STEREOTAXIC NEUROSURGERY (Greek stereos firm, volume, space + taxis creation, arrangement; neurosurgery) — the direction in neurosurgery using a stereotaxic method of destruction or stimulation of conduction paths and kernels of the central nervous system for obtaining medical effect. Development and deployment in a wedge, practice stereotaxic method (see) made possible operative measures on the deep subcrustal and trunk structures of a brain of the person earlier completely unavailable to the neurosurgeon that, in turn, provided a possibility of treatment of a number of the serious illness and states which are not giving in to conservative influences. Use of this method considerably increased efficiency of an operative measure on a brain at its smallest traumatization.
Page of N incorporated achievements of the medical equipment (stereotaxic devices, X-ray equipments, devices for various methods of destruction), neurophysiology (a stereotaxic method, results of studying of functions of subcrustal structures), neurology (results of studying of a pathogeny and clinic of hyperkinesias, pain syndromes, epilepsy and other diseases) and neurosurgery (the equipment and a technique of operations on deep structures of a brain).
Stereotaxic operations are effective as shows the accumulated experience, at various morbid conditions and diseases; parkinsonism, cerebral palsy, the deforming muscular dystonia, aneurisms of vessels and a tumor of a brain, epilepsy, nek-ry mental diseases, pain syndromes, etc. belong to their number. Scope of a stereotaxic method continues to extend steadily and gradually includes all new nosological forms.
A founder S. of N is professor of anatomy Moscow un-that D. N. Zernov, to-ry created the first stereotaxic device intended for anatomic researches and neurosurgical operations on a brain of the person (so-called entsefalometr). This device was shown in 1889 at a meeting physical and mathematical about-va Moscow un-that. Entsefalometr created by D. N. Zernov became a prototype of a row sovr. stereotaxic devices. G. I. Rossolimo in 1906 — 1907 improved entsefalometr, created the new device called by the brain topographer. D. N. Zernov, N. V. Altukhov and G. I. Rossolimo the first suggested about that big role, to-ruyu can play a stereotaxic method in neurosurgery, and successfully confirmed this assumption during operations on a brain of the person.
In 1906 English scientists of Horsley (V. A. N. Horsley) and Clark (R. N of Clarke) developed the design of the stereotaxic device for neyrofiziol. experiments on animals with use of system of rectangular coordinates: three planes, mutually perpendicular to each other in space, were compared with outside bone reference points of a skull of an animal. They created the first stereotaxic atlases of a brain of experimental animals and on their basis a number of researches is executed. However the stereotaxic method entered a wedge, practice only in the 40th 20 century when it is mute. neurologist Spiegel (E. A. Spiegel) and amer. neurosurgeon Uaysiz (H. T. Wycis) created a prototype of modern stereotaxic devices and made the first stereotaxic operations on deep structures of a brain; afterwards such interventions were made by them at many diseases of c. N of page. They possess big merits in development of a new method; they are also creators of the first stereotaxic atlas of a brain of the person. For the last 30 — 40 years in many countries tens of thousands of stereotaxic operations are made. Progress in this area was marked by considerable theoretical and practical results. The Page of N
is the cornerstone a set of methods and the mathematical calculations allowing by means of special devices and methods rentgenol. and funkts. control with a big accuracy to carry out introduction of a cannula (or an electrode) in the certain deeply located structure of a head or spinal cord for impact on it with to lay down. purpose. One of the main tasks in S. of N is definition of exact space ratios between any set structure of a brain and a number of points reference points, to-rymi intracerebral and (or) cranial (ekstrakranialny) anatomic educations serve.
On two x-ray films — in side and perednezadny projections (fig. 1) — determine coordinates of a required point in the depth of a brain in the sagittal and frontal planes. The third coordinate (in the horizontal plane) is calculated on available to two. Rentgenol. the research is an obligatory component of stereotaxic neurosurgical operation.
During the carrying out stereotaxic operation definition of degree of individual variability of localization and the sizes of subcrustal structures is important. A specification is on this matter collected in stereotaxic atlases. For individual correction enter a so-called factor of relativity, to-ry represents the coefficient reflecting a ratio between the sizes of any structure in the stereotaxic atlas i.e. in a reference brain, and the same sizes in a brain of this patient, polucheiny in process rentgenol. inspections. Basis of each stereotaxic atlas are series of photos cuts «standard» a brain, executed in various planes — sagittal, frontal, horizontal, and also slanting.
