Patients with ruptured aneurysmal SAH have severe headache, severe brain swelling and the risk of re-rupture and bleeding at any time. Therefore, surgery should be performed as early as possible,an adequate and efficient preoperative preparation is very important. Head CT and head CTA three-dimensional reconstruction are the examination items that need to be completed as soon as possible before operation. Head CTA reconstruction can determine the size and position of bone flap; It can clearly show the relationship between IA and clinoid process and bone flap; Determine the perforator of vessels; More importantly, this examination can find the calcification of IA or IA carrying vessels, and evaluate the probability of vasospasm or even vascular occlusion after temporary occlusion, so as to formulate a more comprehensive surgical plan. Due to the advantages of condition and CTA, the patients with ruptured IA were not routinely examined by DSA.
Small IA can use single clip to clip the IA neck, but for some IAs, such as wide neck, arteriosclerosis or calcification, irregular IA body, giant aneurysm, etc., single clip cannot be completely clipped. Therefore, there is a method of reconstruction clipping, which refers to clipping aneurysms with multiple clips while shaping the IA neck to restore the original diameter of the IA carrying vessel. Different from the traditional parallel placement of aneurysm clip, the direction of reconstruction clipping is more flexible. It aims to gradually reduce the volume of IA body, reduce its surface tension, retain the diameter of IA carrying vessels, and avoid damaging perforator vessels and surrounding brain tissue.After clipped a large number of aneurysms,we found that lenticular artery and hypothalamic perforating artery were the most vulnerable arteries in middle cerebral aneurysms and anterior communicating aneurysms clipping operation. Therefore, special attention should be paid to whether these two arteries were unobstructed during operation. The "Picket Fence" clipping proposed by Davies and the "Mass Reduction" clipping proposed by Ririko also belong to reconstruction clipping [4] [5]. Using this method combined with intraoperative ultrasound can judge whether IA is completely clamped and whether perforating vessels are unobstructed, reduce postoperative complications and prevent recurrence of IA.
The reconstruction clipping of IA reported in most literatures is carried out by using the pterional approach. The pterional approach can more fully observe the Willis ring, the intraoperative angle is large, which is convenient for IA construction clipping. Pterional approach must open the lateral fissure and lift the temporal lobe to see the vascular structure of the skull base, so it will inevitably damage the brain tissue. Studies have shown that intraoperative brain traction will damage the brain and even lead to permanent neurological deficit[6].With the continuous development of interventional technology, compared with craniotomy clipping, more and more IA patients prefer coil embolization. Therefore, craniotomy as an operation that can cure cerebral aneurysm IA, the surgical incision must be reduced to achieve the purpose of minimally invasive, which makes neurosurgeons explore an approach with less damage.
Since Perneczky put forward the concept of keyhole approach [2], keyhole approach has been applied in more and more craniotomy operations with less trauma and good cosmetic effect. We believe that keyhole is not only the pursuit of small bone window, but the bone window that is suitable for the patient and has the least damage to the patient under sufficient preoperative evaluation (CTA, CT, etc.). A previous meta-analysis of this group proved that the supraorbital lateral keyhole approach is safe and effective, which can reduce the length of hospital stay and reduce the probability of postoperative infection [7]. Statistics show that there is no significant difference in mortality and postoperative complications between supraorbital lateral keyhole approach and pterional approach[8] [9], and this approach can avoid supraorbital nerve, frontal branch of facial nerve, superficial temporal artery and other structures and reduce iatrogenic injury. There were no complications such as frontal nerve injury and masticatory function impairment in 16 patients. Compared with the pterional approach, the supraorbital lateral keyhole approach has some disadvantages, such as narrow intraoperative field of vision and small operable range. These disadvantages can be improved by lengthening surgical instruments and accurate preoperative evaluation [1]. For exposure of IA, intracranial lesions on the brain surface need a bone window as large as the lesion itself to fully expose the lesions, while deep lesions can be exposed through a smaller and more limited approach [6]. Therefore, the "inverted funnel" exposure of anterior circulation aneurysms through a small bone window can be realized. The position of the bone flap is adjusted according to the position of IA. For example, the position of the bone flap of the M1 and M2 aneurysms of the middle cerebral artery is more lateral than that of the anterior communicating aneurysms, so as to fully expose the sphenoid ridge and lateral fissure.
