Artery posterior cerebral

With modern multislice scanners and optimized protocols," CTA images can provide excellent visualization of the primary intracranial arteries (i.e., the proximal anterior, middle, and posterior cerebral arteries), their smaller secondary... 

Cardioembolism Cardioembolism accounts for approximately 30% of all stroke and 25-30% of strokes in the young (age <45 years)." AF accounts for a large proportion of these strokes (15-25%). Symptoms may be suggestive, but they are not diagnostic. Repetitive, stereotyped, transient ischemic attacks (TIAs) are unusual in embolic stroke. The classic presentation for cardioembolism is the sudden onset of maximal symptoms. The size of the embolic material determines, in part, the course of the embolic material. Small emboli can cause retinal ischemic or lacunar symptoms. Posterior cerebral artery territory infarcts, in particular, are often due to cardiac embolism. This predilection is not completely consistent across the various cardiac structural abnormalities that predispose to stroke, and may be due to patterns of blood flow associated with specific cardiac pathologies. 

Brandt T, Steinke W, Thie A et al (2000) Posterior cerebral artery territory infarcts clinical features, infarct topography, causes and outcome 1. Cerebrovasc Dis 10 170-182 Braun M, Chech V, Boscheri A et al (2004) Transcatheter closure of patent foramen ovale (PFO) in patients with paradoxical embolism. Periprocedural safety and mid-term follow-up results of three different device occluder systems. Eur Heart J 25 424-430... 

Chambers BR, Brooder RJ, Donnan GA (1991) Proximal posterior cerebral artery occlusion simulating middle cerebral artery occlusion. Neurology 41 385-390... 

Small hypophyseal and meningeal branches of the ICA are not visible in MR angiographies. The first originating vessel is the ophthalmic artery from the C3 segment. Distally the posterior communicating artery and subsequently the anterior choroidal artery arise from the ICA. A direct origin of the posterior cerebral artery from the ICA is referred to as embryonic type. 

WM lesions are rated separately in four WM areas periventricular, deep, watershed, and subcortical WM. By definition, periventricular WM foci have to be in contact with the ventricular wall, deep WM foci separated from the ventricles by a strip of normal-appearing WM and located outside watershed regions. Watershed regions are the areas located between the territories of two of the main cerebral arteries, like middle cerebral artery and anterior cerebral artery or middle cerebral artery and posterior cerebral artery. The subcortical... 

These include infarcts in the territory of (1) the deep perforators of the MCA, anterior cerebral artery (ACA) and posterior cerebral artery (PCA), posterior communicating artery (PcomA), the lenticulo-striate arteries and the anterior choroidal artery (2) the superficial perforators (white matter medullary branches) of the superficial pial arteries (3) border-zone or junctional infarcts between 1 and 2 (4) combined infarcts. Small (< 1.5 mm infarcts - lacunes) are usually caused by single perforator disease while larger infarcts have a more diverse pathophysiology including embolism and MCA stenosis (Bang et al. 2002). 

Fig. 14.2. Complete right posterior cerebral artery (PCA) territorial infarct.Notice the anterolateral mesencephalic and the inferolateral thalamic infarcts. Old left striatocapsular infarct...

The mesencephalon has four arterial territories anteromedial (paramedian branches of the basilar artery anterolateral (branches from the P2 segment of the PCA) lateral (branches from P2 segment of PCA and from posterior choroidal arteries) and dorsal (branches from PI segment of PCA and superior cerebellar artery). Isolated mesencephalic infarcts are rare because the arteries supplying blood to the mesencephalon (basilar artery, posterior cerebral artery and superior cerebellar artery)... 

Cerebellar infarcts can be grouped in territorial (superior cerebellar artery, anterior inferior cerebellar artery, posterior inferior cerebellar artery and combined), borderzone and lacunar. They are often combined with brain stem infarcts and with superficial posterior cerebral artery or thalamic infarcts. The most common isolated cerebellar infarcts are located in the superior cerebellar artery and posterior inferior cerebellar artery territories (Amarenco 1993 Amarenco et al. 1993,1994). 

Fig. 4.1. The anatomy of the arterial circulation to the brain and eye. Gray indentations into the arterial lumen represent sites at which atherothrombosis is particularly common. ACA, anterior cerebral artery EGA, external carotid artery ICA, internal carotid artery MCA, middle cerebral artery PCA, posterior cerebral artery.

