OBJECTIVE: To investigate microsurgical treatment of pineal region tumors via the Poppen approach. METHODS: Microsurgical treatment of 32 pathologically confirmed pineal tumors and management of hydrocephalus were retrospectively analyzed. RESULTS: The tumors were completely resected in 25 cases, subtotal resection in 4 cases, and partial resection in 3 cases. There were 12 cases of benign tumors and 20 cases of malignant tumors. Hydrocephalus was one of the common postoperative complications, which required intraoperative torticollis shunt or second-stage ventriculo-abdominal shunt. The follow-up ranged from 1 month to 3 years. 24 cases in this group were followed up, 13 cases lived normally, 6 cases lived on their own, 3 cases needed care, and 2 cases died. CONCLUSION: Microsurgical resection of pineal region tumor by Poppen approach is effective, and intraoperative ventriculo-occipital shunt (torticollis shunt) is safe and necessary for most patients with non-traffic hydrocephalus. The Poppen approach (occipital trans-cerebellar approach) of Zhang Zhiyuan, Department of Neurosurgery, Nanjing Military General Hospital, is one of the most respected surgical approaches for pineal region tumors at present. From April 2001 to April 2010, 32 cases of pineal tumor were treated by microsurgery using the Poppen approach with good results, which are summarized as follows. 1.Objects and methods. (1) Clinical data: 24 male cases, 8 female cases; age 15 months~63 years old, average 30.63 years old, including 12 cases <18 years old, 20 cases ≥18 years old. Clinical manifestations: 27 cases of cranial hypertension with different degrees of headache, vomiting, blurred vision and decreased visual acuity, 10 cases of Parinaud syndrome, 9 cases of ataxia, 9 cases of hemiplegia, 4 cases of diplopia, 2 cases of polyuria and 2 cases of impaired consciousness. (2) Imaging examinations: CT and MRI examinations were routinely performed in this group before surgery. The maximum diameter of the tumor was 1.6cm~7cm. 32 cases were accompanied by different degrees of lateral ventricular and anterior triventricular effusion, 5 cases were combined with calcification, and one of them was located in both the saddle area and pineal area. (3) Treatment method: All the patients were placed in prone position, and after opening the bone flap, the dura was cut open before the lateral ventricle occipital angle puncture, gradually draining the cerebrospinal fluid to reduce the cranial pressure, pulling open the inferior medial side of the occipital lobe, and cutting the cerebellar curtain parallel to the lateral side of the straight sinus about 1 cm. When the tumor is small and the boundary is clear, the tumor is mainly separated and resected in the gap enclosed by the large cerebral vein and the basilar vein, or the gap between the basilar vein and the superior cerebellar vein, so as to try to remove the tumor completely; when the tumor is large, the tumor is first resected intratumorally to increase the operating space, and then the tumor is resected while separating the tumor boundary. During the operation, the third ventricle should be opened as much as possible to restore the normal circulation of cerebrospinal fluid. There were 21 cases with left-sided Poppen approach, among which 1 case underwent lateral ventricular drainage and 1 case underwent ventriculo-abdominal shunt before surgery; 19 cases underwent intraoperative ventriculo-occipital shunt; 1 case underwent postoperative lateral ventriculo-abdominal shunt. The right Poppen approach was performed in 11 cases, including 1 case of preoperative ventriculo-abdominal shunt, 6 cases of intraoperative ventriculo-occipital shunt, 2 cases of intraoperative lateral ventricular drainage, and 2 cases of postoperative ventriculo-abdominal shunt. For those with postoperative pathologically confirmed malignant tumors, radiation therapy was performed in all cases. 2.Results. (1) The extent of tumor resection: 25 cases were confirmed by intraoperative microscopy and postoperative MRI as total resection, 4 cases as subtotal resection, and 3 cases as majority resection. (2) Postoperative pathology: 12 cases of benign tumors, including 7 cases of pineal cell tumor, 3 cases of meningioma, 1 case of mature teratoma, and 1 case of cavernous hemangioma. There were 20 cases of malignant tumors, 10 cases of germ cell tumors, 3 cases of pineal germ cell tumors, 2 cases of mixed germ cell tumors, 1 case of immature teratoma, 1 case of choriocarcinoma, 1 case of mixed pineal parenchymal cell tumor, 1 case of diffuse astrocytic glioma, and 1 case of low-grade malignant mucinous tumor. (3) Follow-up: 24 cases were followed up for 1 month to 3 years, 13 cases were working and living normally, 6 cases were living on their own, 3 cases were living in need of care, and 2 cases died. The symptoms of cranial hypertension were significantly relieved in 23 cases and not significantly relieved in 4 cases; ataxia was improved in 5 cases and not improved or aggravated in 4 cases; postoperative muscle strength was improved in 6 cases and hemiparesis was the same as before surgery in 3 cases; diplopia was improved in 2 cases and the same as before surgery in 2 cases; postoperative mental improvement in 2 cases. The MRI was reviewed at follow-up in 24 cases. One patient with subtotal resection recurred at 12 months after surgery (pathology was mixed germ cell tumor) and was operated again; the rest did not see any significant tumor recurrence. During the follow-up period, one case died of pulmonary infection and one case died 10 days after hematoma removal due to brain herniation caused by postoperative epidural hematoma. (4) Postoperative complications: 3 cases of epidural hematoma and 1 case of worsening transient disorder of consciousness. New or aggravated symptoms after surgery: 3 cases of isotropic hemianopia, 3 cases of decreased visual acuity, 3 cases of Parinaud syndrome, and 3 cases of diplopia. 