Twenty-nine patients with basilar artery aneurysms were operated on using one of three approaches: pterional, orbitozygomatical, and subtemporal. The efficiency of surgery and the frequency of surgical complications are analyzed in detail in relation to the data of an angiographic study and the intraoperative pattern. Three (10.3%) patients died in the postoperative period. In most cases, the pterional approach is adequate for clipping almost any aneurysm of the distal portions of the basilar artery; the use of the orbitozygomatical approach in patients with aneurysm of the same location is determined by its extent and/or adhesions with the adjacent brain structures. Current neuroimaging techniques are of the most informative value in choosing a surgical treatment policy in each specific case.

This paper describes the major features of topographic and anatomical studies of CNS structures, CSF circulation system, extracerebral structures and vertebral column. These methods include brain fixation, which is able to prevent post mortem brain deformation due to decalcification (even for block-preparations like "brain-skull base" or "posterior cerebral fossa-cervical spine"). The author also presents the following methods: spatial reconstruction of the brain and skull base subtracted from the series of slices of different thickness and various planes of transection; biopsy investigation of cerebral midline structures and CSF system in relation with skull base and convex structures; staged microdissection of tumors; filling of arterial and venous systems. All these modalities were used in examining the topographical features of craniopharyngiomas, hypophyseal adenomas, parasagittal and sagittal meningiomas, pineal tumors, VIII cranial nerve neurinomas, arachnoid cysts and in developing surgical approaches to the tumors of the third ventricle, skull base and foramen magna.

The ultrastructure of the paravasal formations of the magistral arteries in the brain hemispheres has been studied: the paravasal nerve trunks (components of the external nerve plexus of the arteries, running outside the adventitia and surrounded with liquor) and the artery-stabilizing constructions--strings in the human being and in the dog. The human para-arterial nerve trunks possess the vasa nervorum system, presented by blood capillaries situating at the border of endo- and perineurium, by powerfully developed perineurium, which includes into its composition a system of basal membranes and perineural cells. In the canine para-arterial nerve trunks these formation are absent. In the string composition there are collagenous-fibrillar base represented by tightly packed fasciculi of collagenous fibers, oriented in parallel to the long axis of the string, and by stellate cells. Both the paravasal nerve trunks and the strings are surrounded with flattened cells of the endothelial sheath. They are very much alike with the arachnoidendothelial cells lining the subarachnoidal space.

By means of the light optic and electron microscopic methods atrial ganglia, myocytes, vessels of the right cardiac chambers have been studied in rats 2 days--3 weeks after application of 100 mcg of colchicine on the right nervus vagus. Certain changes of the neural fibers have been described at the area of the application. In the myocardium the microcirculatory bed, focal edema and hypoxic alterations of the myocyte ultrastructure have been revealed. In the ventrical ganglia destruction of some terminals of the preganglionar fibers, chromatolysis and vacuolization of single neurocytes, as well as intraganglionar granule-containing cells have been found. The changes described take place for 7 days and they nearly completely disappear in 10 days. A suggestion is made that some phenomena, in particular, destruction of the preganglionar fibers and changes of the cardiac microcirculatory bed are connected with certain disturbances of the quick transport of substances in the nervus vagus fibers.

In the pia mater of the human cerebral hemisphere certain specific structures named subarachnoid alveoli have been revealed. The best method for their revealing is the method of volumetric microscopy--tracheoscopy--but they can be detected in histological sections, as well. The subarachnoid alveoli are situated in the subarachnoid space between liquor canals. By their form they resemble honeycombs. Their walls have a carcass consisting of argyrophile and collagenous fibres to give the alveoli a definite form. The carcass is lined with arachnoid-endothelial cells. The alveoli are connected with the liquor canals by means of holes in the walls of the canals. The subarachnoid alveoli are connected with each other by means of holes in their walls. The arachnoid-endothelial cells of the subarachnoid alveoli are capable to accumulate colloid substances from the spinal liquor. The walls of the subarachnoid alveoli discharge macrophages into the lumen of the latter. Protective function of the subarachnoid alveoli system contributes to normalization of the spinal liquor composition both under normal and pathological conditions.

Ultrastruct of the dog arachnoid membrane, pia (vascular) mater, internal layer of the dura mater, human arachnoid membrane, subarachnoid alveolar walls and canals transporting liquor into the subarachnoid space have been studied. From the literature analysed and from his own data the author considers the system of the meninges and intermeningeal spaces as a system of extracerebral barriers devided into 3 stdructural-functional groups: 1--barriers dealing with liquor outflow from the subarachnoid space into the blood stream (lgb-I lgb-II); 2--barriers dealing with metabolic processes between the liquor and the borderline tissues (lcb, lmb, lnb, etc.); 3--histo-haematic barriers between blood and tissue elements of the pia mater, dura mater and paravasal nerve trunks of the brain magistral arteries. Morphological substrates of some extracerebral barriers are described at a submicroscopical level.

