Sinusitis

Sylvian fissure meningioma. Classification, symptoms and treatment of neoplasms of the arachnoid meninges

The study was conducted on 18 anatomical specimens (9 left and 9 right hemispheres) of the brain of adults aged 21 to 79 years, whose cause of death was not intracranial pathology. After isolating the brain from the cranial cavity, catheters were inserted into the lumen of the internal carotid arteries to the level of the bifurcation. Next, the arterial system of the brain was thoroughly washed with saline, followed by the introduction of red-colored latex (2-3 ml). After this, the catheters were removed from the lumen of the vessels, and ligatures were applied to the vessels. The drug was immersed in a fixing liquid (96% alcohol and glycerin in a ratio of 4:1) for 3 days. Then microdissection of the Sylvian fissure was performed using a surgical microscope OPTON OPM6-SDFC-XY (at 4-10x magnification) in the following sequence: dissection of the superficial part of the Sylvian fissure, dissection of the deep part of the Sylvian fissure located under the temporal operculum, dissection of the deep part of the Sylvian fissure , located under the frontal and parietal operculum. Next, the most important surgical landmarks were examined: the insular threshold, lenticulostriate arteries, periinsular sulci, M2 and M3 segments of the middle cerebral artery, and insular convolutions. The last stage was a study of the morphology of the tegmentum of the insula (size of the tegmentum, comparison of anatomy over different sections of the insula), modeling of transcortical access by removing parts of the tegmentum over 5 sections of the insula and measuring the size of the peri-insular grooves.

Results

Sylvian fissure

The Sylvian fissure is the most important anatomical landmark on the lateral and basal surface of the brain, located between the frontal, parietal and temporal lobes.

In the Sylvian fissure, basal (proximal) and lateral (distal) segments can be distinguished, each of which in turn consists of superficial and deep parts.

The border between the basal and lateral segments is the anterior Sylvian point (located under the triangular part of the inferior frontal gyrus) - the place where the basal surface of the hemisphere passes into the lateral one.

The superficial part of the Sylvian fissure consists of three main grooves (Fig. 1), which are represented in the lateral segment by three branches: horizontal, ascending and posterior. All 3 grooves begin from the anterior Sylvian point. The posterior sulcus runs distally, between the frontal and parietal lobes superiorly and the temporal lobe inferiorly. The horizontal and ascending sulci rise respectively forward horizontally and upward vertically from the Sylvian point, dividing the inferior frontal gyrus into three parts: the orbital, triangular and tegmental.

Rice. 1. Branches of the superficial part of the Sylvian fissure. The tegmental, triangular and orbital parts of the inferior frontal gyrus - lateral view.

In the basal part of the Sylvian fissure, the deep part (sphenoidal) is formed by the proximal and medial part of the superior temporal gyrus (planum polare) - medially and the lateral and posterior orbital gyrus of the basal surface of the frontal lobe - laterally. This part of the Sylvian fissure extends from the threshold of the insula to the bifurcation of the internal carotid artery. It contains the M1 segment of the middle cerebral artery, the extraparenchymal part of the lenticulostriate arteries and the deep Sylvian vein.

The deep part of the distal segment of the Sylvian fissure is represented by the space formed between the contacting parts (covers) of the frontal, temporal, parietal lobes and the lateral surface of the insula.

The lower wall of the deep part of the distal segment is formed by the temporal operculum (the upper and medial surface of the superior temporal gyrus). It (from front to back), in turn, consists of the following components: the pole area (planum polare), Heschl's anterior gyrus (anterior transverse temporal gyrus) and the temporal area (planum temporale) (Fig. 2).

Rice. 2. Tegmentum and insula - side view.

Planum polare is the most proximal part of the temporal operculum, located between Heschl's gyrus posteriorly and the uncus of the temporal lobe anteriorly. The anterior and posterior sections of the planum polare have different axis relative to the sagittal plane. The posterior part (from Heschl's gyrus to the level of the precentral gyrus) is located at a right angle to the sagittal plane, and the remaining anterior part deviates in the medial direction and forms an acute angle with this plane (Fig. 3). Planum polare covers the lower surface of the anterior lobe of the insula and its threshold (see Fig. 2).

Rice. 3. Frontal sections at the level of the anterior (a) and posterior (b) third of the insula. A - thickness of the operculum, B - length of the anterosuperior (a) and posterosuperior (b) sections located under the frontal and parietal operculum. The arrow indicates the plane of the Sylvian fissure in its anterior and posterior third.

Planum temporale forms the distal part of the temporal operculum and consists of the middle and posterior transverse temporal gyri (the plane of this part of the temporal operculum is oriented perpendicular to the sagittal plane, i.e., more horizontal than the anterior sections of this operculum (see Fig. 3, b).

The anterior transverse temporal gyrus (Heschl) can be easily identified on the temporal operculum due to the pronounced bulge on its surface. It corresponds to the posterior lobe of the insula and the posterior third of the inferior periinsular sulcus (see Fig. 2).

The upper wall of the deep part of the distal segment is formed by the frontal and parietal operculum (see Fig. 2). The frontal operculum includes: the orbital, triangular and tegmental parts of the inferior frontal gyrus and the lower part of the precentral gyrus. It should be noted that in 7 (38%) preparations the triangular part was smaller in size relative to the remaining parts of the inferior frontal gyrus (upward retraction), as a result of which an increase in the width of the Sylvian fissure was observed at this level.

The parietal operculum is formed by the lower part of the postcentral gyrus and the upper parts of the supramarginal gyrus.

The lateral wall of the deep part of the distal segment of the Sylvian fissure is formed by the lateral surface of the insula.

In the deep part of the distal segment there are the M2 and M3 segments of the middle cerebral artery and the deep Sylvian vein.

Insula

The insula is the only lobe of the brain that does not have access to its surface. It is hidden by the parts of the frontal, parietal and temporal lobes located above and below, which form 3 opercula, respectively.

The frontal and parietal tegmentum cover the upper part of the lateral surface of the insula (the resulting space is called the superior insular tegmental fissure). The temporal operculum hides the inferior surface of the insula, resulting in the formation of the inferior insular-operculum fissure. The superior and inferior insula-opercular fissures are components of the deep part of the distal segment of the Sylvian fissure.

If the opercular parts of the frontal, temporal and parietal lobes are removed, the insula appears in the form of a pyramid (Figs. 4 and 5), the apex of which faces the base of the brain. The island is separated from the surrounding tires by three grooves. The anterior periinsular groove separates the anterior surface of the lobe from the frontal operculum; its average length in our study was 26 (24-33) mm. The superior sulcus defines the boundary of the lobe with the frontoparietal operculum; its average length was 56 (52-63) mm. The inferior periinsular sulcus separates the inferior surface of the insula from the temporal lobe. The average length of this groove was 47 (43-51) mm.

Rice. 4. Insular lobe and peri-insular sulci; inferior and lateral view.

Rice. 5. Ostal lobe; side and bottom view.

Fissures and convolutions of the insula

In a morphological study, the deepest and most present in all preparations was the central sulcus of the insula, the average length of which was 32 (24-42) mm. The direction and angle of inclination of the central sulcus of the insula almost completely coincided with the direction of the Rolandic sulcus in 14 cases, and in the remaining 4 cases there was a displacement of the lower end of the Rolandic sulcus by 3–4 mm anteriorly relative to the central sulcus of the insula.

