INTRODUCTION: There are four approaches to the slope or anterior bridge: suboccipital, middle cranial fossa, transtrochanteric, and transtrochanteric. Although the transtympanic approach provides a wide field of vision, the abrasion of the middle rock cone can lead to permanent loss of hearing.The anterior approach to the sigmoid sinus with the resection of Trautman’s triangle (superiorly the suprasellar sinus of the rock, inferiorly the facial neural tube, and posteriorly the sigmoid sinus) is good for exposure of the inferior slope but has limited room for maneuvering on the superior slope due to the presence of the bowed augmentation. Also the anterior approach to the sigmoid sinus presents surgical complications of exposing the sigmoid sinus and labbe vein. Therefore, a middle cranial fossa craniotomy with removal of the anterior rock cone is more advantageous. Indications: upper slope or pre-bridge tumors located medial to the internal auditory canal: meningiomas, trigeminal nerve sheath tumors, slope chordomas, pre-bridge epidermoid cysts. Particularly indicated for medial trigeminal and dumbbell-type tumors. Aneurysms of the superior basilar artery trunk, anterior inferior cerebellar artery, and vertebrobasilar junction. Penetrating arteries between the aneurysm and the brainstem can be visualized. For tumors beyond the lateral aspect of the internal auditory canal, part of the labyrinth needs to be additionally resected. For tumors above the posterior bed eminence, the zygomatic arch needs to be resected. The lower limit of this access is the middle slope, at the junction of the vertebrobasilar artery. Preoperative preparation: lumbar puncture, supine position, 20 degrees of upper body height, and headset to detect brainstem auditory potentials. The headset was covered with an auricle prior to sheet laying. Facial nerve monitoring is given if necessary. Basilar artery trunk aneurysms require bilateral vertebral artery catheter balloon placement to prevent rupture. Surgical approach: anterior border: 1 centimeter in front of the ear, vertically upward to prevent facial nerve injury; superior border is the pterosquamous suture, which should be long enough for future repair. A question mark flap can be used if a wing point approach and zygomatic arch resection are to be combined. The fascial flap is detached from the temporalis muscle with the base below and the muscle turned forward. The zygomatic arch, external auditory canal, and squamous suture are marked. Above the mandibular joint, the lateral aspect of the scalene suture is the edge of the flap, and the anterior inferior edge of the flap is abraded to expose the foramen spinosum. The rocky spine is exposed epidurally until the edge of the rocky bone is identified. Cerebrospinal fluid drainage is helpful for this. After identification of the foramen ovale, the middle meningeal artery is electrocoagulated and severed. Venous hemorrhage at the foramen ovale requires compression. Posterior to the foramen ovale, the greater and lesser petrosal nerves are identified; they are adherent to the dura mater, and shallow scars are visible on the bone. To separate them from the dura, consider cutting both layers of the dura and leaving the nerves on the periosteal dura. Do not retract the large rock superficial nerve to avoid injury to the facial nerve. The dura can be retracted to the rocky spine fixation point. Separating the mandibular nerve from the periosteum reduces the progression of the dura. Two bony landmarks can be observed on the surface of the rocky spine, the arcuate eminence and the trigeminal nerve indentation. The internal auditory canal is slightly anterior to the arcuate eminence at a depth of 7 mm from the bone surface. The geniculate ganglion is at the junction of the internal auditory canal and external auditory canal. The cochlea is at the angle between these two lines. The internal carotid artery and the Eustachian tube are lateral to the Iwata nerve. Figure 4 shows the maximum extent of osteotomy to preserve hearing. On the medial side of the greater Iwaki nerve, anterior to the arcuate eminence and superior to the internal auditory canal in order to avoid damage to the superior and inferior petrosal sinuses, the bone on the posterior surface of the petrosal vertebrae is preserved by denudation of the cancellous bone. diamond bur, grinding the anterior wall of the internal auditory canal posteriorly is also performed taking care not to injure the dura mater of the internal auditory canal. The bone is thoroughly abraded up to the margins, exposing the meninges between the 5th and 7th cranial nerves. A small incision is made in the dura of the posterior cranial fossa with a sharp knife to expose the petrosal vein and AICA in the pontine cerebellar horn pool.Often, tumors in the petrosal