Surgical Treatment of Giant Serpentine Aneurysm of A2-A3 Segment Distal Anterior Cerebral Artery : Technical Case Report
A 49-year-old woman presented with loss of consciousness (LOC) and history of headache. On initial neurologic examination, she had no specific symptoms or previous seizure history. A non-contrast computed tomography scan showed a 3×1.8 cm sized, rim calcified, and round shaped mass lesion in the interhemispheric area, along the anterior falx above the head of the corpus callosum (). Brain T2-weighted structural magnetic resonance image (MRI) scan revealed partially thrombosed, signal voided aneurysm, without parenchymal edema (). Cerebral angiography demonstrated an irregular serpentine aneurysm, involving the entire A2 segment of DACA, measuring 4.5 cm in the anteroposterior dimension and 1.8 cm in the transverse dimension (the proximal portion of aneurysm, ).\nThe patient was given aspirin (100 mg) for elective operation. The patient was placed in the supine position, with the head slightly tilted at 20° degrees in the 3 pin fixation. The right calf lesion was prepped for possible bypass, using a venous interposition graft from the superficial temporal artery to the distal end of the anterior cerebral artery. To secure the wider surgical field, we performed cerebrospinal fluid (CSF) drainage via lumbar puncture and midline bifrontal interhemispheric craniotomy with the neuronavigation system (Medtronics®). 4×4 cm sized bone flap was made, then dura mater was opened with small straight incision. The superior sagittal sinus was ligated, cut, and reflected up and downward bidirectionally (). Under the operating microscope, we advanced with dissection of the interhemispheric fissure and indentified the distal end of the fusiform aneurysm (). After further dissection, the left pericallosal artery was indentified just adjacent to the aneurysm. Thus, at this point, we considered that it might be possible to perform the in situ bypass between right A3 just distal aneurysm sac and left A3. To see the proxymal portion of aneurysm and parent artery, we further dissected the interhemspheric fissure toward anterior direction and were very cautious not to injury the both olfactory nerves (). This complication can be avoided by making wide, precautious dissection to minimize posterior and lateral brain retraction. The aneurysm wall itself was hardly adhesive to both frontal cortex. Therefore, we did not fully dissect the aneurysm from the brain, in order to avoid postoperative parenchymal contusion.\nBlood flow was measured at approximately 20 cm/s, in both distal artery to the fusiform aneurysm and opposite left pericallosal artery. When we placed the temporary clip on the proximal parent artery of aneurysm, blood flow was not visible on the micro-Doppler recording. Thus, we finally decided to perform aneurysm trapping with a right end-to-left side in situ bypass, to preserve the flow to the right DACA.\nBefore anastomosis, the patient was placed into burst suppression with propofol, and the mean arterial pressure was raised 25% above the patient's baseline, in order to improve the collateral circulation. Intraoperatively, both somatosensory and motor evoked potentials were also used for monitoring. At the time of the anastomosis, 2000 IU of heparin was given intravenously.\nBoth arteries were dissected as movable as possible, and a rubber dam was passed under both vessels. After placing two temporary clips on the right side, the distal end of the fusiform aneurysm was cut with sharp microscissors. The atherosclerotic distal artery of the aneurysm was clearly trimmed with jeweler forceps, and marked with marking pen. Two temporary clips were then placed on the left side, and following heparin irrigation, a small arteriotomy was made equal to the opposite arterial opening, using a diamond knife (FD 115D Aesculap, PA, USA). A marking pen is usually used to color the borders of the arteriotomy for idenfication of the margin of the transparent thin vessels. After both toe and heel stitches were placed at the proximal and distal ends of the anastomosis with 10-0 nylon suture (Ethicon Co., NJ, USA), the posterior wall was sutured in a continuous fashion and the anterior wall was sutured in an interrupted pattern. On completion of the end-to-side bypass, robust blood flow in the right DACA was observed in the distal segment to the bypass site (). Temporary clipping time was around 50 minutes. Permanent clips were applied proximal and distal to the aneurysm, without removal of the thrombosed aneurismal mass, because the aneurysm itself was severely stuck to the brain surface. Instead of leaving the thrombosed aneurysm, we aspirated the blood clot from the aneurysm using 14-gauzed needle, to identify total obliteration of the aneurysm and to reduce the mass effect postoperatively (). After meticulous bleeding control, closure was done in the customary fashion.\nThe patient was neurologically intact immediately after surgery. Immediate postoperative CT scan revealed no radiological abnormaliy (). Postoperative cerebral angiography on day 7 demonstrated no residual filling of the aneurysm and excellent flow through a patent bypass into both the DACA vascular territories (). Follow up T2-weighted brain MRI at 3 months after surgery showed remarkably reduced mass size in the interhemispheric area, along the genu portion of corpus callosum ().