Anterior circulation

Middle Cerebral Artery Occlusion and the PROACT Trial The safety and efficacy of lAT in the anterior circulation have been evaluated in two randomized, multicenter, placebo-controlled trials. In the Prolyse in Acute Cerebral Thromboembolism (PROACT) 1 and 11 trials, patients with proximal MCA (Ml or M2 segment) occlusions within 6 hours of symptom onset were treated with recombinant prourokinase (r-pro-UK) or placebo. ... 

Acute ischemic stroke s3miptoms with onset or last known well, clearly defined. Treatment within 6 h of established, nonfluctuating deficits due to Anterior Circulation (carotid/MCA) stroke, between 6 and 8 h mechanical treatment (e.g.. Concentric Retriever) should be considered. The window of opportunity for treatment is less well defined in posterior circulation (vertebral/basilar) ischemia, and patients may have fluctuating, reversible ischemic symptoms over many hours or even days and stiU be appropriate candidates for therapy. 

De Georgia et al. Stroke 2004 63 312-317 Prospective, randomized cooling vs. standard therapy for feasibility and safety 18 of40tx with hypothermia Hypothermia to 33°C with endovascular catheter on safety in pts with anterior circulation stroke and NIHSS >8 Similar clinical outcomes and lesion growth as measured on DWI MRI. Nonsignificant reduction in DWI volume in patients who cooled well. 

Aphasia is seen commonly in patients with anterior circulation strokes. 

Patients usually have multiple signs of neurologic dysfunction on physical examination. The specific deficits observed depend upon the area of the brain involved. Hemi- or monoparesis and hemisensory deficits are common. Patients with posterior circulation involvement may present with vertigo and diplopia. Anterior circulation strokes commonly result in aphasia. Patients may also experience dysarthria, visual field defects, and altered levels of consciousness. 

Large Vessel Occlusive Disease of the Anterior Circulation 4... 

For the acute occlusion in the anterior circulation, no large comparative studies have been carried out to date to validate MRA, perhaps because therapeutic decisions were not dependent on evidence of an arterial occlusion or from its exact localization... 

Using only a few neurological findings the Oxfordshire Community Stroke Project (OCSP) classification allocates strokes to four subgroups, locating them either in the territory of the anterior (total anterior circulation infarct, TACI partial anterior circulation infarct, PACI lacunar infarct, LACI) and the posterior circulation, (posterior circulation infarct, POCI) (Bamford et al. 1991). The OCSP is a clinical syndromic classification, which... 

Subcortical white matter infarcts may mimic a superficial MCA infarct causing a partial anterior circulation syndrome or present as a lacunar syndrome (pure motor, ataxic hemiparesis or sensori motor stroke). Superficial perforating artery infarcts (medullary branches) are often accompanied by cortical spotty lesions. Borderzone and white matter medullary branches infarctions are usually caused by hypoperfusion due lo large vessel occlusion or stenosis (Bogousslavsky 1993 Donnan and Yasaka 1998), but white matter medullary branches infarction can also be caused by cardioembolism (Lee et al. 2003). 

A study by Georgiadis et al. (31) induced hypothermia (target temperature 33°C) in 14 patients with an acute anterior circulation infarction involving at least two thirds of the left MCA territory. Patients received norepinephrine via continuous intravenous infusion and were mechanically ventilated. Hypothermia was initiated 26 h after onset of symptoms as a means to control intracranial hypertension and not for neuroprotection. In that study, static cerebral autoregulation did not appear impaired in the unaffected hemisphere with the use of alpha-stat for pH maintenance. However, the main concern in patients with acute stroke is the perfusion of the affected hemisphere, specifically of the penumbra (18). 

Mrs SL, aged 75, is admitted to hospital unable to speak, swallow or move her right arm and leg, having collapsed when out to dinner with her son. She has an urgent CT scan which reveals an ischaemic stroke of the partial anterior circulation (PAC) type. She had a transient ischaemic attack (TIA) two weeks ago and her son says she has had them infrequently for the last year. She has been treated for hypertension and high cholesterol for the past 2 years and has been taking aspirin. 