The central groove of the insula divides its surface into 2 parts: a large anterior one and a smaller posterior one. The anterior one consists of 3 short gyri: anterior, middle, posterior (delimited by the anterior and precentral sulci of the insula), as well as the not always found accessory and transverse gyri. The posterior part is represented by the anterior and posterior long gyri and the postcentral sulcus located between them (Fig. 6).

Rice. 6. Convolutions of the insula; side and bottom view.

In 15 hemispheres, the anterior, middle and posterior short gyri were well defined, and the remaining 3 hemispheres were distinguished by a smaller middle short gyrus.

The posterior lobe of the insula in all preparations consisted of the anterior and posterior long gyri, but in 13 hemispheres the anterior long gyrus was larger than the posterior one, in 3 both long gyri were the same, and in 2 preparations a larger posterior gyrus was observed.

In the anterior lobe of the insula, at the point of its transition to the posterior part of the frontobasal region, there was a transverse gyrus in 14 hemispheres. An accessory gyrus of the insula, located above the transverse one, was found in 7 hemispheres.

In 2 hemispheres, additional convolutions (without nomenclature designations) were found along the inferior periinsular sulcus, separated from the known convolutions by shallow grooves.

On the surface of the insular lobe, it is also customary to distinguish the apex - the part of the lobe that is most protruding laterally and, therefore, closest to the surface of the cortex, usually located in the area of the middle short gyrus.

The most important surgical landmark during the transsylvian approach to the insula is its threshold (limen), which forms the anterior-basal part of the lobe (“entrance” to the insula). The insular threshold connects the pole of the temporal lobe with the basal parts of the frontal lobe and is shaped like a semicircle. Just medial to the threshold of the insula is the anterior perforated substance.

The sulci and convolutions of the insula have a relatively constant relationship with the tegmental convolutions. The anterior short gyrus of the insula and the corresponding part of the anterior periinsular sulcus are projected onto the orbital part of the frontal operculum; the middle and posterior short gyri correspond to the triangular and opercular parts. The posterior parts of the short posterior gyrus and the anterior part of the long anterior gyrus correspond to the precentral gyrus. The postcentral gyrus covers the remainder of the anterior long gyrus and the anterior portions of the posterior long gyrus. The caudal part of the posterior long gyrus corresponds to the supramarginal gyrus. The inferior periinsular sulcus corresponds approximately to the superior temporal sulcus. The threshold of the insula (and, accordingly, the bifurcation of the middle cerebral artery) is located medial to the temporal operculum.

Thus, the anterior lobe of the insula is hidden from above by the orbital, triangular and tegmental parts of the inferior frontal gyrus and the lower parts of the precentral gyrus, and is covered from below by the planum polare of the superior temporal gyrus.

The posterior lobe on the side of the Sylvian fissure is covered by the postcentral gyrus and the anterior parts of the supramarginal gyrus above and Heschl's gyrus below. The entire insula is projected onto the lateral surface of the brain from the pars opercularis (horizontal branch of the Sylvian fissure) in front to the anterior parts of the supramarginal gyrus in the back.

Thus, the gyri and sulci of the frontal, parietal and temporal operculum correspond to certain gyri and sulci of the insula, which can serve as a guide for transcortical access to various parts of the insula.

Correlation between tectum and insula

The distance between the anterior insular point (the intersection of the anterior and superior periinsular sulci) and the lateral surface of the cortex at the pars triangularis level averaged 22 (18-26) mm, i.e., the thickness of the frontal operculum at this level was 22 mm (Fig. 7 ).

Rice. 7. Thickness of the frontal and parietal operculum; side view.

The length of the straight line connecting the posterior insular point (the intersection of the posterior and superior peri-insular sulci) with a point on the lateral surface of the supramarginal gyrus averaged 31 (28-35) mm (the transverse size of the parietal operculum).

The thickness of the temporal operculum (the distance between the posterior insular point and the lateral surface of the cortex of the superior temporal gyrus) was 32 (27-35) mm.

Thus, there is an increase in the thickness of the tires in the direction from front to back, which makes it difficult to access the posterior sections (long convolutions) of the insula using both transsylvian and transcortical approaches, increasing the depth of the surgical wound.

According to the measurement results, the distance between the insular threshold and the pole of the temporal lobe averaged 20 (15-24) mm.

The frontal and parietal operculum covered the upper surface of the insula (the length of the operculum) by an average of 22 (18-24) mm, the temporal operculum covered the lower surface of the insula at a distance of 15 (11-18) mm. As a result, it was found that with the transsylvian approach, formations located under the frontal operculum are less accessible than those localized under the temporal one (taking into account also the extremely inconvenient superoposterior angle of attack). With transcortical access, this pattern is not observed and the formations under the frontal and temporal operculum are equally accessible.

Projections of the basal ganglia, lateral ventricle and internal capsule relative to the insula

The fence, putamen, globus pallidus, anterior and posterior femur of the internal capsule, and thalamus are located medial to the insula.

The putamen and the globus pallidus (lentiform nucleus) extend from anterior to posterior from the level of the middle short gyrus of the insula to the anterior parts of the posterior long gyrus of the insula. Thus, the lentiform nucleus covers only the central part of the internal capsule from the side of the insula, and its peripheral parts (anterior, superior and posterior) lack this natural barrier (Fig. 8).

Rice. 8. a - horizontal section at the level of the commissure of the arch; top view. Red arrows indicate areas of the internal capsule unprotected by the shell; blue arrow - to the area of the internal capsule covered by the shell; b - convolutions of the insular lobe.

The foramen of Monroe is located medial to the posterior short gyrus, and accordingly the knee of the internal capsule projects to the level of the middle third of the insula (see Fig. 8). Thus, the pyramidal tract and thalamus are localized under the back half insula - anterior and posterior long gyri.

All parts of the lateral ventricle are projected onto the insular lobe. The anterior sections of the anterior horn of the lateral ventricle project onto the anterior periinsular sulcus. The superior periinsular groove corresponds to the posterior parts of the anterior horn, the body and the anterior parts of the vestibule of the lateral ventricle. The posterior 2/3 of the inferior periinsular groove projects onto the inferior horn and vestibule of the lateral ventricle.

Blood supply to the insula

The insula is predominantly supplied by numerous perforating arteries arising from the M2 segment of the middle cerebral artery (Fig. 9).

Rice. 9. a - insular lobe and M2 and M3 segments of the middle cerebral artery. Blue arrows indicate numerous, small-diameter perforating (insular) arteries; white arrow - to a long perforator in the posterosuperior part of the insula; b - a long perforating vessel extending from the M2 segment of the middle cerebral artery (white arrow), in the posterosuperior part of the insula.

The arteries that make up the M2 segment of the middle cerebral artery run along the insular sulci, with the exception of the superior periinsular sulcus, which they cross at right angles (see Fig. 4, blue arrows).

In 17 M1 hemispheres, the segment at the level of the insular threshold ended with a bifurcation; in one hemisphere, trifurcation was observed. The superior trunk supplied blood to the anterior, middle, and posterior short gyri in 15 hemispheres, and in the remaining 3, perforating arteries from both the superior and inferior trunks approached the posterior short gyrus. The anterior long gyrus in 14 hemispheres was supplied with blood from the lower trunk, in 3 hemispheres - from the upper and lower, in one - from the middle. The posterior long gyrus in all preparations was supplied with blood only from the lower part of the M2 segment. In 2 preparations we also found branches extending from the M1 segment and supplying the threshold of the insula.