The fullest modern stereotaxic atlas is the three-volume atlas created in 1977 by group of authors under the leadership of G. Scha-ltenbrand and W. Wahren. In it detailed information on morphology and physiology of subcrustal structures of a brain of the person is given, questions of a technique of a stereo-taksicheekikh of operations are stated, schemes and photos of cuts of a brain in three mutually perpendicular planes of space made with observance of special conditions contain.
For a basis of system of coordinates, in a cut cuts are made, the in-terkomiseuralny line, i.e. the line connecting front and back commissures (commissures), and as the dead center — a point of intersection of this line with the perpendicular recovered in its midpoint in the sagittal plane is taken. The specified line and a perpendicular to it represent two coordinate axes, and the third axis, perpendicular to two previous, passes through a point of the beginning of coordinates. On these axes (planes) frontal, sagittal and horizontal sections of a «reference» brain are made.
During formation of a stereotaxic method there was an opinion that as a basis natural coordinate system it is possible to assume the horizontal planes formed by bone structures of a base of skull. Use of these planes assumes strict symmetry of a skull, edges, however, is observed only in 10% of cases; internal acoustical passes, e.g., can be located in the different planes that nullifies localization value of the specified planes. Nevertheless bone reference points are necessary for definition of the place of imposing of a trepanation opening in bones of a skull, and also are the main at two stereotaxic operations: at hypophysis operations (the Turkish saddle) and at destruction of a gasserov of a node (an oval opening).
For identification of space localization of the subcrustal structure which is subject to destruction use the intracerebral reference points defined on ventrikulogramma in two projections. In the analysis of the pictures executed in a perednezadny projection (fig. 2, a), pay attention to a form, the sizes and degree of fullness side and the third cerebral cavities contrast. In outlines of side ventricles it is possible to define the central part — a body (more contrast part of a shadow adjacent to the centerline) and a front horn (less contrast part of a shadow). Both ventricles are divided by the striola formed by a transparent partition. It begins under a corpus collosum, then goes to the upper edge of a shadow of the third ventricle from top to bottom, to-ry has an appearance of the narrow direct crack thickened in a middle part to 3 — 4 mm in the diameter. Longitudinal diameter of the third ventricle usually makes 14 — 15 mm. Vent-ralny the shadow of a silviyev of a water supply system is visible to the bottom of the third ventricle (a water supply system of a brain, T.), and under it in the form of a triangle the fourth ventricle with its lateral apertures (side gate). As coordinate axes in a direct projection use a midline and the horizontal line, perpendicular to it, drawn on border of an upper and average third of the III ventricle. The dead center of coordinates in this projection is the point of intersection of the specified lines.
In a side projection (fig. 2, b) the extended shadow of a side ventricle is visible, in to-rop easy to distinguish the central part, front, lower and back horns. The major reference point for stereotaxic calculations is the interventricular foramen (Monroe) connecting side and third ventricles. In a picture this opening is presented in the form of the narrow short isthmus directed ventrally and kzad. Directly under an interventricular foramen and slightly kpered from it small cutting (apprx. 2 — 3 mm) — a precomissure is visible.
Back department of a dome of the third ventricle, falling ventrally, passes into a thin shadow of a silviyev of a water supply system. In a point of this transition the back commissure is located. As such main coordinate axis at stereotaxic calculations use the interkomissu-ralny line connecting both commissures. Advantage of this line is that its length does not depend on length of a skull and its anthropological type. Sometimes at stereotaxic calculations use the line connecting the rear edge of an interventricular foramen to a back commissure. Both of these lines, coming to an end in one point, begin at distance of 3,5 — 4 mm from each other down. A dead settlement center of coordinates in a side projection is the middle of the inter-komissuralny line.
Bystry development of S. of N was an incentive for creation new and improvements of the existing stereotaxic devices and devices that, in turn, caused further progress of this field of neurosurgery. Many universal stereotaxic devices are created, to-rye differ from each other in the principle of action, degree of complexity, way of fixing to a skull, system of coordinates etc. Also devices of a special purpose, napr, for hypophysis operations are created.
