Superficial Temporal Artery-Middle Cerebral Artery Anastomosis [Name] Superficial Temporal Artery-Middle Cerebral Artery [Overview] Anastomosis In 1967, Yasargil was the first to successfully anastomose the superficial temporal artery to the middle cerebral artery to treat cerebral ischemic disease. Since then, this procedure has been performed in many countries and has led to the development of various forms of extracranial-intracranial artery anastomosis. (1) Occlusion or stenosis of the internal carotid artery that cannot be reached by extracranial surgery and ischemic symptoms due to insufficient collateral circulation. The so-called “unreachable” extracranial surgery refers to the lesions above the line between the mastoid process and the angle of the mandible (Figure 1). (2) In cases where the middle cerebral artery is narrowed or occluded and cerebral ischemic symptoms occur due to insufficient collateral circulation. (3) Lesions involving the internal carotid artery or middle cerebral artery and requiring blockage of these arteries as treatment, such as internal carotid artery aneurysms in the rocky and cavernous sinus segments, internal carotid artery-cavernous sinus fistula, and pterygoid crest meningioma. The superficial temporal artery-middle cerebral artery anastomosis (STA-MCA) is performed before surgery to provide some of the blood from the external carotid artery to the skull to prevent cerebral ischemia. 4) Diffuse hypoperfusion syndrome: Multiple cerebral artery stenosis or occlusion that cannot be reached by extracranial surgery, resulting in mental retardation, syncope, ataxia, upright cerebral ischemia, etc. (5) Intracarotid hypoperfusion syndrome (5) In the case of stenosis of one internal carotid artery and occlusion of the opposite internal carotid artery, the endarterectomy of the stenotic side can be performed before the superficial temporal artery-middle cerebral artery anastomosis in order to ensure that cerebral ischemia does not occur due to temporary blockage of blood flow during surgery. In summary, the surgical indications for STA-MCA are manifold (Figure 2). Figure 1 The “unreachable” boundary of extracranial surgery above the line from mastoid to mandibular angle Figure 2 Indications for extracranial and intracranial arterial anastomosis 1 – vertebral artery stenosis; 2 – internal carotid artery lesions that are inaccessible to extracranial surgery; 3 – middle cerebral artery stenosis; 4 – arteriovenous malformation; 5 – aneurysm; 6 – posterior cerebral artery stenosis; 7 – basilar artery stenosis; 8 – carotid artery stenosis; 9 – middle cerebral artery stenosis (1) Elderly patients with serious systemic diseases, such as pulmonary, cardiac, renal and hepatic diseases, diabetes mellitus, etc. (2) Those with severe and persistent neurological dysfunction. (3) Those who have internal carotid artery or middle cerebral artery stenosis or occlusion, but no neurological symptoms and normal cerebral blood flow (CBF), indicating adequate collateral circulation. (4) Those with extensive cerebral infarction at the middle cerebral artery supply area or internal capsule, and it is estimated that it is difficult to improve the symptoms even if the anastomosis is successful. (1) Adequate cerebral angiography, including bilateral carotid angiography and vertebral artery angiography on at least one side, should be performed to fully understand the cerebral vascular stenosis and the status of collateral circulation. (2) CT scan to determine the presence or absence and extent of cerebral infarction. (3) Cerebral blood flow measurement. (4) Prepare the scalp as usual. (5) Administer prophylactic antibiotics. [Anesthesia and position] General anesthesia, intraoperative monitoring of arterial pressure to prevent hypotension, no dehydrating drugs. The patient is positioned supine with the head tilted to the opposite side, and the sagittal plane of the skull should be parallel to the ground. (1) The superficial temporal artery is the blood supplying artery and must be carefully protected, not too close to the artery when separating: do not use forceps to clamp directly on the artery. The outer membrane at the end of the anastomosis should not be peeled off too much to avoid necrosis of the arterial wall, resulting in anastomotic opacification. (2) The middle cerebral artery is the recipient artery, the diameter of the tube should not be too thin, the trunk diameter >1.5mm should be selected, <1mm the anastomosis will be easily blocked, making the operation to be a failure. (3) The superficial temporal artery should not be too long or too short, and should not be compressed or twisted along the way. (4) The anastomosis technique must be well trained to minimize the trauma of the anastomosis. (1) Incision: A horseshoe-shaped incision (Figure 3), or an arc-shaped incision (Figure 4) is made centered 6 cm above the external auditory foramen, or a straight incision can be made along the course of the superficial temporal artery. Since the superficial temporal artery is used to anastomose with the middle cerebral artery, the blood supply to the scalp should be considered when making the incision to avoid scalp necrosis. Although the curved incision is larger, there are side branches that supply blood to the flap edges, and there is less chance of scalp necrosis. The scalp and capitellar tendon flap are turned downward. (2) Separation