According to the results of our study, in 5 (27%) hemispheres in the upper part of the posterior lobe, we found perforating arteries of the M2 segment, which differed from other perforators in their larger diameter (see Fig. 9). Of these arteries, only in 2 (11%) hemispheres did they reach the corona radiata.

Lenticulostriate arteries

The branches of the middle cerebral artery of small diameter, perforating the central and lateral parts of the anterior perforated substance, are designated as lenticulostriate. These arteries are usually divided into medial and lateral depending on the location of their origin from the middle cerebral artery.

The medial arteries supply blood to part of the head of the caudate nucleus, the central-medial portion of the putamen, the lateral segment of the globus pallidus, partially the anterior thigh of the internal capsule and the anterosuperior part of the posterior thigh (Fig. 10, a).

Rice. 10. Course of the medial (a) and lateral (b) lenticulostriate arteries. Frontal cut; front view.

The lateral group of arteries supplies the upper part of the head of the caudate nucleus and the anterior femur of the internal capsule, most of the putamen, part of the lateral segment of the globus pallidus and the upper part of the knee and posterior femur of the internal capsule with the adjacent part of the corona radiata (see Fig. 10, b; Fig. 11 ).

Rice. 11. Schematic representation of the arterial system of the insular region. 1 - long perforator from the M2 segment of the middle cerebral artery; 2 - medial lenticulostriate arteries; 3 - lateral lenticulostriate arteries; 4 - short perforators of the M2 segment of the middle cerebral artery.

Although the number of lenticulostriate arteries varies from 5 to 24, occlusion of even one artery can lead to extensive infarction in the area of the subcortical ganglia and internal capsule. The average number of arteries in the study of 18 hemispheres was 8 (3-20).

From the medial third of the M1 segment, the perforating arteries departed in 7 hemispheres, ranging from 1 to 3, in the caudal-dorsal-lateral direction; from the middle third, these arteries departed in 18 specimens in an amount from 2 to 5 and ran in the caudal-dorsal-medial direction.

The lateral lenticulostriate (LLS) arteries originated from the dorsal (or caudal-dorsal) part of the final third of M1 (Fig. 12) and were detected in all preparations. The average number of these arteries is 4. From the point of origin, these arteries first go in a medial direction behind the M1 segment, then turn back, upward and, before entering the anterior perforated substance, laterally.

Rice. 12. a - lateral lenticulostriate arteries arise from the M1 and M2 segments of the middle cerebral artery; b - lateral lenticulostriate arteries arise only from the M1 segment of the middle cerebral artery.

In 5 (28%) hemispheres, the LLS arteries departed from the M2 segment of the middle cerebral artery in the immediate vicinity of the bifurcation (see Fig. 12, a).

It is important to note that in 7 (38%) hemispheres, the lateral lenticulostriate arteries departed from the M1 segment in the form of a single trunk, which then split into separate branches.

The average distance between the entry point of the most lateral lenticulostriate artery into the anterior perforated substance and the threshold of the insula was 16 mm (see Fig. 12, b), and the average length of the lateral lenticulostriate arteries from the place of origin on the M1 segment to the entrance into the anterior perforated substance was 4 mm .

Anatomical boundaries of resection of insular glial tumors

Knowledge of the anatomical features of the insular lobe and possible anatomical boundaries of resection (primarily medial) is extremely important in the surgical treatment of diffusely growing glial tumors of the insula.

Possible boundaries for resection of glial tumors of the islet, in our opinion, are the following anatomical formations: superomedial border - corona radiata (intraoperative landmark - superior periinsular sulcus); inferior medial - lenticular part of the internal capsule; posteromedial - posterior thigh of the internal capsule (no intraoperative landmarks); central medial - extreme and outer capsules or subcortical nuclei (fence/shell), depending on the degree of tumor spread in the medial direction (intraoperative landmark - the appearance of the basal ganglia substance of gray/beige color); anteromedial - anterior part of the anterior thigh of the internal capsule (no intraoperative landmarks); anterobasal - anterior perforated substance (intraoperative landmarks are the threshold of the insula, the M1 segment of the middle cerebral artery and the most distal lenticulostriate artery).

Access modeling

An imitation of transcortical (on 9 hemispheres) and transsylvian (also on 9 hemispheres) approaches was performed. When modeling the transsylvian approach, the following steps were performed: dissection of the superficial part of the Sylvian fissure, dissection of the deep part of the Sylvian fissure located under the temporal operculum, dissection of the deep part of the Sylvian fissure located under the frontal and parietal operculum.

When simulating transcortical access, the opercular parts located above one of 5 zones were removed (Fig. 13): the threshold of the insula, the upper parts of the anterior lobe (under the frontal operculum), the lower parts of the anterior lobe (under the temporal operculum), the upper parts of the posterior lobe (under the parietal operculum). tegmentum) and the lower parts of the posterior lobe (under the temporal tegmentum).

Rice. 13. Sections of the insular lobe of the brain are indicated in different colors. 1 - anterosuperior; 2 - posterosuperior; 3 - posteroinferior; 4 - anterior-inferior; 5 - threshold.

Discussion

Despite its practical importance (up to 25% of all low-grade and up to 10% of all high-grade gliomas are located in the insula) and functional complexity (the insula is surrounded by the Broca and Wernicke speech centers located around the Sylvian fissure, the primary motor and sensory cortex of the facial area, as well as the conductive pathways connecting these areas) of the insula, only a few publications are currently available devoted to the study of the anatomy of this brain region. In addition, the insula has now been shown to play a key role in many processes - from viscerosensory and pain perception to motivational, cognitive control of speech and emotions. T. Wager called the insula the key connecting thinking and the affective sphere, and A. Craig believed that the anterior part of the insula, which receives rich interoreception and has powerful connections with limbic structures, is responsible for self-awareness.

In our work, we focused on the morphological features of the convolutions of the insula and its tegmentum, the specifics of the vascular system of the insular region from the standpoint of the two main approaches used to approach the insula: transsylvian and transcortical.

Classic works describe the insula as the fifth lobe of the brain, shaped like a pyramid and delimited from the surrounding frontal, parietal and temporal lobes by periinsular sulci. Most authors distinguish the anterior, superior and posterior periinsular sulci. A slightly different view is presented in the work of A. Afif et al. , where the insula is represented as a trapezoid, and the authors describe 4 peri-insular grooves: anterior, superior, posterior and inferior. When examining our anatomical material, we adhered to the description of the anterior, superior and posterior periinsular grooves.

As is known, the insular lobe is supplied with blood from numerous perforating arteries arising from the vessels of the M2 segment of the middle cerebral artery lying on it. However, an important practical question arises: can they be coagulated during tumor removal? How deep do these arteries extend in the medial direction and where does their blood supply end?

Before our study, these arteries were described only in three works, and they were first described by G. Varnavas et al. , who discovered perforating arteries of larger diameter in the upper parts of the posterior lobe of the insula in a quarter of the hemispheres studied. The area of blood supply to these arteries was not specified.

N. Tanriover et al. described perforating arteries of larger diameter not only in the superior posterior part of the insula, but also in the lower parts of the posterior lobe.