The posterior communicating artery is the next artery to arise from the internal carotid artery and passes back to join the first part of the posterior cerebral artery, so contributing to the circle of WiUis. Tiny branches supply the adjacent optic chiasm, optic tract, hypothalamus, thalamus and midbrain. 

The basilar artery ascends ventral to the pons to the ponto-midbrain junction in the interpeduncular cistern, where it divides into the two posterior cerebral arteries. Numerous small branches penetrate the brainstem and cerebellum. The basilar artery also gives rise to the anterior inferior cerebellar artery, which supplies the rostral cerebellum, brainstem, inner ear, and the superior cerebellar artery, which supplies the brainstem, superior half of the cerebellar hemisphere, vermis and dentate nucleus. 

The posterior cerebral artery encircles the midbrain close to the oculomotor nerve at the level of the tentorium and supplies the inferior part of the temporal lobe, and the occipital lobe (Marinkovic et al. 1987). Many small perforating arteries arise from the proximal portion of the posterior cerebral artery to supply the midbrain, thalamus, hypothalamus and geniculate bodies. Sometimes a single perforating artery supplies the medial part of each thalamus, or both sides of the midbrain. In approximately 15% of individuals, the posterior cerebral artery is a direct continuation of the posterior commrmicating artery, its main blood supply then coming from the internal carotid artery rather than the basilar artery. 

The circle of Willis. This is formed by the proximal part of the two anterior cerebral arteries connected by the anterior communicating artery, and the proximal part of the two posterior cerebral arteries, which are connected to the distal internal carotid arteries by the posterior communicating arteries. However, approximately 50% of circles have one or more hypoplastic or absent segments, usually one of the communicating arteries, and atheroma may limit the potential for collateral flow (Fig. 4.2). 

Leptomeningeal anastomoses. These may develop on the surface of the brain between cortical branches of the anterior, middle and posterior cerebral arteries and, to a lesser extent, between pial branches of the cerebellar arteries. 

Around the orbit. Branches of the external carotid artery can anastomose with branches of the ophthalmic artery if the internal carotid artery is severely stenosed or obstructed. Collateral flow from the external carotid artery into the orbit then passes retrogradely through the ophthalmic artery to fill the carotid siphon, middle cerebral artery and anterior cerebral artery. Sometimes flow may even reach the posterior cerebral artery and vertebrobasilar system. 

The anterior choroidal artery. This branch of the internal carotid artery can anastomose with the posterior choroidal artery, a branch of the posterior cerebral artery. 

Fig. 5.1. Brain CT images showing a large hypodense (arrows) edematous cerebral infarct in the distribution of the middle cerebral artery, with midline shift. Such large infarcts cause herniation of the cingulate gyrus under the falx cerebri of the ispsilateral uncus under the tentorium to compress the oculomotor nerve, posterior cerebral artery and brainstem and of the contralateral cerebral peduncle to cause ipsilateral hemiparesis.

The presence of cranial neuropathy may result in a misdiagnosis of brainstem stroke. Cranial nerve palsies may result from local pressure from the false internal carotid artery lumen, thromboembolism or hemodynamic compromise to the blood supply of the nerve. Cranial nerve III receives its blood supply from the ophthalmic artery, branches of the internal carotid or the posterior cerebral artery and, consequently, may rarely become ischemic after carotid dissection. 

Small thalamic lesions may cause a pure sensory stroke or sensorimotor stroke, sometimes with ataxia in the same limbs (Schmahmann 2003). However, other deficits may occur in isolation, or in combination depending on which thalamic nuclei are involved. These include paralysis of upward gaze, small pupils, apathy, depressed consciousness, hypersomnolence, disorientation, visual hallucinations, aphasia and impairment of verbal memory attributable to the left thalamus, and visuospatial dysfunction attributable to the right thalamus. Occlusion of a single small branch of the proximal posterior cerebral artery can cause bilateral paramedian thalamic infarction with severe retrograde and anterograde amnesia. 

Diffusion-weighted MRI showing two areas of acute infarction in the left parietal and occipital regions, (b) Magnetic resonance angiography shows aberrant arterial anatomy with the posterior cerebral artery arising directly from the internal carotid artery (arrow) (c) This was confirmed on catheter angiography. 

The cerebral hemispheres and diencephalon receive blood from the anterior and posterior circulations (Figure 3.5). The cerebral cortex receives its blood supply from the three cerebral arteries the anterior and middle cerebral arteries, which are part of the anterior circulation, and the posterior cerebral artery, which is part of the posterior circulation. The diencephalon, basal gan-... 

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