region can be seen here. The subbasal dura of the middle cranial fossa is incised 50 px toward the supraclinoid sinus, and after the temporal lobe has been retracted by the brain pressure plate, the dural incision is extended in a T-shape in the direction of the sinus, and the supraclinoid sinus is ligated and clipped, and the petrosal vein should be attached to the posterior portion of the suprasellar sinus that has been clipped to allow for venous return. Clip the cerebellar vermis. In rock-slanting meningiomas, the dural incision should be made as close as possible to the attachment of the posterior margin of the tumor. Care is taken to avoid injury to the gliding nerve when cutting the cerebellar tegmentum. The cerebellar vermis is retracted to the 2 sides. The trigeminal nerve is held in place by the mouth of Meckel’s capsule, so incision of the dura at the entrance of the meckel’s capsule by 25 px allows freeing of the trigeminal nerve and visualization of the basilar artery trunk of the abducens nucleus. Aneurysms of the basilar artery trunk Aneurysms of the basilar artery trunk tend to be located between nerves 4-5, so the trigeminal is divided inferiorly.Aneurysms of the AICA bifurcation tend to be located between 5-6, so the trigeminal tends to be divided superiorly. The vertebral artery union tends to be located in the lowermost part of the osseous resection window, between 6-7 cranial nerves. The brainstem cannot be drawn posteriorly, when dealing with an anterior aneurysm that grows forward and adheres to the slope. For, posteriorly growing aneurysms, the tip is buried in the cerebral bridge and is encircled by the perforating artery. Backward-growing aneurysms of the vertebral artery union are also encircled by the perforating artery, and care should be taken to preserve the perforating artery during clamping. Rock-slope tumors are classified into four types: upper slope, cavernous sinus, cerebellar vermis, and rock-slope. With upper slope and cavernous sinus tumors, the trigeminal nerve is pushed laterally, whereas rocky-tip and cerebellar tegmental meningiomas push it medially. Most rock-slope meningiomas will grow along the cerebellar vermis and 50% will invade the meckel’s capsule. Therefore, the cerebellar vermis needs to be incised from the posterior edge of the tumor. If the tumor grows into the middle cranial fossa, it should be removed before incising the cerebellar vermis (probably for fear of increased bleeding from the tumor if the superior petrosal sinus is severed). When incising the cerebellar vermis, be careful of the trigeminal nerves that are compressed beneath the superior petrosal sinus. Usually, the 3rd and 4th cranial nerves are pushed up. When opening the meckel’s capsule to remove the tumor, be careful that the trigeminal nerve in the capsule is divided into multiple strings and mixed with the tumor. The cerebellar vermis is retracted to separate the trigeminal nerve from the gliding nerve, and the tumor is excised from the sloping dura. The trophoblastic artery of the tumor, the meningeal artery, can be electrocoagulated and cut between it and nerves 4 and 5, after which the procedure is essentially bloodless. The superior cerebellar artery tends to be encased in the tumor, whereas the AICA and basilar artery are encased only in large tumors. The abducens nerve is often not found until after the tumor is cut. Nerve tone decreases after the tumor is cut.4 and 5 nerves penetrating the dura tend to be involved by the tumor. If preoperative T2-phase magnetic resonance shows peritumoral edema on the brainstem, the thin layer of tumor should be preserved because the arachnoid plane may no longer exist between the tumor and the brainstem in this case. Trigeminal nerve sheath tumors, chordomas, and epidermoid cysts are not tightly adherent to the cranial nerves and brainstem. This is the opposite of a meningioma. The posterior cavernous sinus can be opened, if necessary, by incising the inner wall of meckel’s capsule. parkinson’s triangle is enlarged by retracting the trigeminal nerve downward, and the synovial nerve upward. Hemostasis can be achieved by hemostatic gauze to the cavernous and subrock sinuses. The carotid ring (c4/5) and the motor nerve can be visualized where it crosses Dorello’s canal. The cavernous sinus meningioma should be detected by Doppler microsonography because of the poor demarcation between the cavernous sinus meningioma and the surrounding tissue. Cranial closure: The petrous cusp is covered by a temporal fascial flap and fibrin glue, and the exposed mastoid airspace can also be covered by it; the large airspace of the petrous cusp can be filled with abdominal fat. The dura mater is sutured to the fascial flap to prevent subcutaneous cerebrospinal fluid leakage, and the skull is routinely closed.