U. Ture et al. indicate that approximately 85-90% of insular (arising from the M2 segment) arteries are short and supply blood only to the insular cortex and the extreme capsule, 10% of arteries are of medium length and reach the fence and external capsule, and 3-5% of arteries are long (found in the posterior lobe of the insula), supplying the corona radiata. Damage to the latter during resection of insular tumors can lead to hemiparesis.

Examining our material, we found perforators of the M2 segment of larger diameter only in the upper parts of the posterior long gyri, while only in 2 (11%) hemispheres they supplied blood to the corona radiata. In all other cases, they branched no further than the lateral part of the shell. Consequently, the medial border of the zone of blood supply to the insular arteries is the external capsule, with the exception of the superoposterior parts of the insula, where in a small number of cases the perforating arteries reach the corona radiata.

Since glial tumors of the insular lobe are supplied with blood from M2 segment perforators, one of the stages of tumor removal is its devascularization by coagulation of M2 perforators. However, taking into account the results of the anatomical study, we assume that in the posterior parts of the insula this stage of access (if the large perforating vessel is coagulated) can lead to ischemic damage to the corona radiata and, as a consequence, to neurological deficit.

Preservation of the lenticulostriate arteries is one of the most challenging tasks in insula surgery, and damage to these arteries is considered a major cause of persistent neurological deficits. In this regard, the most lateral lenticulostriate artery becomes important as an intraoperative landmark, accessible only with a transsylvian approach and allowing one to determine the lateral border of the anterior perforated substance. An equally important landmark during the removal of glial tumors from the islet is its threshold, which is also well recognized using the transsylvian approach. According to the results of our anatomical study, the entry point of the most lateral lenticulostriate artery into the anterior perforated substance is located at a distance of 16 mm from the middle of the insular threshold (which approximately corresponds to the results obtained by N. Tanriover et al. - 15.3 mm), and the average length of the lateral lenticulostriate arteries from the point of origin from the M1 segment to the entrance to the anterior perforated substance is 4 mm.

A distinctive feature of the insula is that the lobe cortex does not reach the surface of the brain, which makes direct surgical access to it difficult. The insula is hidden by parts of the temporal, frontal and parietal lobes located above and below it - the tegmentum. In the literature, there are differences in the designation of the insular tires. A number of authors identify three opercula: frontal, parietal and temporal (or fronto-orbital, fronto-parietal and temporal), others describe only two - fronto-parietal and temporal. In our opinion, it is optimal to isolate the frontal, parietal and temporal operculum, since in this case the name and boundaries of the operculum coincide with the lobes in which they are located.

However, the designation options for the tires do not have a fundamental (practical) significance, in contrast to the peculiarities of their structure in the anterior/posterior and superior/inferior sections, which determines the different accessibility of sections of the insula during transcortical and transsylvian access.

The insular lobe, in our opinion, can be naturally divided into several sections (see Fig. 13). The central sulcus divides the insula into anterior and posterior lobes, in each of which the upper part is located under the frontal/parietal operculum, and the lower part is located under the temporal one. Thus, the island is divided into 4 sections: anterosuperior , anteroinferior , posterosuperior , posteroinferior We also consider it appropriate, due to the anatomical proximity to the anterior perforated substance, to isolate in the anteroinferior section threshold islet.

The thickness of the operculum over the anterior lobe of the insula is less than that over the posterior lobe, and the height of the frontal and parietal operculum is greater than the height of the temporal one. Therefore, the depth of the surgical wound in the anterior sections of the insula is less than in the posterior sections.

In addition, the axis of the planum polare, which covers the anterioinferior part of the insula, unlike all other operculum, is oriented at an acute angle to the sagittal plane and is deflected laterally (see Fig. 4), which, together with the upward retraction of the triangular part, increases the free space of the Sylvian fissure at this level and facilitates retraction during the transsylvian approach to the anterior inferior parts of the insula.

Therefore, by modeling the transsylvian approach on anatomical preparations, taking into account the morphology of the cerebral tegmentum covering the insula, we came to the conclusion that the lower parts of the lobe are more accessible than the upper ones (due to the extremely inconvenient superoposterior angle of attack and the greater height of the frontal and parietal tegmentum in comparison with the temporal one) .

The accessibility of the anterosuperior and posterosuperior sections also differs. Despite the fact that the depth of the wound when accessing the anterosuperior sections of the insula is less than the posterosuperior ones (see Fig. 3 and 7), the distance to the superior periinsular sulcus (the length of the anterosuperior and posterosuperior sections located under the frontal and parietal operculum (see Fig. 3, distance B) is greater in the anterosuperior part of the lobe, which leads to the fact that with the transsylvian approach the anterosuperior and posterosuperior parts become equally inaccessible. The smaller thickness of the tires in the anterosuperior part is offset by the greater distance to the superior periinsular groove (see Fig. 3, distance B). ), which makes this section the least accessible with the transsylvian approach.

Thus, the most accessible with the transsylvian approach are the lower zones of the insula (including the threshold), and the least accessible are the upper sections. Therefore, if the tumor is localized in these parts of the insular lobe, a transcortical approach may be recommended, which, unlike the transsylvian one, does not require significant retraction of the medulla and provides a larger surgical corridor.

When modeling transcortical access, the only difference in the accessibility of the insular sections was the greater depth of the surgical wound in the posterior sections compared to the anterior ones. Since the transcortical approach involves resection of a part of the tegmentum projectively located above the tumor-affected part of the insula, the angle of attack (and therefore accessibility) to the upper and lower parts of the lobe, unlike the transsylvian approach, does not differ.

The transcortical approach, regardless of the section of the insula, provides a greater surgical overview and working space compared to the transsylvian approach, however, when the tumor is located at the threshold of the insula, it does not provide reliable proximal control of the lenticulostriate arteries, therefore, when the tumor is localized in this area, the transsylvian approach may be recommended .

Conclusion

Detailed knowledge of the surgical anatomy of the insular region ensures the correct intraoperative determination of a number of the most important anatomical landmarks (insular threshold, peri-insular grooves, the most distal LLS artery) and helps to correctly select the surgical approach option.

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immaturity

Hello! Please tell me, my one month old baby is diagnosed with brain immaturity by ultrasound, here are the ultrasound results. Midline structures are not displaced, differentiated, the pattern of convolutions and sulci is N, the interhemispheric fissure is 1.9 mm, the subarachnoid space is not expanded, vascular pulsation is not strength, echogenicity of the brain parenchyma is not changed, the echo structure of the brain parenchyma is homogeneous, the echo structure of the thalami is not changed, the Sylvian fissure is U-shaped with D and S, the depth of the anterior horns is right 2.6 mm, left 2.4 mm, body depth - right 2.5 mm, left 2.4 mm, anterior horn index 26.5, width of the 3rd ventricle 2.2 mm, cavity of the transparent septum 5.3 mm, periventricular region: structure unchanged, choroid plexuses: dimensions right - 5.2 left - 5.2, the contour is clear, even, the structure is homogeneous! The neurologist said that all the child’s reflexes are normal, he prescribed picamilon 0.02 1/4 2 times a day...

immaturity

Congenital arachnoid cysts are also called leptomeningeal cysts. This term does not include either secondary “arachnoid” cysts (for example, post-traumatic, post-infectious, etc.) or glioepindemal cysts lined with glial tissue and epithelial cells.

