Hirohiko Gibo

The surgical anatomy of the perforating branches of the anterior choroidal artery.

BACKGROUND The available information about certain microanatomic features of the AChA perforators is incomplete. Precise knowledge of these vessels is necessary to understand the consequences of their occlusion and to safely operate in their region. METHODS The AChA perforators were microdissected and examined under the stereoscopic microscope in 10 vascular casts and in 20 hemispheres injected with india ink or radiopaque substance. RESULTS The perforating branches ranged in number from 2 to 9 (mean, 4.6) and in diameter between 90 microm and 600 microm (mean, 317 microm). The most proximal perforator arose 3.2 mm on average caudal to the AChA origin. The most distal (capsulothalamic) perforator varied in size from 200 microm to 610 microm (mean, 431 microm). One or more of the perforators always originated from the AChA (100%), but some of them also from the uncal (33.3%) or parahippocampal branch (10%) of the AChA, either as individual vessels only (70%) or from common trunks (30%). The perforators gave off the peduncular (20%), optic (23.3%), or uncal side branches (26.7%). CONCLUSIONS Our findings concerning the origin, position, number, size, branching, penetration site, and relationships of the AChA perforators gave the anatomic basis for safe operations in patients with AChA aneurysms or mediobasal limbic epilepsy.

Anatomy of the cavernous sinus region

The cavernous region was examined in 20 fetuses, injected with Micropaque, and in 5 adults. The lateral wall of the cavernous region in fetuses was noticed to have four layers. The superficial membrane represents the dural sheath. The second membrane of dense connective tissue involves the trochlear nerve. The third layer, formed by loose connective tissue, involves the oculomotor nerve, and the ophthalmic and maxillary division. The fourth layer, which represents the lateral wall of the cavernous sinus, involves the abducent nerve. The meningohypophyseal trunk can be complete or incomplete. The inferolateral trunk and its branches were found to supply the cavernous portions of the mentioned cranial nerves. The obtained data make the anatomic basis for neurosurgical operations in the cavernous region.

Microsurgical anatomy of the perforating branches of the vertebral artery.

BACKGROUND There is limited data in the literature related to the microanatomic features of the perforating branches of the vertebral artery. METHODS The 44 vertebral arteries and their branches were injected with india ink or a radiopaque substance and examined under the stereoscopic microscope. RESULTS The perforating arteries were noted to range in number from 1 to 11 (mean, 6.5) and in diameter between 100 microm and 520 microm (average, 243 microm). They arose from the vertebral artery (VA) (54.54%), 8 from the right, the left or both VAs. The anterior spinal artery (ASA), which was singular (81.82%), duplicated (13.64%), or plexiform (4.55%), always gave rise to the perforators. The vascular roots of the ASA were the source of the perforators in 95.45% of the brains. The latter vessels arose from the anterolateral arteries in 50% of the cases. The anastomoses involving the perforators, which were present in 40.91% of the brains, varied in diameter between 100 microm and 350 microm (mean, 169 microm). The perforating vessels gave rise to the side branches in 95.45% of the brains that varied in diameter from 100 microm to 300 microm (average, 161 microm). The perforators usually entered the foramen cecum and the anterior median sulcus, and then continued close and parallel to the raphe of the medulla. The perforators can be compressed by a VA aneurysm, which was found in one among the 71 examined patients with cerebral aneurysms. CONCLUSIONS The obtained data give additional information about the vascular anatomy of the pontomedullary region.

The microsurgical anatomy of the premamillary artery.

The 50 premamillary arteries (PremA), arising from 39 posterior communicating arteries (PCoA), were examined in injected human brains. The PremA, which commonly was single (71.8%) and less frequently double (28.2%), more often arose from the PCoA (97.4% ) than from the posterior cerebralartery (PCA) (2.6%). The PremA ranged between 280 and 780 microm in diameter. It gave off side branches to the hypothalamus (23.1%), optic tract (10.2%), mamillary body (17.9%) and the crus cerebri (35.9%). The anastomoses involving the extracerebral segment of the PremA were present in 35.9% of the cases. They varied in caliber from 50 to 230 microm. The intracerebral segment of the PremA ranged from 280 to 490 microm in diameter. Our study gives a precise anatomic basis for safer operations on the aneurysms of the posterior communicating artery and adjacent vessels.

Microsurgical anatomy of the ophthalmic artery and the distal dural ring for the juxta–dural ring aneurysms via the pterional approach

Abstract Microsurgical anatomy for the pterional approach was studied regarding the origin and the course of the ophthalmic artery and the distal dural ring using human cadaveric specimens, with special reference to the surrounding bony structures. In 50 human adult formalin-fixed cadaveric cerebral hemispheres and 10 block specimens of the skull base region including the ophthalmic artery and the carotid dural ring were examined under magnification using an operating microscope. The ophthalmic artery originated from the intradural portion of the internal carotid artery (ICA), except in 5% where the ophthalmic artery originated extradurally. The extradural origin had two patterns: one was that the ophthalmic artery penetrated the bony optic strut (trans-optic strut pattern) and the other was that it coursed into the optic canal proximally to the optic strut without bone penetration (supra-optic strut pattern). The origin of the intradural ophthalmic artery was commonly located at the medial third of the superior wall of the ICA (78%). The ophthalmic artery was commonly taking an S-shaped course in the intradural portion and entered the optic canal over the optic strut. The distal dural ring was tightly adherent to the internal carotid artery; circumferential sectioning of the dural ring is required to mobilize the internal carotid artery. When approaching juxta– dural ring ICA aneurysms via the pterional route, it is important to recognize the extradural origin, especially the trans-optic strut type, and to precisely understand the microsurgical anatomy around the dural ring.

