The PICA is divided into five segments: the anterior medullary segment along the front of the medulla the lateral medullary segment, which courses beside the medulla and extends to the origin of the glossopharyngeal, vagal, and accessory nerves the tonsillomedullary segment, which courses around the caudal half of the cerebellar tonsil the telovelotonsillar segment, which courses in the cleft between the tela choroidea and the inferior medullary velum rostrally and the superior pole of the cerebellar tonsil caudally and finally, its cortical segment, with its course over the cerebellar surface. In exceedingly rare cases, there have also been reports of the PICA originating from the trigeminal artery. Knowledge of the anatomic distribution of. Possible variations include the C3 origin from the vertebral artery (VA) or the ascending cervical artery the C2 and C1 origins from the occipital artery via the embryonic proatlantal arteries (occipito-cerebellar variant) the ascending pharyngeal artery via the embryonic hypoglossal artery (pharyngo-cerebellar variant) and origin from various meningeal branches through the artery of the falx cerebelli. of the PICA: anterior medullary, lateral medullary, tonsillomedullary, telovelotonsillar, and the cortical segments. Like other structures in the central nervous system, the cerebellum consists of grey matter and white matter: Grey matter located on the surface of the cerebellum. The reported is study aimed at a critical review of the overall results of a personal series of PICA aneurysms, treated by the senior author, R. The complex anatomy of PICA and its intimate relationships with medulla, lower cranial nerves, and jugular tubercle makes the surgical treatment of these aneurysms fascinating. The variations of the PICA origin follow the metameric arrangement also seen at the spinal cord level. Anatomical Structure and Divisions The cerebellum consists of two hemispheres which are connected by the vermis, a narrow midline area. Aneurysms of the posterior inferior cerebellar artery (PICA) are uncommon. The proximal PICA is the equivalent of a radiculopial artery that enlarged because of its annexed cerebellar territory via the primitive choroidal plexus of the fourth ventricle. Variations that occur are due to the embryologic development of these vessels 3, 4. The PICA is the cerebellar artery with the most variations, which may range from unilateral or bilateral absence to being duplicated with different possible origins. Two vessels with known anatomical variations are the posterior inferior cerebellar artery (PICA) and the anterior cerebral artery (ACA). Posterior inferior cerebellar artery (PICA) origin of a trigeminal artery. The authors describe the microsurgical anatomy of the posterior inferior cerebellar artery (PICA) with an extradural origin and discuss its importance as a common variation. According to the results of Lister ct al. Knowledge of the functional arterial anatomy of the cerebral arteries is important to recognize and understand some of the frequent important anatomical variants and to avoid unexpected technical complications in the endovascular neuroradiological practice. The remainder of the intracranial arteries is unremarkable. The PICA has close anatomical rela tions to the roots of the cranial nerves in the brain stem. 18.1 Right ICA angiogram in lateral view in early (a) and late (b) arterial phases and 3D reconstruction (c) reveal a persistent trigeminal artery on the right side supplying the right PICA ( arrows).
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