Definition and etiology. Congenital arachnoid cysts are a developmental anomaly resulting from division or duplication of the arachnoid membrane (thus, they are actually intraarachnoid cysts).

The etiology of these lesions has long been the subject of debate. The most common theory is that they develop due to a slight developmental abnormality of the arachnoid membrane around the 15th week of gestation, when cerebrospinal fluid (CSF) begins to be produced to gradually replace the extracellular substance between the outer and inner arachnoid membranes (endomenings).

The developmental anomaly hypothesis is confirmed by the usual location of arachnoid cysts at the level of normal arachnoid cisterns, their random appearance in siblings, the presence of concomitant anomalies of vein architecture (for example, the absence of the Sylvian vein) and the presence of other congenital anomalies (agenesis of the corpus callosum and Marfan syndrome).

It is still unclear why arachnoid cysts tend to expand. Electron microscopy and ultracytochemical analysis showed increased activity of the Na + and K + pump in the cyst wall compared with the normal arachnoid, supporting the theory of active production of cerebrospinal fluid by the membrane lining the cyst, which has morphological similarities with the subdural neuroepithelium and the neuroepithelial lining of the arachnoid granulation. On the other hand, cine-MPT and live endoscopic video have shown that some arachnoid cysts may enlarge when CSF is trapped by the valve mechanism.

The pressure gradient for the movement of cerebrospinal fluid into the arachnoid cyst will be provided by a transient increase in cerebrospinal fluid pressure caused by the systolic oscillation of the cerebral arteries or the transmitting pulsation of the veins.

Specific problems in determining pathogenesis concern intraventricular cysts. Some authors present them as a kind of “internal” meningocele; according to others, they are formed from the arachnoid layer and are transported along with the choroid plexus when it protrudes through the choroidal fissure.

Anatomical classification and topographic distribution of intracranial arachnoid cysts.

I. Intracranial arachnoid cysts:

A) Frequency of occurrence. Congenital arachnoid cysts are reported to account for approximately 1% of nontraumatic intracranial mass lesions. This rather old indicator was obtained by correlating clinical experience in the pre-CT/MRI era (0.7-2% of mass lesions) and autopsy data (0.1-0.5% of incidental findings at autopsy); In recent years, an increase in the incidence of these formations has been described. Intracranial arachnoid cysts are almost always solitary and sporadic.

They occur 2-3 times more often in men than in women, and 3-4 times more often on the left side of the brain than on the right. The appearance of bilateral, more or less symmetrical cysts has been described in healthy children, as well as in children with neurological disorders, although this is rare. In the latter case, especially in patients with bitemporal cysts, the differential diagnosis should be made with damage resulting from perinatal hypoxia.

Based on information provided from large mixed series (including both children and adults), it appears that the largest proportion of childhood cases occurs in the first two years of life.

b) Anatomical distribution. The typical localization of arachnoid cysts is within the middle cranial fossa, where 30-50% of the damage was found. Another 10% occurs in the medullary convex, 9-15% are found in the suprasellar region, 5-10% in the quadrimenal plate cistern, 10% in the cerebellopontine angle, and 10% in the midline of the posterior fossa. The anatomical classification and topographic distribution of the different types of arachnoid cysts are given in the table below.

II. Supratentorial arachnodal cysts:

A) Sylvian fissure cysts. Lateral sulcus cysts account for about half of all cases in adults and a third of cases in children. Galassi et al. divided Sylvian fissure cysts into three types depending on their size and relationship (CT with metrizamide) with normal cerebrospinal fluid spaces:

- Type I: cysts are small, biconvex or semicircular, freely communicating with adjacent cisterns.

- Type II: medium-sized cysts, rectangular in shape, associated with the anterior and middle parts of the temporal fossa with a moderate mass effect; they communicate or do not communicate with adjacent tanks.

- Type III: cysts are large, round or oval, occupying the middle cranial fossa almost completely, causing constant and severe compression of adjacent nerve structures, resulting in displacement of the ventricles and midline; connections with the subarachnoid space are absent or non-functional.

Lateral sulcus cysts can present clinically at any age, but are more likely to become symptomatic in childhood and adolescence than in adulthood, and in most studies, infants and toddlers account for about 1/4 of the cases.

The diagnosis is often made by chance. Symptoms that occur are often nonspecific, with headache being the most common complaint. Among the focal symptoms in advanced cases, slight proptosis and contralateral paresis of the central type are possible. Seizures and signs of increased intracranial pressure represent the clinical onset in approximately 20-35% of patients. When signs of increased intracranial pressure appear acutely, they are usually the result of a sharp increase in cyst volume due to subdural or intracystic hemorrhage.

Mental disturbances are found in only 10% of cases, but developmental delay and behavioral disturbances are common in children with large cysts and are almost constant and severe in patients with bilateral cysts.

Local convexity of the skull and/or asymmetrical macrocrania are characteristic signs observed in half of the patients. CT scan in such cases reveals outward protrusion, thinning of the temporal scales and anterior displacement of the lesser and greater wings of the sphenoid bone. Cysts appear as clear formations between the dura mater and the malformed brain with cerebrospinal fluid density and no contrast enhancement. The ventricles of the brain are usually of normal size or slightly dilated. MRI reveals T1-hypointense and T2-hyperintense formations.

Vascular examination is useful to determine the relationship of arteries and veins to the cyst wall. In order to determine the presence or absence of communication between the cyst and the subarachnoid space, flow cine sequences have recently been used, which can replace CT with metrizamide. This may be especially important in asymptomatic patients and in patients with nonspecific clinical symptoms. In this regard, additional information that may indicate the need for surgical intervention can be obtained by monitoring ICP. Perfusion MRI and SPECT are also used, the latter helping to assess cerebral perfusion around the cyst wall.

There are three surgical treatment options, used alone or in combination:
- Marsupialization by craniotomy
- Endoscopic cyst removal
- Cyst shunting

Open removal of the cyst is considered the optimal surgical procedure. Successful results range from 75 to 100%, and surgical mortality is almost zero. There are two issues to note regarding open surgery:
- Total removal of the arachnoid cyst is no longer considered advisable; large holes in the cyst wall are sufficient to ensure the passage of cerebrospinal fluid through the cyst cavity and reduce the risk of damage to adjacent brain structures. Moreover, partial opening of the cyst can also prevent the leakage of cerebrospinal fluid into the subdural space and the development of postoperative subdural hygromas.
- All vessels that cross the cyst cavity or lie on the cyst wall are normal and therefore should be preserved.

In recent years, endoscopic cyst removal has been proposed as an alternative to open surgery. Endoscopy is also used as an adjunct to open surgery to reduce the size of the surgical approach. Positive results of endoscopic techniques range from 45 to 100%.

Cyst shunting is clearly safer, but is accompanied by a high frequency of additional surgical procedures (about 30%) and lifelong dependence on the shunt.

Examples of arachnoid cysts of the Sylvian fissure according to Galassi.

b) Sellar cysts. Sellar cysts are the second most common supratentorial location among intracranial arachnoid cysts. There are slightly more men affected than women: the ratio is about 1.5/1. Cysts can be divided into two groups:
- Suprasellar cysts located above the diaphragm of the sella turcica.
- Intrasellar cysts located in the cavity of the sella turcica.

