THE THALAMOGENICULATE PERFORATORS OF THE POSTERIOR CEREBRAL-ARTERY - THE MICROSURGICAL ANATOMY

The thalamogeniculate (TG) arteries of 30 forebrain hemispheres were examined. These vessels varied from 2 to 12 in number (mean, 5.7), and from 70 to 580-mu-m in caliber (mean, 345.8-mu-m). The average caliber of all the TG vessels per posterior cerebral artery ranged from 700 to 3400-mu-m (mean, 1972-mu-m). The TG arteries most often originated as individual vessels; however, in 26.67% of the hemispheres examined they shared a common site of origin, and 33.33% of the hemispheres they arose from common stems. The common stems ranged from 320 to 800-mu-m in diameter (mean, 583-mu-m). The TG branches arose from the crural or ambient (P2) segment of the posterior cerebral artery in 80% of the hemispheres, from the P2 and the quadrigeminal (P3) segment in 20%, from both the distal segment of the posterior cerebral artery and the common temporal artery (13.33%), or from the distal segment and either the calcarine (3.33%) or parieto-occipital artery (3.33%). The TG arteries usually penetrated the medial geniculate body (100%), pulvinar thalami (80%), brachium of the superior colliculus (53.33%), or lateral geniculate body (13.33%). The collateral branches of the TG arteries were noted to reach the medial geniculate body (76.67%), pulvinar (70%), brachium of the superior colliculus (40%), crus cerebri (40%), and lateral geniculate body (6.67%). The anastomoses were present in 66.67%, usually between the TG vessels and the medial posterior choroidal artery (33.33%), or the mesencephalothalamic artery (26.67%). They ranged in number from 1 to 3 (mean, 1.2), and in caliber from 90 to 400-mu-m (mean, 197-mu-m). In spite of the anastomoses, the TG arteries must be spared during surgery within the ambient cistern.