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MCA Aneurysm: Sylvian Fissure Dissection

October 07, 2015


Let's go ahead and review technical nuances for microsurgical dissection of the Sylvian fissure. This technique is one of the most important principles in microsurgery. This is a 42 year old female who presented with a six millimeter right-sided anterior temporal artery aneurysm. Patient positioning is standard. Skull clamp placement is demonstrated. Curvilinear incision is used just behind the hair line. The incision does not necessarily need to be extended more posteriorly as the approaches essentially focused over the Sylvian fissure. The extent of head turn depends on the location of the pathology. In this case, 30 to 45 degrees will be appropriate. Here's another closer view of the incision just in front of the tragus, STA was palpated so that it can be preserved. Here's the Sylvian fissure. The extent of exposure is also evident. Dissection of the fissure starts with opening of the thick arachnoid bands along the superior aspect of the fissure. I like using jeweler forceps to gently avulse the thick arachnoid bands while preserving the superficial veins. This method is quite efficient. Next short dissection is used to further advance the dissection of the arachnoid bands. Again, the superficial veins are protected as much as possible dynamic retraction using the suction device is quite effective. Next, the spreading action of the forceps are used to deeply dissect towards the insular and the M2 branches. This maneuver is very important for the inside to outside dissection of the fissure. Again, you can see the insular is exposed more distally along the fissure. And I dissect from deep to superficial in order to disconnect the interdigitating frontal and temporal operculum. I dissect along their vessels. Here's the more anterior aspect of the fissure. The vessels are a great source of navigation to dissect through the fissure, especially when subarachnoid hemorrhage is present and clear dissection plans are not available. Here is more dissection along the, anterior aspect of the fissure. Generous arachnoidal dissection provides adequate intercisternal pathways to find vascular pathology within the fissure. And at the same time minimizes the use of forceful retraction to immobilize the frontal and temporal lobes. Ample amount of time is spent to sharply dissect the arachnoid bands while minimizing peel injury. You can see the suction is gently moved sporadically and not aggressively in order to avoid peel injury. Here is further dissection of the Sylvian fissure along its sphenoidal segment. Again from inside to outside technique, preserving the veins joining the sphenoparietal sinus. Here's the more proximal part of the MCA territory, the temporal polari or the anterior part of the temporal lobe can be quite adherent to the frontal lobe. Very thin arachnoid bands can be carefully avulsed. Here's the M1. Here's the anterior temporal artery aneurysm, anterior temporal artery , very broad based aneurysm, which is typical feature of these aneurysms. Further arachnoidal dissection, more anteriorly Allows vivification of the proximal M1, for proximal control use of the mouth switch to keep the image in focus while allowing continuation of by manual dissection is also demonstrated. Here's the thick arachnoid bands bands toward the optical carotid cisterns and the clinoid process. I can see the vein is carefully preserved along the sphenoidal segment of the fissure. Irrigation is used to clear the operative field, aggressive suctioning over the peel membranes and surfaces is avoided. Here's further exposure of the optical carotid cisterns. Here's the proximal ICA. Generous dissection of the arachnoid bands allows the gravity to mobilize the frontal lobe against the proximal ICA. It's continuation toward the MCA. Location of the aneurysm more distally, proximal control is secured. You can see generous dissection of the arachnoid bands allows exposure without aggressive mobilization or brain transgression. Here's is again the very broad base of the aneurysm. The entire MCA complex is visible and the aneurysm can next be clip ligated without significant injury to the surrounding neurovascular structures. Thank you.

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