Abstract
The adjectives dorsal and ventral, are traditionally never put on the intracranial structures, the intracranial arteries in particular, except for the thalamic and hypothalamic nuclei. The thalamus which originally meant a room or space was used by Galen to indicate the anterior portion of the lateral ventricle from where animal spirit flew into the optic nerve. He named what we now call thalamus“glutia or nates (buttocks)”because of the morphological similarity. In the medieval era, the lateral ventricles were found to have nothing to do with the optic nerves and the name “thalamus” was then given to the nates of Galen. This is the reason why the superior or superficial part of the thalamus is expressed as “dorsal” and the inferior part is referred to as “ventral”. This naming is not applicable to the intracranial arteries. Kobayashi and his collaborators coined the term “internal carotid (IC) dorsal wall aneurysms” or IC-dorsal aneurysms which actually were located on the anterior wall of IC; subsequently Nutik called aneurysms arising from the posterior wall of IC nearby the anterior clinoid process “ventral paraclinoid aneurysms”. These names are very confusing. They also coined the term “carotid cave aneurysms”. The carotid cave or the clinoid space is a space between the dural ring (distal ring) and the proximal ring or more exactly a space surrounding the genu (C3) portion of the internal carotid, covered superiorly by the superficial layer of the dura of the anterior clinoid process and inferiorly by the deep layer of the anterior clinoid dura and its continuation “carotico-oculomotor” membrane. Intracranial aneurysms are classified according to the location where their necks arise, such as IC-posterior communicating aneurysms, IC-superior hypophyseal aneurysms etc. Most of carotid cave aneurysms are arising from the C3 portion of IC and growing into the carotid cave, therefore they should be called “aneurysms of the IC C3” or “clinoid segment aneurysms”. If we want to stress aneurysmal neck being located nearby the dural ring (distal ring) so that clipping of the aneurysms needs removal of the anterior clinoid process, incision of the dural ring or unroofing of the optic canal, such aneurysms may be called “juxta-clinoid aneurysms” including IC-C3 aneurysms, IC-ophthalmic aneurysms, IC-superior hypophyseal aneurysms, IC-C2 anterior wall aneurysms, IC-C2 posterior wall aneurysms and some aneurysms arising from the intracavernous (C4) portion of IC. (Original angiographical naming of sections of IC by Fischer (1938) is modified anatomically by Fukushima (1995) as follows: C1 IC bifurcation to the posterior communicating artery; C2, the posterior communicating artery to the dural ring; C3, the dural ring to the carotico-oculomotor membrane; C4, the carotico-oculomotor membrance to the meningohypophyseal trunk; C5, the meningohypophyseal trunk to the foramen lacerum)
