Skull base reconstruction is an important part of skull base tumor surgery. Bone, dural and local soft tissue defects of the skull base left after skull base surgery increase the incidence of postoperative cerebrospinal fluid leakage, intracranial and extracranial infections and brain bulge. Selection of appropriate repair materials and methods for reliable and durable skull base reconstruction may improve outcomes. From June 2003 to August 2007, we performed 14 cases of anterolateral skull base tumor resection and skull base reconstruction, which are reported as follows. Data and methods 1. General data: 7 male and 7 female cases, age 1.5-67 years old, average 37.7 years old. 2. Pathological types: meningioma in 4 cases, nerve sheath tumor in 2 cases, enucleated cell tumor in 2 cases, sarcoma in 2 cases, synovial chondromatosis in 2 cases, neurofibroma in 1 case, chondroblastoma in 1 case. 3. Tumor invasion and surgical approach: 3 cases of tumor invasion to anterior skull base and sphenoid sinus, 11 cases of invasion to lateral skull base and middle cranial fossa. There were 3 cases of transfrontal approach, 3 cases of anterior auricular-inferior temporal-inferior temporal fossa approach, 3 cases of anterior auricular curved combined craniofacial incision, 2 cases of transmandibular approach, 2 cases of combined craniofacial approach with expanded Weber-Fugerson incision, and 2 cases of Weber-Fugerson incision with combined craniofacial approach. Fugerson incision via maxillary approach in 1 case. Among the 3 cases of anterior skull base tumors, 2 cases used capillary tendon membrane and titanium plate to repair the anterior skull base defect and the three-layer repair technique of frontoparietal periosteum to repair the dural defect, 1 case used muscle and fibrin glue to repair the skull base leak. 11 cases of middle cranial fossa and lateral skull base tumors, 5 cases used local temporal muscle flap flap to repair the bony defect of the middle skull base and occlude the dead space; 4 cases directly sutured the dural gap and used muscle and In one case, the craniofacial dead space was occluded with a free rectus abdominis flap; in one case, the torn dura was directly sutured and reinforced with pterygoid muscle, buccal fat pad, gelatin sponge and fibrin glue. Titanium plates were applied to repair bony defects at the skull base in 3 cases. One case developed cerebrospinal fluid leakage and intracranial infection at 3 weeks after surgery, followed by hydrocephalus, which was treated conservatively with lumbar puncture tube and external ventricular puncture drainage, combined with intravenous and intrathecal application of sensitive antibiotics to control the infection, and then ventriculoperitoneal shunt was performed, and the patient had a Karnofsky score of 40 at 6-month follow-up. One patient developed facial nerve injury, which healed 2 months after surgery. The remaining patients did not have any complications related to skull base reconstruction, such as cerebrospinal fluid leakage, wound infection, or necrosis of the graft flap. Discussion Skull base reconstruction is an important part of skull base surgery, and its importance is evident from a multicenter study in 2003 that reported 1307 cases of combined craniofacial surgery for malignant tumors of the skull base and 1028 cases (78.16% ) of reconstruction [1]. The concept of skull base reconstruction should be carried out throughout the perioperative period and the treatment process. If the cap tendon membrane or periosteal flap is too small, the blood supply of the repair material may be affected by the pulling of the blood vessels, which may delay the healing and make the reconstruction fail. If necessary, multidisciplinary participation is needed to develop a plan, such as the involvement of plastic surgery for complex myocutaneous flap transfer and radiotherapy for postoperative radiotherapy plan, in order to avoid radiation necrosis in the reconstructed area. The supply vessels or anastomosing vessels of the required myocutaneous flap, such as the superficial temporal artery and deep temporal artery, should be protected from the time of skin incision during the operation. After surgery, close observation should be made for necrosis of the metastatic flap and cerebrospinal fluid leakage. The principle and important purpose of skull base reconstruction is to establish a reliable barrier between intracranial and extracranial structures to avoid cerebrospinal fluid leakage and intracranial infection. The key is the repair of the dura mater, which should be as dense and impermeable as possible. In a case of meningioma in our group, the tumor invaded the lateral skull base and middle cranial fossa. Because of the tight adhesion of the tumor to the dura at the base of middle cranial fossa, the dura was torn when the lesion was removed from the lateral skull base, and the dural fissure was sutured during the operation, and the pterygoid muscle and buccal fat pad were sutured here for reinforcement, and then reinforced with gelatin sponge and fibrin glue. However, cerebrospinal fluid leakage and secondary intracranial infection developed 3 weeks after surgery. We conclude that the biggest lesson of this case is that dural repair is not reliable, and repairing the dura from below is more difficult because of the deep surgical field, and it is more reasonable to repair from inside the skull, just like a roof leak, it is easier to plug the leak from outside the roof. In addition, if too much repair material is used, the dura mater will be torn again due to the chewing action that pulls the pterygoid muscle and buccal fat pad. In