surface of the occipital lobe Parieto-occipital sulcus, to the cuneus and the precuneus Splenial, or the posterior pericallosal branch, sometimes anastomoses with the anterior cerebral artery (ACA), and may not be present if the ACA wraps around the corpus callosum Development The prenatal development of the posterior cerebral arteries in the fetus comes relatively late and arises from the fusion of several embryonic vessels near the caudal ends of the posterior communicating arteries supplying the mesencephalon and diencephalon. The PCA begins as such, as a continuation of the PCommA in the fetus with only 10–30% of fetuses having a prominent basilar origin. The fetal carotid origin of the PCA usually regresses as the vertebral and basilar arteries develop with the PCommA reducing is size. In most adults, the PCA sources from the anterior portion of the basilar artery. Only about 19% of adults retain PCommA dominance of the PCA with 72% having dominant basilar origin, and the rest having either equal prominence between PCommA and basilar artery, or a single exclusive source. Clinical significance Stroke Contralateral loss of pain and temperature sensations. Visual field defects (contralateral hemianopsia with macular sparing). Prosopagnosia with bilateral obstruction of the lingual and fusiform gyri. Superior Alternating Syndrome (Weber's syndrome) Ipsilateral deficits of oculomotor nerve, Contralateral deficits of facial nerve (only lower face, upper face receives bilateral input), vagus nerve and hypoglossal nerve Horner's Syndrome Signs and symptoms: Structures involved Peripheral territory (Cortical branches) Homonymous hemianopsia (often upper quadrantic): Calcarine cortex or optic radiation nearby. Bilateral homonymous hemianopsia, cortical blindness, awareness or denial of blindness; tactile naming, achromatopia (color blindness), failure to see to-and-fro movements, inability to perceive objects not centrally located, apraxia of ocular movements, inability to count or enumerate objects, tendency to run into things that the patient sees and tries to avoid: Bilateral occipital lobe with possibly the parietal lobe involved. Verbal dyslexia without agraphia, color anomia: Dominant calcarine lesion and posterior part of corpus callosum. Memory defect: Hippocampal lesion bilaterally or on the dominant side only. Topographic disorientation and prosopagnosia: Usually with lesions of nondominant, calcarine, and lingual gyrus. Simultanagnosia, hemivisual neglect: Dominant visual cortex, contralateral hemisphere. Unformed visual hallucinations, peduncular hallucinosis, metamorphopsia, teleopsia, illusory visual spread, palinopsia, distortion of outlines, central photophobia: Calcarine cortex. Complex hallucinations: Usually nondominant hemisphere. Central territory (Ganglionic branches) Thalamic syndrome: sensory loss (all modalities), spontaneous pain and dysesthesias, choreoathetosis, intention tremor, spasms of hand, mild