The latter are much less common and occur exclusively in children.

The term sella cysts does not include empty sella syndrome, intrasellar and/or suprasellar diverticula of the arachnoid membrane. Metrizamide CT or cine-MPT aids in the differential diagnosis by showing lack of contrast enhancement and absence of cerebrospinal fluid flow within a true cyst.

Intrasellar arachnoid cysts are asymptomatic in approximately half of the cases. Headache is the most common complaint in symptomatic patients, and endocrinological disturbances are often observed with this location of the cyst. Suprasellar cysts, on the contrary, most often present with headaches, visual disturbances and neuroendocrine symptoms are typical. Hydrocephalus typically occurs when cyst expansion obstructs the flow of cerebrospinal fluid from the foramina of Monro and/or basal cisterns. With large cysts, posterior dislocation of the brainstem may develop with secondary compression of the aqueduct of Sylvius, which can lead to dilatation of the ventricles.

This process occurs relatively slowly, for this reason, signs of intracranial hypertension (swelling of the optic disc, optic nerve atrophy occur, although often, but relatively late.

Hypopituitarism is common, mostly with impaired metabolism of growth hormone and ACTH. Delayed menstruation may also be noted. A rare but typical manifestation of cysts above the sella turcica is the “doll's head” symptom, characterized by slow, rhythmic movements of the head in an anteroposterior direction.

In the pre- and neonatal period and early childhood, echoencephalography is a useful diagnostic tool to monitor the evolution of these types of lesions during the first months of life. If possible, an MRI should be performed to assess the multilevel connections between the cyst and the surrounding neural structures and ventricles, which is necessary for planning surgical treatment. MRI (or contrast-enhanced CT as an alternative) is also important for the differential diagnosis between supra sellar arachnoid cysts and other possible cystic lesions of the sellar region (eg, Rathke's pouch cyst, cystic craniopharyngioma, epidermoid cyst, etc.).

The rapid development of endoscopic technologies has significantly changed the treatment of sellar cysts. The endoscopic transnasal approach is ideal for intrasellar cysts, replacing the traditional microsurgical approach to these lesions. Cysts located above the sella turcica are treated only by opening the roof of the cyst (endoscopic transventricular vengriculocystostomy) compared to opening both the roof of the cyst and the bottom of the cyst (ventriculocisternostomy), the latter method is actually considered safer and, compared with ventriculocystostomy, is associated with lower relapse rate (5-10% versus 25-40%).

Shunt operations are practically not performed. Although relatively safe, they are associated with a surprisingly high rate of reoperation. Microsurgical excision, dissection, or marsupialization are reserved for cases where endoscopic techniques are not feasible or for patients with cysts extending beyond the ventricle (eg, suprasellar arachnoid cyst involving the medial temporal lobe).

It is important to remember that, regardless of surgical treatment, existing endocrinological disorders resolve in rare cases, which requires adequate drug therapy. Visual signs and symptoms of intracranial hypertension resolve after surgery.

V) Cerebral convex cysts. They are relatively rare (4-15% of all intracranial arachnoid cysts), and women are affected more often than men. We distinguish two main types of these cysts:
- Hemispherical cysts, huge accumulations of fluid extending over the entire or almost the entire surface of one hemisphere of the brain.
- Focal cysts are usually small formations associated with the cerebral surface of the hemispheres.

Hemispheric cysts are considered expanded lateral sulcus cysts, characterized by a compressed rather than enlarged lateral sulcus and the absence of temporal lobe aplasia. They are most often found in children with macrocrania, a prominent anterior fontanelle, and cranial asymmetry. CT and MRI in most cases allow a differential diagnosis with chronic fluid accumulation in the subdural space (subdural hygroma and hematoma).

Localized cranial protrusion usually suggests the presence of a solitary cyst. Children typically have no neurological symptoms, while adults often develop focal neurological deficits and/or seizures. Differential diagnosis is made from low-grade neuroglial tumors, usually using MRI.

The treatment of choice is microsurgical marsupialization. There is no need to remove the medial wall of the cyst, which is closely connected to the cerebral cortex. Shunt implantation is recommended only in cases of recurrence, although this method has also been proposed as a primary procedure in children with hemispheric cysts due to immature absorption capacity and the high risk of failure of open surgery. In such cases, it is recommended to install a shunt with a programmable valve to effectively control the pressure inside the cyst and favor the development of natural pathways for the outflow of cerebrospinal fluid.

G) Interhemispheric cysts. Interhemispheric cysts are quite rare, accounting for 5-8% of intracranial arachnoid cysts in all age groups. There are two main types:
- Interhemispheric cysts associated with partial or complete agenesis of the corpus callosum
- Parasagittal cysts not accompanied by defects in the formation of the corpus callosum

Macrocrania is observed in a large percentage of cases, and two-thirds of patients develop symptoms of intracranial hypertension. Localization: A bulging skull is the second most common manifestation. Hydrocephalus is mild or absent in patients with parasagittal cysts, but is relatively common in patients with interhemispheric cysts.

On MRI, interhemispheric arachnoid cysts are differentiated by a typically wedge-shaped appearance on coronal sections sharply separating the falx on one side. Primary agenesis of the corpus callosum and type IC holoprosencephaly may have a similar appearance on MRI; however, an interhemispheric cyst of the occipital horns of the lateral ventricles can be easily differentiated, since the occipital horns are displaced by the cyst and the basal ganglia are normally divided.

The method of choice is craniotomy with removal of the cyst. This allows you to normalize intracranial pressure. Because of the significantly high complication rate, bypass procedures should only be considered as a second choice in complex cases.

d) Cysts of the quadrigeminal plate area. Cysts of the quadrigeminal plate region account for 5-10% of all intracranial arachnoid cysts. Most of them are diagnosed in children, with a higher frequency in girls than boys.

Clinical manifestations depend on the direction of cyst growth. Most of these cysts develop upward into the posterior part of the interhemispheric fissure or downward into the fossa of the superior cerebellar vermis, in some cases with the possibility of supratentorial infratentorial expansion. Because of their close location to the cerebrospinal fluid pathways, they are usually diagnosed in childhood due to secondary obstructive hydrocephalus. Abnormalities in pupil reaction or eye movement may be detected due to compression of the quadrigeminal plate or stretching of the trochlear nerve; however, impairment of upward gaze is relatively rarely diagnosed. When growth is directed to the lateral side and into the cisterns, hydrocephalus is usually absent, but focal symptoms are determined.

Sagittal and coronal MRI sections clearly show the connection of the cyst with the supratentorial and infratentorial structures and ventricles.

As with sella cysts, modern neuroendoscopic techniques have significantly changed the treatment tactics for these types of lesions, which were previously considered technically difficult. In case of small formations (< 1 см), вызывающих вторичную тривентрикулярную гидроцефалию, вентрикулостомию третьего желудочка следует рассматривать как необходимое хирургическое лечение. При крупных образованиях должна быть выполнена вентрикулоцистостомия, по возможности в сочетании с вентрикулостомией третьего желудочка у пациентов с гидроцефалией. Хотя на момент написания в литературе описаны небольшие серии наблюдений, исследователи однозначно пришли к выводу, что эндоскопическое удаление кист области четверохолмной пластины является безопасным и успешным практически во всех случаях.