of the superficial temporal artery: this is performed under the surgical microscope. The posterior branch of the superficial temporal artery is located on the medial surface of the turned capitellar tendon flap of the scalp. It is carefully separated from the vascular bed. To avoid damaging the artery, the separation is done together with some soft tissue around the artery to facilitate preservation of the trophoblastic vessels of the artery and to facilitate pulling with forceps. When small branches are encountered in the separation, they should be cut off after bipolar electrocoagulation, which should be slightly distant from the artery to avoid injury to the artery; or cut off after ligating with nylon thread. The superficial temporal artery should be separated enough to reach the bone window centered 6 cm above the ear without tension, and the proximal end should be temporarily clamped with a non-invasive arterial clip, and the lumen should be flushed with heparin saline at the severed end. It is then covered with a cotton pad wet with 3% poppy base to prevent drying and arterial spasm.(3) Craniotomy: The temporalis muscle is incised at the corresponding place of the isolated posterior branch of the superficial temporal artery, and the temporalis muscle is pushed away from the skull. A 4-cm diameter circumferential drilling craniotomy was done with 6 cm on the external auditory foramen as the center, or 4 holes were drilled for osteoplastic flap craniotomy (Figure 3 and Figure 4). The dura is cut in a horseshoe or star shape. The site of the bone window is both where the posterior branch of the superficial temporal artery passes and where the middle cerebral artery is normally located. The two are in close proximity to each other, facilitating anastomosis. (4) Separation of the artery: The arachnoid membrane of the lateral fissure is incised, from which the middle cerebral artery is found, and a segment of about 10 mm in length is separated and cut off after bipolar electrocoagulation of the small branches to separate the artery from the cerebral cortex (Figure 5). A rubber strip was padded between the artery and the cerebral cortex (Figure 6). At this point, the superficial temporal artery is pulled to this segment of the middle cerebral artery and its length is measured so that a tension-free end-lateral anastomosis can be made with the middle cerebral artery. The overgrown superficial temporal artery is clipped and the outer membrane of the artery end of 2-3 mm is stripped to make it smooth and neat for anastomosis. The ends of the separated middle cerebral artery are clamped with a non-invasive miniature arterial clip, and an incision is made in the wall of the middle cerebral artery 2 to 3 mm long with a razor blade broken off with a sharp blade (Figure 7). The lumen is flushed with heparin saline to clean out the clot and prepare the anastomosis. (5) Anastomosis of the artery: A single-stranded nylon suture of 9-0 to 11-0 is used. Two stitches are first placed at the ends of the anastomosis for fixation (Figure 8), and then one stitch is placed in the anterior and posterior walls at the midpoint between the two stitches, and 2 to 3 stitches are placed between each of the two adjacent stitches, usually 6 to 8 stitches are placed in each of the anterior and posterior walls (Figure 9). The arterial clip on the superficial temporal artery is relaxed a little before ligating the last stitch to flush out the air and blood clots in the lumen, and then the sutures are quickly ligated. After the anastomosis is completed, remove the distal one arterial clip on the middle cerebral artery first, then loosen the proximal one, at which time the artery is seen to be filled, and finally remove the arterial clip on the superficial temporal artery, and see that the artery is fuller and pulsating, indicating that the anastomosis is patent (Figure 10). If the anastomosis bleeds, a cotton pad can be used to stop the bleeding by pressing lightly for a few moments, and a stitch can be added at the rupture if there is more blood leakage. After stopping the bleeding, cover the anastomosis and each artery with 3% poppy base cotton piece to prevent and release the spasm. (6) Cranial closure: The dura is interrupted and sutured, leaving a gap for the superficial temporal artery to pass through loosely. The bone fragments are repositioned, also leaving a gap for the artery to pass through. The same care should be taken not to compress or kink the superficial temporal artery during muscle suturing (Figure 11). Blood from the superficial temporal artery can be perfused into the middle cerebral artery after the arterial anastomosis (Figure 12). [Postoperative management] (1) Maintain blood pressure and maintain adequate perfusion. (2) Take 0.6g of enterosoluble aspirin orally 3 times a day and 25-50mg of pansentine 3 times a day to prevent platelet agglutination of the anastomosis to form thrombus. (3) Postoperative selective external carotid arteriography was performed to observe the patency of the anastomosis. Cerebral blood flow measurement was also done to understand whether the perfusion volume was increased. (1) Ischemic necrosis of the scalp margin. (2) Subdural hematoma and hydromas. (3) Pseudoaneurysm formation at the anastomosis. (4) Neurological deficit due to temporary blockage of the middle cerebral artery. (5) Gastrointestinal bleeding.