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Topic

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Posterior cerebral artery (P4 Segment)

The P4 segment of the posterior cerebral artery (PCA) represents the cortical branches that supply the occipital lobe and portions of the inferior temporal lobe. These branches arise distal to the calcarine artery and parieto-occipital artery, extending across the medial and inferior occipital surfaces. The P4 segment is responsible for primary visual cortex perfusion, making it vital for vision. It forms collateral anastomoses with branches of the middle cerebral artery (MCA) and anterior cerebral artery (ACA), contributing to cortical circulation in the posterior brain.

Synonyms

  • Cortical branches of PCA

  • Distal PCA segment

  • PCA P4 cortical distribution

Function

  • Provides arterial supply to the visual cortex (calcarine cortex) in the occipital lobe

  • Perfuses the inferior temporal lobe and posterior parietal-occipital cortex

  • Maintains blood flow for visual processing, object recognition, and visuospatial integration

  • Contributes to collateral circulation with MCA and ACA territories

MRI Appearance

T1-weighted images (non-contrast):

  • P4 branches appear as linear flow voids along the medial and inferior occipital sulci

  • Vessel lumen not well visualized without angiographic sequences

T2-weighted images:

  • Arteries demonstrate flow voids (black signal) against surrounding brain tissue

  • Adjacent hyperintensity in cortex may suggest ischemia or infarction in PCA territory

MRA (Magnetic Resonance Angiography):

  • TOF (time-of-flight) or contrast-enhanced MRA shows distal cortical branches of the PCA extending across occipital sulci

  • Normal arteries appear as bright, enhancing linear vessels

  • MRA is excellent for detecting distal PCA stenosis, occlusion, aneurysm, or AVMs

T1 Post-Contrast (Gadolinium-enhanced MRI):

  • P4 branches demonstrate intense vascular enhancement

  • Useful in combination with MRA for evaluating fine cortical branches or collateral flow

CT Appearance

Non-contrast CT:

  • Arteries are not directly seen

  • Acute PCA thrombosis may appear as a hyperdense artery sign in the calcarine or parieto-occipital sulci

  • Infarctions in P4 distribution show low-density cortical/subcortical changes in the occipital lobe

CT Angiography (CTA):

  • Clearly demonstrates P4 cortical branches and their distribution to the occipital and inferior temporal lobes

  • Contrast opacifies the lumen, allowing evaluation of stenosis, occlusion, aneurysms, or AVMs

  • CTA is a key tool for stroke mapping and preoperative planning in posterior circulation

MRI images

Posterior cerebral artery (P4 Segment) 1

MRI images

Posterior cerebral artery (P4 Segment)