III. Subtentorial arachnoid cysts. Cysts of the arachnoid membrane of the posterior cranial fossa are quite rare and account for about 15% of all intracranial cysts. It is necessary to distinguish them from other cystic malformations of the posterior fossa, namely Dandy-Walker malformation and cystic evagination of the choroidal plexus. The main differential features of these various pathological conditions are given in the table below.

Localization of the pathological focus with MRI of the brain begins with determining the location of the lesion in relation to the tentorium of the cerebellum. Therefore, formations above the tentorium are classified as supratentorial, and everything below is classified as infratentorial.

MRI of the brain. Midsagittal section. tentorium cerebellum (arrow).

Above the tentorium are the cerebral hemispheres. Each hemisphere of the brain consists of four lobes - frontal, parietal, occipital and temporal. If the pathology is located in the hemisphere, then it is necessary to decide which lobe it belongs to. To do this, you first need to find the grooves that serve as the boundaries of the lobes.
The central sulcus (sulc.centralis) is better visible in the sagittal plane. It is located in the middle between the parallel precentral and postcentral sulci. There are many options for the structure and course of the furrow. Usually it has a significant extent and goes in the anterior-inferior direction from the interhemispheric fissure to the Sylvian fissure, which it does not always reach. The lower end of the furrow either continues in its main direction or bends back. The central sulcus may be interrupted along the way. In the transverse plane on the upper sections, the groove has the greatest extent, reaching almost to the interhemispheric fissure. The lower the cut, the shorter the central groove on it. At the level of the lateral ventricles it is barely visible. The central sulcus separates the frontal and parietal lobes.

MRI of the brain. Lateral sagittal section. Central sulcus (arrow).

MRI of the brain. Axial slice. Central sulcus (arrows).

MRI of the brain. Axial section at the level of the roof of the lateral ventricles. Central sulcus (arrows).

MRI of the brain. Borders of the frontal and parietal lobes in the axial plane.

Another important groove is the Sylvian fissure (fissura cerebri lateralis). On sagittal sections it goes from bottom to top in the anteroposterior direction (Fig. 32). In the axial plane, the Sylvian fissure itself also deviates backward, while its branches are directed perpendicularly towards the interhemispheric fissure. The Sylvian fissure separates the frontal and parietal lobes from the temporal lobe.

MRI of the brain. Lateral sagittal section. Sylvian fissure (arrows).

MRI of the brain. Axial section at the level of the third ventricle. Sylvian fissure (arrows).

MRI of the brain. Borders of the frontal, parietal, temporal and occipital lobes on a sagittal section.

To delimit the parietal lobe, you also need to find the parieto-occipital sulcus (sulc. parietooccipitalis). This groove in the sagittal plane can be traced on the median and medial sections. It extends from the surface of the brain downwards, has a considerable extent and is often segmented. In the transverse plane, the parieto-occipital sulcus extends almost perpendicular to the interhemispheric fissure (Fig. 36) and gives off many small branches. Thus, the boundaries of the parietal lobe are the central sulcus with the frontal lobe, the parieto-occipital sulcus with the occipital lobe, the Sylvian fissure and the superior temporal sulcus (angular gyrus) with the temporal lobe.

MRI of the brain. Medial sagittal section. Parieto-occipital sulcus (arrow).

MRI of the brain. Axial slice. Parieto-occipital sulcus (arrow).

MRI of the brain. Borders of the parietal lobe on the medial sagittal section.

The next important dividing groove is the collateral groove (sulc.collateralis). On sagittal sections, it is visible as the inferolateral border of the parahippocampal gyrus, in the region of the pole of the temporal lobe (Fig. 38). It is easier to see in the axial plane in sections at the level of the midbrain (Fig. 39). When the axial plane of the slices is tilted backward, it is visible simultaneously with the temporo-occipital sulcus. The temporo-occipital groove (sulc. temporooccipitalis) on lateral sagittal sections runs sinuously backward along the border of the brain with the temporal bone and then bends upward (Fig. 40). On axial sections at the level of the Varoliev bridge, it is located in the anteroposterior direction. Thus, the border of the temporal lobe (Fig. 41) with the frontal and parietal lobes is the Sylvian fissure, with the occipital lobe - the temporo-occipital sulcus and the collateral sulcus.

MRI of the brain. Sagittal section. Collateral groove (arrow).

MRI of the brain. Axial slice. Collateral groove (arrows).

MRI of the brain. Axial section at the level of the Varoliev bridge. Temporo-occipital sulcus (arrows).

MRI of the brain. Axial section at the level of the cerebral peduncles. Borders of the temporal lobe.

To determine the boundaries of the occipital lobe, we already have all the landmarks. The border with the parietal lobe is the medially located parieto-occipital sulcus, and the border with the temporal lobe is the laterally located temporo-occipital sulcus.

MRI of the brain. Coronal section. Border sulci (SPO - parieto-occipital sulcus, STO - temporo-occipital sulcus, SCol - collateral sulcus).

MRI of the brain. Borders of the occipital lobe on the medial sagittal section.

Usually localization by lobes is sufficient to describe hemispheric pathologies. In some cases, when reference to gyri or functional areas is required, we recommend using the appropriate atlases (A.V. Kholin, 2005).
With centrally (axially) located space-occupying formations, the ventricles of the brain and the subcortical (basal) nuclei located around them may be involved. The optic thalamus, hypothalamus, subthalamus, and epithalamus belong to the diencephalon, a component of the brain stem.

MRI of the brain. Axial slice. Lateral ventricles and subcortical nuclei (NC - caudate nucleus, NL - lenticular nucleus, Th - thalamus optic). Parts of the brainstem (lower midbrain, pons, and medulla oblongata) and the cerebellum are located infratentorially.

The midbrain only partially occupies the supratentorial space; a significant part of it passes through the hole in the tentorium into the posterior cranium. hole. The paired legs of the brain and roof (tectum) are always clearly visible from behind. The roof of the midbrain lies posterior to the aqueduct and consists of the quadrigeminal plate.

MRI of the brain. Midsagittal section. Brainstem (V3 - third ventricle, V4 - fourth ventricle, Q - plate quadrigeminal, Mes - midbrain, P - pons, C - cerebellum, M - medulla oblongata).

The border between the midbrain and the pons is the superior sulcus, and the border with the medulla oblongata is the inferior sulcus of the pons. The bridge has a characteristic protruding front part. The posterior surface of the pons is a continuation of the medulla oblongata. At the upper border of the bridge between its abdomen and the middle cerebellar peduncle, the trigeminal nerves (n. trigeminus, V pair) begin. They are clearly visible on transverse MR sections, as they run horizontally forward and have a thickness of about 5 mm. The trigeminal nerve is divided into 3 branches - optic (1), maxillary (2) and mandibular (3). They all go forward into Meckel's cavity to the trigeminal ganglion. From here, branch 3 goes down through the foramen ovale, and branches 1 and 2 go through the cavernous sinus, along its lateral wall. Then, branch 1 enters the orbit through the superior foramen, and branch 2 exits the cranial cavity through the foramen rotundum.
The III, IV and VI pairs of cranial nerves, which provide movement of the eyeball, are usually not visualized on MRI scans.

MRI of the brain. Axial slice. Trigeminal nerves (arrow).

