Microsurgical Clip Obliteration of Middle Cerebral Aneurysm Using Intraoperative Flow Assessment

This is a case of a patient with a right middle cerebral artery aneurysm. The authors described the surgical clipping of this aneurysm and ultrasonic flow probe analysis. The patient described is 59 years old and right-handed.

Nine years ago, the patient experienced an episode of nausea and vomiting. After sleeping for several hours, he awakened with a left-sided hemiparesis. He was admitted to a local hospital and told that he had experienced a stroke.

He recovered after several weeks with a mild residual left-sided weakness. The patient continued to do well until about three weeks ago when he experienced an episode of confusion after sexual intercourse that lasted approximately 10 minutes. An MRI and MRA scan showed the old infarct on the right side of the brain.

In addition, the MRA showed a right middle cerebral artery aneurysm. A lumbar puncture was negative for subarachnoid hemorrhage. The patient fully recovered and was discharged home as an outpatient.

A CT angiogram was performed to further delineate the aneurysm. This MRI scan shows the areas of prior cerebral infarction as indicated by the green arrows, which mark out encephalomalacia in the right lenor nucleus. There is concomitant expansion of the right lateral ventricle as indicated by the orange arrows in the right lower panel.

Furthermore, the yellow arrow in the upper right panel indicates a small area of flow void that raised concerns for a possible intracranial aneurysm. The MRI study bursts out as a middle cerebral artery aneurysm seen in the mid portion of the M1 segment of the vessel. This lesion is superiorly directed as indicated by the yellow arrow and is approximately two centimeter proximal to the middle cerebral artery bifurcation as indicated by the red arrow.

Here we see a three dimensional CTA angiogram as it rotates in the surgeon's view. Initially, we see the aneurysm itself emanating off of the middle cerebral artery. The anterior temporal branch is visualized coming off just proximal to the origin of the aneurysm.

Now coming into view, we see the large traversing sylvan vein. This overlies the sylvan fissure. Just to the right of the sylvan vein, we can see the middle cerebral artery bifurcation and associated M two branches, a large branch and two smaller branches.

As we zoom in, we begin to see the aneurysm itself and the neck of the aneurysm in what will be the true surgeon's view down the middle cerebral artery. This gives the closest and most realistic Approximation of the surgical view. Now, the surgical team begins to Work to position the patient.

The assistant begins to attach the Mayfield device to the patient's bed. This articulating arm will allow the patient head to be fixed in the appropriate position for surgery. The skull clamp of the Mayfield device is then affixed to the scalp and a pressure of 60 to 80 pounds of torque is applied to firmly affix the head for the operative procedure.

The assistant then clamps the articulating arm from the bed to the head frame and the final position is achieved. Note that the right malar eminences are slightly elevated and the head is turned to the left for this right cerebral artery aneurysm. We can see in this view that the right side of the patient's forehead is marked with the word yes, which is an essential step in the preoperative part of this procedure.

When checking in for surgery, the patient is asked to indicate on which side of the head the surgery will be performed. This is checked against the preoperative notes and imaging studies at the time of surgery. In order to confirm that all surgical personnel are in agreement as to on which side of the head the surgery will be performed.

This step is known as the surgical timeout. The surgeon now begins to mark the incision. The incision will extend from the region of the root of the zygoma to the right frontal area.

Following the marking of the incision, the wound is encircled, but benzoin adhesive, a series of barrier adhesive drapes are then applied. This permits the isolation of the wound for final draping. As a final maneuver.

The surgeon scratches the incision line to permanently mark as the ink is washed away during the preparation of the skin. The final positioning of the patient reveals the isolated cranial incision site, a triangle stand, which permits the anesthesiologist to have access to the patient's face during the procedure and trays placed over the patient's body for the scrub nurse. After the scan has been thoroughly prepared with an alcohol and soap solution, a series of sterile drapes are placed circumferentially around the wound.

Following this, an iodine impregnated drape is placed on the scalp. Additional barrier drapes are placed to cover the patient's body. A second layer of draping is then Applied by the surgical team with a wound.

Now fully prepared Instrumentation, including suction devices are brought into the field and a bag is placed below the patient's head to capture patient and or blood products. The surgical team now make an incision in the scalp. Bleeding vessels from the scalp edges are controlled with the use of blue rainy clips.

The clips are removed at the end of the procedure. The scalp is then reflected anteriorly and the Bovie cautery is used to dissect and elevate the temporal muscle away from the outer table of the skull with the appropriate region of the skull now exposed, an air twist drill is brought into position to create several bur holes circumferentially around the wound. The air power jigsaw is then used to cut the craniotomy incision.

A number three Penfield instrument is then used to elevate the bone flap with the bone flap. Elevated number four zero neuron sutures are used to tack the dura to the inner table of the skull. This will prevent post-operative du hematoma is used to remove additional bone at the medial OID wing.

This will increase the operative exposure. A number four zero neuron suture has been used to elevate the dura and a number 15 blade is used to create the initial incision in the dur matter. Matson bomb scissors are then used to complete the dural opening, and with this we begin to see the exposure of the syl and fissure.

The dural flap has been tacked anteriorly to the temporals muscle, exposing the frontal and temporal lobes. At this point, microcord patties are placed and retractors are brought into position to place the Sylvie and OID on tension to begin the sylvan dissection. With retractors in position, the surgical team is now ready to proceed to perform the remainder of the operation Under microscopic visualization.