Ruptured anterior circulation aneurysms are traditionally clipped by pterional approach. The treatment of superficial temporal artery and sphenoid crest during pterional approach is very time-consuming. Statistics show that the operation time of clipping IA through pterional approach is higher than that through supraorbital lateral keyhole approach [9] [10]. Long operation time and long-term exposure of brain tissue to non physiological environments such as air, normal saline and dressing will lead to damage to nerves and vessels on the brain surface [11].Therefore, the supraorbital lateral keyhole approach with shorter operation time can reduce the probability of brain injury, especially for elderly patients. When using this approach, an extended clip holder was used, and the remaining instruments were not specially made.For the supraorbital lateral keyhole approach, large size and wide neck IA need larger incision and bone flap to apply multiple clips in different directions[12], so the bone flap produced by construction clipping IA is larger than that produced by simple clipping.Some literatures have pointed out that the larger frontal sinus is a contraindication of the supraorbital lateral keyhole approach[13], but the current bone wax and intraoperative disinfection make us no longer think that this is a contraindication of this approach. Because the frontal lobe is lifted during the operation, olfactory nerve injury may occur after the operation. According to the literature, the pterional approach clamping of ruptured IA has a high probability of olfactory nerve injury[14]. In a recent statistics, the probability of olfactory nerve injury was about 12% (23/188) by clamping ruptured IA through the supraorbital lateral keyhole approach[15].The frontal lobe was carefully separated to protect the olfactory nerve. There was no olfactory injury in 16 patients. The use of intraoperative electrophysiological monitoring during ruptured IA clipping can reduce the incidence of complications[16]. We routinely used EEG monitoring and motor nerve evoked potential monitoring during operation, and began monitoring after temporarily blocking the IA carrying vessels to ensure the normal neural function of the blood supply area of the IA carrying vessels. Intraoperative aneurysm rupture is a common emergency. Careful and gentle separation of aneurysm neck, sharp separation of arachnoid and slow traction of brain tissue can greatly reduce the risk of intraoperative IA rupture.Many doctors worry that too small bone window may not be able to control bleeding in the event of intraoperative rupture of IA through the supraorbital lateral keyhole approach. This shows that the small bone window of this approach can send the instrument near IA for hemostasis. Controlling the proximal end of the IA carrying vessel is the consensus of clipping. It is equally important to fully expose and control the distal end of the IA carrying vessel, so as to "isolate" IA, minimize the blood flow in IA and ensure the safety of operation.Hitoshi et al. believes that patients with poor Fisher grade (grade IV) before operation should not be treated by keyhole approach, and the risk of intraoperative IA re- rupture is very high [11]. Among 16 patients in this group, 3 (18.8%) were Fisher grade 4, and there was no re-rupture during operation.Therefore, whether the patients with severe condition and high preoperative Fisher grade are suitable for IA clipping via supraorbital lateral keyhole approach remains to be further studied. The 16 patients could take care of themselves after operation, and the scar of head incision was not obvious.
IA rupture will cause brain tissue swelling and increased intracranial pressure. In order to obtain sufficient operation space and reduce the traction of brain tissue, we routinely performed lateral ventricular puncture and drainage cerebrospinal fluid before operation. After the operation, open the drainage tube and slowly release about 50ml of cerebrospinal fluid, which is enough to expose the carotid pool. It is reported in the literature that a patient with ruptured anterior communicating aneurysm underwent extraventricular drainage before operation. After drainage of 50ml cerebrospinal fluid, brain stem herniation secondary occurred [15].Rapid cerebrospinal fluid drainage may lead to accidental rebleeding of IA, so the drainage should be slow and mild [17]. At present, there are no guidelines for cerebrospinal fluid drainage volume and drainage speed in patients with ruptured IA. Therefore, it is necessary to release cerebrospinal fluid intermittently and in a small amount to prevent complications such as cerebral hernia caused by releasing cerebrospinal fluid under low intracranial pressure. If the patient has mental state change and unequal pupil after drainage, be alert to cerebral herniation secondary caused by low intracranial pressure. Postoperative cerebrospinal fluid drainage in patients with ruptured IA is considered to be a beneficial method for the disease [18].We routinely removed the extraventricular drainage tube to prevent intracranial infection, performed lumbar cistern puncture and drainage, monitored the intracranial pressure with the intracranial pressure monitor, and removed the drainage tube one week later. Intracranial pressure monitor can reduce the pain caused by frequent lumbar puncture after operation, and record the intracranial pressure for easy analysis.