Operations in arterial aneurysms and arteriovenous malformations of the brain

Surgical treatment of arterial aneurysms

There are two fundamentally different approaches to the surgical treatment of aneurysms:

1. Traditional intracranial access with the discharge of the supporting arteries and the switching off of the aneurysm from the general blood flow by clipping its neck or forced occlusion of the aneurysm-bearing artery (trapping). In rare especially complex cases enveloping an aneurysmal sac with a muscle or special synthetic materials (surgigel, tachocomb) is used.
2. The endovascular method, the essence of which consists in carrying out all manipulations aimed at turning off the aneurysm, inside the vessel under the control of X-rays. Constant occlusion of an aneurysm is achieved by the introduction of either a detachable balloon catheter or special microcoils (coils).

The intracranial method of turning off the aneurysm is technically more complicated and traumatic for the patient, but takes the leading place in terms of reliability.

The operation consists in carrying out osteoplastic trepanation of the skull, wide opening of the basal cisterns with aspiration of the cerebrospinal fluid, which allows to reduce the brain in volume and improve access to the arteries of the base of the brain. Using an operating microscope and a microsurgical technique, the carrier artery is first isolated, then one or two outflow arteries are allocated. This is done for the purpose of the possibility in the case of intraoperative rupture of the aneurysm of the application of temporary clips. The main stage is the allocation of the aneurysm neck. The body of an aneurysm, with the exception of giant aneurysms, is usually not excised. It is enough to impose a clip on the aneurysm neck, reliably turning it off from the blood stream. Self-shrinking removable spring clips, developed in the 70s of the XX century by S. Drake and M. Yasargil, are used all over the world.

Intracranial operations can be reconstructive and deconstructive. All surgeons tend to perform reconstructive surgeries, which make it possible to turn off the aneurysm while retaining all the leading and leading arteries. In cases where, due to the peculiarities of the anatomical location and the shape of the aneurysmal sac, it can not be turned off reconstructively; Turn off the aneurysm along with the artery. Most often, such an operation ends with a cerebral infarction and development of a severe neurological deficit in the patient. Sometimes neurosurgeons in such situations prefer not to turn off the artery, but envelop the aneurysm with a muscle or special synthetic materials in order to strengthen the wall from the outside with developing fibrosis in response to a foreign body.

Endovascular operations are performed by inserting a detachable balloon catheter into the aneurysmal cavity through a common carotid artery (an aneurysm of the carotid basin) or through the femoral (aneurysm of the vertebrobasilar basin). To turn off an aneurysm from the blood stream, special balloon-catheters are used to design F.A. Serbinenko. The balloon is injected into the cavity of an aneurysm under X-ray control, it is filled with a fast-hardening silicone mass. The volume of the injected silicone should exactly correspond to the volume of the internal cavity of the aneurysm. Excess of this volume can lead to rupture of the aneurysmal sac. The introduction of a smaller volume will not ensure a reliable occlusion of the aneurysm. In some cases, it is not possible to turn off the balloon aneurysm while maintaining the patency of the arteries. In these cases it is necessary to sacrifice the supporting artery, turning it off with an aneurysm. Before turning off the aneurysm, a trial occlusion is performed by inserting saline into the balloon. If the neurological deficit does not deepen within 25-30 minutes, the balloon is filled with silicone and permanently left in the cavity of the bearing artery, turning it off with an aneurysm. In the last decade, the replacement of the balloons in most clinics comes with detachable micro-arms. The most progressive product of new technologies are electrolytically separated platinum micro-arms. By August 2000, more than 60,000 patients were operated by this method worldwide. The probability of a reconstructive operation using a spiral is much higher, and the probability of an intraoperative rupture of an aneurysm is lower than with the use of a balloon.

Evaluating both methods, it should be noted that until now the leading place is occupied by the intracranial. And this method, as more reliable and manageable, it is necessary to carry out the majority of operations. Endovascular operations should be performed only those aneurysms, the direct switching-off of which is associated with significant traumatization of the brain.