The facial nerve (n. facialis, VII pair) and the vestibulocochlearis nerve (n. vestibulocochlearis, VIII pair) exit their trunk together, the facial nerve is slightly medial, and go in one bundle, crossing the pontocerebellar cistern, and go into the internal auditory opening temporal bone. In the internal auditory canal, the vestibular branch runs in the posterior superior and inferior quadrants, the cochlear branch in the inferior, and the facial nerve in the anterior superior. The VII nerve enters the labyrinth (labyrinthine segment), runs inside the temporal bone to the geniculate body, turns back and passes under the lateral semicircular canal (tympanic segment) and exits the temporal bone through the stylomastoid foramen (foramen stylomastoideum). Next, the nerve goes to the salivary gland, where it divides into terminal branches. On MRI scans in sections 3-5 mm thick, the VII and VIII nerves are not separated and are designated as the auditory nerve. With thinner sections, the course of each nerve can be visualized separately.

MRI of the brain. Axial slice. Auditory nerve.

The medulla oblongata begins from the lower border of the pons. At the level of the foramen magnum it passes into the spinal cord. From it depart from the IX to XII pairs of cranial nerves, of which the initial part of the hypoglossal nerve (n. hypoglossus, XII pair) and, in the form of a single complex, IX, X, XI pairs are sometimes visible on transverse MRI.
The IV ventricle runs from the aqueduct above to the foramen of Majendie below. It is located between the brainstem in front and the velum and cerebellar peduncles in the back.
The cerebellum is located posterior to the pons and medulla oblongata. It is connected to the brain stem by the superior, middle and inferior cerebellar peduncles. The cerebellum consists of a midline vermis and paired hemispheres.

MRI of the brain. Axial slice. Cerebellum (CV - cerebellar vermis, CH - cerebellar hemisphere).

MRI in St. Petersburg, carried out by us, always clearly indicates the localization of the lesion in the conclusion, which is necessary for comparison with the clinic and deciding on the possibility and scope of the operation.

The aqueduct of Sylvius is part of the central cerebral canal and serves to connect the cavities of the third and fourth ventricles in the brain. It is located under the quadrigeminal area, surrounded by gray matter, the nuclei of the cranial (oculomotor and trochlear) nerves and other brain structures. When viewed through a section of the midbrain, it resembles a diamond or triangle.

Functions of the Sylvian aqueduct

The Sylvian aqueduct, connecting the ventricles with each other, ensures the trophic function of these structures. Incoming nutrients form the correct functioning of brain cells. The aqueduct of Sylvius circulates cerebrospinal fluid (CSF) and creates pressure. Liquor is a colorless liquid that is located in the ventricles of the brain in the subarachnoid space.

It will keep the brain and spinal cord suspended, providing its protection and creating conditions for its vital functions. Cerebrospinal fluid also participates in metabolic processes, delivering oxygen and nutrients from the bloodstream to nerve cells. Hormones are produced and processes in the body are regulated by the brain.

Types of pathologies and clinical symptoms

The Sylvian aqueduct performs important functions, so pathological processes lead to disruption of the brain.

The most common causes of dysfunction of the aqueduct are narrowing (stenosis), obstruction of the lumen by a tumor, and congenital anomalies of the development of the aqueduct.

The most common disease caused by changes in the structure of the canal is hydrocephalus.

It is an accumulation of cerebrospinal fluid in the cavities (ventricles) of the brain. It can develop in both children and adults.

In childhood, it develops in newborns.

The cause of cerebral hydrocele is anomalies in the development of the Sylvian aqueduct, provoked by severe stress, bad habits, infectious processes in the mother, birth trauma and non-compliance with doctor’s recommendations.

It is easy to detect brain hydrocephalus in a baby: the head is enlarged in size, he is restless (cries constantly). The forehead increases in size, veins bulge in the frontal and temporal areas, it grows slowly and slowly gains mass, develops slowly (begins to sit by 10 months, crawl by 12 months), and cannot smile. There is a characteristic divergent squint, deep-set eyes due to the overhang of the forehead, etc. By the age of one year, babies begin to experience convulsions.

In children over 2 years of age, the causes of hydrocephalus are head injuries and tumors. The clinical picture is different. Children are bothered by headaches accompanied by nosebleeds, pressing pain in the eye area, restless sleep, and lack of coordination due to damage to the cerebellum. They are hyperactive, irritable (they want more attention). They also cannot control the act of urination, during which a large amount of urine is released (polyuria). Over time, they lose vision, they develop bluish circles before their eyes, obesity, and convulsions.

In adults, hydrocephalus develops as a complication of other diseases.

After a stroke, traumatic brain injury, tumors, degenerative changes in dementia and encephalopathy, the likelihood of developing cerebral hydrocele is very high.

It can be detected by the following symptoms:

headaches that appear after sleep (caused by compression in the foramen magnum and increased intracranial pressure;
dyspeptic disorders (nausea, vomiting in the morning);
drowsiness;
depression of consciousness from stupor to coma caused by compression of the medulla oblongata;
dysfunction of the oculomotor muscles;
congestion in the optic nerve head, causing decreased visual acuity.

Hydrocephalus against the background of dementia (dementia) develops within 20-30 days and is manifested by apathy to everything that happens, decreased memory (does not remember your age), and confuses daytime with nighttime.

Apraxia also occurs; a person lying down can simulate walking, but in a standing position he cannot do this. Hydrocephalus in dementia differs in that there are no problems with urination and vision.

Diagnosis of the disease

When the first symptoms appear, you should immediately consult a neurologist. After collecting complaints and asking about the possible causes of the pathology, instrumental research methods will be prescribed.

Computed tomography is used to determine normal/pathological processes in brain structures. With its help, benign and malignant neoplasms, changes in the contours of the ventricles and subarachnoid space are identified.

MRI is used to determine the type of hydrocephalus.

Cisternography is performed to determine the direction of the flow of cerebrospinal fluid and the location of its accumulation.

Angiography of cerebral vessels - the presence of occlusion in the arteries.

Treatment methods

Treatment of pathology of the cerebral aqueduct is based on eliminating the underlying disease that led to the development of stenosis or occlusion.

Conservative treatment is used to eliminate clinical symptoms.
Non-steroidal anti-inflammatory drugs (ketolac, ketanov, nimesil) are effective in combating pain.

To combat edematous syndrome, diuretic drugs (furosemide, veroshpiron, mannitol) are used.

In order to dilate blood vessels, vasoactive substances are needed, which also prevent the development of cerebral edema (magnesium sulfate).

To ensure restful sleep - phenobarbital.

The most effective is complex treatment, combining conservative and surgical measures.

For better outflow of cerebrospinal fluid in the area of the brain canal and ventricles, additional openings are surgically created. Then a bypass is performed (connection to the right atrium, abdominal cavity, etc.) in order to get rid of the accumulation of cerebrospinal fluid in the cavities of the brain.

If there is a tumor in the area of the Sylvian aqueduct, it is removed surgically.

Prevention of diseases associated with pathologies of the Sylvian aqueduct

Prevention of hydrocephalus in children:

compliance with pediatricians’ recommendations, monthly/annual medical examinations of children;
compliance with safety precautions when transporting children;
proper child care;
annual examinations with a neurologist.

It is almost impossible to prevent the development of hydrocephalus in adults.

Prevention:

healthy lifestyle;
proper nutrition;
adequate physical activity;
taking B vitamins.