The most widespread devices for S. of N are based on system of polar coordinates. The principle of their action is that the electrode (cannula) is entered into a brain towards a point of the purpose under certain corners. These corners are defined by the line, to-ruyu lead from the end of the cannula entered on insignificant depth into a brain, and the line of the direction her to a point of the purpose (the zero line).
The existing devices can be divided into two groups: the devices of rather simple design fixed in a small trepanation opening in bones of a skull on external cranial reference points and devices of more difficult design, in to-rykh fix the head of the patient by means of the special emphasis which is screwed in in a bone of a skull under rentgenol. control.
Due to the development of stereotaxic surgery, complication of its techniques and increase in requirements to the accuracy of hit in the set structure of a brain and for specification of localization of the end of an electrode (cannula) in subcrustal structures of a brain began to use the COMPUTER to stereotaxic calculations. Difficult mathematical calculations are offered, to-rye allow to define the provision of the end of an electrode in a brain both at direct, and at the electrode which is moving forward sideways.
Active development was gained by the method of a stereotaxic computer tomography based on receiving series of images of the cuts of a brain serving for exact determination of coordinates of any point in deep structures of a brain by means of the computer (see the Tomography computer). (
At stereotaxic a biopsna of the deep-located tumors of a brain the technique of data migration of a computer tomography on usual kraniogramma is applied.
Efficiency of any stereotaxic operation first of all depends on the accuracy of hit of the active end of a cannula (electrode) in the set subcrustal structure. At inaccuracy of calculations serious complications as in most cases the subcrustal structure (target) which is subject to destruction (stimulation) is located in close proximity to other functionally important structures of a brain are possible.
Stereotaxic operation consists of several stages. The choice of the purpose, i.e. the structure which is subject to destruction (stimulation) is made before operation. As at different diseases these structures are various, their right choice is one of the main objectives. The most general stages of stereotaxic operation following: anesthesia and imposing of a trepanation opening; installation of the stereotaxic device; contrasting of system of cerebral cavities; definition on the roentgenograms executed in two projections, intracerebral reference points and calculation for these reference points of localization of the set structure according to data of the stereotaxic atlas; comparison of space localization of required subcrustal structure to coordinate system of the stereotaxic device and transfer of the obtained data on the directing device of the device; introduction to the set subcrustal structure of a cannula (electrode) under control of x-ray films or electron-optical converters; radiological and functional control of accuracy of hit; destruction (stimulation) of subcrustal structure; removal of a cannula (electrode), removal of the device, closing of an operational wound.
Position of the patient on the operating table depends on a technique and the nature of stereotaxic operation. So, at operations on basal kernels of a brain, at a transnasal hypophysectomy, etc. the patient lies on spin (the person up), and at a stereotaxic dentatoto-miya, a percutaneous tractotomy, etc. — on a stomach (facedown).
Methods of anesthesia at stereotaxic operations are also various and depend on character and problems of operation. At nek-ry diseases (e.g., at parkinsonism, pain syndromes, etc.) local anesthesia with easy premedication is used. The neyroleptanalgeziya is quite often applied, cover advantage in a possibility of bystry awakening of the patient that allows to check effect of operation and to be convinced of lack of complications. At the diseases which are followed by the expressed hyperkinesias the intratracheal anesthesia by means of anesthetics is shown.
The choice of the place for imposing of a trepanation opening in bones of a skull defines that point of bark of a great brain, through to-ruyu a cannula (electrode) will be entered into subcrustal kernels. At the same time meet three conditions: the injection site of a cannula (electrode) shall be at safe distance from functionally important zones of bark of a great brain; advance of a cannula (electrode) on the way to the set structure shall not be followed by damage of other important structures of a brain; the way of a cannula (electrode) to the set structure shall be whenever possible shorter. Introduction of a cannula (electrode) through bark of back department of an average frontal crinkle almost completely meets the listed conditions.
Rigid fixing of the head of the patient is carried out in a special head restraint, in strictly sagittal plane by means of two screws which are screwed in in frontal area to a bone.
Contrasting of ventricular system — an obligatory and important stage of each stereotaxic operation. In S. N apply two methods of contrasting of cerebral cavities: pneumoencephalography (see) and ventrikulografiya (see).
Definition of space localization of the stereotaxic subcrustal structure chosen for an operative measure is the most difficult and responsible stage of operation. It includes definition of the main intracerebral reference points, calculation on the basis of these reference points of coordinates of the subcrustal structure which is subject to destruction (stimulation), control of accuracy of hit in it.