Features of surgical technique for the extirpation of arteriovenous malformations

Extirpation, or removal of arteriovenous malformation, refers to the most complex operations in neurosurgery. It requires not only high surgical technique of the surgeon and good technical equipment of the operating room (microscope, micro-instrument), but also knowledge of the features of extrusion. To AVM can not be treated as a tumor, it can not be removed in parts, you need to accurately distinguish the leading arterial vessels from the draining veins, be able to sequentially isolate them, coagulate and cross. The bleeding that occurs during surgery from the vessels of the AVM, the unprepared surgeon can be confusing, and any panic in such an operation is fraught with serious consequences, up to a lethal outcome. Therefore, a surgeon going to such a complex operation, you need to know about all of its features, possible complications and methods of dealing with them.

The first condition is that you can not go to surgery without having a complete idea of the size of the malformation, its location and all sources of blood supply. The error can lead to the fact that the surgeon during the operation inevitably bumps into the walls of the AVM and damages them. Insufficient in size trepanation window greatly complicates the surgeon's actions and allows for atraumatic operation. The trepanation window should be 1.5-2 times larger than the maximum size of the AVM.

The dura mater is dissected by an arcuate incision bordering on all sides of the AVM and exceeding its dimensions by 1.5-2 cm. With the convectional location of the AVM, it is very important not to damage the draining veins, which are more often contoured and translucent through a thin shell. Eversion of the dura is also an important and crucial moment. On the one hand, the membrane can be soldered to the draining veins and vessels of the AVM, and on the other hand, the vessels of the envelope can participate in the blood supply of the AVM. This step should be performed using optics and, if it is not possible to easily separate the envelope from the vessels of the AVM, it should be cut off and left with the border cut.

It is important to correctly assess the boundaries of malformation and over the perimeter of the perimeter, coagulated and dissected arachnoid and soft shells. Draining veins persist. The main feeding arteries are located in subarachnoidal cisterns or deep in furrows, so they can be isolated with minimal trauma.

Determining the sources of blood supply, it is necessary to distinguish between them the main and secondary. Initiation of arteriovenous malformation should be near the main sources of blood supply, but you can not damage and switch off the drainage veins. In AVM, there is a certain balance between incoming and outflowing blood, the slightest difficulty in the outflow of blood inevitably leads to a sharp increase in the volume of AVM, overstretching of its venous vessels and simultaneous rupture of several of them. If not surface vessels are damaged, but intracerebral, then blood rushes into the brain and subarachnoid spaces, causing a sharp prolapse of the brain. To avoid this, you should know the following rules:

