Artery posterior communicating

Historically, the French neurologist Charles Foix in 1923 first described the syndrome of infarction in the PCA territory as a thalamocapsular deficit (Foix and Masson 1923). The PCAs arise from the BA, but about 30% of patients have a hypo- or aplastic PI segment with the PCA nourished by the ICA through the posterior communicating artery (Margolis et al. 1971). 

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. 

The posterior communicating artery offers significant variations in size and is often not sufficiently visible in MRA. If it is utilized for a collateral circulation, it can increase in signal and size, but lacking detection in MR angiography in patients with proximal stenosis does not permit an assessment of the lack of collateral flow (Hartkamp et al. 1999 Hoksbergen et al. 2003). 

Fig. 5.29a,b. Giant aneurysm of the posterior communicating artery in an infant. Due to recirculating blood, there is marked spin saturation within the aneurysm on unenhanced TOF-MRA (a). The entire aneurysm is visualized after contrast enhancement (b)... 

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). 

Jongen JCF, Franke CL, Ramos LMP et al (2004) Direction of flow in posterior communicating artery on magnetic resonance angiography in patients with occipital lobe infarcts. Stroke 35 104-108... 

Hendrikse and coworkers (2001) investigated whether the presence of borderzone infarcts is related to the collateral ability of the CW in symptomatic and asymptomatic patients with unilateral occlusion of the ICA. They found that in patients with unilateral ICA occlusion, the presence of collateral flow via the posterior communicating artery in the circle of Willis is associated with a low prevalence of borderzone infarcts and that asymptomatic patients with an ICA occlusion do not have an increased collateral function of the CW. Figure 15.10 shows the four patterns of collateral flow via the CW to the hemisphere ipsilateral to the ICA occlusion. 

Fig. 15.10. The four patterns of collateral flow via the circle of Willis to the hemisphere ipsilateral to the ICA occlusion. A1 segment indicates A1 segment of ipsilateral ACA, PcomA indicates posterior communicating artery...

Fig. 15.12. An asymptomatic 54-year-old patient suffering from left internal carotid artery occlusion (left) shows excellent collateralization via the posterior communicating artery and a sufficient filling of the ipsilateral middle cerebral artery (middle). As a consequence, perfusion MRI (time-to-peak) detects only a slight asymmetry and delay of contrast agent arrival in the parietal parts of the middle cerebral artery territory (right)...

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 anterior choroidal artery arises from the last section of the internal carotid artery, just beyond the posterior communicating artery origin, and supplies the optic tract, internal capsule, medial parts of the basal ganglia, the medial part of the temporal lobe, thalamus, lateral geniculate body, proximal optic radiation and midbrain. Occasionally it arises from the proximal middle cerebral artery or posterior communicating artery. Minor twiglets... 

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). 

Fig. 12.5. A "time of flight" MR angiogram of the circle of Willis in a patient with no posterior communicating arteries.

Intracranial aneurysms are not congenital but develop over the course of life. Approximately 10% of aneurysms are familial, and candidate genes identified thus far include those coding for the extracellular matrix. Saccular aneurysms tend to occur at branching points on the circle of Willis and proximal cerebral arteries approximately 40% on the anterior communicating artery complex, 30% on the posterior communicating artery or distal internal carotid artery, 20% on the middle cerebral artery and 10% in the posterior... 

Unruptured aneurysms not associated with SAH should normally be clipped or coiled if they are symptomatic, for instance if there is a third nerve palsy caused by a posterior communicating artery aneurysm (Fig. 30.2) (Raps et al. 1993). The optimal management of incidental unruptured asymptomatic aneurysms is unclear because the risk of rupture is... 

Posterior communicating artery Posterior cerebral artery... 

Middle cerebral artery Posterior communicating artery... 

Fig. 1.6 Cross-section illustrating the distribution of blood to the walls of the midbrain. The tectum is supplied by branches of the superior cerebellar artery. The medial aspects of the peduncular and tegmental regions are vascularized by branches of the basUar artery. The lateral peduncular and tegmental regions are supplied by branches of the posterior communicating artery. Note that these small arteries, which enter the walls of the central nervous system from the periphery, are functional end arteries and do not anastomose with adjacent arteries (See also Color Insert)...

Most arterial aneurysms arise at the bifurcation of major arteries, and this is also true for the intracranial location. Around 85% of all intracranial aneurysms originate from the anterior circulation. The most common location (30%-35%) is the anterior communicating artery (Acorn). However, many of these so-called Acorn aneurysms do have their origin at the A1/A2 junction of the anterior cerebral artery and do not involve the anterior communicating artery. Internal carotid and posterior communicating artery aneurysms account for 30% and middle cerebral artery (MCA) bifurcation aneurysms for 20%. Around 15% of intracranial aneurysms arise at the vertebrobasilar circulation. Half of them develop at the basilar tip (with various degrees of involvement of the PI segments) and the other 50% from other posterior fossa vessels. Aneurysms of the anterior inferior cerebellar artery (AICA) and vertebral artery (VA) aneurysms without involvement of the VA-PICA junction or the vertebrobasilar site are extremely rare. 

Aneurysms of the internal carotid artery account for about 30%-40% of all intracranial aneurysms. Therefore, the ICA is the most frequent aneurysm bearing artery. In descending frequency ICA aneurysms do occur at the following sites posterior communicating artery (52%), termination of ICA... 

The majority of posterior communicating artery (Pcom) aneurysms arise from the ICA at the origin of the Pcom. True Pcom aneurysms are rare and might be more difficult to catheterize. About 30%-40% of... 

Perneczky A, Czech T (1984) Prognosis of oculomotor palsy following subarachnoid hemorrhage due to aneurysms of the posterior communicating artery. Zentralbl Neurochir 45 189-195... 

The anatomic substrate of potential collateral pathways (particularly involving the circle of Willis) must also be assessed, which requires angiographic study of the intracranial circulation from selective carotid and vertebral injections. Prospective identification of major breaks within the circle of Willis that result in partial or complete isolation of the cerebral circulation [e.g. ipsilateral absent Al segment and posterior communicating artery (PCoA)], is often enough to dissuade one from performing a balloon test... 

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