The inner layer of the dura and the arachnoid mater of the dog brain were studied in the electron microscope after injection of 0.2–0.5 ml autogenous blood into the subdural space. The arachnoid of the excretory canals and the structural elements of the inner layer of the dura (cells of the meningeal layer, the layer of collagen fibrils and microfibrils, the wall of the blood capillaries of the internal capillary network) form the morphological substrate of the CSF-blood barrier-I between the CSF and blood in the capillaries of the internal capillary network of the dura. Red blood cells were found to penetrate from the subdural space into the substance of the dura, where they concentrated around the capillaries of the internal capillary network but did not actually penetrate into the arachnoid.

The pia mater of the human brain hemispheres has liquor canals which form a continuous network communicating with the cisterns of the brain base. The wall of the liquor canals is formed by a fibro-collagenous framework covered from two sides with the arachnoidendothelium. In the canal walls there are openings, through which the lumens of the canals communicate with the lumens of alveoli. The liquor canals are divided into the circulatory and excretory ones. The circulatory canals are disposed in the depth of the cerebral sulci, the secretory canals--on the surface of the convolutions. The liquor moves along the circulatory canals from the cisterns of the brain base onto the surface of cerebral hemispheres. Excretory canals adjoin the arachnoid membrane which is part of its wall (the "roof"). In the "roof" of the liquor canals the fibrocollagenous basis and the number of layers of the arachnoid--endothelium are reduced, the intercellular spaces between the cells of the arachnoidendothelium are dilated. Through the roofs of the liquor canals the liquor is excreted from the subarachnoid space into the subdural space. Inside the liquor canals there are arteries of the pia mater hung up to the canal walls by trabeculae (cords) of a dense connective tissue.

The ultrastructure of cellular spots was studied--growths of the external arachnoidendothelial layer of the arachnoid membrane of the human cerebral hemispheres. The peculiarities of their ultrastructure depending on the stage of their development were revealed. "Young", cellular spots were formed by accumulations of osmiophobic round-shaped cells that are lined from the outside by osmiophilic cells like the whole of the arachnoid membrane surface. "Mature" cellular spots contain great number of oxmiophobic (viable) cells located in a immediate proximity of the subdural space, and they form the main source of viable arachnoidenodthelial cells found in the subdural fluid. The author believes that these cells penetrate together with the subdural fluid flow into the dura mater where, under specific conditions, they may become a source of arachnoidendothelial chippings.

The ultrastructure of the intraadventitial and paravasal nerve trunks of the superficial adventitial plexus in major vessels of the basis cerebri in man and in dogs under normal conditions and with a subarachnoidal hemorrhagic effusion was studied at the submucroscopic level. Unlike the ultrastructure of the intra-adventitial nerve trunks the paravasal ones, lying in the cerebrospinal fluid (CSF), have an endothelial sheath that substitutes the epineurium and also has a perineurium endowed with an abundantly developed system of basal membranes containing aplanated cells and bands of collagen fibrils. With a subarachnoidal hemorrhagic effusion was in evidence the disruption of the "CSF-neural barrier". The endothelial cells break" away and fall into the CSF, the basal membrane undergoes lysis, which, apparently, contributes to the penetration of various components of the subarachuoidally effused blood deep into the nerve trunks. This results in changes occurring in the ultrastructure of axones of the pulpous and, to a lesser extent,pulpousless nerve fibers.

An ex tempore mixture of fibrinogen (1%--4 ml) and 0.2 ml thrombin solutions forming a compact clot of fibrin in the subarachnoid space was introduced into the cisterna magna of dogs. To dissolve the fibrin clot 2 ml of a fibrinolysin solution with an activity of 400 units were introduced into the same cisterna 10--15 minutes thereafter. A total of 26 experiments were set up, of which 13 were served as controls with separate introduction of the mixture ingredients. Through serial vertebral angiography with a 50 per cent urotrast solution it was found that following introduction of the fibrinogen and thrombin mixture the lumen of the basilar artery and of its branches contracts on the average up to 89.2 +/- 1 per cent. After introduction of fibrinolysis the diameter of the artery initially increases up to 116.3 +/- 2.5 per cent. In 3 hours time a pronounced spasm of the basilar artery and of its branches is seen to develop up to 80.9 +/- 3.6 per cent and after 24 hours -- up to 73.9 +/- 2.1 per cent. The spasm persists for up to 10 days, but its intensity gradually declines. During subsequent 11--18 days the diameter of the brain base arteries returns back to normal. In control experiments no development of protracted spasm was demonstrated. Hence, it is established that the appearance of fibrinolysis products formed in the spinal fluid consequent upon dissolution of a clot of fibrin containing no blood cells is attended by the development of a protracted spasm involving major arteries of the brain.