Embolization of plaque debris or thrombus may block a more distal vessel. Emboli are usually the cause of obstruction of the anterior circulation intracranial vessels (Lhermitte et al. 1970 Ogata et al. 1994), at least in white males in whom intracranial disease is relatively rare. Since emboli follow the prevailing direction of flow in a vessel, most emboli... 

It may be difficult to distinguish between some partial anterior circulation syndromes and a lacunar stroke. 

Partial anterior circulation infarcts (Fig. 9.4) are caused by occlusion of a branch of the middle cerebral artery, or rarely the trunk of the anterior cerebral artery. They are usually... 

Some anterior circulation syndromes, usually classified as partial anterior circulation syndromes, are caused by boundary zone infarcts. The rare anterior choroidal artery distribution infarcts, which can be defined only by the CT or MRI pattern, are probably caused by microvascular disease as well as embolism, and they can lead to a partial anterior circulation syndrome or lacunar syndrome (Hupperts et al. 1994). 

Lacunar syndromes are defined clinically. They are highly predictive of small, deep lesions affecting the motor and/or sensory pathways in the corona radiata, internal capsule, thalamus, cerebral peduncle or pons. Although a few patients have a partial anterior circulation infarct (Bamford et al. 1987 Anzalone and Landi 1989 Arboix et al. 2007), the great majority have small iirfarcts, which are sometimes visible on CT, more often on MRI. These are caused by presumed occlusion of a small perforating artery affected by intracranial small vessel disease (see Fig. 10.2). There is no visual field defect, no new cortical... 

Fig. 9.4. Axial T2-weighted MRI scans (a-c) and a magnetic resonance angiogram (d) showing a right partia anterior circulation infarct secondary to right carotid occlusion.

Headache is not uncommon around the time of stroke onset. It is more often severe in primary intracerebral hemorrhage than ischemic stroke, and more often severe with posterior than anterior circulation strokes. If the headache is localized at all, it tends to be over the site of the lesion. Headache is more common in cortical and posterior circulation than lacunar infarcts (Kumral et al. 1995). Severe unilateral neck, orbital or scalp pain suggests internal carotid artery dissection, particularly if there is an ipsilateral Horner s syndrome. Severe occipital headache can occur with vertebral artery dissection. Headache is also a particular feature of venous infarcts. Unusual headache in the days before stroke would suggest giant cell arteritis or perhaps a mass lesion rather than a stroke. 

Some overlap exists between the clinical classification (Bamford et al. 1991) and the etiological TOAST classification. In a large hospital-based series of patients with ischemic stroke, total and partial anterior circulation infarcts were most likely to be caused by large artery atherosclerosis, cardioembolism or both (Wardlaw et al. 1999). 

Total anterior circulation syndromes or brainstem strokes often cause some drowsiness, but in smaller lesions, consciousness is normal. Therefore if consciousness is impaired and yet the focal deficit is mild, it is important to ... 

So far predictive models only apply to a small proportion of patients and are not sufficiently accurate to inform treatment decisions in routine clinical practice. The various subtypes of ischemic stroke have very different outcomes patients with total anterior circulation infarction (TACI) have just as poor an outcome as those with primary intracerebral hemorrhage (Table 16.1). The best single predictor of early death is impaired consciousness, but many other predictors of survival have been identified (Table 16.2). Many of these variables are inter-related, but prognostic models based on independent variables do not provide much more information than an experienced clinician s estimate (Counsell and Dennis 2001 Counsell et al. 2002). 

LACI, lacunar infarct TACI, total anterior circulation infarct PACI, partial anterior circulation infara POCI, posterior circulation infarct Dep, functionally dependent (Rankin 3-5) Indep, functionally independent (Rankin 0-2). Source From Bamford et al. (1991),... 

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