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  • By Author: Rhoton, Albert L. x
  • By Author: Gibo, Hirohiko x
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Hirohiko Gibo, Carla Lenkey and Albert L. Rhoton Jr.

✓ The microsurgical anatomy of the supraclinoid portion of the internal carotid artery (ICA) was studied in 50 adult cadaver cerebral hemispheres using × 3 to × 40 magnification. The ICA was divided into four parts: the C1 or cervical portion; the C2 or petrous portion; the C3 or cavernous portion; and the C4 or supraclinoid portion. The C4 portion was divided into three segments based on the origin of its major branches: the ophthalmic segment extended from the origin of the ophthalmic artery to the origin of the posterior communicating artery (PCoA); the communicating segment extended from the origin of the PCoA to the origin of the anterior choroidal artery (AChA); and the choroidal segment extended from the origin of the AChA to the bifurcation of the carotid artery. Each segment gave off a series of perforating branches with a relatively constant site of termination. The perforating branches arising from the ophthalmic segment passed to the optic nerve and chiasm, infundibulum, and the floor of the third ventricle. The perforating branches arising from the communicating segment passed to the optic tract and the floor of the third ventricle. The perforating branches arising from the choroidal segment passed upward and entered the brain through the anterior perforated substance. The anatomy of the ophthalmic, posterior communicating, anterior choroidal, and superior hypophyseal branches of the C4 portion was also examined.

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Hirohiko Gibo, Christopher C. Carver, Albert L. Rhoton Jr., Carla Lenkey and Robert J. Mitchell

✓ The microsurgical anatomy of the middle cerebral artery (MCA) was defined in 50 cerebral hemispheres. The MCA was divided into four segments: the M1 (sphenoidal) segment coursed posterior and parallel to the sphenoid ridge; the M2 (insular) segment lay on the insula; the M3 (opercular) segment coursed over the frontoparietal and temporal opercula; and the M4 (cortical) segment spread over the cortical surface. The Sylvian fissure was divided into a sphenoidal and an operculoinsular compartment. The M1 segment coursed in the sphenoidal compartment, and the M2 and M3 segments coursed in the operculoinsular compartment. The main trunk of the MCA divided in one of three ways: bifurcation (78% of hemispheres), trifurcation (12%), or division into multiple trunks (10%). The MCA's that bifurcated were divided into three groups: equal bifurcation (18%), inferior trunk dominant (32%), or superior trunk dominant (28%). The MCA territory was divided into 12 areas: orbitofrontal, prefrontal, precentral, central, anterior parietal, posterior parietal, angular, temporo-occipital, posterior temporal, middle temporal, anterior temporal, and temporopolar. The smallest cortical arteries arose at the anterior end and the largest one at the posterior end of the Sylvian fissure. The largest cortical arteries supplied the temporo-occipital and angular areas. The relationship of each of the cortical arteries to a number of external landmarks was reviewed in detail.