this case, the cerebrospinal fluid leak appeared at 3 weeks after surgery, suggesting that we should achieve reliable and durable skull base reconstruction, strengthen the follow-up even after the patient is discharged from the hospital, and deal with complications early. Another patient with saddle-nodular meningioma developed cerebrospinal fluid nasal leak after surgery. After conservative treatment was ineffective, cranial repair was performed, and the cerebrospinal fluid leak was seen as multiple small foramina on the pterygoid plateau, and the leak was closed with temporalis muscle pulp mixed with fibrin glue, and the repair was satisfactory. After resection of olfactory sulcus meningioma, the defect at the sieve plate should be routinely repaired, but the passage of olfactory filaments in this area made the repair difficult, so bioprotein glue and temporalis muscle adhesive were used to close it. However, there is no obvious intracranial or extracranial communication pathway at the saddle node and pterygoid plateau, so it is easy to ignore the skull base repair. This case suggests that whenever the dura is broken, we should be alert to the occurrence of cerebrospinal fluid leakage and need to properly repair the skull base, even if there are tiny holes on the pterygoid plateau. There is no special need for bony reconstruction of the skull base [2], and Shah et al. reported 115 anterior skull base tumors treated with a combined craniofacial approach, and the anterior skull base was reconstructed with tipped ostium, and no meningeal brain expansion was seen in the defect at long-term follow-up [3]. However, for larger defects with anterolateral skull base greater than 3 cm, skull base bone reconstruction should be performed to prevent pulsatile proptosis and cerebral bulge [4]. Bone defects with cosmetic implications, such as zygomatic prominence, should also be repaired as much as possible. In five cases of skull base defects less than 3 cm in our group, only the dural defect was repaired without reconstruction of the skull base bone, and no complications related to brain herniation occurred. For the larger bony defect of the anterior skull base, a titanium plate was used to repair the defect, establishing a rigid barrier and covering both sides of the titanium plate with hemorrhagic tissue, without the occurrence of brain herniation or infection. The role of skull base reconstruction also includes occluding the dead cavity left after tumor resection to avoid fluid accumulation and infection; covering or isolating the internal carotid artery to prevent vascular rupture due to tumor or infection erosion. At the same time, skull base reconstruction can help restore the skull surface shape and meet the aesthetic needs. Although this does not involve function, it affects the patient’s quality of life to a great extent, so it should also be paid attention to. The materials currently used for skull base reconstruction can be divided into two categories: autologous and allogeneic sources. Autologous materials include fat, periosteum, capitellum, layered cranial cap bone, ribs, fibula, etc.; local muscle flaps, such as temporalis muscle and its fascial flap; tipped muscle flaps from adjacent parts, such as pectoralis major, rhomboid, latissimus dorsi, sternocleidomastoid muscle, etc. Autologous tissues have the advantages of being easy to obtain and economical. The disadvantages are the limited source of tissue, the limited area that can be reached, the difficulty of three-dimensional shaping, the absorption and necrosis of the transplanted tissue flap, and the legacy of complications in the donor area, such as the application of the transferred temporalis muscle flap to fill the dead cavity at the base of the skull can lead to collapse of the temporal area, which is aesthetically displeasing. Jacobsen et al. pioneered microvascular surgery, which made it possible to use free flap graft for skull base reconstruction [5]. Their main advantage is their large size and good blood flow, which can be used to occlude huge dead spaces. It is commonly used for the repair of extensive dural, bony, and peripheral soft tissue defects [6,7], and many authors have reported that the application of free tissue flaps with vascular tissues has fewer complications and better confined repair than the application of local tissue flaps [8-10].Califano et al. reviewed cases of anterior skull base reconstruction at Memorial Sloan-Kettering Cancer Center and found that the use of free flaps and The complications of anterior skull base reconstruction with a tipped flap were 31% and 35%, respectively, with no statistical difference. However, as the complexity and extent of tumor resection increases, the use of free flaps increases. In contrast, for patients requiring dural reconstruction, the complication of applying a free flap was 20%, which was lower than that of a tipped flap [11]. However, the application of a free tissue flap with a vascular tip is relatively complex, time-consuming, and can cause damage to the donor area. The most widely used free tissue flap is the rectus abdominis flap, which was used to occlude the huge craniofacial dead space left after tumor resection in a patient with enucleocytoma in our group. The available allograft materials for skull base reconstruction are artificial dura and titanium plate. Artificial materials are easy to apply, time-saving, ample sources, not limited by the size of the defect area, biocompatible, and easy to shape.Janecka reviewed the application of 156 allografts in 100 patients with an average follow-up of 5 years and only 5% complications, noting that