1. AVM is allocated and leading arteries at a distance from the main drainage veins.
2. If the leading arteries and draining veins are located close, using microtechnology, the drainage vein is excreted and fenced off with cotton strips.
3. If the venous wall becomes damaged during isolation and bleeding is severe, you can not clinch or coagulate it. It is necessary to attach a wadded strip moistened with hydrogen peroxide and press it with a spatula so that the bleeding decreases, but the blood flow through the vein is preserved.
4. Coagulation or clipping of the vein will lead to a decrease in the outflow of blood and to the complications already described, so it is better to wait and achieve complete hemostasis without turning off the vein. Even if the first time the blood seeps past the quilted jacket, do not rush. After 5-10 minutes, the bleeding usually stops. It is even better to carry out a hemostasis with a hemostatic sponge like "Spongostan".
5. Before coagulation of the leading artery, you need to make sure that this is not a vein, because and scarlet blood flows through the veins. But since the venous wall is thinner than the arterial wall, then by color it is more red than the artery. Sometimes a turbulent flow of blood can be seen through the microscope. Arteries have a faint pink color. With coagulation with a weak current, the venous wall is easily contracted, and a large artery is poorly liable to coagulation. But this is not enough to accurately identify the artery and vein. In case of doubt, you can put a removable vascular clip on the putative artery. If no reaction followed, then it is an arterial vessel. If, literally, AVM starts to increase in volume and the pulsation increases, the vein was clipped, and the clip should be removed immediately.
6. It is necessary to distinguish malformation from all sides, but primarily from sources of blood supply. In this case, a thin suction resected the brain tissue, which lies before the body of the malformation, but so as not to injure its vessels. All the secondary arteries and veins that occur on the path are sequentially coagulated and intersect. Such vessels can be several dozen. If bleeding occurs not from the body of the malformation, but from the leading or withdrawing vessels to 1.5-2 mm in diameter, they should be coagulated with bipolar tweezers.
7. As the main feeding arteries are turned off, the volume of malformation can decrease and its color becomes darker. However, one should not rest until the AVM is removed completely, because Secondary arteries that can cause serious bleeding when the malformation wall is damaged are not yet turned off.
8. Removing AVM, the surgeon can leave unnoticed her areas in the brain substance. Especially it is dangerous if the arterial inflow to them is preserved, and the outflow is disturbed. In these cases, immediately after the removal of the arteriovenous malformation, "bloating" of the brain and bleeding from the walls of the brain wound can begin. There may be several sources of bleeding. Bleeding areas should be covered with cotton strips, lightly pressed with a spatula and quickly start consistently around each source of bleeding, resect the brain substance and, finding the leading arterial vessel, coagulate or clip it.
9. Before closing the wound, you need to make sure that hemostasis is reliable, for which the anesthetist artificially creates a mild arterial hypertension. You can not sew the shell against a background of low blood pressure. A number of authors try to explain the acute swelling of the brain after removal of AVM by its acute hyperemia, due to the elimination of the source of "revelation". Especially it is dangerous in those cases when the main leading arteries have a length of more than 8 cm. However, Yashargil is convinced that acute "swelling" is only a consequence of non-radical extirpation of AVM.
10. If, in spite of all the precautions, you still prematurely turned off the drainage vein and AVM increased in volume, you should urgently lower your blood pressure to 70-80 mmHg. This can prevent multiple ruptures of its vessels and allow you to find feeding arteries and consistently turn them off.
11. If nevertheless multiple bursts of AVM vessels have occurred, do not rush to coagulate them, this will only increase the bleeding. Press them with cotton strips moistened with hydrogen peroxide, and as soon as possible look for feeding arteries and turn them off. Only such tactics will save the life of the patient.
12. If the surgeon overestimates his abilities and during the operation realized that he can not produce radical extirpation, he can stop the operation if:
    • a) the outflow from AVM has not been violated;
    • b) the arterial inflow to it is reduced;
    • c) hemostasis is ideal even against the background of artificial arterial hypertension.
13. You can not intentionally go for partial removal of arteriovenous malformation.
14. Going to surgery, you must always think about the possible blood transfusion. The larger the size of the AVM, the more blood will be required during the operation.
15. Blood loss up to 1 liter can be compensated by plasma replacement solutions, however, large blood loss requires blood transfusion. We recommend that the blood sample be taken up to 200 ml at the patient before the operation 1-2 times, and reinfusion should be performed during the operation. This allows in most cases to do without donor blood.
16. The radicality of extirpation of AVM is indicated by a change in the coloration of all draining veins: they become dark cherry-colored. Preservation of at least one bright red vein indicates a non-surgical operation.

Along with radical extirpation of arteriovenous malformation, endovascular occlusion of AVM has been introduced in recent years. For this purpose, the introduction of various thrombi substances into the malformation vessels is used. Earlier these were compositions based on glue compounds - cyanocrylates. Now the most promising is embolin, which is a 10% solution of low molecular weight linear polyurethane in anhydrous dimethylsulfoxide. Embolin during contact with the blood causes rapid development of thrombus fibrillar-elastic consistency. In most cases AVM can be turned off subtotally (90-95%), this is enough to prevent its repeated rupture. Endovascular occlusion is most indicated to patients with AVM subcortical ganglia and a bridge, as well as with giant AVM of any location. In a number of cases, endovascular embolization of AVM is performed as the first stage before its radical extirpation. This achieves a reduction in blood loss during an open surgery.

Malformations of small and medium volume can also be coagulated by a directed proton beam, but the application of this method is possible only in clinics that are equipped with a linear accelerator. In this regard, the method has not yet found wide application.

[1], [2], [3], [4], [5], [6], [7]