The blood supply of the hypoglossal nerve: The microsurgical anatomy of its cisternal segment

BACKGROUND While the characteristics of the vasculature of the second (intracanalicular) segment of the hypoglossal nerve are well known, the vascularization of the first (cisternal) segment of this nerve has not been examined so far. Many pathologic processes and malformations can be located in the premedullary cistern, which may affect the vasculature of the cisternal segment. Consequently, we decided to examine the blood supply of the cisternal segment. METHODS The anatomic features of the cisternal segment and its vasculature were examined in 15 hypoglossal nerves after injection of india ink and gelatin into the vertebrobasilar arterial system. RESULTS The cisternal segment was noted to consist of 3-15 long roots, which usually formed two trunks of the hypoglossal nerve. The roots of each nerve received blood from the anterolateral and the lateral medullary arteries, which ranged from 3 to 5 in number and between 100 microns and 500 microns in caliber. These arteries may arise from the perforating branches or the pontomedullary branch of the basilar artery; the vertebral artery or its perforators; the anterior spinal artery or its vascular roots; the posterior spinal artery; and the posterior inferior cerebellar artery. The main hypoglossal arteries, which ranged in diameter from 20 microns to 80 microns, always coursed along the dorsal surface of the roots of the hypoglossal nerve. CONCLUSIONS The cisternal segment of the hypoglossal nerve was always vascularized by several vessels, which mainly originated from the vertebral artery and its branches. This observation was discussed from the neurosurgical point of view.

Ultrastructure and immunohistochemistry of the trigeminal peripheral myelinated axons in patients with neuralgia

OBJECTIVE Detailed ultrastructural and immunohistochemical examination of the trigeminal axons surrounded by the peripheral type of the myelin could add new information about the extent of the trigeminal nerve lesion in neuralgia. PATIENTS, MATERIALS AND METHODS The examination comprised, firstly, the 10 trigeminal nerve roots (TNRs) in which the neurovascular contact was found in 20% of the cases, and the 2 additional control TNRs. Secondly, the biopsy specimens were taken from 6 patients with trigeminal neuralgia and 2 patients with trigeminal neuropathy following a partial TNR rhizotomy. The specimens were examined under the electron microscope (EM) and/or using the immunohistochemical (IHC) methods. RESULTS In addition to the central zone of demyelination, the EM examination of the TNR also revealed alterations of the peripheral myelin, i.e. deformation, thickening, demyelination and remyelination, as well as changes of the peripheral axons, that is, atrophy or hypertrophy, neurofilaments increase, loss of the myelin and sprouting occasionally. Some Schwann cells were also damaged. The IHC examination usually showed a moderate immune reaction against neuron-specific enolase (NSE) and protein gene product 9.5 (PGP9.5), but sporadically weaker reaction against the S-100 protein, synaptophysin (SY), neurofilament protein (NFP) and glial fibrillary acidic protein (GFAP). The substance P (SP) and calcitonin gene-related peptide (CGRP) immunoreactivity was weak at some sites, but strong at some other places. CONCLUSIONS The pathological changes affect not only the central nerve fibers of the TNR, but also some of the peripheral axons, their myelin sheath and Schwann cells. These are signs of the retrograde ultrastructural and biochemical alterations, which could participate in the pathophysiological mechanism underlying the trigeminal neuralgia.

The Trigeminal Vasculature Pathology in Patients With Neuralgia

Objective.—To examine the possible pathological changes of the trigeminal vasculature in patients with neuralgia.

Microanatomy of the Intrachoroidal Vasculature of the Lateral Ventricle

OBJECTIVE: Intraventricular surgery requires a detailed knowledge of the microanatomy of the choroid plexus vasculature. METHODS: Twenty choroid plexuses were microdissected, and two additional plexuses were prepared for microscopic examination. RESULTS: The choroid plexus was perfused primarily by the anterior choroidal artery (AChA) and the lateral posterior choroidal artery (LPChA). The AChA, which averaged 650 &mgr;m in diameter, most often (in 75% of cases) divided into the medial and lateral trunks, which averaged 450 &mgr;m in diameter. The medial trunk gave off the bush-like intrachoroidal branches, whereas the lateral trunk divided into the parallel arteries. The inferior LPChA was present in 50% of the hemispheres, both the inferior and superior LPChAs in 40%, and their common trunk in 10%. In 40%, the LPChA, which averaged 670 &mgr;m in diameter, divided into the terminal trunks, with a mean diameter of 490 &mgr;m. The anastomoses involving the trunks of the LPChA and other choroidal arteries averaged 310 &mgr;m in diameter. All primary intrachoroidal branches of the AChA and LPChA were divided into three groups. The parallel branches, which averaged from 220 to 230 &mgr;m in diameter, coursed along the lateral part of the choroid plexus. The tortuous glomus vessels, which averaged 310 &mgr;m in size, originated from the AChA (45%), the LPChA (15%), or both (40%). The bush-like vessels, with a mean diameter between 155 and 190 &mgr;m, ramified into smaller twigs, up to the intrachoroidal capillaries. CONCLUSION: The data obtained on the microanatomy of the intrachoroidal vasculature may have certain neurosurgical implications.

Clinical implications of computer assisted surgical design in a carotid cave aneurysm.

In this report we demonstrate the application of computer assisted geometric design in the surgery of a carotid cave aneurysm. The method and basic concepts have been previously reported.(1) In this case report we referred to the previously published atlas of clinical images to input anatomical data. This enabled us to demonstrate and adequately identify microneurostructures for surgical simulation. The concepts and basic methods of computer assisted geometric design of microneurostructures are described.