titanium and porous polyethylene plates are compatible [12]. In our group, titanium plates were applied to repair bony defects of the skull base in 3 cases, and no infection occurred. The choice of skull base repair material can be decided according to the size of the defect, the location of the defect, and the individual patient. For small to medium defects, local or adjacent tipped tissue flaps can be used; for large defects, free tissue flaps can be used. The frontoparietal fascia, periosteum, and capitellum are most commonly used in the anterior skull base; the temporalis muscle and its fascia are most commonly used in the lateral skull base; and free tissue flaps are used in the central or medial areas. Areas where the patient has had surgery or radiation therapy cannot be used as restorative material, and free tissue flaps are required. In obese patients, the rectus abdominis flap is not appropriate because of its poor blood flow, and the anterolateral femoral flap can be used. In this group, we applied a three-layer repair “sandwich” method to reconstruct the anterior skull base: the first layer is to flip the frontal cap tendon and periosteal flap along the anterior skull base at the orbital rim, and the posterior end is fixed by suturing with the dura at the pterygoid winglet and platform, and if it is not compact, it is reinforced with muscle and bioprotein glue. This layer is thick and well hematopoietic, forming a reliable barrier between the inner and outer skull. The second layer is a titanium plate placed over this layer of tendon membrane and fixed to repair larger bony defects, provide rigid support, and prevent brain herniation. The titanium plate is histocompatible, easy to shape, easy to access, shortens the operation time and does not increase the chance of infection. The third layer is taken from the frontoparietal periosteum to repair the frontal lobe dural defect. Two longitudinal incisions were made perpendicular to the coronal incision and parallel to each other posteriorly to remove the frontoparietal periosteum. (Figure 2) This method was used to repair the anterior skull base defect in our group without associated complications. Gok et al. used broad fascia to close the bony defect of the anterior skull base and the dural defect respectively, separated by a cranial periosteum with blood flow, treating 17 cases with a mean follow-up of 25 months without complications such as cerebrospinal fluid leak, meningitis, abscess, or tension pneumothorax [13].Sinha et al. repaired the anterior skull base bone defect with a titanium plate and autologous cranial cap bone, isolating the intracranial and extracranial structures with a periosteal flap and reported 20 cases, of which 15 cases were followed up for more than 1 year without cerebrospinal fluid leak, hematoma, infection or graft exposure [14]. Regardless of the repair method, the dural closure repair is the key. In our group, temporalis muscle flap was applied to repair the middle cranial fossa and lateral skull base defects in 5 cases, which can occlude the dead space, reduce infection, and facilitate aesthetics. In one case of enucleocytoma, after resection of the tumor, the tumor was considered to be prone to recurrence, so the anterior temporalis muscle flap was transferred and filled between the middle cranial fossa and the inferior temporal fossa to establish a muscular barrier between the possible recurrence of the tumor and the intracranial structures, aiming at delaying the time of intracranial invasion. The key to applying the temporal muscle flap is to preserve the blood supply arteries to the temporal muscle, most notably the deep temporal artery, and stripping the temporal muscle close to the temporal bone surface avoids damaging this vessel. After tumor resection, the temporalis muscle was cut according to the size of the remaining dead space, and care was taken to avoid distal tension, because the distal end is often the critical area for repair and the area most prone to flap necrosis, which has been reported to be as high as 27% [15], and there was no case of necrosis in this group. Skull base reconstruction has greatly contributed to the development of skull base surgery and has enabled the routine resection of skull base tumors that were inoperable thirty or forty years ago. There is now a trend toward less damaging and complex skull base repair, partly because new advances in repair techniques and materials have made skull base repair more minimally invasive, such as small anterolateral skull base defects that can be repaired endoscopically. At the same time, with the deepening of disease understanding, extended resection is no longer pursued for some tumors because it does not improve the prognosis. In addition, with the development of neuroimaging technology, such as virtual reality and navigation, it is possible to locate the lesion more precisely and design the scope of bone resection, which reduces the incidence of skull base defect or reduces the area and volume of the defect. Especially, the concept of minimally invasive surgery is gradually gaining popularity, so that we no longer pursue to make it bigger and more thorough, but pay more attention to reduce surgical complications, try to cut the tumor completely under the premise of ensuring the patient’s safety, function and aesthetic needs, and combine with radiotherapy and chemotherapy to improve the survival time and quality of patients. However, no matter what, skull base reconstruction is still an important part of skull base surgery, and its development will certainly continue to advance the progress of skull base surgery.