3. Discussion. The tumor in the pineal region is deeply located and adjacent to important vascular and neural structures, so it is more difficult to operate. In addition, the pathological types of tumors in the pineal region are complex, and the proportion of mixed tumors is relatively high, with varying sensitivity to radiotherapy and/or chemotherapy. More and more scholars advocate microsurgical total resection as the treatment of choice for pineal region tumors. There are various surgical approaches for pineal tumors, and choosing the appropriate surgical approach can improve the success rate and reduce complications. The Poppen approach is currently one of the most commonly used surgical approaches, which has the following advantages: (1) the deep venous system is kept under direct vision, which is not easily damaged and most of them do not require sacrificing the pontine vein; (2) the tumor supplying artery can be controlled at an early stage; (3) the field of view is open and suitable for lateralization (3) wide field of view, which is suitable for larger tumors growing laterally and/or protruding into the ventricles; (4) intraoperative lateral ventricle-occipital pool shunt can be performed; (5) convenient operation, which can avoid the risk of air embolism. However, the Poppen approach also has its disadvantages: (1) it is difficult to reveal the contralateral tegmental area and thalamus; (2) the deep venous system needs to be fully dissected to fully reveal the tumor; (3) the medial occipital vein may be damaged, causing occipital infarction and edema and resulting in hemianopia. In our department, most of the tumors in the pineal region are treated by the Poppen approach, which has been modified according to clinical practice. The surgery is summarized as follows. (a) Modified postural incision. We adopt the prone position, fix the head and advocate to make a horseshoe-shaped incision on the left side of the occipital area to facilitate surgical operation. However, if the tumor is obviously growing on one side, then choose ipsilateral craniotomy. 11 cases in this group have tumor growth on the right side, so the right Poppen approach is adopted. The natural anatomical gap of the pineal region was utilized, and the occipital lobe was pulled outward and upward from within the longitudinal fissure to obtain a larger surgical space. (ii) Management of hydrocephalus. Tumors in the pineal region can block the midbrain aqueduct, which can lead to non-traffic hydrocephalus and produce cranial hypertension. After craniotomy via the Poppen approach, the lateral ventricular occipital horn can be directly punctured to release cerebrospinal fluid and reduce intracranial pressure. Most of them can obtain good exposure, effectively reduce traction and avoid traction on the medial side of the occipital lobe leading to postoperative isotropic hemianopia. No additional incision for extraventricular drainage is required. Attention was paid to the slow release of cerebrospinal fluid, and the height of the drainage port was not lower than the operative area to avoid the formation of epidural and subdural hematomas in the distal septal area. The presence of epidural hematoma in three cases in this group after surgery may be related to the rapid release of cerebrospinal fluid. Preoperative extraventricular drainage or ventriculo-abdominal shunt is not possible unless the patient is already in critical cranial hypertension before surgery. Preoperative extraventricular drainage does not facilitate adequate intraoperative collapse of brain tissue and increases the risk of intracranial infection. Although the deep veins, especially the basilic vein and its branches, have extensive anastomotic traffic with the superficial cerebral veins and have strong compensatory capacity for collateral circulation, it takes some time for the collateral circulation to open, so there will be temporary local cerebral blood flow obstruction after surgery, which will aggravate local edema and lead to Therefore, postoperative temporary local cerebral blood flow return obstruction may occur, which may aggravate local edema and lead to the occurrence of non-traffic hydrocephalus. In addition, long-term tumor compression may lead to adhesions in the third ventricle, and it is still uncertain whether and when the midbrain conduit can be recanalized after surgery. In this group, it was difficult to maintain the patency of the middle cerebral aqueduct in the short term after surgery. Most of the patients in this group underwent intraoperative lateral ventricle-occipital pool shunt, and the hydrocephalus was significantly relieved after surgery, and no non-traffic hydrocephalus occurred. (C) Intraoperative venous protection and management of venous hemorrhage. Four gaps were formed between the deep veins in the pineal region. The decision of which venous gaps to use for tumor resection was based on the abundance of the mid-basilar segment of the basal vein and its geniculate branches. The third gap is the inferior basilic vein gap, which is the gap between the basilic vein on one side and the large cerebral vein, where most of the operations of the Poppen approach are performed. There is a rich anastomosis between the deep and superficial cerebral veins, and dissection of a single vessel does not have serious consequences. When a vein breaks and bleeds, hemostasis can be achieved by compressing the vessel break with gelatin sponge, and if necessary, sharply disconnecting the vein from the tumor and stopping the bleeding with electrocoagulation. As the main deep vein draining the medial occipital cortex, the medial occipital vein converges into the large cerebral vein below the basilar vein, and care should be taken to avoid damage to it in order to avoid postoperative occipital cortical blindness. (d) Most of the tumors in the pineal region are supplied by the posterior internal and posterior external branches of the posterior cerebral artery and partly by the superior cerebellar artery. The use of this approach can deal with the tumor blood supply artery at an early stage, reduce tumor bleeding and keep the visual field clear. The main complications of tumor surgery in the pineal region include isotropic hemianopia, Parinaud's syndrome, diplopia and hydrocephalus. In our group, the results of microsurgery with Poppen approach for pineal region tumor were good, with fewer complications and mostly transient. Intraoperative lateral ventricle-occipital pool shunt is necessary and safe for most patients, which can effectively relieve hydrocephalus and avoid postoperative deterioration due to non-traffic hydrocephalus, or secondary surgery after surgery.