Accuracy of hit in the set subcrustal structure is controlled radiological. For this purpose after introduction of a cannula (electrode) on the calculated depth make control pictures in two projections, identical subjects, to-rye are necessary for stereotaxic calculations. Then from settlement pictures the main reference points of N transfer the center of required structure to control. If the cannula (electrode) is entered precisely, then the center of its active end shall match the specified point. In case of the discrepancy exceeding 1 mm correction of the direction of a cannula (electrode) is necessary.
At the stereotaxic operation made under local anesthesia, reliable criterion of accuracy of hit in required subcrustal structure is the wedge, effect (e.g., disappearance of a tremor, rigidity, pains) coming directly on the operating table. This effect is, as a rule, observed in 1 — 1,5 min. after hit in a required point, i.e. before use of destruction.
An important component of functional operations at all levels of a nervous system is electrostimulation. The wide experience of electrostimulation of various structures of a brain of the person is accumulated (many kernels of a visual hillock, subthalamic area, a pale sphere, a shell, kernels of a cerebellum, etc.) - Data on neuro and patofiziol are obtained. the organizations of a number of the processes proceeding with participation of subcrustal structures of a brain (about the functional organization of subcrustal structures, their interrelations, speeds of carrying out nervous impulses, a pathogeny of a tremor, rigidity, hyperkinesias, pain syndromes).
Besides, electrostimulation of subcrustal structures of a brain is an informative stage of the majority of stereotaxic operations and is considered as one of the main methods of identification of subcrustal structures. The method allows to control the accuracy of hit of the tool in the set structure. At the majority of operations on deep structures of a brain electrostimulation is applied for the purpose of definition of provision of the end of an electrode in relation to the internal capsule of a brain, directly prilezhit edges to a lateral surface of a ventrolateralny kernel of a thalamus and a medial surface of a pale sphere.
Electrostimulations of subcrustal structures are used also as independent to lay down. method. In this case apply implantation of long-term electrodes in deep structures of a brain.
A main objective and the final stage of each stereotaxic operation is destruction of kernels or conduction paths of a head or spinal cord. In this regard one of the most important problems of stereotaxic surgery — development of the most effective, simple and safe method of destruction of brain fabric.
The methods of destruction applied in S. by N divide into four groups: physical, electric, chemical and mechanical. From them and widespread two are the most effective — local freezing and high-frequency thermocoagulation, to-rye most meet S.'s requirements of N.
Local freezing is made by means of the special devices allowing to create on the active end of the thin cannula entered into depth of a brain, low temperature — minus 150 — 170 ° (see. Cryosurgery ). In a result in to the planned subcrustal structure the sphere of the frozen brain fabric of the set volume is created. After thawing there is a gradual rassasyvaniye of the site of brain fabric subjected to cryoinfluence.
High-frequency thermocoagulation is carried out by means of the special generators giving an impulse current of high frequency on an electrode. It is applied both mono - and bipolar coagulation. On the end of an electrode create temperature leading to destruction of brain fabric. Temperature is taken the thermal sensor on the end of an electrode. Sometimes apply other methods of destruction (anode electrolysis, induction heating, subsection of brain fabric a special stereoentsefalotom, etc.).
Are engaged in development and improvement of a recent trend in neurosurgery in many countries of the world. Are created World and European scientific about-va functional and stereotaxic neurosurgery, to-rye will regularly organize and carry out the international congresses and symposiums on problems C. of N. The international magazine «Applied neurophysiology» is issued. In the USSR materials on various questions C. of N are located in the Questions of Neurosurgery magazine; monographs are published.
Bibliography: Abrakov L. V. Fundamentals of stereotaxic neurosurgery, JI., 1975, bibliogr.; Kandel E. I. Stereotaxic neurosurgery, in book: First Vsesoyuz. congress neyrokhir., t. 5, page 195, M., 1972; it, Functional and stereotaxic neurosurgery, M., 1981, bibliogr.; Atlas for stereotaxy of the human brain, ed. by G. Schaltenbrand a. W. Wahren, Stuttgart, 1977; Stereotaxy of the human brain, ed. by G. Schaltenbrand a. A. E. Walker, N. Y., 1982.
E. I. Kandel.