Initial work under the microscope Begins but dissection of the syl fissure. The large Sylvie vein that has been identified preoperatively is now seen and micro scissors dissection takes place to expose the vein both on the right and left side. This will give flexibility in terms of handling the vein during the procedure.

In addition, a retractor is placed sub frontally so as to expose the medial Sylvie and fissure. This will permit greater flexibility in dissecting the syl and fisure. Here we see medial dissection near the optic nerve exposing the region over the internal corroded artery with the anterior temporal artery emanating from the syl fissure.

Further dissection reveals that the syl vian vein tends to migrate towards the frontal lobe. The syl fissure is therefore opened to the right of this large vein, further exposing the syl region. Now dissection is performed distally in the Syl fisure exposing the MCA bifurcation.

The OID is lies posterior to the MCA complex and the middle cerebral artery. M1 branch is visualized inferiorly and deeper in the syl vian fissure anterior to the MCA bifurcation, A traversing vein is identified and ligated so as to further improve exposure. With this exposure complete, we can now see the anterior temporal branch and also posterior to the artery.

We see perforating vessels that are now traversing behind the artery itself on the right side of the middle cerebral artery. We also see additional perforating vessels comprising an entire complex of perforating vessels on the posterior aspect of the M1 artery. Additional dissection on the posterior aspect of the artery begins to reveal the aneurysm neck and a portion of the aneurysm dome may also be seen projecting away from the surgeon's view.

The perforating vessel previously noted is also seen. Additional dissection fully reveals the neck of the aneurysm on the left hand side of the M1 artery as well. Here we can see the extent of the aneurysm neck with a portion of the proximal dome also visualized on the right hand side of the artery.

Further dissection reveals the posterior neck of the aneurysm on this site as well. These combinations of maneuvers are performed to reveal the full extent of the aneurysm neck. An important next step is to now measure the flow in the distal branches of the middle cerebral artery.

This is done using the ultrasonic flow probe. Irrigation is performed as the flow probe is placed around the vessel. This maneuver allows for detection of flow, which is measured in the 30 mil per minute range for flow in this branch.

This is somewhat lower than many M two branches and may reflect some of the athema disease that can be seen in the vessel. A second smaller probe is now used to visualize the flow in the smaller branch. This is a 1.5 millimeter probe and this gives readings in the 10 mil per minute range.

Assessing flow in these two vessels will allow the surgeon to have a better understanding of flow, both pre and post clipping. This is a schematic view of the transonic ultrasonic perivascular flow sensor using a wide beam illumination, two transducers pass ultrasonic signals back and forth, alternating intersection with the flowing liquid in an upstream and downstream direction. The flow meter then derives an accurate measure of the transit time it takes for ultrasound waves to travel across the transducers.

The difference between the upstream and downstream integrated times is a measure of the volume of the flow as compared to velocity. As we examine the operative perspective from the 3D CTA, we can see how this correlates with the intraoperative view of the surgeon. Here is the middle cerebral artery, both on the CTA and on the slightly lower magnification intraoperative view, and then finally a higher magnification operator view.

We see the M two branch, which is reflected here on this image and the second smaller branch, which is reflected here on the CTA. Finally, the large sylvan vein that was seen on the CTA is also seen at the surgery retractor to the left. The emanating anterior temporal branch, which comes off of the MCA is also seen here at its origin and here at the slightly higher magnification view.

The neck of the aneurysm, which is seen here, is barely visualized on the CTA in the operator view. It is difficult to see this in the lower power operator view, but in a higher power view. With the retraction to the left, we can see the formation of the aneurysm here, and we know that the neck of the aneurysm is extending In this region.

There is atherosclerosis, which is seen as the yellow component of the blood vessel throughout in this patient. For the surgical clipping procedure, a small rubber dam is placed around the M1 artery in between the perforating vessels and the M1 segment itself. This is being performed so that the perforating vessels will be protected during the clipping procedure.

A fenestrated clip at 45 degree angle is brought around the M1 segment of the vessel and secured into position so as to exclude the aneurysm neck from the circulation. The clip is nestled into position and the blades are closed to fully exclude the aneurysm. The perforating vessels are protected from the clip blades by the rubber dam inspection reveals that the artery appears to be well reconstructed.

However, posteriorly there may be a small remnant. The clip is therefore moved posteriorly to ensure a complete clipping with the clip moved posteriorly along the vessel. The full neck of the aneurysm is now excluded from the circulation.

After this blood flow is checked again in the distal M two branches to ensure that no significant compromise of the M1 segment has occurred. Blood flows measured both in the smaller M two branch and in the large M two branch, which was originally read out in the 30 mil per minute range now reads a flow of 50 mil per minute indicating improved flow along the M1 segment. The rubber dam is now removed and the perforating vessels behind the artery are inspected.

Each of the perforating vessels has good turg and color indicating that there is blood flow. It is seen that the tip of the clip blades do not compromise the perforating vessels in any way with the perforating vessels. Thus inspected.

It is concluded that the aneurysm clipping has been successful and the risk of intraoperative stroke is greatly reduced. Following the clipping procedure, the patient awakening was neurologically intact and was discharged without complication three days after surgery. In this case, the flow probe was used to confirm good pre and post clipping flow In the M two distill segments, this is important to ensure that the clip procedure itself does not compromise flow in the M1 segment.

This is particularly important in patients with athero maus vessels, which may have a compromised inner luminal diameter. Following clipping alternatives to this procedure would include intraoperative angiography. The authors would like to acknowledge the contributions of Dr.Fadi Charbel in developing the CHARBEL flow probe.