|Year : 2020 | Volume
| Issue : 1 | Page : 55-57
Musings about surgery for intra-cranial arterio-venous malformations
National Neurosciences Mission, Adarsha Super-Specialty Hospital, Manipal-Udupi, Karnataka, India
|Date of Submission||22-Aug-2020|
|Date of Acceptance||03-Sep-2020|
|Date of Web Publication||1-Oct-2020|
Dr. A Raja
National Neurosciences Mission, Adarsha Super-Specialty Hospital, Manipal-Udupi, Karnataka
Source of Support: None, Conflict of Interest: None
Introduction: Neurosurgery has evolved with the times and as with all things with a rich history, there is much to be learnt from experience and much to be re-iterated in the present.
Aims and objectives: To reinforce the key basic points in AVM surgery, for the benefit of all neurosurgeons operating on AVMs.
Materials: Based on personal experience from over he author recollects integral points and principles of the surgical management of intra-cranial arterio-venous malformations (AVMs), highlighting the basic elements such as planning, exposure, equipment use, intra-operative identification, and safe approach, execution and hemostasis.
Conclusion: The success of AVM surgery depends highly on methodical planning and precise execution.
Keywords: Arterio-venous malformations, AVM, surgery, microsurgery
|How to cite this article:|
Raja A. Musings about surgery for intra-cranial arterio-venous malformations. J Cerebrovasc Sci 2020;8:55-7
With advancement in technology and developments in neurosurgery, the present-day neurosurgeon may not have the opportunity or the exposure to surgery for arterio-venous malformations (AVM) of the brain and spinal cord.,,
Since I studied at a time when microsurgery in India was at its infancy and interventional techniques had not evolved completely, I had the opportunity of witnessing AVM surgeries,,,, without a microscope, and the good fortune to operate with a microscope, on around 100 cases of cranial AVM, which included 13 posterior fossa AVM. I learnt a lot from whatever I had seen as an assistant surgeon as well as an operating surgeon, which I have attempted to recollect here.
| Proper Planning|| |
Before embarking on surgery, one needs to study the angiograms in detail to get an idea about the major feeding vessels and draining vessels, which helps to avoid accidents during surgery. As a policy, it is better that the operating surgeon carries out the investigation himself/herself. If fortunate enough to have an interested radiologist, his/her presence during the angiography and advice on appropriate pictures to be studied could aid in obtaining a comprehensive idea about the malformation.
| Adequate Exposure|| |
I have always insisted on turning an adequate flap. One may err on the side of a larger flap, but it is better than turning a smaller flap which may hinder the approach to the feeding vessels.
| Verifying Equipment|| |
A good suction is very important. One must make sure of the availability of at least two properly working suction apparatus, preferably with nozzles with keyhole thumb control and the ability to increase or decrease the suction pressure.
| Practical Tip to Avoid Complications|| |
Though it may appear trivial – some of these steps described have been very helpful in avoiding problems.
It is very important to keep instruments well inside the instrument table, to prevent inadvertent slippage of the instruments on to the operative field, which may be catastrophic.
| Bipolar Forceps|| |
It is preferable to have one forceps with a tip of 2 mm which can be of use to coagulate thin-walled veins before they are divided.
| Availability of Temporary Clips and Smaller Weck Clips|| |
It is always advisable and advantageous to have temporary clips, both regular ones and mini clips, with the appropriate applicators. Applying temporary clips before permanent clipping or dividing helps in identifying feeder vessels. Weck clips are useful in clipping the vessels in addition to bipolar coagulation as, at times, the coagulated vessel may open up and result in torrential haemorrhages and hence after coagulation, it is better to apply these haemostatic clips and divide between two clips. I have not had the necessity to use hypotension in operating on these malformations and my preference has been to maintain the blood pressure within the normal range.
| Proximal Control of Feeders|| |
After adequate exposure with a microscope, the proximal feeders have to be identified to confirm that they are feeding the lesion. Temporary aneurysm clip application may be helpful, but one has to bear in mind that putting a clip on a single vessel will make the malformation either less pulsatile or will make the circulating blood change colour. At times, more than two/three vessels may have to be clipped and one has to wait, and see. One must remember that a malformation may get blood supply from different vessels situated at different points and all may not be in the same area. It is not practical to apply temporary occlusion to all vessels, so, after applying temporary clips, one has to look for changes in the venous flow in the nearby vessels and decrease in turgidity of the lesion. If this happens, one may go ahead in coagulating/clipping and dividing the vessel. In smaller malformations, this step is relatively easier.
| Approaching the Malformation|| |
In many of these cases, if there had been previous bleed with glial changes, the glial plane will be the safe bet. Usually, malformations may be associated with some atrophy of the adjoining brain and there will be dilation of the sulci. These provide good entry points to the malformation, and slowly one must go in a circumferential manner to identify the arterial feeder to be occluded.
| Feeder Clipping|| |
While clipping the feeder, one has to go as near the malformation as possible, to avoid occluding the feeder from which the branches supplying the normal brain may arise. Though it is classically described in all operative surgery texts, practically, it is a difficult task. Now, with intraoperative indocyanine green angiography, things have been made easier.,
| Dissection|| |
The presence of underlying haematoma was considered advantageous, and it is supposed to dissect the malformation from its bed. One should not be carried away by this statement and think that after the surface dissection of feeders, and after entering the haematoma, the malformation will come off. It does not happen. When one goes through the haematoma, there are multiple fine as well as medium-sized vessels which arise from the underlying brain. These have to be coagulated and divided, or they might lead to a troublesome bed haematoma. Thus, till the last of these vessels are coagulated and divided, one cannot be complacent in AVM surgery.,,,
| Dealing With the Veins|| |
Though it is said that it is better to leave the draining veins intact till the end, it is practically not possible to leave all the veins. One has to choose two or three large veins which are superficially placed to preserve, and take the other vessels and go around dissecting, or it may not be possible to proceed with the removal of the lesion. It is safer to divide the vessels where the normal arterial wall is seen rather than in the malformation where it is very difficult to coagulate the abnormal walled vessel.
Though it is said that malformations situated in the non-dominant frontal or temporal pole are easier to remove, nothing can be taken for granted. Some of these malformations may have drainage to the deep venous system or may have feeders and draining veins towards the basal dura. Unless one is careful in anticipating and controlling these vessels, rupture of this may lead to catastrophe.
In a nutshell, the successful surgery for these malformations,, has to involve meticulous planning and a methodical, painstaking, step-by-step surgical approach. One has to remember that once we embark upon surgery, there is no retracting, or turning back. Unlike in tumour surgeries where one may choose to go in for a total excision at a later date, here, there is no such option, and hence right from the first to the final step, it has to be a well-thought-of and well-planned procedure.
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Conflicts of interest
There are no conflicts of interest.
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