliminary and critical report

The evolution of CT signs of small, deep infarcts of the cerebral hemispheres in thirty adults, in the first five weeks, has been retrospectively studied. The relevant literature has been reviewed and an attempt has been made to present a synthesis, accompanied by a commentary. It is impossible now to give the frequency of each type of evolution, but the main data are as follows: The shortest delay of visibility of an hypodense area is about 17 to 19 h, but at 27 h the densities may still be normal. The evolution of the hypodense area is also variable: after a minimum attenuation is reached--at approximately 72 h--there is a risk of "fogging effect", which reduces the visibility of ischemic lesions; it could be seen from the end of the 1st week to the beginning of the 4th, but its frequency and its duration have yet to be better determined. In our series, contrast enhancement has been found in the gray matter of the basal ganglia between the 8th and the 22nd days--but according to some observations recorded in the literature, it may be found from the second to the twenty sixth day--and there was no obvious contrast enhancement in the white matter. The significance of the evolving CT signs is discussed in connection with the clinical applications, principally in the management of these patients, and with the attempts to correlate the clinical and CT findings.

Computerized tomographic abnormalities in patients with transient episodes of focal neurological dysfunction

Forty patients with episodes of transient neurological dysfunction lasting less than 24 hr had abnormal CT scan findings. Eight patients had intracranial mass lesions and 32 had vascular lesions i.e. ischemic, infarction, hematoma. Seventeen patients had hypodense lesions consistent with tissue infarction; whereas 12 patients had isodense enhancing lesions consisting with tissue ischemia. In eight patients with isodense enhancing lesions, this was no neurological deterioration following carotid endarterectomy. In 3 patients who had transient ischemic attacks with CT evidence of hypodense lesions there was clinical and CT deterioration following carotid surgery.